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Approach to an Obstetrical Case
11
Approach to an Obstetrical Case TIMOTHY J. PARKINSON, JOS J. VERMUNT AND DAVID E. NOAKES
E
ach case of dystocia is a clinical problem that may be solved if a correct procedure is followed. The successful management of the case requires obtaining a history from the owner or attendant, a focused clinical examination, and specific examination of the reproductive tract. There should be careful differentiation between a labour that is not fully established from one that has become interrupted, and a careful diagnosis should be made of any faulty fetal disposition before attempting any correction. There should also be a differentiation between whether the labour has been interrupted due to a problem with the birth process per se, and whether other disease processes are interfering with it.
Causes and Classification of Dystocia A normal birth occurs when the expulsive forces are sufficient to propel a fetus of normal size and disposition through a birth canal of adequate size. Dystocia occurs when any of these are abnormal or insufficient. Thus the causes of dystocia can be considered in terms of the: • Expulsive forces • Adequacy of the birth canal • Size and disposition of the fetus Difficult birth will occur when the expulsive forces are insufficient, when the birth canal is of inadequate size and shape, or when the presenting diameter of the fetus is unable to pass through the normal birth canal because it is too large or its disposition prevents it from doing so. An overview of the types and causes of dystocia are given in Fig. 11.1. Defects of the expulsive forces and of the adequacy of the birth canal are commonly referred to as maternal dystocia, whereas those due to defects of the presentation of the fetus or to its disproportion (i.e., with respect to the size of its dam) are known as fetal dystocia. However, there will be times when it can be difficult to identify the primary cause and others when there will be a change in the dominant cause during the course of the dystocia.
Defects of Expulsive Forces Defects of expulsive forces generally refer to intrinsic defects of uterine contractility, nervous voluntary inhibition of labour, or failure of contraction due to mineral/hormonal imbalances (primary inertia), or to exhaustion of either the uterine muscle itself or depletion of pituitary oxytocin stores (secondary inertia). Failure of contraction of abdominal muscles during second stage labour can also occur.
Defects of the Adequacy of the Birth Canal The birth canal consists of the internal tubular organs of the reproductive tract from the uterine horns and body to the vulva. Abnormalities of any part of these structures can lead to dystocia. Such abnormalities include function disturbances of the genitalia (e.g., incomplete cervical dilation; torsion of the uterus), obstructions (e.g., neoplasia), or mechanical abnormalities (e.g., double cervix; remnants of the paramesonephric ducts). Rarely, the uterus can be displaced into a subpubic position or through a hernia in the abdominal wall. Abnormalities of the surrounding tissues can, likewise, lead to dystocia. Such tissues include the pelvis (e.g., heritable pelvic malconformation such as occurs in Belgian Blue cattle and brachycephalic dog breeds; fractures of the pelvic bones; sacroiliac dislocation), the bladder (e.g., prolapse into the vagina), or excess intrapelvic fat,
Faulty Fetal Disposition During pregnancy, particularly in monotocous species such as cattle, horses, sheep, and goats, the fetus assumes a disposition within the uterus which is such that the space occupied is as little as possible: for example, the vertebral column and limbs will be flexed to varying degrees. In order to negotiate the birth canal unaided, these joints need to be extended. The term ‘faulty’ or ‘abnormal fetal disposition’ is used to describe the situation in which the fetus has failed to assume the disposition that enables it to be expelled unaided per vaginam. The universally accepted terminology to describe these abnormalities is that first defined by Benesch. This involves the use of the terms presentation, position, and posture, each of which has a specific meaning in relation to veterinary obstetrics (Fig. 11.2). Presentation signifies the relationship between the longitudinal axis of the fetus and the maternal birth canal. These may be: • Longitudinal presentation, which can be anterior or posterior, depending on which fetal extremity is entering the pelvis; • Transverse presentation; ventral or dorsal, according to whether the dorsal or ventral aspect of the trunk is presented; and • Vertical presentation; ventral or dorsal. Vertical presentations are very rare, and only the obliquely vertical ‘dog-sitting’ presentation in the horse needs to be considered in detail. Position indicates the surface of the maternal birth canal to which the fetal vertebral column is applied. It can be dorsal, ventral, and left or right lateral. 203
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Dystocia Maternal Inadequate expulsive forces Uterine inertia Primary
Secondary
• Overstretching
Myometrial ‘exhaustion’
• Incorrect oestrogen progesterone ratio • Inadequate secretion of oxytocin and prostaglandin secretion
Weak abdominal straining • Age • Debility • Pain • Herniation of uterus
• Failure of receptor regulation/development • Ca2+ and/or Mg2+ deficiency • Fatty infiltration of myometrium • Nervous voluntary inhibition • Hysteria
Fetal
Inadequate size of birth canal Incomplete dilation Inadequate pelvis or constriction of birth canal • Immature • Uterus > Torsion > Displacement • Cervix > ‘Ringwomb’ > Duplication • Vagina > Stricture > Neoplasms > Cystocoele > Prolapse > Vestigial structures
• Fracture
Fault disposition
Oversize
Relative and Congenital Fetal absolute monsters pathology • Small litter
• Ascites
• Breed
• Anasarca
• Breed deformity • Prolonged gestation
• Presentation • Position • Posture
• Emphysema
• IVM/IVF derived embryos
Feto-maternal (pelvic) disproportion
• Vulva > Stricture > Incomplete relaxation
Obstructive dystocia
• Fig. 11.1
The causes of dystocia.
Posture refers to the disposition of the movable appendages of the fetus and involves flexion or extension of the neck or limb joints, for example, lateral flexion of the neck or hock flexion posture. Disproportion: Fetomaternal disproportion occurs when the fetus is larger than the capacity of the pelvis through which it has to pass. Disproportion may occur if the fetus is larger than normal, either in terms of its absolute size or of the size of particular parts of its body (notably shoulders and/or pelvis), or if the pelvic canal of the dam is too small or is of incorrect shape.
History and General Examination History Before examining the animal, an effort should be made to obtain a pertinent history of the case from the owner/attendant. Key points to be elicited from the history are summarized in Fig. 11.3. Perhaps the most important aspects of the history are (i) the duration of labour and (ii) attempts that have already been made to assist the birth. The parity of the animal is the third key aspect because the incidence of different types of dystocia varies markedly with parity. For livestock, it is generally obvious whether the animal is primigravida or multigravida, but this can be rather less obvious in other species. The duration of labour is important inasmuch as it is one of the key determinants of outcome for mother and fetus and often constrains the options available to the obstetrician for managing the case. Calculating the time the start of labour is often difficult because the signs of the onset of first stage labour are sufficiently vague and indistinct to easily escape the attention of an attendant. The onset of second stage labour, which is typified by vigorous and frequent straining, appearance of the amnion, expulsion of fetal fluids, appearance of a fetal extremity, and/or recumbency of the animal, are easier to recognize; this will typically be identified by an attendant as the ‘start of labour’. Even so, in intensively managed livestock, it is by no means uncommon for the onset of
even second stage labour to pass unnoticed and for the animal to be presented once a dystocia is obviously present, but with little indication of its duration. As a generalization, it is reasonably certain that some form of obstructive dystocia exists if several hours have elapsed since the onset of second stage labour. The fetus can survive a moderate period of dystocia in most species, but this depends on the extent to which the fetus has traversed the birth canal before the labour is arrested. Thus, if the cause of the dystocia is relatively simple, such as slight fetomaternal disproportion or a minor limb malposture, and the case has not been neglected, fetal and maternal survival are often good. On the other hand, fetal survival of dystocia in the mare is short, as the normal course of delivery is so rapid and separation of the placenta occurs so quickly once second stage has commenced that any delay generally results in the death of the foal. If the dystocia has not been noticed until 24 or more hours after the start of second stage labour has started, the fetus is likely to have died and will often have started to become putrefied and decompose. Managing these cases is difficult because straining efforts have commonly ceased, fetal fluids have been entirely lost, and the uterus has started to contract down onto the retained fetus. In polytocous species, fetuses may survive for some time behind a point of obstruction, but eventually they will also die and/or start to decompose. It is valuable to discover whether an attempt has already been made to assist the delivery. This may not only provide useful information about the type of dystocia that is (or is not) present, but may also provide evidence of whether injury has been caused either to the genital tract or to the musculoskeletal system of the animal. All of this information helps the obstetrician to provide a prognosis for mother and fetus for the outcome of the birth. It is particularly important to determine whether any drugs (commonly calcium, antibiotics, or oxytocin) have been given before assistance is requested, as this may affect the subsequent management of the case and will undoubtedly affect meat or milk withholding times for livestock.
CHAPTER 11 Approach to an Obstetrical Case
Presentation Longitudinal Anterior
Posterior
Transverse
Ventrotransverse
Dorsotransverse
Bicornual
Oblique (vertical) Ventro-vertical (“dog sitting”)
Dorsovertical
Ventral position (posterior presentation)
Posture Forelimb Flexion Shoulder
Carpus
Hindlimb flexion
Hip
Hock
Bilateral hip flexion “breech presentation”
Neck flexion
Lateral
• Fig. 11.2
Ventral
The vulva should next be inspected. Parts of a fetus may be protruding, and it may be possible to assess the nature of the dystocia from these. Are exposed fetal parts moist or dry, or swollen emphysematous or oedematous? Such evidence serves not only as a guide to the duration of the condition but also to the effort that will be necessary to correct it. If parts of the amnion protrude, what is their condition? Are they moist and glistening with fluid caught up in their folds? If so, their exposure is recent, and the case is an early one. If, however, the membranes are dry and dark in colour, it may be taken that the case is protracted. Attention should also be paid to the nature of the discharge from the vulva, especially if neither fetus nor membranes are presented. Fresh blood, especially if profuse, generally indicates recent injury to the birth canal. A dark brown, fetid discharge indicates a grossly delayed case. When dealing with the bitch and cat, the degree of abdominal distension should be observed, for it may be possible to make an estimate of the number of fetuses that occupy the uterus. The onset of vomiting, together with a great increase in thirst, should be regarded as grave signs in the bitch.
Detailed Examination of the Animal
Position
Ventral position (anterior presentation)
205
Abnormalities of fetal presentation, position, and posture.
General Examination The animal’s physical and general condition should be noted. If recumbent, is she merely resting, is she exhausted, or is she suffering from a metabolic disease? Body temperature and pulse rate should be noted and the significance of abnormalities considered. Cattle should be routinely assessed for the presence of hypocalcaemia, and the possibility of toxic mastitis should not be overlooked.
