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The trouble with vacuum extraction
Currenr Obsrerrics & Gyoecolog.v (I 999) 9,4 145 0 1999 Harcourt
Brace & Co. Ltd
Operative techniques
The trouble with vacuum extraction
A. Vacca Within the strict confines of randomized controlled trials, vacuum extraction has been shown to be a safe method for assisting a woman to give birth. Yet, in the area of general obstetric practice serious injuries associated with the procedure, such as subgaleal haemorrhage, skull fracture and intracranial injury, continue to be reported. There is little doubt that many of the problems and unfavourable results encountered after vacuum delivery are a consequence of incorrect use of the instrument and should, therefore, be preventable. Incorrect use of the vacuum extractor may occur for a number of reasons, namely, uncertainty of the indications for the procedure, lack of familiarity with the equipment, inadequate knowledge for the correct use of the instrument, inadequate training of the operators, incorrect technique of vacuum extraction and a lack of awareness of the safety measures. This review examines these important issues and presents a number of strategies aimed at reducing the rate of complications associated with vacuum extraction.
INTRODUCTION Concerns continue to be expressed about vacuum extraction as a method of assisted vaginal delivery with regard to the injuries sustained by the neonate and mother and also about the reported inefficiency of the instrument to achieve vaginal birth.’ Nevertheless,the vacuum extractor has been recommended as the instrument of first choice for assisted vaginal delivery.? in spite of the fact that the evidence on which the recommendation is based has been questioned.’ At the same time there has been a growing awareness that many problems and unfavourable results associated with this procedure may occur for one or more of the following reasons? l
l
l
uncertainty of the indications for vacuum extraction in present-day obstetric practice lack of familiarity with vacuum equipment and incorrect choice of cups inadequate knowledge for the correct use of the vacuum extractor
Dr Aldo Vacca, Director Obstetric Locked Mail Bag No 3, Caboolture
Services, Caboolture Qld 4510, Australia
Hospital,
inadequate training and experience of the operators and training supervisors incorrect technique of vacuum extraction lack of awarenessof the safety measures for vacuum extraction. This review will address some of the issuesthat influence the outcome of vacuum extraction and suggest strategies for reducing the adverse effects associated with this method of delivery. EFFECTS OF VACUUM EXTRACTION Effects on the infant Reported effectsof vacuum extraction may be classified as those with potentially serious clinical implications for the newborn infant and those that have little clinical significance, but may cause considerable parental anxiety. Subgaleal haemorrhage (SGH) and, to a lesser extent, intracranial injury are uncommon, but serious, neonatal complications associated with the vacuum extractor.5.6Clinically-significant SGH is almost always preceded by difficult vacuum extraction often
42
Current Obstetrics & Gynaecology
associated with failure of the procedure or with the use of forceps to complete the birth after vacuum extraction has failed to deliver the baby.’Early and prompt recognition of subgaleal bleeding, careful monitoring of the baby’s condition and transfusion with blood or colloid if necessarywill reduce morbidity and should prevent mortality from this condition.8.9 Avoiding difficult vacuum extractions and prolbnged traction is a simple and effective method of preventing SGH.‘O The chignon or vacuum-induced caput succedaneum, cup markings, abrasions and cephalhaematomas are less serious scalp effects that may cause anxiety to parents and birth attendants by their cosmetic appearances,but only rarely are they associated with long-term sequelaefor the infant.“,‘* Parents will be reassuredif they receive appropriate explanation and assurances that the lesions will disappear without leaving any permanent marking on the infant’s scalp. Retinal haemorrhages occur more frequently following vacuum extraction than after normal or forceps delivery. The clinical significance of retinal haemorrhages is unclear as they appear to be transient lesions leaving no residual ill effects.” Effects on the mother There is considerableevidenceto suggestthat vacuum extraction is less likely than forceps delivery to cause injury to the birth canal and to the muscles of the maternal pelvic floor.‘3-‘SNevertheless, serious injury has been reported,’ but critical analysis of these reports has often revealed the presenceof complicating factors, for example, use of the instrument before the cervix is completely dilated or the sequential application of forceps after failed vacuum extraction.16
