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Analgesia and anesthesia for obstetrics, inhalation methods
ANALGESIA W. ALLEN
AND ANESTHESIA FOR OBSTETRICS, INHALATION METHODS” CONROY,
CAPT.,
M.C., A. U.
S., CHICAGO,
ILL.
T
HE problems of pain relief in labor by inhalation methods have been obscured many times by the emphasis usually placed on actual drugs and apparatus. It would seem more fruitful to consider what distresses and disturbances that delivery causes mother and fetus, and what degree of narcosis will decrease or eliminate these undesirable phases of an otherwise physiologic process. With these in mind, one could then marshal drugs, methods and skills to reach the desired effects. The average primipara of these civilized days is unfortunately encouraged in her fear of an unknown experience, by the careless use of the word “pains” by her friends, mother and doctor. She does experience “labor” in its simplest meanin g, but unlike her primitive sister, her work is attended by varying degrees of real pain. This distress must not be confused with the underlying contractions of the uterus. Means are in existence to eliminate the pain without markedly affecting the uterine contractions, just as pain in any muscle may be alleviated by drugs, and without loss of consciousness. The first step, then will be to divorce her from the fallacious and harmful idea that she must be relieved of either consciousness or memory of the birth process in. order to undergo it jn any degree of comfort. Not till she understands that there can be consciousness and memory of labor without distress, will we eliminate some of the hazards of overuse of drugs. Too much narcosis, whether from nonvolatiIe or volatile agents, leads to fetal respiratory embarrassment, and to weakening of the uterine contractions. We may use light hypnosis with nonvolatile drugs like the barbiturates, scopolamine and paraldehyde. In quite moderate dosage, these induce a state of mental relaxation which enables us to gain the apprehensive mother’s confidence. We must, if possible, convince her that freedom from pain is obtainable while she consciously assists in the “work” that her uterus does. Even where we later fail to achieve analgesia, we may help her tolerate some pain if she has the knowledge that possible harm to her baby is being avoided. The term analgesia is literally used here, not as an improper substitute for the word amnesia. A patient who is in a deep sleep, and is aroused to wild activity by pain cannot be said to be freed of pain. To call this effect analgesia is misleading to ourselves, because safe doses of barbiturates and similar drugs are not analgesic, that is, they do not eliminate pain. *Read
.xt a meeting
of the Chicago
Gynecological
81
Society,
Oct.
15, 1943.
82
AMERICAN
JOURNAI,
Oh’ OBSTETRICS
AND
GYNECOLOGY
Having obtained t,he mother’s confidence before her labor contractions have acquired any element of intolerable pain, we must next watch for the degree and character of what true pain does accompa.ny the individual contractions as their amplitude increases. During the first stage and early second stage, the tolerance to pain may be greater than normal, due to the light hypnosis already mentioned, and some will be willing to fortify it by small doses of opiates. If the pain factor increases rapidly in severity, we must turn quickly to safer methods before confidence in us is lost. It. is excellent practice to observe the rapidity of onset, severity, and duration of the pain factor of each contraction, as soon as labor becomes painful enough to require stronger measures. (See Fig. 1.) A hand on the uterus? and the sound of the patient’s breathing and her outcries will tell us quickly whether pain comes early or late in t.he contraction, how severe it is, and how persistent. Since for each subject, the pain element will usually parallel t,he nature of the uterine contraction, it suffices to make a mental graph of contraction alone.
Fig. l.-Types of contraction pain. prolonged perception of pain; 0, late, perception ; E, pain-free contraction.