Large Animal Species The animal should be effectively restrained in a clean environment, for the safety of the veterinarian, any assistants, and the animal concerned. In the case of the mare (Fig. 11.4), cow, ewe, and doe goat, it is usually easier if they remain standing; the sow is best examined in lateral recumbency. One should never forget that large animals can collapse suddenly during examination, so it is important to ensure that (i) the animal can be easily extracted from the restraint if it does collapse and (ii) the obstetrician’s hand/ arm does not become trapped inside the animal when it collapses. It may be necessary to sedate the animal before examining her – ideally, at a sufficiently early stage in the proceedings that she does not become fractious, but to a level that does not result in unplanned collapsing/recumbency. A decision whether to use epidural anaesthesia should likewise be made as early as possible. If the fetus is dead and/or the uterus is grossly contaminated, the epidural should be given before a vaginal examination is performed in order to minimize the risk of infecting the neural canal. It is impossible to perform obstetrical procedures aseptically in any animal species, but the amount of contamination of the genital tract should be kept as low as possible. To this end, plentiful supplies of clean hot water with soap or surgical scrub should be available, as well as a table or bench covered with a sterile cloth on which instruments may be placed. Making sure that any bedding is clean (e.g., clean straw placed behind the animal) is also helpful. Because the floor is often wet and slippery, application of sand or grit is a worthwhile precaution. The external genitalia and surrounding parts are thoroughly washed, and the tail is held or tied to one side. The obstetrician’s hand and arms should be cleaned in water from a different bucket. The first vaginal examination usually provokes reflex defecation: more washing of animal and obstetrician is required. Some obstetricians prefer to wear a disposable plastic sleeve during examination of the animal: certainly this reduces the need for repeated rewashing of the obstetrician’s arms, but some find it more difficult to differentiate tissues within the uterus when wearing a sleeve. When gross contamination of the uterus is present (e.g., in cases of bacterial abortions or when a putrefying fetus is present), it is very strongly advised that a sleeve should be worn. In the mare a
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General history
History of the dystocia
Primiparous or multiparous?
Has an examination already been made? Has any assistance been given? Have any drugs been given?
Full term or premature?
Has a ‘water-bag’ appeared at the vulva? When?
When did straining begin? Slight? Intermittent? Frequent? Forceful?
Previous breeding history
Any loss of fluid? What fluid?
Has straining stopped again? When?
Management during pregnancy
Has any part of the fetus appeared at the vulva?
Have any fetuses already been delivered? Alive/dead? (polytocous species)
Still eating? Drinking? Signs of illness?
• Fig. 11.3
Key points in the obstetrical history of a case.
• Fig. 11.4 Mare with dystocia, restrained in stocks for vaginal examination and correction of dystocia.
• Fig. 11.5
clean tail bandage is applied because the tail hairs are frequently introduced into the vulva and vagina which can cause quite severe lacerations. Without the previous induction of epidural anaesthesia and the resultant paralysis of the rectum, it is almost impossible to make a vaginal examination in the cow without introducing some faecal contamination. There is little serious consequence of mild contamination, fortunately; but the greater the contamination that occurs, the greater the risk of postpartum uterine infection. The next stage is to perform a vaginal examination in order to establish the patency of the birth canal, the orientation of the fetus, and the position of its movable parts (i.e., head, limbs, tail). Copious lubrication should be introduced to the birth canal at the start of the vaginal examination. In the majority of cases, some part of the fetus occupies the vagina – the head, a limb, or limbs. Some difficulty can initially be experienced in recognizing the fetal parts being palpated if they are covered by amnion. To overcome this, the torn edges of the amniotic sac should be identified and opened, and the hand inserted so that the fingers come into direct contact with the fetus. It is often necessary to repel the fetus back into the uterus to ascertain the nature and direction of displaced parts. If continued straining makes this difficult, the induction of epidural anaesthesia should be considered at once, but it should be remembered that the dam’s expulsive effort may be required after any corrective procedure has been performed.
Recognition of the head is not difficult; the mouth and tongue, the orbits, and the ears are generally obvious. In the case of limbs, the first requirement is to ascertain whether it is a forelimb or hindlimb. There are two main ways of assessing this: the orientation of the feet and the flexion of the joints of the limb. If the plantar aspect of the digit is downwards, it is most likely to be a forelimb; if the plantar aspect is upwards, it is most likely to be a hindlimb. This ‘rule of thumb’ nearly always holds true for the cow/ewe/doe, but in the mare, it is not uncommon for the fetus to be in the ventral position, so more caution is needed. The direction of flexion of the limb joints differs between forelimb and hindlimb: if the fetlock and the joint immediately above it flex in the same direction, it is a forelimb. Conversely, if the fetlock and joint above it flex in the opposite direction, it is a hindlimb (Fig. 11.5). If more than one limb is present, it must be established that they are either fore or hind and if they are from the same fetus. If nothing is present in the vagina, the cervix should next be examined. First, it should be determined whether the cervix is completely dilated. If the cervix is largely, but not fully, dilated, a ‘lip’ of tissue will be evident, usually at the caudal end of the cervix. If less dilated, the cervical structure will be obvious, and there may even still be mucous within it. In the latter case the
Determining whether presented limbs are fore- or hindlimbs. The olecranon and hock are easy to confuse during vaginal examination: however, in the forelimb, the first two movable joints (fetlock and carpus) flex in the same direction, whereas in the hindlimb, the first two movable joints (fetlock and hock) flex in the opposite directions.
first thing to consider is whether the first stage of labour is not yet complete; i.e., the second stage of labour has not yet begun, and the animal requires more time. On the other hand, failure of cervical dilation can be a sign of dystocia. For example, the cervix usually fails to fully dilate in cases of uterine torsion, and failure of the fetus to impact the internal os of the cervix (i.e., through some form of faulty disposition) can also lead to partial failure of cervical dilation. Finally, it should be ascertained whether the cervix is incompletely dilated as the dystocia has been neglected, and the cervix has started to close again. This will usually be accompanied by complete loss of fetal fluids and often by obvious signs that the fetus has died and is starting to decompose. When the fetus has not fully entered the birth canal, deeper palpation is needed to determine what parts are presented. For example, palpating the fetal tail and perineum means that there is a high likelihood that the fetus is in ‘breech’ presentation. Likewise, if a flexed neck is palpated and a search on one or other side reveals ears and occiput, the case is one of lateral deviation of the head. Similarly, presentation of the head but not of forelimbs can indicate flexion of the carpi or of the shoulders. In the mare (and sometimes in ruminants), it may indicate that the fetus is in a dorsotransverse presentation, or perhaps occupying both horns (bicornual gestation). Finally, the presentation of a plethora of limbs may indicate simultaneous presentation of twins, fetal abnormalities such as schistosoma reflexa or limb duplication, or a ventrotransverse or vertical presentation. It may be worthwhile trying to assess the viability of the fetus, inasmuch as this can influence the options for management of the case. For cattle, however, it should be noted that, with increasing herd sizes and the associated improvements of the skills and knowledge of farm staff, it is increasingly unusual for the calf to be alive at the time when obstetrical assistance is requested. Viability can be assessed by attempting to elicit reflexes such as corneal/ palpebral, suck, anal (if in posterior presentation), and limb withdrawal. Palpation for the presence of a pulse in the umbilicus may be feasible when the fetus is in posterior longitudinal presentation. In the neglected or protracted case, assessment of the exact nature of the dystocia and methods of correction may be more difficult. The vaginal wall becomes progressively more oedematous, so that even the insertion of a hand and arm becomes difficult, and there is no room in which to carry out manipulations. Loss of fluid results in the dam’s mucous membranes and fetal parts becoming dry. Contraction of the uterus directly on the irregular contour of the fetus makes retropulsion difficult or even impossible. In general, these cases have to be managed by relaxing the uterine muscle with a spasmolytic, such as clenbuterol, and/or by infusing replacement fluids into the uterus, and always by the use of large quantities of obstetrical lubricant. In such cases, it may be necessary to estimate the time interval since the fetus died. Fetal emphysema and detachment of hair means that the fetus has been dead for at least 24 to 48 hours. If there is no emphysema and the cornea is cloudy and grey, then it will have been dead for 6 to 12 hours.
Dog and Cat The bitch, unless an exceptionally large one, should be placed standing on a table. It is preferable that a person with whom the animal is familiar should hold its head and be warned that even some quiet stoical bitches may resent a vaginal examination. Fetal numbers may be assessed in some bitches by gentle abdominal palpation or, more commonly, by the use of transabdominal ultrasonography. Ultrasonography has the added advantage of being
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able to determine whether the pups are alive by identifying the beating fetal heart. At a later stage in the examination, it might also be necessary to take radiographs. As a general rule, the operator will proceed to make a digital examination per vaginam, especially in early cases in which it is likely that obstruction is the cause of the delay and also in protracted ones in which it is estimated that a single fetus only remains unborn. Nevertheless, cases will be met in which it is obvious that inertia has supervened, and there are several fetuses to be delivered, in which case immediate Caesarean surgery or hysterectomy is indicated. Whether or not the hair is clipped from the area around the vulva before making a vaginal examination will depend on the length of the coat. In long-coated animals, it is a great convenience to do so; although it is impossible to render the area sterile, it should be thoroughly cleansed beforehand. Sometimes on raising the tail it is seen that part of a fetus, a head or hind parts, is protruding from the vulva. Such a finding is more common in the cat than the bitch. The case is a simple one; traction on the exposed parts effects delivery without difficulty and, provided this assistance has been forthcoming early, it is probable that parturition will proceed normally. Occasionally, it is found that the vagina is occupied by a fetal head or buttocks which have become impacted. In the majority, however, the pelvic canal is unoccupied and obstruction occurs at the inlet. The fetal disposition should then be determined. If the head is present, but the occiput and ears are palpated rather than the mouth, it is likely to be a case of vertex presentation. If a single limb is felt, but there is no sign of the head, the case is probably one of lateral deviation of the head. If the presentation is posterior, the tail may be recognized (although sometimes it is directed forwards over the fetal back). The hindlimbs may have entered the pelvis or they may be retained (flexed). The fetus may have rotated into ventral or lateral position. Determination of fetal viability by attempting to elicit reflexes is unreliable.
Obstetrical Equipment Manipulative Deliveries per vaginam in Large Animals The most important obstetrical instruments are the clean and gentle hands and arms of the obstetrician. There is, however, an array of equipment that can be used to assist in obstetrical procedures; arguably, the obstetrician should aim to possess a minimum of essential equipment and to be thoroughly conversant with the use of each item. For the veterinarian doing ambulatory visits to farms, studs, and other livestock units where parturient animals are kept, it is advisable to have a dedicated collection of core obstetrical instruments and other equipment that is always available in an emergency; in addition, a dedicated Caesarean surgery kit is also important (see Chapter 16 and, when working with cattle, a fetotomy kit (Chapter 15) should be carried. Simple instruments that are easy to handle and convenient to sterilize are best. More complex equipment is occasionally required, and the important consideration is to know when the use of such complicated instruments is indicated. With the availability of better sedatives and anaesthetic agents and improved methods for fetotomy and Caesarean surgery, many of the long-established items of obstetrical instrumentation have become obsolete, and veterinarians have lost the skills to use them effectively. Despite this, many of
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D A B
E
C
F
G
• Fig. 11.6 Essential obstetrical equipment for use in cattle and horses. (A) Obstetrical snares made of cotton rope, nylon, or webbing. The snares have loops in both ends. (B) Traction bars for use with (A). (C) Obstetrical chain and (D) handles for applying traction. (E) Krey’s hook (Krey-Schottler double jointed hooks). (F) Snare introducer for use with cord or chain snares. (G) Kühn’s obstetrical crutch.
them can be very helpful at times and, for completeness, some of the more useful ones in cattle, and to a very much lesser extent in horses, are shown in Fig. 11.6. The most essential instruments are:
Obstetrical Snares • Obstetrical snares are essential. Snares can be cord or chains. • Cord snares are ~1 m lengths, with loops, of cotton rope (clothes line), nylon cord, or webbing (see Fig. 11.6A) (a finer cord for snaring the mandible is essential) and traction bars (see Fig. 11.6B). If cord snares are used, it is advisable to have at least two sets; they can be sterilized between uses. • An alternative to snares that many veterinarians prefer to use is Moore’s obstetrical chains (see Fig. 11.6D) with handles (see Fig. 11.6C). Many veterinarians find these easier to use than rope snares. Their main advantage is that they are heavier and do not move so readily when they are repositioned during intrauterine or intravaginal manipulation. It is also easier to clean them after use than cord snares. • A snare introducer (see Fig. 11.6F) is also valuable for placing snares in tight spaces. It can be used with ropes as well as chains. A bull ring is an effective substitute Traction • A means of applying traction is also essential. Traction may be applied using a block and tackle or a calving aid such as an HK calf puller or Vink calving jack (Fig. 11.7). Additional Equipment • Obstetrical hooks and crutches. The main use of these is in fetotomy, and their use is described more fully in Chapter 14.