Studies comparing vacuum extraction and forceps delivery have consistently shown that the vacuum extractor is less likely than forceps to complete the delivery.”A number of predisposing factors have been linked to unsuccessfulor difficult vacuum extractions: applications of the vacuum cup that are paramedian or deflexingj,” use of soft cups in preferenceto rigid CUPS’~ vacuum extractions from the midpelvis or from higher stations’” occipitolateral or posterior positions with deflexion and asynclitism of the head” extractions attempted before full dilatation of the cervix?’ cephalopelvic disproportion, relative or true.?’ UNCERTAINTY OF THE INDICATIONS FOR VACUUM EXTRACTION Indications Operators should classify indications for vacuum extraction into standard (lower risk) and special (higher risk) categories (Table 1). Use of the vacuum extractor in the special indication groups demands a high level of clinical and technical skill, and for this reason they should be regarded as contraindications for vacuum extraction unless the operator has received adequate training to perform these more complex procedures. Contraindications
INEFFICIENCY OF VACUUM EXTRACTION
Cephalopelvic disproportion, high station of the fetal head, face presentation, gestation less than 36 weeks, incompletely dilated cervix, and general anaesthesia should be considered contraindications for vacuum extraction.4
Table 1 Classification of indications for vacuum extraction
Selection of patients for vacuum extraction
Standard indications (lower risk) delay in the second stage of labour with the fetal head stationed - at the outlet of the pelvis - on the pelvic floor (occasional malposition) - in the midpelvis (frequent malposition) suspected fetal compromise (subacute fetal distress) elective shortening of the second stage Higher risk indications (trial of vacuum extraction) delay in the second stage of labour where there is a suspicion of borderline disproportion (large baby, small mother, previous difficult birth) suggestiveevidence of fetal compromise (acute fetal distress) combination of fetal, maternal and mechanical factors Highest risk indication (consider Caesareansection) delay or fetal compromise associated with malposition in a multipara when the cervix is not quite fully dilated and disproportion has been confidently excluded delivery of the second twin when the head is not quite engaged or the cervix is not completely dilated brow presentation after symphysiotomy
When a specific indication for expediting birth exists, a number of factors that influence the outcome should be carefully addressedbefore vacuum extraction is attempted:” l l
l l l
assessmentof maternal and fetal condition efficiency of uterine contractions and maternal expulsive effort confirmation of complete dilatation of the cervix precise localization of the site of the flexion point accurate determination of station, position and moulding of the fetal head.
Careful evaluation of the information obtained from the examination will make it possible to selectpatients who are suitable for vacuum extraction and to grade the procedures according to the level of operative skills required (Table 2).
The trouble with vacuum extraction Table 2
43
Selection of patients for vacuum extraction
Station
Fetal distress
Moulding
Method of delivery
Outlet Low pelvis Mid pelvis Mid pelvis Mid pelvis Mid pelvis High pelvis
Yes or no Yes or no No No Yes Yes Yes or no
Slight to advanced Slight to advanced Moderate Advanced Moderate Advanced Slight to advanced
VE VE (malposition occasionally) VE (malposition frequently) Trial of VE (or Caesarean section) Trial of VE (or Caesarean section) Caesarean section Caesarean section
VE: vacuum extraction
Table 3 Knowledge, clinical reasoning and technical skills for vacuum extraction
. . . . . . . . . . . .
Indications - standard (lower risk) and special (higher risk) Contraindications - absolute and relative Selection of patients - core selection criteria and associated factors Preliminaries - expulsivc powers, maternal position and analgesia Technical principles - determining site of the flexion point Correct choice of vacuum cup - Soft cup, Anterior cup or Posterior cup Technique for achieving correct (flexing median) application of the vacuum cap Technique of vacuum extraction - for standard and rotational procedures Method of traction and prevention of cup detachment Safety measures for the prevention of maternal and fetal injury Correct diagnosis and prompt management of serious injury Clinical audit and critical review of vacuum extractions
LACK OF FAMILIARITY EQUIPMENT
WITH THE
Problems arise when operators fail to understand how the design of a vacuum cup may enhance or restrict the cup’s manoeuvrability and how these design features are meant to be used to achieve flexing median applications in all positions of the occiput.” Manoeuvrability of cups with dome-attached handles (the Soft cups) or tubing (the Malmstrom-type cups and Anterior cups) is restricted by the handles or tubing making contact with labial or perineal tissues.The Posterior cup, on the other hand, is not restricted by the maternal soft tissues because the suction tube is in the same plane as the body of the cup. This unique feature allows the cup to be inserted through the introitus, manoeuvred beyond the caput and be directed toward and over the flexion point.4.2z For these reasons use of Soft cups, Malmstromtype and Anterior design cups should be restricted to outlet procedures and non-rotational low vacuum extractions.23 For rotational procedures the vacuum cup of choice is one of the Posterior designs, provided the operator has been trained in its use.“.‘” DEFICIENT KNOWLEDGE OR INCORRECT TECHNIQUE It is beyond the scope of this review to present the detailed knowledge and technical skills required for
