Pain Relief during Labor
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《新英格兰医药杂志》
The pain of childbirth is arguably one of the most severe types of pain a woman will endure in her lifetime. Relief of the pain of childbirth has always been controversial. Misinterpretations of biblical scripture ("In sorrow thou shalt bring forth children") resulted in centuries of denial of pain relief, as clergy insisted that suffering in labor was consistent with divine intent.1 Fifteenth-century midwives were burned at the stake for offering pain relief during labor.2 The modern era of anesthetics began with the first demonstration of inhalational anesthesia during surgery at the Massachusetts General Hospital in 1846; a few months later, James Young Simpson, a Scottish obstetrician, administered ether to a woman during childbirth. The strong appeal of anesthesia for relieving childbirth pain and the consumer demand for it rapidly ascended to the highest levels of society. In 1853, Britain's Queen Victoria received chloroform during the birth of her eighth child, Prince Leopold.3 Nonetheless, concerned about the possible adverse effects of this new method, Simpson wrote, "It will be necessary to ascertain anesthesia's precise effect, both upon the action of the uterus and on the assistant abdominal muscles; and its influence, if any, upon the child."4 This quote is remarkable, given that today, more than a century and a half later, the possible effects of anesthesia on the progress of labor and on the neonate continue to concern anesthesiologists, obstetricians, and patients.
There are nearly 4 million births in the United States each year, and approximately 60 percent of women giving birth receive epidural analgesia.5 Retrospective studies have consistently demonstrated a strong association between the use of epidural analgesia and an elevated rate of cesarean delivery, particularly when epidural analgesia is used in early labor. These findings have been difficult to interpret, however. A possible explanation is selection bias: perhaps women with difficult or dysfunctional labor, who are more likely than women experiencing an easy labor to have a cesarean delivery, are also more likely to choose epidural analgesia. Well-conducted studies indicate that the degree of pain experienced during early labor is greater among women who ultimately go on to have cesarean deliveries than among those who deliver vaginally.6,7,8
It is also plausible, however, that epidural analgesia may truly increase the likelihood that cesarean delivery will be required. Lower-body muscle weakness resulting from epidural analgesia may inhibit normal fetal rotation and descent and maternal expulsive efforts, particularly when the epidural agent is administered in early labor. Some retrospective observational studies have shown a higher incidence of fetal malpresentations among women who received an epidural analgesic during labor, particularly early labor5; a possible explanation is that the early intervention may have interfered with the normal mechanisms of labor.
To address these concerns, modern-day epidural analgesia administered during labor consists of low doses of local anesthetic and adjuvant medications, allowing adequate pain relief without clinically significant effects on motor function.5 Recently, the use of combined spinal–epidural analgesia (which involves the injection of minimal doses of medications directly into the spinal, rather than epidural, space) has facilitated profound analgesia without concomitant motor block; moreover, the ability of women to ambulate while receiving this method of pain relief has added even greater flexibility in analgesic options. Current approaches to the individualization of treatment according to a woman's pain level and stage of labor have improved obstetrical outcomes and maternal satisfaction. For example, the incidence of instrumental vaginal delivery has been shown to be lower with the use of low-dose epidural infusions and combined spinal–epidural administration of analgesic agents than it is with more traditional analgesic techniques.9
Over the past decade, several randomized, controlled trials and sentinel-event studies (i.e., studies assessing obstetrical outcomes in settings in which there has been a large increase in the use of epidural analgesia over a short period of time, while rates of other interventions have remained stable), collectively including many thousands of patients, have convincingly demonstrated that regional analgesia during labor, as compared with other methods of pharmacologic pain relief, does not necessarily increase the risk of cesarean delivery.10,11 However, there is still a concern that the initiation of regional analgesia in early labor will result in a higher incidence of operative delivery than its initiation during later stages of labor.