Of these, probably the most useful is the Krey double-jointed hooks (see Fig. 11.6D). Less widely used are Obermeyer’s anal hook, Harms’s sharp or blunt paired hooks on a fine chain, and Blanchard’s long, flexible cane hook. These are useful when performing fetotomy to enable traction to be applied to various fetal segments. Kühn’s obstetrical crutch (see Fig. 11.6G) can also be useful for repelling the fetus in a tight space. • Detorsion rods and bar are valuable aids to managing uterine torsion in the cow, and many veterinarians in cattle practice choose to have these as a part of their core kit. Equipment for manipulative delivery of small animal fetuses is described in Chapter 18.
Specialised Equipment Fetotomy is arguably the best alternative to the Caesarean surgery for delivering a dead, decaying, or emphysematous calf, so carrying a fetotomy kit is recommended. The kit includes a wire saw fetotome, cutting wire, handles and wire cutters, a fetotome threader, an introducer for positioning the cutting wire, and a set of Krey’s hooks. General Equipment A general kit should be readily at hand alongside the obstetrical equipment. This consists of the following: • Casting rope, halter, a ‘general purpose’ rope • Buckets for washing water, antiseptic detergent • A source of light (e.g., powerful torch and spare batteries) • Core drugs: antibiotic, oxytocin, clenbuterol, local anaesthetic, analgesic (i.e., NSAID), injectable calcium (for cattle), sedatives; plus needles and syringes that are appropriate for the drug and its route of administration
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A • Fig. 11.7
Calving aids: (A) Vink calving jack, (B) HK calf puller. (Photo courtesy J. Malmo.)
Dystocia
Is the dam viable?
no
Euthanise dam, recover fetus if it is viable
yes Is the fetus viable?
yes
May survival of fetus be compromised by vaginal delivery?
no Will health/survival of dam be compromised by vaginal delivery?
no no
yes
Deliver by Cesarean
Delivery by manipulation and/or traction
yes Delivery by Cesarean or fetotomy
• Fig. 11.8
Decision pathway for managing dystocia.
Consideration of Treatment General The ideal outcome for any obstetrical procedure is the delivery of live and viable young without compromising the health or future fertility of the dam. When both fetus and dam are alive at the start of the procedure, this is indeed the primary measure of success. Nonetheless, there are situations in which the fetus is not viable or is dead at the start of the procedure. There are also situations in which the fetus is not viable, but the way in which that fetus is delivered will have a significant effect upon whether or not the dam survives (and/or is healthy and fertile). Finally, there are occasions when neither the fetus nor the dam are viable, in which case euthanasia may be the most humane and most cost effective way of resolving the situation. Hence a cascade of decisions has to be made (Fig. 11.8). If neither dam nor fetus will survive, euthanasia is appropriate. If the dam may survive, but the fetus
will not, a decision regarding the most appropriate obstetrical method to extract the fetus while minimizing the risk to the dam has to be made. Rarely, the fetus may be viable but the dam not, in which case euthanasia of the dam/post mortem Caesarean may be a way of salvaging the fetus. Finally, if both dam and fetus are viable, different decisions have to be made about the best way of separating them. No less important than this decision process is an assessment of the duration of the dystocia and the attempts that have been made to deliver the fetus. For example, a carpal flexion is a very simple dystocia to correct if the case is presented soon after the onset of second stage labour. If the dystocia has been neglected for a significant period of time, the fetal fluids will have been lost, the uterus may be contracting down on the fetus, and the fetus may be severely impacted in the birth canal. In such circumstances, manipulative correction of even such a simple faulty posture may not be feasible. If the dystocia has been neglected for even longer, the
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fetus may have started to decompose and become emphysematous, so that vaginal delivery of the intact fetus is no longer possible. In cattle the duration and degree of traction to which the cow has been subjected is a major determinant of the outcome of subsequent Caesarean surgery. Similarly, in horses the duration of dystocia and the degree of trauma to the uterus significantly affect the outcome of subsequent interventions. However, with the advent of new and safer anaesthetic agents, Caesarean surgery should not be considered as ‘the last resort’ but as an effective method of treatment when used appropriately. Moreover, fetotomy should not be disregarded as a method of treating dystocia: in cattle, it probably remains the treatment of choice for grossly neglected cases in which the calf is decomposing and emphysematous or if the uterus is grossly contaminated. Taken together, therefore, there should be an early commitment in the management of an obstetrical case as to whether it should be managed by manipulation plus or minus traction, by fetotomy, or by Caesarean surgery. As a general rule, failure to make progress by manipulation and/or traction within a reasonable period of time means that the original decision about the management of the case should be review, and the decision to proceed to an alternative method (Caesarean, fetotomy) should be made before either the veterinarian or patient become exhausted. The adverse consequence of traction that is either excessive in force or duration (such as laceration and contusion of maternal soft tissues, perineal laceration, rectovaginal fistula, pelvic nerve damage, hindlimb paralysis, or sacroiliac dislocation) are so wellknown that there is no merit in persisting with traction beyond a point when it has ceased to result in progress towards the delivery of the fetus. Of course, veterinarians will sometimes be pressurized by owners into performing Caesarean surgery when it is not necessary, particularly in cows with muscular hypertrophic calves or brachycephalic/ achondroplastic bitches, purely because owners want to ensure the birth of live offspring. Likewise, owners will sometimes request the use of severe and prolonged traction rather than pay for the cost of Caesarean surgery. An ethical dilemma can then ensue as the veterinarian tries to balance the welfare of the patient with the expectations of its owner.
Horse The first consideration is whether attempts at correction should be made with the animal standing or recumbent, or restrained and sedated, or under caudal epidural or general anaesthesia. The decision will be influenced in part by the size and temperament of the mare, by the type of dystocia, by the personnel to assist with the delivery, and by the accessibility of faculties for general anaesthesia and surgery (Miller 2010). Not infrequently, the operator begins manipulative correction with the mare unsedated and standing but soon realizes that, for success, restraint and/or sedation will be required. It is important in such cases that this decision be made early so that neither obstetrician nor mare becomes exhausted as the result of prolonged, futile efforts. In all severe cases the operator should consider the advisability of seeking the assistance of a colleague, for it is always possible that the combined efforts of two will succeed where those of one alone fail. Relatively simple abnormalities, such as carpal flexion or lateral or downwards deviation of the head, can often be corrected using the hand alone, particularly when the mare is comparatively small
and straining has been eliminated. However, it must be remembered that the limbs of the thoroughbred newborn foal are very long (70% of their adult length), which requires a substantial amount of space to facilitate flexion and extension. When, however, one of the more difficult forms is present, such as transverse presentation, ventral position, or impaction of the fetus in the pelvis, or when there is laceration of the vagina or vulva, it is generally best to anaesthetize the animal at the outset, particularly in a hospital environment. One of the advantages of general anaesthesia is that by changing the position of the mare – for example, so that she is in dorsal or lateral recumbency or even suspended by her hindlimbs (the anaesthetists will not be very enthusiastic about this approach because of pressure on the diaphragm!) – the change in the pressures on the fetus within the uterus can be utilised to facilitate correction. Whenever fetotomy is required, both sedation and caudal epidural anaesthesia should be used. In veterinary hospitals, general anaesthesia is preferable because the foal is almost always already dead and will not be affected by transplacental transfer of anaesthetic agents. The value of partial fetotomy as a treatment of equine dystocia in which the fetus is dead or deformed has long been recognized. Vandeplassche (1980) considered partial fetotomy to be the method of choice for rapid, safe correction of dystocia that cannot be resolved by manipulation. However, Frazer (2001) noted that fetotomy should be avoided when the reproductive tract of the mare is already traumatized by failed attempts at manual correction. Carluccio et al. (2007) described that deliveries could commonly be made with just two cuts. The indications for partial fetotomy are shown in Table 11.1. Sequelae of fetotomy have remained surprisingly consistent over many years: the survival rate is between 85% and 90%, around 25% to 35% of mares have retained fetal membranes and/or postpartum endometritis, and fertility in the first season after fetotomy is around 30% to 40% (Vandeplassche 1980, Ras et al. 2014). With improved methods of general anaesthesia and aseptic surgery, Caesarean surgery has a definite place in equine obstetrics, particular indications being maternal dystocia due to bicornual gestation, uterine torsion, and narrow or deformed pelvis, as well as those cases of fetal dystocia in which there is oversize or faulty fetal disposition combined with maternal injury or when the uterus has contracted on to a dead, emphysematous foal. In the series of Caesarean cases reported by Abernathy-Young et al. (2012), 75% were due to dystocia, with most of the remainder due to concurrent maternal disease (i.e., colic) that compromised the fetus. Interestingly, 16% of the Caesarean were performed after a failure of partial fetotomy. Survival rates have not changed much over the years, however: Vandeplassche (1980) recorded 81% survival whereas the figure achieved by Abernathy-Young et al. (2012) was 84%. Hodder et al. (2012) noted that survival of emergency Caesareans was lower than that for elective surgery (75% vs 100%). Foal survival is poor for emergency Caesareans, as most foals were dead or severely compromised before the onset of surgery.