correct use of the vacuum extractor (Table 3). A variety of teaching resources has been produced for this puTpose,4.Km!2 and individuals who wish to obtain more information are advised to refer to them. A few key issues will be mentioned, however, since they are sometimes overlooked and because they are important for a successfuloutcome. Preliminary steps Operators should begin with an explanation of the nature of vacuum extraction to the mother and outline her role in the procedure.4She should be placed in the lithotomy position with a wedge under one buttock to produce some lateral tilt and instructed on the method of pushing in this position. Infiltration of the perineum with a local anaesthetic agent will usually suffice for all non-rotational and rotational procedures. Some mothers will have received regional analgesia for pain relief during the course of the labour and operators should know how to modify their vacuum extraction technique to compensate for the loss of bearing-down sensation without substituting increased traction for decreased maternal expulsive effort. For outlet and low vacuum extractions, episiotomy is required only for the usual obstetric indications, but for procedures from the mid pelvis, episiotomy should be performed when the head descends to the level of the pelvic floor to allow the operator to direct traction along the axis of the birth canal. Correct and incorrect applications of the cup For practical purposes, complete flexion of the fetal head exists when the mentovertical diameter points in the direction of descent.24In a normally-moulded fetal head, the mentovertical diameter emerges on the sagittal suture approximately 3 cm in front of the posterior fontanelle. This ‘flexion point’ is an important landmark for vacuum extraction because ideal application of the vacuum cup is achieved when the centre of the cup is superimposed over the flexion point and the cup is symmetrically placed over the sagittal suture. Correct (flexing median) cup application is a prerequisite for successful vacuum extraction and operators should learn how to achieve such applications consistently in all positions of the occiput.4*‘o
44
Current Obstetrics & Gynaecology
Traction principles and technique When the fetal head is stationed in mid pelvis, traction should be directed downward, initially toward the floor to keep the flexion point in line with the axis of the pelvis. Complete detachment of the cup may be prevented by exerting counter-pressure on the cup with the finger and thumb of the non-pulling hand and by ceasing to pull when the contraction passes and the mother stops pushing.” Rotational vacuum extraction technique Rotational vacuum extractions, like rotational forceps deliveries, are more complex procedures and should not be attempted unless the operator has been adequately trained in the use of the Posterior cup.” Internal rotation occurs automatically as the head descendsprovided the application of the cup is flexing and median and traction is directed along the line of the axis of the pelvis.‘.” LACK OF AWARENESS OF SAFETY MEASURES Safety of vacuum extraction begins with a classification of indications into standard and special categories (Table 1); in general, procedures in the standard group have a greater margin of safety, whereas the special uses of the instrument will be contraindications for all but the most experienced operators. In addition, safety may be enhanced if vacuum extractions are classified according to the degree of anticipated mechanical difficulty determined by evaluating station, position and moulding of the fetal head (Table 2). Correct application of the vacuum cup as a factor exercising a major influence on outcome cannot be over-emphasized; failure of vacuum extraction and injury to the infant or mother are reduced when the application of the cup is flexing median.” The amount of traction force required for delivery will be inversely proportional to the efficiency of the maternal expulsive powers. For this reason the operator should ensure that maternal expulsive effort and uterine contractions are effective. Descent of the fetal head should occur with each pull; traction that does not cause the head to descend is more likely to cause SGH.“’ Cup detachment should not be regarded as a safety feature of vacuum extraction but should be seen as a warning sign of incorrect technique or, occasionally, of cephalopelvic disproportion. Delivery of the fetal head should be completed within 15 min of applying the cup. If the duration of the procedure exceeds this time limit or if descent of the head does not occur easily, traction should be discontinued and the delivery completed by Caesarean section. Forceps should not be applied to the fetal head if vacuum extraction fails, unless the head has descended to the outlet of the pelvis.