In this issue of the Journal, Wong et al. report the results of a large, randomized, controlled trial in which intrathecal administration of an opioid by a combined spinal–epidural technique at the first request for pain relief during labor was compared with parenteral administration of opioid analgesia at the first request for pain relief, with deferral of regional analgesia.12 This adequately powered investigation improves on previous studies, in that patients randomly assigned to "early" regional analgesia had the combined spinal–epidural analgesia administered truly early in labor, in most cases at or near a cervical dilatation of 2.0 cm, whereas most of the patients assigned to receive regional analgesia after a delay had a cervical dilatation at or near 5.0 cm when it was initiated. The results are quite reassuring; no significant differences were observed between the two groups in the rates of cesarean delivery and instrumental vaginal delivery. In fact, the authors noted that progression of labor was more rapid in the group randomly assigned to early regional analgesia — a finding that has been noted by some investigators to be associated with combined spinal–epidural analgesia, as compared with conventional epidural techniques.5
An additional finding was that Apgar scores at one minute were lower in the neonates whose mothers had been given systemic opioid analgesia, even though the agent was administered many hours before birth. One might argue that this finding is inconsequential, since the five-minute Apgar scores did not differ significantly between the groups and since the umbilical-cord blood-gas levels were normal in both groups. Nonetheless, systemic narcotics readily cross the placental barrier and often cause maternal sedation and nausea. A recent consensus statement from the American College of Obstetricians and Gynecologists underscores the relative benefits of neuraxial over parenteral analgesia in "allowing for an alert participating woman and an alert neonate."13
Why is the study by Wong et al. important? The common belief in many maternity units that a laboring woman is "not ready yet" for epidural analgesia forces women to endure hours of extra pain, often while they receive less-than-adequate alternative methods of pain relief, such as systemic narcotics, with a concomitant increase in side effects for both themselves and their newborns. As noted by the American College of Obstetricians and Gynecologists, "There is no other circumstance where it is considered acceptable for an individual to experience untreated severe pain, amenable to safe intervention, while under a physician's care. In the absence of a medical contraindication, maternal request is sufficient medical indication for pain relief during labor."13 Moreover, the Joint Commission on Accreditation of Healthcare Organizations recently declared pain to be the "fifth vital sign," thus underscoring the importance of proper and timely pain management.14
Women in labor deserve to have as many options as possible at their disposal to ensure a safe and satisfying birth experience both for themselves and for their infants. For women who wish to experience an unmedicated (i.e., natural) childbirth, an increasingly wide variety of nonpharmacologic methods of support are available.15 However, for those who experience severe pain in early labor and desire analgesia, the findings reported by Wong et al. make it clear that safe, effective pain relief with the use of regional anesthetics should not be withheld simply because an arbitrary degree of cervical dilatation has not yet been achieved.
Source Information
From Brigham and Women's Hospital, Boston.
References
Cohen J. Doctor James Young Simpson, Rabbi Abraham De Sola, and Genesis chapter 3, verse 16. Obstet Gynecol 1996;88:895-898.
Lurie S. Euphemia Maclean, Agnes Sampson, and pain relief during labour in 16th century Edinburgh. Anaesthesia 2004;59:834-835.
Caton D. What a blessing she had chloroform: the medical and social response to the pain of childbirth from 1800 to the present. New Haven, Conn.: Yale University Press, 1999.
Simpson W. The works of JY Simpson. Edinburgh: Adam and Charles Black, 1871.
Eltzschig HK, Lieberman ES, Camann WR. Regional anesthesia and analgesia for labor and delivery. N Engl J Med 2003;348:319-332.
Hess PE, Pratt SD, Soni AK, Sarna MC, Oriol NE. An association between severe labor pain and cesarean delivery. Anesth Analg 2000;90:881-886.
Panni MK, Segal S. Local anesthetic requirements are greater in dystocia than in normal labor. Anesthesiology 2003;98:957-963.
Alexander JM, Sharma SK, McIntire DD, Wiley J, Leveno KJ. Intensity of labor pain and cesarean delivery. Anesth Analg 2001;92:1524-1528.
Comparative Obstetric Mobile Epidural Trial (COMET) Study Group UK. Effect of low-dose mobile versus traditional techniques on mode of delivery: a randomised controlled trial. Lancet 2001;358:19-23.
Sharma SK, McIntire DD, Wiley J, Leveno KJ. Labor analgesia and cesarean delivery: an individual patient meta-analysis of nulliparous women. Anesthesiology 2004;100:142-148.
Segal S, Su M, Gilbert P. The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis. Am J Obstet Gynecol 2000;183:974-978.
Wong CA, Scavone BM, Peaceman AM, et al. The risk of cesarean delivery with neuraxial analgesia given early versus late in labor. N Engl J Med 2005;352:655-665.
Pain relief during labor. ACOG committee opinion no. 295. Washington, D.C.: American College of Obstetricians and Gynecologists, July 2004.
Improving the quality of pain management through measurement and action. Oakbrook Terrace, Ill.: Joint Commission on Accreditation of Healthcare Organizations, March 2003 (monograph). (Accessed January 28, 2005, at http://www.jcaho.org/news+room/health+care+issues/pain+mono_jc.pdf.)
Simkin PP, O'Hara M. Nonpharmacologic relief of pain during labor: systematic review of five methods. Am J Obstet Gynecol 2002;186:Suppl:S131-S159.(William Camann, M.D.)