Cattle The most common cause of dystocia in cattle is fetomaternal disproportion, with faulty disposition of the fetus being the next most common in both beef and dairy cattle (Meijering 1984, Citek et al. 2011). In principle, these dystocias can be delivered by correction of the fetal disposition or delivery by traction. However, the most important factor in determining the course of action in
CHAPTER 11 Approach to an Obstetrical Case
211
TABLE Prevalence of different forms of dystocia in mares undergoing fetotomy 11.1
Cause of Dystocia
Vandeplassche
Carluccio
Total
72
31
103
6
1
7
(3.4%)
Anterior presentation: flexion, deformity, or ankylosis of forelegs
12
18
30
(14.7%)
Breech presentation with ankylosis
17
5
22
(10.8%)
8
8
(3.9%)
5
30
(14.7%)
’Dog-sitting’ position
1
1
(0.5%)
Others
3
3
(1.5%)
72
204
Anterior presentation: lateral or ventral deviation of the head Anterior presentation: hydrocephalus or two heads
Posterior presentation, hock flexion Transverse presentation
Total
25
132
(%) (50.5%)
Derived from Vandeplassche (1972, 1980) and Carluccio et al. (2007).
bovine dystocias is not (usually) the cause of the dystocia, but the interval that has elapsed between its onset and the presentation of the case for examination. In neglected or protracted cases, there is often severe impaction of parts of the fetus in the pelvis; the greater part of the fetal fluids has often been lost, and there is insufficient space to repel the fetus; the fetal skin and the vaginal mucosa have lost their natural lubrication, whereas the vagina and vulva are often swollen, and manipulation is rendered difficult. Correction of the dystocia, whether due to faulty disposition or fetomaternal disproportion, in such cases may prove very difficult and may necessitate an early decision to undertake fetotomy or Caesarean surgery in preference to attempting vaginal delivery. Fetomaternal disproportion is more common in heifers than in multigravida cows (Zaborski et al. 2009). Traction is the first method of delivery that should be attempted in most cases of fetomaternal disproportion. Before traction is applied, the vagina and those parts of the fetus occupying it must be thoroughly lubricated with copious application of several litres of a proprietary cellulose-based obstetrical lubricant. In cases in which the fetal disposition is normal and the disproportion is slight, it is a comparatively simple matter to apply snares to the fetal extremities (i.e., the limbs and head) and, adhering to the principles described in Chapter 14, the fetus is delivered by traction. As a rule, the animal remains standing during the application of snares but often goes down during the passage of the calf ’s head through the vulva. More severe disproportion requires more careful assessment and, as described previously, an early decision to use an alternative to traction when this is unlikely to be successful. Traction, however, must be employed with care because excessive traction can not only cause damage to the dam, but can also cause the fetus to become so tightly impacted in the birth canal that its subsequent delivery by Caesarean surgery or fetotomy can become difficult or impossible. Hence the amount of traction must be limited to that of three persons or a calving aid and the progress of the operation must be very closely scrutinized by the veterinarian. If no progress is made after 5 minutes or if the fetus becomes lodged and fails to yield to 5 minutes of further traction, then partial or total fetotomy or Caesarean surgery should be performed (Chapters 15 and 16).
Faulty fetal disposition is more common in parous cows than in primigravida. When faulty disposition is the cause of the dystocia, an assessment needs to be made of the measures that will be needed to correct it. Sometimes the space required for correction is lost due to the effects of continual straining or the contracted uterus. If so, one or all of caudal epidural anaesthesia, clenbuterol, and/or infusion of replacement fetal fluids should be given without delay. Occasionally, inducing epidural anaesthesia will allow an animal that has become recumbent to rise, which makes any manipulative procedures easier because the veterinarian can stand and the intraabdominal pressure is reduced. Management of dystocia due to fetal ‘monsters’ again requires an early assessment of the best means of delivering the calf. Many ‘fetal monsters’ cannot be delivered intact per vaginam and will require either fetotomy (usually) or Caesarean surgery (sometimes). It should, however, be noted that for fetal monsters for which Caesarean surgery is the method of choice (e.g., schistosoma reflexus in which the head and limbs are directed towards the pelvic inlet), fetotomy is contraindicated.
Sheep and Goat The ability of a veterinarian to resolve dystocia in the ewe or doe largely depends on the operator’s ability to pass a hand through the pelvis into the uterus. Primigravid animals of the smaller breeds sometimes foil attempts of even the smallest hand to traverse their birth canal, making delivery by Caesarean surgery the best option for success. Cases of fetomaternal disproportion are relatively uncommon, except in ewes carrying a singleton fetus. Most cases have normal fetal disposition, so once the head has been repelled from the pelvic inlet, gentle traction upon the limbs effects delivery. Use of a lambing snare (Fig. 11.9) to control the direction of the head is often helpful in cases of fetomaternal disproportion. When there is malposture of the limbs or head, repositioning after retropulsion is, as a rule, relatively easy. Retropulsion, replacement of lost fetal fluids, and correction of a faulty disposition are made much easier by, first, giving causal epidural anaesthesia and, second, elevating the hindquarters of the ewe. This can be done by rolling her on to her back and having an assistant pull both hind legs upwards and
212
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Obstetrics and Surgery of the Reproductive System
• Fig. 11.9
Lambing snare.
forwards. It is especially important to ensure that the presented parts all belong to the same fetus. The young, in cases of twins and triplets, are small and retropulsion and reposition are seldom difficult. Gentleness is critical in handling dystocias of the ewe and doe, as it extremely easy to damage the birth canal, pelvis or obturator nerve. Likewise, great care must be taken during intravaginal manipulations that the mucous membrane at the pelvic inlet is not lacerated. It is an accident that may occur quite simply, particularly when a finger is being used to lever a head or limb upwards. Such lacerations are usually followed by infection and possibly death. In most cases in which manipulation and delivery per vaginam is not possible, delivery by Caesarean surgery is usually the best option.
Pig In the sow, the ease with which obstructive dystocia can be relieved depends almost entirely on the operator’s ability to pass a hand through the pelvic inlet. Provided this is possible, it is usually a relatively easy matter to grip the head or hind parts and withdraw the fetus. In small gilts and in sows of breeds such as the Vietnamese pot-bellied breed, the use of a lambing snare (see Fig. 11.9) may be useful to apply traction to the head. The disposition of the limbs is seldom of much consequence. When assistance is given early in the dystocia (i.e., within an hour or two of the onset of second stage labour), removal of the obstructing fetus is often followed by the normal expulsion of the remainder. Assistance in the sow is frequently delayed, however; in these cases the obstetrician will be well advised to remove as many piglets from the uterine body and cornua as are within reach. The subsequent course will depend chiefly on the measure of delay and thus the degree of inertia which has supervened. It may be found in an hour or so that normal expulsion has recommenced or that on further examination more fetuses are accessible to manual extraction, and by continued attention to the sow in this manner the whole litter can be removed. It is worth remembering that intravaginal and intrauterine manipulations will stimulate the release of endogenous oxytocin and thus stimulate myometrial contractions. Quite often,
however, complete inertia has developed and no further progress follows the removal of the accessible fetuses. In these, Caesarean surgery is the only means of saving the sow. The strategic use of oxytocin to induce myometrial contractions can be used to treat overt cases of dystocia and also to hasten the expulsion of piglets if there is an extended time interval before the arrival of the next, thus preventing stillbirth. It is important to give low doses of oxytocin because it is a potent ecbolic, and large dose rates will cause spasm of the myometrium rather than rhythmical peristaltic-like contractions. In addition, the myometrium will become refractory to its effect, and it may be necessary to increase the dose rate in order to obtain a response. The dose of oxytocin is therefore critical to its successful use in farrowing. Mota-Rojas et al. (2006) noted that too high of a dose (or too rapid elevation of blood concentrations, particularly by IV administration) was associated with higher rates of fetal asphyxia/fetal distress, but that a low dose of oxytocin (0.083 IU/kg) gave a useful acceleration of parturition without causing fetal distress (Mota-Rojas et al. (2005) and improved survival of piglets experiencing dystocia (GonzálezLozano et al. 2009). Jackson (1996) observed that the greatest problem in porcine obstetrics was to know when a parturient sow had expelled all her piglets. Good, but not infallible, indications of the end of labour are that the sow rises, passes a large volume of urine, and then resumes recumbency in an attitude of contentment. When it is suspected that parturition is incomplete, the clinician should pass a hand as far as possible into the uterus and sweep it gently about the abdomen in the hope of balloting indirectly a piglet in an adjacent segment of the long uterine horn. Transabdominal ultrasonography can potentially be used to locate a retained fetus (see Chapter 17). The presence of retained fetal membranes is even more difficult to determine. When the clinical manifestations suggest that a fetus (or fetuses) is still retained and there has been no response to the administration of ecbolics, the only approach would be an exploratory laparotomy. Sows and gilts will often survive the presence of retained piglets, which sometimes become mummified (see Chapter 17). Because they are occasionally seen in the uteri of culled sows and gilts at the abattoir, it is likely that, although the mothers survived, they were infertile.
Dog and Cat The primary consideration in the management of a case of dystocia in the bitch or queen is whether one should attempt delivery per vaginam or immediately resort to Caesarean surgery. Factors that will influence the decision are: • The cause of dystocia, whether obstruction or primary inertia; • The duration of second stage labour and hence the condition of the fetuses and the uterine muscle; and • The number of fetuses retained and their viability. When the case is recent (i.e., a few hours only), attempting vaginal delivery may be appropriate. A modest degree of fetomaternal disproportion with the fetus in anterior or posterior presentation may be resolved by traction using the fingers only (see Figs 18.1 and 18.4), or finger and vectis, or forceps (these should be used with great care to prevent trauma to both dam and offspring); this traction will succeed in effecting delivery, and parturition will then proceed normally. Similarly, in cases of faulty fetal disposition, such as vertex posture or breech, traction may succeed after correction of the abnormal posture. Increasingly commonly, however, the decision is likely to proceed directly to Caesarean surgery. Certainly, in cases of gross fetomaternal disproportion (which is very common with litters of
one or two) or in cases in which the dystocia is of more than a few hours duration, Caesarean surgery is indicated. The obstetrical justification for this decision is that it is very likely that secondary inertia has supervened and removal of the obstructed fetus will not alter the ultimate outcome. This decision is often, however, subordinate to an economic justification: Caesarean surgery is used to minimize the risk of death of the dam and litter of pups or kittens – both of which may be valuable. The question sometimes arises of whether one should first attempt to remove the presented fetus per vaginam before performing surgery. It is highly likely that this fetus is contaminated, and withdrawing it through an abdominal wound may predispose to development of peritonitis. There is also, of course, the possibility that forceps interference will subject the bitch or queen to greater risk. Many veterinarians are of the view that the risk to the dam and the rest of the litter is minimized if the presented fetus is removed during the Caesarean surgery unless there is a very clear indication indeed for its removal per vaginam. The length of time for which the fetus will remain alive after the onset of second stage labour also has to be considered. It is very improbable that the presented fetus will live longer than 6 to 8 hours, for by that time its placenta will have completely separated. The remaining fetuses, however, may be alive for much longer periods. Thus it is possible that after 36 hours’ delay, the presented fetus may be dead with early signs of emphysema, yet those occupying the anterior parts of the cornua may be alive. After a delay of 48 hours, this is highly unlikely to occur. Hysterectomy may be chosen as an alternative to Caesarean surgery (see Chapter 19). Robbins and Mullen (1994) showed that newborn survival rates of 75% for dogs and 42% for cats are comparable to the outcomes of Caesarean surgery to treat dystocia.