After vacuum extraction has been completed, the baby’s head should be examined and re-examined at regular intervals if the extraction was difficult for evidence of SGH.*” TOWARD A BETTER OUTCOME To achieve consistently good results with the vacuum extractor, operators should possess all the relevant knowledge, clinical reasoning and technical skills essential for vacuum extraction (Table 3). Since the operator does not work in isolation, attitudes of training supervisors, policy makers and midwifery staff will also greatly influence the extent to which vacuum extraction is accepted as a method of assisted vaginal delivery.” With the continuing decline in the number of mid cavity instrumental deliveries in favour of Caesarean sections, training of obstetricians to perform the more complex vaginal procedures has become increasingly difticult.~5~~” Furthermore, structured training programmes in vacuum extraction are not common in places where forceps are the preferred method of assisted delivery. To help correct this deficiency, teaching resources on the subject of vacuum extraction have been produced that may be incorporated into training programmes or used by clinicians for self-directed learning and review.J.l92? REFERENCES I. Drife JO. Choice and inslrumcnlal dclivcry. Br J Obstct Gynaecol 1996; 103: 608 61 I. 2. Chalmers JA, Chalmers I. The obstetric vacuum extractor is the instrument of’ lirst choice for opcrativc vaginal dclivcry. Br J Obstet Gynaecol 1989; 96: 505 506. 3. Gram JM. The whole duty of obstetricians. Br J Obstet Gvnaccol 1997: 104: 387-392. 4. V&ca A. Handbook of Vacuum Extraction in Obstclric Practice. London: Edward Arnold, 1992. 5. Govaert P. Vanhacsebrouck P. dc Praetcr C. Mocns K. Lcrov J. Vacuum extraction, bone injury and neonatal subgalcal blcedina. Eur J Pedialr 1992; 151: 532~535. 6. IHall SC. Simultaneous occurrence or intracranial and subgaleal hemorrhages complicating vacuum extraction delivery. J Pcrinatol 1992; 12: 185-187. 7. Chadwick LJJ, Pemberlon PJ, Kurinczuk JJ. Neonatal subgaleal haematoma: associated risk factors, complications and oulcome. J Paediatr Child Health 1996: 32: 228.232. 8. Vacca A. Birth by vacuum extraction: neonatal outcome J Paediatr Child Health 1996; 32: 204 206. 9. Cavlovich FE. Subgaleal hcmorrhagc in the neonalc. JOGNN 1995; 24: 397404. IO. Bird GC. The use of the vacuum extractor. Clin Obstel Gynaecol 1982; 9: 641-66 I II. Garcia J. Anderson J, Vacca A, Elbournc D. Grant A. Chalmers I. Views or women and their medical and midwifery attendants about instrumental delivery using vacuum extraction and rorceps. J Psychosom Obsiei Gynaccol. 1985; 4: I 9. 12. Vacca A. Vacuum extraction: ract and opinion. In: Cosmi EV, Montanino G (eds.) Proceedings of the 2nd World Congress on labor and delivery. London: The Parthenon Publishing Grow. 1998: 64-69. 13. Joha&n RB, Menon VJ. Vacuum extraction vs rorccps delivery. (Cochrane Review) In: The Cochrane Library. Issue 2. Ox&d: Update Sonware; 1998. Updated quarterly. 14. Sultan AH, K a m m MA, Hudson CN, Barlram Cl. Third degree anal sphincter tears: risk factors and outcome or primary repair. BMJ 1994: 308: 887 891.
The trouble with vacuum extraction 15. Sultan AH, Johanson RB, Carter JE. Occult anal sphincter trauma in a randomised study of forceps and ventouse delivery. Br J Obstct Gynaecol 1996; 103: 845. 16. Vacca A. Grant A, Wyatt G, Chalmers I. Portsmouth operative delivery trial: a comparison of vacuum extraction and forceps delivery. Br J Obstet Gynaecol 1983; 90: 1107~1112. 17. Bird CC. The importance of flcxion in vacuum extraction dclivcry. Br J Obstet Gynaecol 1976; 83: 194200. 18. Johanson R, Menon V. Soft versus rigid vacuum extractor cups. (Cochrane Review) In: The Cochrane Library, Issue 2. Oxford: Update Software; 1998. Updated quarterly. 19. O’Grady JP. Gimovsky ML, Mcllhargic CJ. Vacuum extraction in modern obstetric practice. New York: The Parthenon Publishing Group, 1995. 20. Cohn M, Barclay C, Fraser R, zaktama M, Johanson R, Anderson D. Walker C.A multicentre randomised trial comparing delivery with a silicone rubber cup and rigid metal vacuum extractor cups, Br J Obstet Gynaecol 1989; 96: 545555 I.
45
21. Philpott RH. The recognition of cephalopelvic disproportion. Clin Obstet Gynaecol 1982; 9: 609-624. 22. Vacca A. Vacuum extraction. In: Choices with childbirth: progress of labour and vacuum extraction. Brisbane, Vacca Research, 1997 (on CD ROM). 23. Johanson RB, Rice C, Doyle M et al. A randomised prospective study comparing the new vacuum extractor policy with forceps delivery. Br J Obstet Gynaecol 1993; 100: 524-530. 24. Rydberg E. The mechanism of labour. Springtield: Charles C Thomas, 1954. 25. Botill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Forceps and vacuum delivery: a survey of North American residency programs. Obstet Gynecol 1996; 88:622-625. 26. O’Grady JP, Mcllhargie CJ. Instrumental Delivery In: O’Grady JP, Gimovsky ML, Mcllhargie CJ (eds) Operative obstetrics. Baltimore; Williams and Wilkins, 1995; 177-208.