A., Early,
brief
pain
brief perception of pain ; B, early, perception; D, late, prolonged pain
Regardless of the inhalation agent used, the principle is the same. We must counteract the pain as rapidly as it builds up, without serious interference to the uterine contraction or hazard to the fetus. If the mother experiences severe pain almost simultaneously with the onset of the contraction, our efforts must be vigorous and swift. If the pain appears late, we content ourselves with the administration of oxygen till pain does appear. If pain is severe or persistent, we are taxed to provide enough pain relief to keep the mother from panicky ineffectuality. For obstetrical analgesia, nitrous oxide remains our best weapon. Even the tyro will obtain fair results, and with safety, if the color of the patient is kept reasonably pink for the comparatively short time of each contraction, and if overoxygenation is achieved immediately after each contraction. Nitrous oxide may give t,he desired resu1t.s with as low a concentration as 50 per cent where the pain element is minor, and may be used in its pure form for the brief and violently
CONROY
:
ANALGESIA
AND
ANESTHESIA,
INHALATION
METHODS
83
painful contractions occasionally seen. (The lungs and tissues do have a small oxygen reserve.) When commencing to use nitrous oxide, it is wise to give it liberally, even to complete anesthesia, during one or two contractions, to fortify the patient’s confidence in our ability to spare her distress. Using our mental graph of the character of pain, we then modify the gas mixture for each subsequent contraction. If the peak of pain is reached early, the mother is instructed not to delay in asking for the gas, the instant she feels the uterus begin to contract. Better still, if the anesthetist is closely observing the abdomen manually, the first hardening of the uterus is a warning to start With the breathing bag already full with administration immediately. 70 per cent to 100 per cent nitrous oxide, and the valves and gas flow arranged so that all of each expiration is spilled into the outside air, the face piece is applied and the patient instructed to take two maximal inhalations as quickly as she is able. This gives a rapid displacement of the iuert nitrogen from the lungs and achieves an analgesic level of the nitrous oxide before the contraction reaches it,s peak. As the second breath is being taken, the woman is instructed to hold that breath, and strain as if at stool. She will do this effectively once she is confident such activity will be relatively painless. If we know from previous observa,tion that the contraction is short-lived, the breathing bag may be flushed now with pure oxygen. If it is going to be prolongedly painful, the gas is reduced to a level of 85 per cent or less, so that subsequent inhalations will be carrying in adequate oxygen. Where the onset of pain perception is preceded by a period of painless contraction, three or even four rapid, full breaths of 70 per cent to 90 per cent nitrous oxide will be effective and safe. The longer time will a.llow for more complete flushing out of the inert nitrogen, but over such a period, the oxygen reserves would be depleted, hence the need for its addition to the gas. Subsequent gas flows for the expulsion efforts to follow will be adjusted to the anesthetist’s mental picture of the curve of pain being experienced. In all cases, flushing with pure oxygen for several breaths, as the uterus relaxes, is essential, to fortify both the mother’s and fetus’ tissues for the next contraction, when placental oxygen exchange will be reduced by the narrowing of the uterine sinuses and compression of the cord. In addition to observation of maternal color, it is wise to have a means for the anesthetist to observe constantly any slowing of the fetal heart rate. A heavy stethoscope bell to be taped over the site of fetal heart sounds, and having tubing long enough to reach to the head of the delivery table has been described’ for such a purpose. Slowing of the fetal heart, regardless of cause and time, should be the signal to increase the mother’s oxygen intake immediately. The other gaseous anesthetics may be, and are, used in a similar fashion. However, nitrous oxide is pleasant and noninflammable, while
84
AMERICA?;
.JOT’RNAI,
OF
OBSTETRICS
AND
GYNECOLOGP
ethylene has an unpleasant odor Ibat m;\y lead to llilllscil, and is infnmrnahle. Its potency is only slightly more than that. of nit,rous oxide? so little is gained in oxygelration. ( ‘~~clopropanc offers possibilities of unlimited oxygenation, and is pleasant, but it tocr is ii~flamruable, and its very potency makes it easy to “overshoot the nmrk,” prodnc.ing a diminution in uterine contractions. Of the. volatile liquids, ethyl ether is most commonly used, but all too often eit,her ineffectually or to the point of actual anesthesia, lvitb reduction of uterine contract,ions. The safety factor is great, and it,s slowness to take effect may be no drawback where the pain of contraction is slow in developing to intolerable levels. Where pain is explosive, It is almosi useless, unless a state of near-anesthesia is mailltained constantly. ITsed this way. an increase in nausea) operative interference and fetal apnea, is to be expected. Fetal apnea is rare \vith nitrous oxide a,lont. nausea is uncommon, and operative interference minimal. Chloroform and vinyl ether come closest t,o duplicating the action of nitrous oxide, but. the hazards of their use are many and well known. Liver damage is the most feared, but cardiac effects are more frequent and probably quite as dangerous. Other inhalation agents have not received adequate trial as yet-. When there is need for further analgesia or full anesthesia at the moment. of expulsion or extra&on of the fetus, nitrous oxide-oxygen Thorough procaine infiltration of the perialone is usually inadequate. neum, or the addition of small nmount~s of ether to the breathing bag arc the safest supplementa.tion.
Summary The obliterat,ion of the pain element of labor contractions is readily accomplished without, loss of the patient’s cooperation, and without interference with the strength of contractions, or danger to the fetus. Nitrous oxide, combined with oxygen inhalations and supplemented during expulsion, has been found adequate and safe in the hands of are available almany. It, and the apparatus for its administration most universally no-w, and personnel who know its use are much more plentiful than for the more complicated procedures frequently a& vacated.*
Reference 1. Waters, R. M., and Harris, in Tdabor, Am. a. Surg. *Papers
by
Drs.
Buxbaum.
.J. W.: Factors Influencing 48: 129-131, 1940. Fitweralrl,
Thomson
ant1
the Safety Brown,
and
of Pain Menget%
Relief follow.