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References Abernathy-Young KK, LeBlanc MM, Embertson RM, et al. J Am Vet Med Assoc 2012;241:927. Carluccio A, Contri A, Tosi U, et al. J Am Vet Med Assoc 2007;230: 1502. Citek J, Hradecka E, Rehout V, Hanusova L. Anim Sci Pap Rep. 2011; 29:109. Frazer GS. Fetotomy technique in the mare. Equine Vet Educ. 2001;13:151. Gonzalez-Lozano M, Mota-Rojas D, Velazquez-Armenta EY, et al. Can Vet J. 2009;50:1273. Hodder ADJ, Adkins AR, Adams PL, et al. Australian Equine Veterinarian. 2012;31(3):66. Jackson PGG. Handbook of Veterinary Obstetrics. London: WB Saunders; 1996. Meijering A. Livest Prod Sci. 1984;11:143. Miller CD. Clinical Theriogenology. 2010;2:338. Mota-Rojas D, Nava-Ocampo AA, Trujillo ME, et al. Reprod Toxicol. 2005;20:255. Mota-Rojas D, Trujillo ME, Martínez J, et al. Anim Reprod Sci. 2006;92:123. Ras A, Rapacz-Leonard A, Ras-Norynska M, Baranski W. Vet Rec. 2014;174:407. Robbins MA, Mullen HS. Vet Surg. 1994;23:48. Vandeplassche M. Equine Vet J. 1972;4:105. Vandeplassche M. Equine Vet J. 1980;12:45. Zaborski D, Grzesiak W, Szatkowska I, et al. Reprod Domest Anim. 2009;44:540.
Approach to an Obstetrical Case TIMOTHY J. PARKINSON, JOS J. VERMUNT AND DAVID E. NOAKES
E
ach case of dystocia is a clinical problem that may be solved if a correct procedure is followed. The successful management of the case requires obtaining a history from the owner or attendant, a focused clinical examination, and specific examination of the reproductive tract. There should be careful differentiation between a labour that is not fully established from one that has become interrupted, and a careful diagnosis should be made of any faulty fetal disposition before attempting any correction. There should also be a differentiation between whether the labour has been interrupted due to a problem with the birth process per se, and whether other disease processes are interfering with it.
Causes and Classification of Dystocia A normal birth occurs when the expulsive forces are sufficient to propel a fetus of normal size and disposition through a birth canal of adequate size. Dystocia occurs when any of these are abnormal or insufficient. Thus the causes of dystocia can be considered in terms of the: • Expulsive forces • Adequacy of the birth canal • Size and disposition of the fetus Difficult birth will occur when the expulsive forces are insufficient, when the birth canal is of inadequate size and shape, or when the presenting diameter of the fetus is unable to pass through the normal birth canal because it is too large or its disposition prevents it from doing so. An overview of the types and causes of dystocia are given in Fig. 11.1. Defects of the expulsive forces and of the adequacy of the birth canal are commonly referred to as maternal dystocia, whereas those due to defects of the presentation of the fetus or to its disproportion (i.e., with respect to the size of its dam) are known as fetal dystocia. However, there will be times when it can be difficult to identify the primary cause and others when there will be a change in the dominant cause during the course of the dystocia.
Defects of Expulsive Forces Defects of expulsive forces generally refer to intrinsic defects of uterine contractility, nervous voluntary inhibition of labour, or failure of contraction due to mineral/hormonal imbalances (primary inertia), or to exhaustion of either the uterine muscle itself or depletion of pituitary oxytocin stores (secondary inertia). Failure of contraction of abdominal muscles during second stage labour can also occur.
Defects of the Adequacy of the Birth Canal The birth canal consists of the internal tubular organs of the reproductive tract from the uterine horns and body to the vulva. Abnormalities of any part of these structures can lead to dystocia. Such abnormalities include function disturbances of the genitalia (e.g., incomplete cervical dilation; torsion of the uterus), obstructions (e.g., neoplasia), or mechanical abnormalities (e.g., double cervix; remnants of the paramesonephric ducts). Rarely, the uterus can be displaced into a subpubic position or through a hernia in the abdominal wall. Abnormalities of the surrounding tissues can, likewise, lead to dystocia. Such tissues include the pelvis (e.g., heritable pelvic malconformation such as occurs in Belgian Blue cattle and brachycephalic dog breeds; fractures of the pelvic bones; sacroiliac dislocation), the bladder (e.g., prolapse into the vagina), or excess intrapelvic fat,
Faulty Fetal Disposition During pregnancy, particularly in monotocous species such as cattle, horses, sheep, and goats, the fetus assumes a disposition within the uterus which is such that the space occupied is as little as possible: for example, the vertebral column and limbs will be flexed to varying degrees. In order to negotiate the birth canal unaided, these joints need to be extended. The term ‘faulty’ or ‘abnormal fetal disposition’ is used to describe the situation in which the fetus has failed to assume the disposition that enables it to be expelled unaided per vaginam. The universally accepted terminology to describe these abnormalities is that first defined by Benesch. This involves the use of the terms presentation, position, and posture, each of which has a specific meaning in relation to veterinary obstetrics (Fig. 11.2). Presentation signifies the relationship between the longitudinal axis of the fetus and the maternal birth canal. These may be: • Longitudinal presentation, which can be anterior or posterior, depending on which fetal extremity is entering the pelvis; • Transverse presentation; ventral or dorsal, according to whether the dorsal or ventral aspect of the trunk is presented; and • Vertical presentation; ventral or dorsal. Vertical presentations are very rare, and only the obliquely vertical ‘dog-sitting’ presentation in the horse needs to be considered in detail. Position indicates the surface of the maternal birth canal to which the fetal vertebral column is applied. It can be dorsal, ventral, and left or right lateral. 203
204 Pa rt 3
Obstetrics and Surgery of the Reproductive System
Dystocia Maternal Inadequate expulsive forces Uterine inertia Primary
Secondary
• Overstretching
Myometrial ‘exhaustion’
• Incorrect oestrogen progesterone ratio • Inadequate secretion of oxytocin and prostaglandin secretion
Weak abdominal straining • Age • Debility • Pain • Herniation of uterus
• Failure of receptor regulation/development • Ca2+ and/or Mg2+ deficiency • Fatty infiltration of myometrium • Nervous voluntary inhibition • Hysteria
Fetal
Inadequate size of birth canal Incomplete dilation Inadequate pelvis or constriction of birth canal • Immature • Uterus > Torsion > Displacement • Cervix > ‘Ringwomb’ > Duplication • Vagina > Stricture > Neoplasms > Cystocoele > Prolapse > Vestigial structures
• Fracture
Fault disposition
Oversize
Relative and Congenital Fetal absolute monsters pathology • Small litter
• Ascites
• Breed
• Anasarca
• Breed deformity • Prolonged gestation
• Presentation • Position • Posture
• Emphysema
• IVM/IVF derived embryos
Feto-maternal (pelvic) disproportion
• Vulva > Stricture > Incomplete relaxation
Obstructive dystocia
• Fig. 11.1
The causes of dystocia.
Posture refers to the disposition of the movable appendages of the fetus and involves flexion or extension of the neck or limb joints, for example, lateral flexion of the neck or hock flexion posture. Disproportion: Fetomaternal disproportion occurs when the fetus is larger than the capacity of the pelvis through which it has to pass. Disproportion may occur if the fetus is larger than normal, either in terms of its absolute size or of the size of particular parts of its body (notably shoulders and/or pelvis), or if the pelvic canal of the dam is too small or is of incorrect shape.
History and General Examination History Before examining the animal, an effort should be made to obtain a pertinent history of the case from the owner/attendant. Key points to be elicited from the history are summarized in Fig. 11.3. Perhaps the most important aspects of the history are (i) the duration of labour and (ii) attempts that have already been made to assist the birth. The parity of the animal is the third key aspect because the incidence of different types of dystocia varies markedly with parity. For livestock, it is generally obvious whether the animal is primigravida or multigravida, but this can be rather less obvious in other species. The duration of labour is important inasmuch as it is one of the key determinants of outcome for mother and fetus and often constrains the options available to the obstetrician for managing the case. Calculating the time the start of labour is often difficult because the signs of the onset of first stage labour are sufficiently vague and indistinct to easily escape the attention of an attendant. The onset of second stage labour, which is typified by vigorous and frequent straining, appearance of the amnion, expulsion of fetal fluids, appearance of a fetal extremity, and/or recumbency of the animal, are easier to recognize; this will typically be identified by an attendant as the ‘start of labour’. Even so, in intensively managed livestock, it is by no means uncommon for the onset of
even second stage labour to pass unnoticed and for the animal to be presented once a dystocia is obviously present, but with little indication of its duration. As a generalization, it is reasonably certain that some form of obstructive dystocia exists if several hours have elapsed since the onset of second stage labour. The fetus can survive a moderate period of dystocia in most species, but this depends on the extent to which the fetus has traversed the birth canal before the labour is arrested. Thus, if the cause of the dystocia is relatively simple, such as slight fetomaternal disproportion or a minor limb malposture, and the case has not been neglected, fetal and maternal survival are often good. On the other hand, fetal survival of dystocia in the mare is short, as the normal course of delivery is so rapid and separation of the placenta occurs so quickly once second stage has commenced that any delay generally results in the death of the foal. If the dystocia has not been noticed until 24 or more hours after the start of second stage labour has started, the fetus is likely to have died and will often have started to become putrefied and decompose. Managing these cases is difficult because straining efforts have commonly ceased, fetal fluids have been entirely lost, and the uterus has started to contract down onto the retained fetus. In polytocous species, fetuses may survive for some time behind a point of obstruction, but eventually they will also die and/or start to decompose. It is valuable to discover whether an attempt has already been made to assist the delivery. This may not only provide useful information about the type of dystocia that is (or is not) present, but may also provide evidence of whether injury has been caused either to the genital tract or to the musculoskeletal system of the animal. All of this information helps the obstetrician to provide a prognosis for mother and fetus for the outcome of the birth. It is particularly important to determine whether any drugs (commonly calcium, antibiotics, or oxytocin) have been given before assistance is requested, as this may affect the subsequent management of the case and will undoubtedly affect meat or milk withholding times for livestock.
CHAPTER 11 Approach to an Obstetrical Case
Presentation Longitudinal Anterior
Posterior
Transverse
Ventrotransverse
Dorsotransverse
Bicornual
Oblique (vertical) Ventro-vertical (“dog sitting”)
Dorsovertical
Ventral position (posterior presentation)
Posture Forelimb Flexion Shoulder
Carpus
Hindlimb flexion
Hip
Hock
Bilateral hip flexion “breech presentation”
Neck flexion
Lateral
• Fig. 11.2
Ventral
The vulva should next be inspected. Parts of a fetus may be protruding, and it may be possible to assess the nature of the dystocia from these. Are exposed fetal parts moist or dry, or swollen emphysematous or oedematous? Such evidence serves not only as a guide to the duration of the condition but also to the effort that will be necessary to correct it. If parts of the amnion protrude, what is their condition? Are they moist and glistening with fluid caught up in their folds? If so, their exposure is recent, and the case is an early one. If, however, the membranes are dry and dark in colour, it may be taken that the case is protracted. Attention should also be paid to the nature of the discharge from the vulva, especially if neither fetus nor membranes are presented. Fresh blood, especially if profuse, generally indicates recent injury to the birth canal. A dark brown, fetid discharge indicates a grossly delayed case. When dealing with the bitch and cat, the degree of abdominal distension should be observed, for it may be possible to make an estimate of the number of fetuses that occupy the uterus. The onset of vomiting, together with a great increase in thirst, should be regarded as grave signs in the bitch.
Detailed Examination of the Animal
Position
Ventral position (anterior presentation)
205
Abnormalities of fetal presentation, position, and posture.
General Examination The animal’s physical and general condition should be noted. If recumbent, is she merely resting, is she exhausted, or is she suffering from a metabolic disease? Body temperature and pulse rate should be noted and the significance of abnormalities considered. Cattle should be routinely assessed for the presence of hypocalcaemia, and the possibility of toxic mastitis should not be overlooked.