Brace & Co. Ltd
Operative techniques
The trouble with vacuum extraction
A. Vacca Within the strict confines of randomized controlled trials, vacuum extraction has been shown to be a safe method for assisting a woman to give birth. Yet, in the area of general obstetric practice serious injuries associated with the procedure, such as subgaleal haemorrhage, skull fracture and intracranial injury, continue to be reported. There is little doubt that many of the problems and unfavourable results encountered after vacuum delivery are a consequence of incorrect use of the instrument and should, therefore, be preventable. Incorrect use of the vacuum extractor may occur for a number of reasons, namely, uncertainty of the indications for the procedure, lack of familiarity with the equipment, inadequate knowledge for the correct use of the instrument, inadequate training of the operators, incorrect technique of vacuum extraction and a lack of awareness of the safety measures. This review examines these important issues and presents a number of strategies aimed at reducing the rate of complications associated with vacuum extraction.
INTRODUCTION Concerns continue to be expressed about vacuum extraction as a method of assisted vaginal delivery with regard to the injuries sustained by the neonate and mother and also about the reported inefficiency of the instrument to achieve vaginal birth.’ Nevertheless,the vacuum extractor has been recommended as the instrument of first choice for assisted vaginal delivery.? in spite of the fact that the evidence on which the recommendation is based has been questioned.’ At the same time there has been a growing awareness that many problems and unfavourable results associated with this procedure may occur for one or more of the following reasons? l
l
l
uncertainty of the indications for vacuum extraction in present-day obstetric practice lack of familiarity with vacuum equipment and incorrect choice of cups inadequate knowledge for the correct use of the vacuum extractor
Dr Aldo Vacca, Director Obstetric Locked Mail Bag No 3, Caboolture
Services, Caboolture Qld 4510, Australia
Hospital,
inadequate training and experience of the operators and training supervisors incorrect technique of vacuum extraction lack of awarenessof the safety measures for vacuum extraction. This review will address some of the issuesthat influence the outcome of vacuum extraction and suggest strategies for reducing the adverse effects associated with this method of delivery. EFFECTS OF VACUUM EXTRACTION Effects on the infant Reported effectsof vacuum extraction may be classified as those with potentially serious clinical implications for the newborn infant and those that have little clinical significance, but may cause considerable parental anxiety. Subgaleal haemorrhage (SGH) and, to a lesser extent, intracranial injury are uncommon, but serious, neonatal complications associated with the vacuum extractor.5.6Clinically-significant SGH is almost always preceded by difficult vacuum extraction often
42
Current Obstetrics & Gynaecology
associated with failure of the procedure or with the use of forceps to complete the birth after vacuum extraction has failed to deliver the baby.’Early and prompt recognition of subgaleal bleeding, careful monitoring of the baby’s condition and transfusion with blood or colloid if necessarywill reduce morbidity and should prevent mortality from this condition.8.9 Avoiding difficult vacuum extractions and prolbnged traction is a simple and effective method of preventing SGH.‘O The chignon or vacuum-induced caput succedaneum, cup markings, abrasions and cephalhaematomas are less serious scalp effects that may cause anxiety to parents and birth attendants by their cosmetic appearances,but only rarely are they associated with long-term sequelaefor the infant.“,‘* Parents will be reassuredif they receive appropriate explanation and assurances that the lesions will disappear without leaving any permanent marking on the infant’s scalp. Retinal haemorrhages occur more frequently following vacuum extraction than after normal or forceps delivery. The clinical significance of retinal haemorrhages is unclear as they appear to be transient lesions leaving no residual ill effects.” Effects on the mother There is considerableevidenceto suggestthat vacuum extraction is less likely than forceps delivery to cause injury to the birth canal and to the muscles of the maternal pelvic floor.‘3-‘SNevertheless, serious injury has been reported,’ but critical analysis of these reports has often revealed the presenceof complicating factors, for example, use of the instrument before the cervix is completely dilated or the sequential application of forceps after failed vacuum extraction.16