AND ANESTHESIA FOR OBSTETRICS, INHALATION METHODS” CONROY,
CAPT.,
M.C., A. U.
S., CHICAGO,
ILL.
T
HE problems of pain relief in labor by inhalation methods have been obscured many times by the emphasis usually placed on actual drugs and apparatus. It would seem more fruitful to consider what distresses and disturbances that delivery causes mother and fetus, and what degree of narcosis will decrease or eliminate these undesirable phases of an otherwise physiologic process. With these in mind, one could then marshal drugs, methods and skills to reach the desired effects. The average primipara of these civilized days is unfortunately encouraged in her fear of an unknown experience, by the careless use of the word “pains” by her friends, mother and doctor. She does experience “labor” in its simplest meanin g, but unlike her primitive sister, her work is attended by varying degrees of real pain. This distress must not be confused with the underlying contractions of the uterus. Means are in existence to eliminate the pain without markedly affecting the uterine contractions, just as pain in any muscle may be alleviated by drugs, and without loss of consciousness. The first step, then will be to divorce her from the fallacious and harmful idea that she must be relieved of either consciousness or memory of the birth process in. order to undergo it jn any degree of comfort. Not till she understands that there can be consciousness and memory of labor without distress, will we eliminate some of the hazards of overuse of drugs. Too much narcosis, whether from nonvolatiIe or volatile agents, leads to fetal respiratory embarrassment, and to weakening of the uterine contractions. We may use light hypnosis with nonvolatile drugs like the barbiturates, scopolamine and paraldehyde. In quite moderate dosage, these induce a state of mental relaxation which enables us to gain the apprehensive mother’s confidence. We must, if possible, convince her that freedom from pain is obtainable while she consciously assists in the “work” that her uterus does. Even where we later fail to achieve analgesia, we may help her tolerate some pain if she has the knowledge that possible harm to her baby is being avoided. The term analgesia is literally used here, not as an improper substitute for the word amnesia. A patient who is in a deep sleep, and is aroused to wild activity by pain cannot be said to be freed of pain. To call this effect analgesia is misleading to ourselves, because safe doses of barbiturates and similar drugs are not analgesic, that is, they do not eliminate pain. *Read
.xt a meeting
of the Chicago
Gynecological
81
Society,
Oct.
15, 1943.
82
AMERICAN
JOURNAI,
Oh’ OBSTETRICS
AND
GYNECOLOGY
Having obtained t,he mother’s confidence before her labor contractions have acquired any element of intolerable pain, we must next watch for the degree and character of what true pain does accompa.ny the individual contractions as their amplitude increases. During the first stage and early second stage, the tolerance to pain may be greater than normal, due to the light hypnosis already mentioned, and some will be willing to fortify it by small doses of opiates. If the pain factor increases rapidly in severity, we must turn quickly to safer methods before confidence in us is lost. It. is excellent practice to observe the rapidity of onset, severity, and duration of the pain factor of each contraction, as soon as labor becomes painful enough to require stronger measures. (See Fig. 1.) A hand on the uterus? and the sound of the patient’s breathing and her outcries will tell us quickly whether pain comes early or late in t.he contraction, how severe it is, and how persistent. Since for each subject, the pain element will usually parallel t,he nature of the uterine contraction, it suffices to make a mental graph of contraction alone.
Fig. l.-Types of contraction pain. prolonged perception of pain; 0, late, perception ; E, pain-free contraction.