Large Animal Species The animal should be effectively restrained in a clean environment, for the safety of the veterinarian, any assistants, and the animal concerned. In the case of the mare (Fig. 11.4), cow, ewe, and doe goat, it is usually easier if they remain standing; the sow is best examined in lateral recumbency. One should never forget that large animals can collapse suddenly during examination, so it is important to ensure that (i) the animal can be easily extracted from the restraint if it does collapse and (ii) the obstetrician’s hand/ arm does not become trapped inside the animal when it collapses. It may be necessary to sedate the animal before examining her – ideally, at a sufficiently early stage in the proceedings that she does not become fractious, but to a level that does not result in unplanned collapsing/recumbency. A decision whether to use epidural anaesthesia should likewise be made as early as possible. If the fetus is dead and/or the uterus is grossly contaminated, the epidural should be given before a vaginal examination is performed in order to minimize the risk of infecting the neural canal. It is impossible to perform obstetrical procedures aseptically in any animal species, but the amount of contamination of the genital tract should be kept as low as possible. To this end, plentiful supplies of clean hot water with soap or surgical scrub should be available, as well as a table or bench covered with a sterile cloth on which instruments may be placed. Making sure that any bedding is clean (e.g., clean straw placed behind the animal) is also helpful. Because the floor is often wet and slippery, application of sand or grit is a worthwhile precaution. The external genitalia and surrounding parts are thoroughly washed, and the tail is held or tied to one side. The obstetrician’s hand and arms should be cleaned in water from a different bucket. The first vaginal examination usually provokes reflex defecation: more washing of animal and obstetrician is required. Some obstetricians prefer to wear a disposable plastic sleeve during examination of the animal: certainly this reduces the need for repeated rewashing of the obstetrician’s arms, but some find it more difficult to differentiate tissues within the uterus when wearing a sleeve. When gross contamination of the uterus is present (e.g., in cases of bacterial abortions or when a putrefying fetus is present), it is very strongly advised that a sleeve should be worn. In the mare a
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General history
History of the dystocia
Primiparous or multiparous?
Has an examination already been made? Has any assistance been given? Have any drugs been given?
Full term or premature?
Has a ‘water-bag’ appeared at the vulva? When?
When did straining begin? Slight? Intermittent? Frequent? Forceful?
Previous breeding history
Any loss of fluid? What fluid?
Has straining stopped again? When?
Management during pregnancy
Has any part of the fetus appeared at the vulva?
Have any fetuses already been delivered? Alive/dead? (polytocous species)
Still eating? Drinking? Signs of illness?
• Fig. 11.3
Key points in the obstetrical history of a case.
• Fig. 11.4 Mare with dystocia, restrained in stocks for vaginal examination and correction of dystocia.
• Fig. 11.5
clean tail bandage is applied because the tail hairs are frequently introduced into the vulva and vagina which can cause quite severe lacerations. Without the previous induction of epidural anaesthesia and the resultant paralysis of the rectum, it is almost impossible to make a vaginal examination in the cow without introducing some faecal contamination. There is little serious consequence of mild contamination, fortunately; but the greater the contamination that occurs, the greater the risk of postpartum uterine infection. The next stage is to perform a vaginal examination in order to establish the patency of the birth canal, the orientation of the fetus, and the position of its movable parts (i.e., head, limbs, tail). Copious lubrication should be introduced to the birth canal at the start of the vaginal examination. In the majority of cases, some part of the fetus occupies the vagina – the head, a limb, or limbs. Some difficulty can initially be experienced in recognizing the fetal parts being palpated if they are covered by amnion. To overcome this, the torn edges of the amniotic sac should be identified and opened, and the hand inserted so that the fingers come into direct contact with the fetus. It is often necessary to repel the fetus back into the uterus to ascertain the nature and direction of displaced parts. If continued straining makes this difficult, the induction of epidural anaesthesia should be considered at once, but it should be remembered that the dam’s expulsive effort may be required after any corrective procedure has been performed.
Recognition of the head is not difficult; the mouth and tongue, the orbits, and the ears are generally obvious. In the case of limbs, the first requirement is to ascertain whether it is a forelimb or hindlimb. There are two main ways of assessing this: the orientation of the feet and the flexion of the joints of the limb. If the plantar aspect of the digit is downwards, it is most likely to be a forelimb; if the plantar aspect is upwards, it is most likely to be a hindlimb. This ‘rule of thumb’ nearly always holds true for the cow/ewe/doe, but in the mare, it is not uncommon for the fetus to be in the ventral position, so more caution is needed. The direction of flexion of the limb joints differs between forelimb and hindlimb: if the fetlock and the joint immediately above it flex in the same direction, it is a forelimb. Conversely, if the fetlock and joint above it flex in the opposite direction, it is a hindlimb (Fig. 11.5). If more than one limb is present, it must be established that they are either fore or hind and if they are from the same fetus. If nothing is present in the vagina, the cervix should next be examined. First, it should be determined whether the cervix is completely dilated. If the cervix is largely, but not fully, dilated, a ‘lip’ of tissue will be evident, usually at the caudal end of the cervix. If less dilated, the cervical structure will be obvious, and there may even still be mucous within it. In the latter case the
Determining whether presented limbs are fore- or hindlimbs. The olecranon and hock are easy to confuse during vaginal examination: however, in the forelimb, the first two movable joints (fetlock and carpus) flex in the same direction, whereas in the hindlimb, the first two movable joints (fetlock and hock) flex in the opposite directions.
first thing to consider is whether the first stage of labour is not yet complete; i.e., the second stage of labour has not yet begun, and the animal requires more time. On the other hand, failure of cervical dilation can be a sign of dystocia. For example, the cervix usually fails to fully dilate in cases of uterine torsion, and failure of the fetus to impact the internal os of the cervix (i.e., through some form of faulty disposition) can also lead to partial failure of cervical dilation. Finally, it should be ascertained whether the cervix is incompletely dilated as the dystocia has been neglected, and the cervix has started to close again. This will usually be accompanied by complete loss of fetal fluids and often by obvious signs that the fetus has died and is starting to decompose. When the fetus has not fully entered the birth canal, deeper palpation is needed to determine what parts are presented. For example, palpating the fetal tail and perineum means that there is a high likelihood that the fetus is in ‘breech’ presentation. Likewise, if a flexed neck is palpated and a search on one or other side reveals ears and occiput, the case is one of lateral deviation of the head. Similarly, presentation of the head but not of forelimbs can indicate flexion of the carpi or of the shoulders. In the mare (and sometimes in ruminants), it may indicate that the fetus is in a dorsotransverse presentation, or perhaps occupying both horns (bicornual gestation). Finally, the presentation of a plethora of limbs may indicate simultaneous presentation of twins, fetal abnormalities such as schistosoma reflexa or limb duplication, or a ventrotransverse or vertical presentation. It may be worthwhile trying to assess the viability of the fetus, inasmuch as this can influence the options for management of the case. For cattle, however, it should be noted that, with increasing herd sizes and the associated improvements of the skills and knowledge of farm staff, it is increasingly unusual for the calf to be alive at the time when obstetrical assistance is requested. Viability can be assessed by attempting to elicit reflexes such as corneal/ palpebral, suck, anal (if in posterior presentation), and limb withdrawal. Palpation for the presence of a pulse in the umbilicus may be feasible when the fetus is in posterior longitudinal presentation. In the neglected or protracted case, assessment of the exact nature of the dystocia and methods of correction may be more difficult. The vaginal wall becomes progressively more oedematous, so that even the insertion of a hand and arm becomes difficult, and there is no room in which to carry out manipulations. Loss of fluid results in the dam’s mucous membranes and fetal parts becoming dry. Contraction of the uterus directly on the irregular contour of the fetus makes retropulsion difficult or even impossible. In general, these cases have to be managed by relaxing the uterine muscle with a spasmolytic, such as clenbuterol, and/or by infusing replacement fluids into the uterus, and always by the use of large quantities of obstetrical lubricant. In such cases, it may be necessary to estimate the time interval since the fetus died. Fetal emphysema and detachment of hair means that the fetus has been dead for at least 24 to 48 hours. If there is no emphysema and the cornea is cloudy and grey, then it will have been dead for 6 to 12 hours.
Dog and Cat The bitch, unless an exceptionally large one, should be placed standing on a table. It is preferable that a person with whom the animal is familiar should hold its head and be warned that even some quiet stoical bitches may resent a vaginal examination. Fetal numbers may be assessed in some bitches by gentle abdominal palpation or, more commonly, by the use of transabdominal ultrasonography. Ultrasonography has the added advantage of being
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able to determine whether the pups are alive by identifying the beating fetal heart. At a later stage in the examination, it might also be necessary to take radiographs. As a general rule, the operator will proceed to make a digital examination per vaginam, especially in early cases in which it is likely that obstruction is the cause of the delay and also in protracted ones in which it is estimated that a single fetus only remains unborn. Nevertheless, cases will be met in which it is obvious that inertia has supervened, and there are several fetuses to be delivered, in which case immediate Caesarean surgery or hysterectomy is indicated. Whether or not the hair is clipped from the area around the vulva before making a vaginal examination will depend on the length of the coat. In long-coated animals, it is a great convenience to do so; although it is impossible to render the area sterile, it should be thoroughly cleansed beforehand. Sometimes on raising the tail it is seen that part of a fetus, a head or hind parts, is protruding from the vulva. Such a finding is more common in the cat than the bitch. The case is a simple one; traction on the exposed parts effects delivery without difficulty and, provided this assistance has been forthcoming early, it is probable that parturition will proceed normally. Occasionally, it is found that the vagina is occupied by a fetal head or buttocks which have become impacted. In the majority, however, the pelvic canal is unoccupied and obstruction occurs at the inlet. The fetal disposition should then be determined. If the head is present, but the occiput and ears are palpated rather than the mouth, it is likely to be a case of vertex presentation. If a single limb is felt, but there is no sign of the head, the case is probably one of lateral deviation of the head. If the presentation is posterior, the tail may be recognized (although sometimes it is directed forwards over the fetal back). The hindlimbs may have entered the pelvis or they may be retained (flexed). The fetus may have rotated into ventral or lateral position. Determination of fetal viability by attempting to elicit reflexes is unreliable.