Studies comparing vacuum extraction and forceps delivery have consistently shown that the vacuum extractor is less likely than forceps to complete the delivery.”A number of predisposing factors have been linked to unsuccessfulor difficult vacuum extractions: applications of the vacuum cup that are paramedian or deflexingj,” use of soft cups in preferenceto rigid CUPS’~ vacuum extractions from the midpelvis or from higher stations’” occipitolateral or posterior positions with deflexion and asynclitism of the head” extractions attempted before full dilatation of the cervix?’ cephalopelvic disproportion, relative or true.?’ UNCERTAINTY OF THE INDICATIONS FOR VACUUM EXTRACTION Indications Operators should classify indications for vacuum extraction into standard (lower risk) and special (higher risk) categories (Table 1). Use of the vacuum extractor in the special indication groups demands a high level of clinical and technical skill, and for this reason they should be regarded as contraindications for vacuum extraction unless the operator has received adequate training to perform these more complex procedures. Contraindications
INEFFICIENCY OF VACUUM EXTRACTION
Cephalopelvic disproportion, high station of the fetal head, face presentation, gestation less than 36 weeks, incompletely dilated cervix, and general anaesthesia should be considered contraindications for vacuum extraction.4
Table 1 Classification of indications for vacuum extraction
Selection of patients for vacuum extraction
Standard indications (lower risk) delay in the second stage of labour with the fetal head stationed - at the outlet of the pelvis - on the pelvic floor (occasional malposition) - in the midpelvis (frequent malposition) suspected fetal compromise (subacute fetal distress) elective shortening of the second stage Higher risk indications (trial of vacuum extraction) delay in the second stage of labour where there is a suspicion of borderline disproportion (large baby, small mother, previous difficult birth) suggestiveevidence of fetal compromise (acute fetal distress) combination of fetal, maternal and mechanical factors Highest risk indication (consider Caesareansection) delay or fetal compromise associated with malposition in a multipara when the cervix is not quite fully dilated and disproportion has been confidently excluded delivery of the second twin when the head is not quite engaged or the cervix is not completely dilated brow presentation after symphysiotomy
When a specific indication for expediting birth exists, a number of factors that influence the outcome should be carefully addressedbefore vacuum extraction is attempted:” l l
l l l
assessmentof maternal and fetal condition efficiency of uterine contractions and maternal expulsive effort confirmation of complete dilatation of the cervix precise localization of the site of the flexion point accurate determination of station, position and moulding of the fetal head.
Careful evaluation of the information obtained from the examination will make it possible to selectpatients who are suitable for vacuum extraction and to grade the procedures according to the level of operative skills required (Table 2).
The trouble with vacuum extraction Table 2
43
Selection of patients for vacuum extraction
Station
Fetal distress
Moulding
Method of delivery
Outlet Low pelvis Mid pelvis Mid pelvis Mid pelvis Mid pelvis High pelvis
Yes or no Yes or no No No Yes Yes Yes or no
Slight to advanced Slight to advanced Moderate Advanced Moderate Advanced Slight to advanced
VE VE (malposition occasionally) VE (malposition frequently) Trial of VE (or Caesarean section) Trial of VE (or Caesarean section) Caesarean section Caesarean section
VE: vacuum extraction
Table 3 Knowledge, clinical reasoning and technical skills for vacuum extraction
. . . . . . . . . . . .
Indications - standard (lower risk) and special (higher risk) Contraindications - absolute and relative Selection of patients - core selection criteria and associated factors Preliminaries - expulsivc powers, maternal position and analgesia Technical principles - determining site of the flexion point Correct choice of vacuum cup - Soft cup, Anterior cup or Posterior cup Technique for achieving correct (flexing median) application of the vacuum cap Technique of vacuum extraction - for standard and rotational procedures Method of traction and prevention of cup detachment Safety measures for the prevention of maternal and fetal injury Correct diagnosis and prompt management of serious injury Clinical audit and critical review of vacuum extractions
LACK OF FAMILIARITY EQUIPMENT
WITH THE
Problems arise when operators fail to understand how the design of a vacuum cup may enhance or restrict the cup’s manoeuvrability and how these design features are meant to be used to achieve flexing median applications in all positions of the occiput.” Manoeuvrability of cups with dome-attached handles (the Soft cups) or tubing (the Malmstrom-type cups and Anterior cups) is restricted by the handles or tubing making contact with labial or perineal tissues.The Posterior cup, on the other hand, is not restricted by the maternal soft tissues because the suction tube is in the same plane as the body of the cup. This unique feature allows the cup to be inserted through the introitus, manoeuvred beyond the caput and be directed toward and over the flexion point.4.2z For these reasons use of Soft cups, Malmstromtype and Anterior design cups should be restricted to outlet procedures and non-rotational low vacuum extractions.23 For rotational procedures the vacuum cup of choice is one of the Posterior designs, provided the operator has been trained in its use.“.‘” DEFICIENT KNOWLEDGE OR INCORRECT TECHNIQUE It is beyond the scope of this review to present the detailed knowledge and technical skills required for