A., Early,
brief
pain
brief perception of pain ; B, early, perception; D, late, prolonged pain
Regardless of the inhalation agent used, the principle is the same. We must counteract the pain as rapidly as it builds up, without serious interference to the uterine contraction or hazard to the fetus. If the mother experiences severe pain almost simultaneously with the onset of the contraction, our efforts must be vigorous and swift. If the pain appears late, we content ourselves with the administration of oxygen till pain does appear. If pain is severe or persistent, we are taxed to provide enough pain relief to keep the mother from panicky ineffectuality. For obstetrical analgesia, nitrous oxide remains our best weapon. Even the tyro will obtain fair results, and with safety, if the color of the patient is kept reasonably pink for the comparatively short time of each contraction, and if overoxygenation is achieved immediately after each contraction. Nitrous oxide may give t,he desired resu1t.s with as low a concentration as 50 per cent where the pain element is minor, and may be used in its pure form for the brief and violently
CONROY
:
ANALGESIA
AND
ANESTHESIA,
INHALATION
METHODS
83
painful contractions occasionally seen. (The lungs and tissues do have a small oxygen reserve.) When commencing to use nitrous oxide, it is wise to give it liberally, even to complete anesthesia, during one or two contractions, to fortify the patient’s confidence in our ability to spare her distress. Using our mental graph of the character of pain, we then modify the gas mixture for each subsequent contraction. If the peak of pain is reached early, the mother is instructed not to delay in asking for the gas, the instant she feels the uterus begin to contract. Better still, if the anesthetist is closely observing the abdomen manually, the first hardening of the uterus is a warning to start With the breathing bag already full with administration immediately. 70 per cent to 100 per cent nitrous oxide, and the valves and gas flow arranged so that all of each expiration is spilled into the outside air, the face piece is applied and the patient instructed to take two maximal inhalations as quickly as she is able. This gives a rapid displacement of the iuert nitrogen from the lungs and achieves an analgesic level of the nitrous oxide before the contraction reaches it,s peak. As the second breath is being taken, the woman is instructed to hold that breath, and strain as if at stool. She will do this effectively once she is confident such activity will be relatively painless. If we know from previous observa,tion that the contraction is short-lived, the breathing bag may be flushed now with pure oxygen. If it is going to be prolongedly painful, the gas is reduced to a level of 85 per cent or less, so that subsequent inhalations will be carrying in adequate oxygen. Where the onset of pain perception is preceded by a period of painless contraction, three or even four rapid, full breaths of 70 per cent to 90 per cent nitrous oxide will be effective and safe. The longer time will a.llow for more complete flushing out of the inert nitrogen, but over such a period, the oxygen reserves would be depleted, hence the need for its addition to the gas. Subsequent gas flows for the expulsion efforts to follow will be adjusted to the anesthetist’s mental picture of the curve of pain being experienced. In all cases, flushing with pure oxygen for several breaths, as the uterus relaxes, is essential, to fortify both the mother’s and fetus’ tissues for the next contraction, when placental oxygen exchange will be reduced by the narrowing of the uterine sinuses and compression of the cord. In addition to observation of maternal color, it is wise to have a means for the anesthetist to observe constantly any slowing of the fetal heart rate. A heavy stethoscope bell to be taped over the site of fetal heart sounds, and having tubing long enough to reach to the head of the delivery table has been described’ for such a purpose. Slowing of the fetal heart, regardless of cause and time, should be the signal to increase the mother’s oxygen intake immediately. The other gaseous anesthetics may be, and are, used in a similar fashion. However, nitrous oxide is pleasant and noninflammable, while
84
AMERICA?;
.JOT’RNAI,
OF
OBSTETRICS
AND
GYNECOLOGP
ethylene has an unpleasant odor Ibat m;\y lead to llilllscil, and is infnmrnahle. Its potency is only slightly more than that. of nit,rous oxide? so little is gained in oxygelration. ( ‘~~clopropanc offers possibilities of unlimited oxygenation, and is pleasant, but it tocr is ii~flamruable, and its very potency makes it easy to “overshoot the nmrk,” prodnc.ing a diminution in uterine contractions. Of the. volatile liquids, ethyl ether is most commonly used, but all too often eit,her ineffectually or to the point of actual anesthesia, lvitb reduction of uterine contract,ions. The safety factor is great, and it,s slowness to take effect may be no drawback where the pain of contraction is slow in developing to intolerable levels. Where pain is explosive, It is almosi useless, unless a state of near-anesthesia is mailltained constantly. ITsed this way. an increase in nausea) operative interference and fetal apnea, is to be expected. Fetal apnea is rare \vith nitrous oxide a,lont. nausea is uncommon, and operative interference minimal. Chloroform and vinyl ether come closest t,o duplicating the action of nitrous oxide, but. the hazards of their use are many and well known. Liver damage is the most feared, but cardiac effects are more frequent and probably quite as dangerous. Other inhalation agents have not received adequate trial as yet-. When there is need for further analgesia or full anesthesia at the moment. of expulsion or extra&on of the fetus, nitrous oxide-oxygen Thorough procaine infiltration of the perialone is usually inadequate. neum, or the addition of small nmount~s of ether to the breathing bag arc the safest supplementa.tion.
Summary The obliterat,ion of the pain element of labor contractions is readily accomplished without, loss of the patient’s cooperation, and without interference with the strength of contractions, or danger to the fetus. Nitrous oxide, combined with oxygen inhalations and supplemented during expulsion, has been found adequate and safe in the hands of are available almany. It, and the apparatus for its administration most universally no-w, and personnel who know its use are much more plentiful than for the more complicated procedures frequently a& vacated.*
Reference 1. Waters, R. M., and Harris, in Tdabor, Am. a. Surg. *Papers
by
Drs.
Buxbaum.
.J. W.: Factors Influencing 48: 129-131, 1940. Fitweralrl,
Thomson
ant1
the Safety Brown,
and
of Pain Menget%
Relief follow.