Obstetrical Equipment Manipulative Deliveries per vaginam in Large Animals The most important obstetrical instruments are the clean and gentle hands and arms of the obstetrician. There is, however, an array of equipment that can be used to assist in obstetrical procedures; arguably, the obstetrician should aim to possess a minimum of essential equipment and to be thoroughly conversant with the use of each item. For the veterinarian doing ambulatory visits to farms, studs, and other livestock units where parturient animals are kept, it is advisable to have a dedicated collection of core obstetrical instruments and other equipment that is always available in an emergency; in addition, a dedicated Caesarean surgery kit is also important (see Chapter 16 and, when working with cattle, a fetotomy kit (Chapter 15) should be carried. Simple instruments that are easy to handle and convenient to sterilize are best. More complex equipment is occasionally required, and the important consideration is to know when the use of such complicated instruments is indicated. With the availability of better sedatives and anaesthetic agents and improved methods for fetotomy and Caesarean surgery, many of the long-established items of obstetrical instrumentation have become obsolete, and veterinarians have lost the skills to use them effectively. Despite this, many of
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D A B
E
C
F
G
• Fig. 11.6 Essential obstetrical equipment for use in cattle and horses. (A) Obstetrical snares made of cotton rope, nylon, or webbing. The snares have loops in both ends. (B) Traction bars for use with (A). (C) Obstetrical chain and (D) handles for applying traction. (E) Krey’s hook (Krey-Schottler double jointed hooks). (F) Snare introducer for use with cord or chain snares. (G) Kühn’s obstetrical crutch.
them can be very helpful at times and, for completeness, some of the more useful ones in cattle, and to a very much lesser extent in horses, are shown in Fig. 11.6. The most essential instruments are:
Obstetrical Snares • Obstetrical snares are essential. Snares can be cord or chains. • Cord snares are ~1 m lengths, with loops, of cotton rope (clothes line), nylon cord, or webbing (see Fig. 11.6A) (a finer cord for snaring the mandible is essential) and traction bars (see Fig. 11.6B). If cord snares are used, it is advisable to have at least two sets; they can be sterilized between uses. • An alternative to snares that many veterinarians prefer to use is Moore’s obstetrical chains (see Fig. 11.6D) with handles (see Fig. 11.6C). Many veterinarians find these easier to use than rope snares. Their main advantage is that they are heavier and do not move so readily when they are repositioned during intrauterine or intravaginal manipulation. It is also easier to clean them after use than cord snares. • A snare introducer (see Fig. 11.6F) is also valuable for placing snares in tight spaces. It can be used with ropes as well as chains. A bull ring is an effective substitute Traction • A means of applying traction is also essential. Traction may be applied using a block and tackle or a calving aid such as an HK calf puller or Vink calving jack (Fig. 11.7). Additional Equipment • Obstetrical hooks and crutches. The main use of these is in fetotomy, and their use is described more fully in Chapter 14.
Of these, probably the most useful is the Krey double-jointed hooks (see Fig. 11.6D). Less widely used are Obermeyer’s anal hook, Harms’s sharp or blunt paired hooks on a fine chain, and Blanchard’s long, flexible cane hook. These are useful when performing fetotomy to enable traction to be applied to various fetal segments. Kühn’s obstetrical crutch (see Fig. 11.6G) can also be useful for repelling the fetus in a tight space. • Detorsion rods and bar are valuable aids to managing uterine torsion in the cow, and many veterinarians in cattle practice choose to have these as a part of their core kit. Equipment for manipulative delivery of small animal fetuses is described in Chapter 18.
Specialised Equipment Fetotomy is arguably the best alternative to the Caesarean surgery for delivering a dead, decaying, or emphysematous calf, so carrying a fetotomy kit is recommended. The kit includes a wire saw fetotome, cutting wire, handles and wire cutters, a fetotome threader, an introducer for positioning the cutting wire, and a set of Krey’s hooks. General Equipment A general kit should be readily at hand alongside the obstetrical equipment. This consists of the following: • Casting rope, halter, a ‘general purpose’ rope • Buckets for washing water, antiseptic detergent • A source of light (e.g., powerful torch and spare batteries) • Core drugs: antibiotic, oxytocin, clenbuterol, local anaesthetic, analgesic (i.e., NSAID), injectable calcium (for cattle), sedatives; plus needles and syringes that are appropriate for the drug and its route of administration
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A • Fig. 11.7
Calving aids: (A) Vink calving jack, (B) HK calf puller. (Photo courtesy J. Malmo.)
Dystocia
Is the dam viable?
no
Euthanise dam, recover fetus if it is viable
yes Is the fetus viable?
yes
May survival of fetus be compromised by vaginal delivery?
no Will health/survival of dam be compromised by vaginal delivery?
no no
yes
Deliver by Cesarean
Delivery by manipulation and/or traction
yes Delivery by Cesarean or fetotomy
• Fig. 11.8
Decision pathway for managing dystocia.
Consideration of Treatment General The ideal outcome for any obstetrical procedure is the delivery of live and viable young without compromising the health or future fertility of the dam. When both fetus and dam are alive at the start of the procedure, this is indeed the primary measure of success. Nonetheless, there are situations in which the fetus is not viable or is dead at the start of the procedure. There are also situations in which the fetus is not viable, but the way in which that fetus is delivered will have a significant effect upon whether or not the dam survives (and/or is healthy and fertile). Finally, there are occasions when neither the fetus nor the dam are viable, in which case euthanasia may be the most humane and most cost effective way of resolving the situation. Hence a cascade of decisions has to be made (Fig. 11.8). If neither dam nor fetus will survive, euthanasia is appropriate. If the dam may survive, but the fetus
will not, a decision regarding the most appropriate obstetrical method to extract the fetus while minimizing the risk to the dam has to be made. Rarely, the fetus may be viable but the dam not, in which case euthanasia of the dam/post mortem Caesarean may be a way of salvaging the fetus. Finally, if both dam and fetus are viable, different decisions have to be made about the best way of separating them. No less important than this decision process is an assessment of the duration of the dystocia and the attempts that have been made to deliver the fetus. For example, a carpal flexion is a very simple dystocia to correct if the case is presented soon after the onset of second stage labour. If the dystocia has been neglected for a significant period of time, the fetal fluids will have been lost, the uterus may be contracting down on the fetus, and the fetus may be severely impacted in the birth canal. In such circumstances, manipulative correction of even such a simple faulty posture may not be feasible. If the dystocia has been neglected for even longer, the
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fetus may have started to decompose and become emphysematous, so that vaginal delivery of the intact fetus is no longer possible. In cattle the duration and degree of traction to which the cow has been subjected is a major determinant of the outcome of subsequent Caesarean surgery. Similarly, in horses the duration of dystocia and the degree of trauma to the uterus significantly affect the outcome of subsequent interventions. However, with the advent of new and safer anaesthetic agents, Caesarean surgery should not be considered as ‘the last resort’ but as an effective method of treatment when used appropriately. Moreover, fetotomy should not be disregarded as a method of treating dystocia: in cattle, it probably remains the treatment of choice for grossly neglected cases in which the calf is decomposing and emphysematous or if the uterus is grossly contaminated. Taken together, therefore, there should be an early commitment in the management of an obstetrical case as to whether it should be managed by manipulation plus or minus traction, by fetotomy, or by Caesarean surgery. As a general rule, failure to make progress by manipulation and/or traction within a reasonable period of time means that the original decision about the management of the case should be review, and the decision to proceed to an alternative method (Caesarean, fetotomy) should be made before either the veterinarian or patient become exhausted. The adverse consequence of traction that is either excessive in force or duration (such as laceration and contusion of maternal soft tissues, perineal laceration, rectovaginal fistula, pelvic nerve damage, hindlimb paralysis, or sacroiliac dislocation) are so wellknown that there is no merit in persisting with traction beyond a point when it has ceased to result in progress towards the delivery of the fetus. Of course, veterinarians will sometimes be pressurized by owners into performing Caesarean surgery when it is not necessary, particularly in cows with muscular hypertrophic calves or brachycephalic/ achondroplastic bitches, purely because owners want to ensure the birth of live offspring. Likewise, owners will sometimes request the use of severe and prolonged traction rather than pay for the cost of Caesarean surgery. An ethical dilemma can then ensue as the veterinarian tries to balance the welfare of the patient with the expectations of its owner.
Horse The first consideration is whether attempts at correction should be made with the animal standing or recumbent, or restrained and sedated, or under caudal epidural or general anaesthesia. The decision will be influenced in part by the size and temperament of the mare, by the type of dystocia, by the personnel to assist with the delivery, and by the accessibility of faculties for general anaesthesia and surgery (Miller 2010). Not infrequently, the operator begins manipulative correction with the mare unsedated and standing but soon realizes that, for success, restraint and/or sedation will be required. It is important in such cases that this decision be made early so that neither obstetrician nor mare becomes exhausted as the result of prolonged, futile efforts. In all severe cases the operator should consider the advisability of seeking the assistance of a colleague, for it is always possible that the combined efforts of two will succeed where those of one alone fail. Relatively simple abnormalities, such as carpal flexion or lateral or downwards deviation of the head, can often be corrected using the hand alone, particularly when the mare is comparatively small
and straining has been eliminated. However, it must be remembered that the limbs of the thoroughbred newborn foal are very long (70% of their adult length), which requires a substantial amount of space to facilitate flexion and extension. When, however, one of the more difficult forms is present, such as transverse presentation, ventral position, or impaction of the fetus in the pelvis, or when there is laceration of the vagina or vulva, it is generally best to anaesthetize the animal at the outset, particularly in a hospital environment. One of the advantages of general anaesthesia is that by changing the position of the mare – for example, so that she is in dorsal or lateral recumbency or even suspended by her hindlimbs (the anaesthetists will not be very enthusiastic about this approach because of pressure on the diaphragm!) – the change in the pressures on the fetus within the uterus can be utilised to facilitate correction. Whenever fetotomy is required, both sedation and caudal epidural anaesthesia should be used. In veterinary hospitals, general anaesthesia is preferable because the foal is almost always already dead and will not be affected by transplacental transfer of anaesthetic agents. The value of partial fetotomy as a treatment of equine dystocia in which the fetus is dead or deformed has long been recognized. Vandeplassche (1980) considered partial fetotomy to be the method of choice for rapid, safe correction of dystocia that cannot be resolved by manipulation. However, Frazer (2001) noted that fetotomy should be avoided when the reproductive tract of the mare is already traumatized by failed attempts at manual correction. Carluccio et al. (2007) described that deliveries could commonly be made with just two cuts. The indications for partial fetotomy are shown in Table 11.1. Sequelae of fetotomy have remained surprisingly consistent over many years: the survival rate is between 85% and 90%, around 25% to 35% of mares have retained fetal membranes and/or postpartum endometritis, and fertility in the first season after fetotomy is around 30% to 40% (Vandeplassche 1980, Ras et al. 2014). With improved methods of general anaesthesia and aseptic surgery, Caesarean surgery has a definite place in equine obstetrics, particular indications being maternal dystocia due to bicornual gestation, uterine torsion, and narrow or deformed pelvis, as well as those cases of fetal dystocia in which there is oversize or faulty fetal disposition combined with maternal injury or when the uterus has contracted on to a dead, emphysematous foal. In the series of Caesarean cases reported by Abernathy-Young et al. (2012), 75% were due to dystocia, with most of the remainder due to concurrent maternal disease (i.e., colic) that compromised the fetus. Interestingly, 16% of the Caesarean were performed after a failure of partial fetotomy. Survival rates have not changed much over the years, however: Vandeplassche (1980) recorded 81% survival whereas the figure achieved by Abernathy-Young et al. (2012) was 84%. Hodder et al. (2012) noted that survival of emergency Caesareans was lower than that for elective surgery (75% vs 100%). Foal survival is poor for emergency Caesareans, as most foals were dead or severely compromised before the onset of surgery.