correct use of the vacuum extractor (Table 3). A variety of teaching resources has been produced for this puTpose,4.Km!2 and individuals who wish to obtain more information are advised to refer to them. A few key issues will be mentioned, however, since they are sometimes overlooked and because they are important for a successfuloutcome. Preliminary steps Operators should begin with an explanation of the nature of vacuum extraction to the mother and outline her role in the procedure.4She should be placed in the lithotomy position with a wedge under one buttock to produce some lateral tilt and instructed on the method of pushing in this position. Infiltration of the perineum with a local anaesthetic agent will usually suffice for all non-rotational and rotational procedures. Some mothers will have received regional analgesia for pain relief during the course of the labour and operators should know how to modify their vacuum extraction technique to compensate for the loss of bearing-down sensation without substituting increased traction for decreased maternal expulsive effort. For outlet and low vacuum extractions, episiotomy is required only for the usual obstetric indications, but for procedures from the mid pelvis, episiotomy should be performed when the head descends to the level of the pelvic floor to allow the operator to direct traction along the axis of the birth canal. Correct and incorrect applications of the cup For practical purposes, complete flexion of the fetal head exists when the mentovertical diameter points in the direction of descent.24In a normally-moulded fetal head, the mentovertical diameter emerges on the sagittal suture approximately 3 cm in front of the posterior fontanelle. This ‘flexion point’ is an important landmark for vacuum extraction because ideal application of the vacuum cup is achieved when the centre of the cup is superimposed over the flexion point and the cup is symmetrically placed over the sagittal suture. Correct (flexing median) cup application is a prerequisite for successful vacuum extraction and operators should learn how to achieve such applications consistently in all positions of the occiput.4*‘o
44
Current Obstetrics & Gynaecology
Traction principles and technique When the fetal head is stationed in mid pelvis, traction should be directed downward, initially toward the floor to keep the flexion point in line with the axis of the pelvis. Complete detachment of the cup may be prevented by exerting counter-pressure on the cup with the finger and thumb of the non-pulling hand and by ceasing to pull when the contraction passes and the mother stops pushing.” Rotational vacuum extraction technique Rotational vacuum extractions, like rotational forceps deliveries, are more complex procedures and should not be attempted unless the operator has been adequately trained in the use of the Posterior cup.” Internal rotation occurs automatically as the head descendsprovided the application of the cup is flexing and median and traction is directed along the line of the axis of the pelvis.‘.” LACK OF AWARENESS OF SAFETY MEASURES Safety of vacuum extraction begins with a classification of indications into standard and special categories (Table 1); in general, procedures in the standard group have a greater margin of safety, whereas the special uses of the instrument will be contraindications for all but the most experienced operators. In addition, safety may be enhanced if vacuum extractions are classified according to the degree of anticipated mechanical difficulty determined by evaluating station, position and moulding of the fetal head (Table 2). Correct application of the vacuum cup as a factor exercising a major influence on outcome cannot be over-emphasized; failure of vacuum extraction and injury to the infant or mother are reduced when the application of the cup is flexing median.” The amount of traction force required for delivery will be inversely proportional to the efficiency of the maternal expulsive powers. For this reason the operator should ensure that maternal expulsive effort and uterine contractions are effective. Descent of the fetal head should occur with each pull; traction that does not cause the head to descend is more likely to cause SGH.“’ Cup detachment should not be regarded as a safety feature of vacuum extraction but should be seen as a warning sign of incorrect technique or, occasionally, of cephalopelvic disproportion. Delivery of the fetal head should be completed within 15 min of applying the cup. If the duration of the procedure exceeds this time limit or if descent of the head does not occur easily, traction should be discontinued and the delivery completed by Caesarean section. Forceps should not be applied to the fetal head if vacuum extraction fails, unless the head has descended to the outlet of the pelvis.
After vacuum extraction has been completed, the baby’s head should be examined and re-examined at regular intervals if the extraction was difficult for evidence of SGH.*” TOWARD A BETTER OUTCOME To achieve consistently good results with the vacuum extractor, operators should possess all the relevant knowledge, clinical reasoning and technical skills essential for vacuum extraction (Table 3). Since the operator does not work in isolation, attitudes of training supervisors, policy makers and midwifery staff will also greatly influence the extent to which vacuum extraction is accepted as a method of assisted vaginal delivery.” With the continuing decline in the number of mid cavity instrumental deliveries in favour of Caesarean sections, training of obstetricians to perform the more complex vaginal procedures has become increasingly difticult.~5~~” Furthermore, structured training programmes in vacuum extraction are not common in places where forceps are the preferred method of assisted delivery. To help correct this deficiency, teaching resources on the subject of vacuum extraction have been produced that may be incorporated into training programmes or used by clinicians for self-directed learning and review.J.l92? REFERENCES I. Drife JO. Choice and inslrumcnlal dclivcry. Br J Obstct Gynaecol 1996; 103: 608 61 I. 2. Chalmers JA, Chalmers I. The obstetric vacuum extractor is the instrument of’ lirst choice for opcrativc vaginal dclivcry. Br J Obstet Gynaecol 1989; 96: 505 506. 3. Gram JM. The whole duty of obstetricians. Br J Obstet Gvnaccol 1997: 104: 387-392. 4. V&ca A. Handbook of Vacuum Extraction in Obstclric Practice. London: Edward Arnold, 1992. 5. Govaert P. Vanhacsebrouck P. dc Praetcr C. Mocns K. Lcrov J. Vacuum extraction, bone injury and neonatal subgalcal blcedina. Eur J Pedialr 1992; 151: 532~535. 6. IHall SC. Simultaneous occurrence or intracranial and subgaleal hemorrhages complicating vacuum extraction delivery. J Pcrinatol 1992; 12: 185-187. 7. Chadwick LJJ, Pemberlon PJ, Kurinczuk JJ. Neonatal subgaleal haematoma: associated risk factors, complications and oulcome. J Paediatr Child Health 1996: 32: 228.232. 8. Vacca A. Birth by vacuum extraction: neonatal outcome J Paediatr Child Health 1996; 32: 204 206. 9. Cavlovich FE. Subgaleal hcmorrhagc in the neonalc. JOGNN 1995; 24: 397404. IO. Bird GC. The use of the vacuum extractor. Clin Obstel Gynaecol 1982; 9: 641-66 I II. Garcia J. Anderson J, Vacca A, Elbournc D. Grant A. Chalmers I. Views or women and their medical and midwifery attendants about instrumental delivery using vacuum extraction and rorceps. J Psychosom Obsiei Gynaccol. 1985; 4: I 9. 12. Vacca A. Vacuum extraction: ract and opinion. In: Cosmi EV, Montanino G (eds.) Proceedings of the 2nd World Congress on labor and delivery. London: The Parthenon Publishing Grow. 1998: 64-69. 13. Joha&n RB, Menon VJ. Vacuum extraction vs rorccps delivery. (Cochrane Review) In: The Cochrane Library. Issue 2. Ox&d: Update Sonware; 1998. Updated quarterly. 14. Sultan AH, K a m m MA, Hudson CN, Barlram Cl. Third degree anal sphincter tears: risk factors and outcome or primary repair. BMJ 1994: 308: 887 891.
The trouble with vacuum extraction 15. Sultan AH, Johanson RB, Carter JE. Occult anal sphincter trauma in a randomised study of forceps and ventouse delivery. Br J Obstct Gynaecol 1996; 103: 845. 16. Vacca A. Grant A, Wyatt G, Chalmers I. Portsmouth operative delivery trial: a comparison of vacuum extraction and forceps delivery. Br J Obstet Gynaecol 1983; 90: 1107~1112. 17. Bird CC. The importance of flcxion in vacuum extraction dclivcry. Br J Obstet Gynaecol 1976; 83: 194200. 18. Johanson R, Menon V. Soft versus rigid vacuum extractor cups. (Cochrane Review) In: The Cochrane Library, Issue 2. Oxford: Update Software; 1998. Updated quarterly. 19. O’Grady JP. Gimovsky ML, Mcllhargic CJ. Vacuum extraction in modern obstetric practice. New York: The Parthenon Publishing Group, 1995. 20. Cohn M, Barclay C, Fraser R, zaktama M, Johanson R, Anderson D. Walker C.A multicentre randomised trial comparing delivery with a silicone rubber cup and rigid metal vacuum extractor cups, Br J Obstet Gynaecol 1989; 96: 545555 I.
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21. Philpott RH. The recognition of cephalopelvic disproportion. Clin Obstet Gynaecol 1982; 9: 609-624. 22. Vacca A. Vacuum extraction. In: Choices with childbirth: progress of labour and vacuum extraction. Brisbane, Vacca Research, 1997 (on CD ROM). 23. Johanson RB, Rice C, Doyle M et al. A randomised prospective study comparing the new vacuum extractor policy with forceps delivery. Br J Obstet Gynaecol 1993; 100: 524-530. 24. Rydberg E. The mechanism of labour. Springtield: Charles C Thomas, 1954. 25. Botill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Forceps and vacuum delivery: a survey of North American residency programs. Obstet Gynecol 1996; 88:622-625. 26. O’Grady JP, Mcllhargie CJ. Instrumental Delivery In: O’Grady JP, Gimovsky ML, Mcllhargie CJ (eds) Operative obstetrics. Baltimore; Williams and Wilkins, 1995; 177-208.