Cattle The most common cause of dystocia in cattle is fetomaternal disproportion, with faulty disposition of the fetus being the next most common in both beef and dairy cattle (Meijering 1984, Citek et al. 2011). In principle, these dystocias can be delivered by correction of the fetal disposition or delivery by traction. However, the most important factor in determining the course of action in
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TABLE Prevalence of different forms of dystocia in mares undergoing fetotomy 11.1
Cause of Dystocia
Vandeplassche
Carluccio
Total
72
31
103
6
1
7
(3.4%)
Anterior presentation: flexion, deformity, or ankylosis of forelegs
12
18
30
(14.7%)
Breech presentation with ankylosis
17
5
22
(10.8%)
8
8
(3.9%)
5
30
(14.7%)
’Dog-sitting’ position
1
1
(0.5%)
Others
3
3
(1.5%)
72
204
Anterior presentation: lateral or ventral deviation of the head Anterior presentation: hydrocephalus or two heads
Posterior presentation, hock flexion Transverse presentation
Total
25
132
(%) (50.5%)
Derived from Vandeplassche (1972, 1980) and Carluccio et al. (2007).
bovine dystocias is not (usually) the cause of the dystocia, but the interval that has elapsed between its onset and the presentation of the case for examination. In neglected or protracted cases, there is often severe impaction of parts of the fetus in the pelvis; the greater part of the fetal fluids has often been lost, and there is insufficient space to repel the fetus; the fetal skin and the vaginal mucosa have lost their natural lubrication, whereas the vagina and vulva are often swollen, and manipulation is rendered difficult. Correction of the dystocia, whether due to faulty disposition or fetomaternal disproportion, in such cases may prove very difficult and may necessitate an early decision to undertake fetotomy or Caesarean surgery in preference to attempting vaginal delivery. Fetomaternal disproportion is more common in heifers than in multigravida cows (Zaborski et al. 2009). Traction is the first method of delivery that should be attempted in most cases of fetomaternal disproportion. Before traction is applied, the vagina and those parts of the fetus occupying it must be thoroughly lubricated with copious application of several litres of a proprietary cellulose-based obstetrical lubricant. In cases in which the fetal disposition is normal and the disproportion is slight, it is a comparatively simple matter to apply snares to the fetal extremities (i.e., the limbs and head) and, adhering to the principles described in Chapter 14, the fetus is delivered by traction. As a rule, the animal remains standing during the application of snares but often goes down during the passage of the calf ’s head through the vulva. More severe disproportion requires more careful assessment and, as described previously, an early decision to use an alternative to traction when this is unlikely to be successful. Traction, however, must be employed with care because excessive traction can not only cause damage to the dam, but can also cause the fetus to become so tightly impacted in the birth canal that its subsequent delivery by Caesarean surgery or fetotomy can become difficult or impossible. Hence the amount of traction must be limited to that of three persons or a calving aid and the progress of the operation must be very closely scrutinized by the veterinarian. If no progress is made after 5 minutes or if the fetus becomes lodged and fails to yield to 5 minutes of further traction, then partial or total fetotomy or Caesarean surgery should be performed (Chapters 15 and 16).
Faulty fetal disposition is more common in parous cows than in primigravida. When faulty disposition is the cause of the dystocia, an assessment needs to be made of the measures that will be needed to correct it. Sometimes the space required for correction is lost due to the effects of continual straining or the contracted uterus. If so, one or all of caudal epidural anaesthesia, clenbuterol, and/or infusion of replacement fetal fluids should be given without delay. Occasionally, inducing epidural anaesthesia will allow an animal that has become recumbent to rise, which makes any manipulative procedures easier because the veterinarian can stand and the intraabdominal pressure is reduced. Management of dystocia due to fetal ‘monsters’ again requires an early assessment of the best means of delivering the calf. Many ‘fetal monsters’ cannot be delivered intact per vaginam and will require either fetotomy (usually) or Caesarean surgery (sometimes). It should, however, be noted that for fetal monsters for which Caesarean surgery is the method of choice (e.g., schistosoma reflexus in which the head and limbs are directed towards the pelvic inlet), fetotomy is contraindicated.
Sheep and Goat The ability of a veterinarian to resolve dystocia in the ewe or doe largely depends on the operator’s ability to pass a hand through the pelvis into the uterus. Primigravid animals of the smaller breeds sometimes foil attempts of even the smallest hand to traverse their birth canal, making delivery by Caesarean surgery the best option for success. Cases of fetomaternal disproportion are relatively uncommon, except in ewes carrying a singleton fetus. Most cases have normal fetal disposition, so once the head has been repelled from the pelvic inlet, gentle traction upon the limbs effects delivery. Use of a lambing snare (Fig. 11.9) to control the direction of the head is often helpful in cases of fetomaternal disproportion. When there is malposture of the limbs or head, repositioning after retropulsion is, as a rule, relatively easy. Retropulsion, replacement of lost fetal fluids, and correction of a faulty disposition are made much easier by, first, giving causal epidural anaesthesia and, second, elevating the hindquarters of the ewe. This can be done by rolling her on to her back and having an assistant pull both hind legs upwards and
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• Fig. 11.9
Lambing snare.
forwards. It is especially important to ensure that the presented parts all belong to the same fetus. The young, in cases of twins and triplets, are small and retropulsion and reposition are seldom difficult. Gentleness is critical in handling dystocias of the ewe and doe, as it extremely easy to damage the birth canal, pelvis or obturator nerve. Likewise, great care must be taken during intravaginal manipulations that the mucous membrane at the pelvic inlet is not lacerated. It is an accident that may occur quite simply, particularly when a finger is being used to lever a head or limb upwards. Such lacerations are usually followed by infection and possibly death. In most cases in which manipulation and delivery per vaginam is not possible, delivery by Caesarean surgery is usually the best option.
Pig In the sow, the ease with which obstructive dystocia can be relieved depends almost entirely on the operator’s ability to pass a hand through the pelvic inlet. Provided this is possible, it is usually a relatively easy matter to grip the head or hind parts and withdraw the fetus. In small gilts and in sows of breeds such as the Vietnamese pot-bellied breed, the use of a lambing snare (see Fig. 11.9) may be useful to apply traction to the head. The disposition of the limbs is seldom of much consequence. When assistance is given early in the dystocia (i.e., within an hour or two of the onset of second stage labour), removal of the obstructing fetus is often followed by the normal expulsion of the remainder. Assistance in the sow is frequently delayed, however; in these cases the obstetrician will be well advised to remove as many piglets from the uterine body and cornua as are within reach. The subsequent course will depend chiefly on the measure of delay and thus the degree of inertia which has supervened. It may be found in an hour or so that normal expulsion has recommenced or that on further examination more fetuses are accessible to manual extraction, and by continued attention to the sow in this manner the whole litter can be removed. It is worth remembering that intravaginal and intrauterine manipulations will stimulate the release of endogenous oxytocin and thus stimulate myometrial contractions. Quite often,
however, complete inertia has developed and no further progress follows the removal of the accessible fetuses. In these, Caesarean surgery is the only means of saving the sow. The strategic use of oxytocin to induce myometrial contractions can be used to treat overt cases of dystocia and also to hasten the expulsion of piglets if there is an extended time interval before the arrival of the next, thus preventing stillbirth. It is important to give low doses of oxytocin because it is a potent ecbolic, and large dose rates will cause spasm of the myometrium rather than rhythmical peristaltic-like contractions. In addition, the myometrium will become refractory to its effect, and it may be necessary to increase the dose rate in order to obtain a response. The dose of oxytocin is therefore critical to its successful use in farrowing. Mota-Rojas et al. (2006) noted that too high of a dose (or too rapid elevation of blood concentrations, particularly by IV administration) was associated with higher rates of fetal asphyxia/fetal distress, but that a low dose of oxytocin (0.083 IU/kg) gave a useful acceleration of parturition without causing fetal distress (Mota-Rojas et al. (2005) and improved survival of piglets experiencing dystocia (GonzálezLozano et al. 2009). Jackson (1996) observed that the greatest problem in porcine obstetrics was to know when a parturient sow had expelled all her piglets. Good, but not infallible, indications of the end of labour are that the sow rises, passes a large volume of urine, and then resumes recumbency in an attitude of contentment. When it is suspected that parturition is incomplete, the clinician should pass a hand as far as possible into the uterus and sweep it gently about the abdomen in the hope of balloting indirectly a piglet in an adjacent segment of the long uterine horn. Transabdominal ultrasonography can potentially be used to locate a retained fetus (see Chapter 17). The presence of retained fetal membranes is even more difficult to determine. When the clinical manifestations suggest that a fetus (or fetuses) is still retained and there has been no response to the administration of ecbolics, the only approach would be an exploratory laparotomy. Sows and gilts will often survive the presence of retained piglets, which sometimes become mummified (see Chapter 17). Because they are occasionally seen in the uteri of culled sows and gilts at the abattoir, it is likely that, although the mothers survived, they were infertile.
Dog and Cat The primary consideration in the management of a case of dystocia in the bitch or queen is whether one should attempt delivery per vaginam or immediately resort to Caesarean surgery. Factors that will influence the decision are: • The cause of dystocia, whether obstruction or primary inertia; • The duration of second stage labour and hence the condition of the fetuses and the uterine muscle; and • The number of fetuses retained and their viability. When the case is recent (i.e., a few hours only), attempting vaginal delivery may be appropriate. A modest degree of fetomaternal disproportion with the fetus in anterior or posterior presentation may be resolved by traction using the fingers only (see Figs 18.1 and 18.4), or finger and vectis, or forceps (these should be used with great care to prevent trauma to both dam and offspring); this traction will succeed in effecting delivery, and parturition will then proceed normally. Similarly, in cases of faulty fetal disposition, such as vertex posture or breech, traction may succeed after correction of the abnormal posture. Increasingly commonly, however, the decision is likely to proceed directly to Caesarean surgery. Certainly, in cases of gross fetomaternal disproportion (which is very common with litters of
one or two) or in cases in which the dystocia is of more than a few hours duration, Caesarean surgery is indicated. The obstetrical justification for this decision is that it is very likely that secondary inertia has supervened and removal of the obstructed fetus will not alter the ultimate outcome. This decision is often, however, subordinate to an economic justification: Caesarean surgery is used to minimize the risk of death of the dam and litter of pups or kittens – both of which may be valuable. The question sometimes arises of whether one should first attempt to remove the presented fetus per vaginam before performing surgery. It is highly likely that this fetus is contaminated, and withdrawing it through an abdominal wound may predispose to development of peritonitis. There is also, of course, the possibility that forceps interference will subject the bitch or queen to greater risk. Many veterinarians are of the view that the risk to the dam and the rest of the litter is minimized if the presented fetus is removed during the Caesarean surgery unless there is a very clear indication indeed for its removal per vaginam. The length of time for which the fetus will remain alive after the onset of second stage labour also has to be considered. It is very improbable that the presented fetus will live longer than 6 to 8 hours, for by that time its placenta will have completely separated. The remaining fetuses, however, may be alive for much longer periods. Thus it is possible that after 36 hours’ delay, the presented fetus may be dead with early signs of emphysema, yet those occupying the anterior parts of the cornua may be alive. After a delay of 48 hours, this is highly unlikely to occur. Hysterectomy may be chosen as an alternative to Caesarean surgery (see Chapter 19). Robbins and Mullen (1994) showed that newborn survival rates of 75% for dogs and 42% for cats are comparable to the outcomes of Caesarean surgery to treat dystocia.
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