There are nearly 4 million births in the United States each year, and approximately 60 percent of women giving birth receive epidural analgesia.5 Retrospective studies have consistently demonstrated a strong association between the use of epidural analgesia and an elevated rate of cesarean delivery, particularly when epidural analgesia is used in early labor. These findings have been difficult to interpret, however. A possible explanation is selection bias: perhaps women with difficult or dysfunctional labor, who are more likely than women experiencing an easy labor to have a cesarean delivery, are also more likely to choose epidural analgesia. Well-conducted studies indicate that the degree of pain experienced during early labor is greater among women who ultimately go on to have cesarean deliveries than among those who deliver vaginally.6,7,8
It is also plausible, however, that epidural analgesia may truly increase the likelihood that cesarean delivery will be required. Lower-body muscle weakness resulting from epidural analgesia may inhibit normal fetal rotation and descent and maternal expulsive efforts, particularly when the epidural agent is administered in early labor. Some retrospective observational studies have shown a higher incidence of fetal malpresentations among women who received an epidural analgesic during labor, particularly early labor5; a possible explanation is that the early intervention may have interfered with the normal mechanisms of labor.
To address these concerns, modern-day epidural analgesia administered during labor consists of low doses of local anesthetic and adjuvant medications, allowing adequate pain relief without clinically significant effects on motor function.5 Recently, the use of combined spinal–epidural analgesia (which involves the injection of minimal doses of medications directly into the spinal, rather than epidural, space) has facilitated profound analgesia without concomitant motor block; moreover, the ability of women to ambulate while receiving this method of pain relief has added even greater flexibility in analgesic options. Current approaches to the individualization of treatment according to a woman's pain level and stage of labor have improved obstetrical outcomes and maternal satisfaction. For example, the incidence of instrumental vaginal delivery has been shown to be lower with the use of low-dose epidural infusions and combined spinal–epidural administration of analgesic agents than it is with more traditional analgesic techniques.9
Over the past decade, several randomized, controlled trials and sentinel-event studies (i.e., studies assessing obstetrical outcomes in settings in which there has been a large increase in the use of epidural analgesia over a short period of time, while rates of other interventions have remained stable), collectively including many thousands of patients, have convincingly demonstrated that regional analgesia during labor, as compared with other methods of pharmacologic pain relief, does not necessarily increase the risk of cesarean delivery.10,11 However, there is still a concern that the initiation of regional analgesia in early labor will result in a higher incidence of operative delivery than its initiation during later stages of labor.
In this issue of the Journal, Wong et al. report the results of a large, randomized, controlled trial in which intrathecal administration of an opioid by a combined spinal–epidural technique at the first request for pain relief during labor was compared with parenteral administration of opioid analgesia at the first request for pain relief, with deferral of regional analgesia.12 This adequately powered investigation improves on previous studies, in that patients randomly assigned to "early" regional analgesia had the combined spinal–epidural analgesia administered truly early in labor, in most cases at or near a cervical dilatation of 2.0 cm, whereas most of the patients assigned to receive regional analgesia after a delay had a cervical dilatation at or near 5.0 cm when it was initiated. The results are quite reassuring; no significant differences were observed between the two groups in the rates of cesarean delivery and instrumental vaginal delivery. In fact, the authors noted that progression of labor was more rapid in the group randomly assigned to early regional analgesia — a finding that has been noted by some investigators to be associated with combined spinal–epidural analgesia, as compared with conventional epidural techniques.5
An additional finding was that Apgar scores at one minute were lower in the neonates whose mothers had been given systemic opioid analgesia, even though the agent was administered many hours before birth. One might argue that this finding is inconsequential, since the five-minute Apgar scores did not differ significantly between the groups and since the umbilical-cord blood-gas levels were normal in both groups. Nonetheless, systemic narcotics readily cross the placental barrier and often cause maternal sedation and nausea. A recent consensus statement from the American College of Obstetricians and Gynecologists underscores the relative benefits of neuraxial over parenteral analgesia in "allowing for an alert participating woman and an alert neonate."13
Why is the study by Wong et al. important? The common belief in many maternity units that a laboring woman is "not ready yet" for epidural analgesia forces women to endure hours of extra pain, often while they receive less-than-adequate alternative methods of pain relief, such as systemic narcotics, with a concomitant increase in side effects for both themselves and their newborns. As noted by the American College of Obstetricians and Gynecologists, "There is no other circumstance where it is considered acceptable for an individual to experience untreated severe pain, amenable to safe intervention, while under a physician's care. In the absence of a medical contraindication, maternal request is sufficient medical indication for pain relief during labor."13 Moreover, the Joint Commission on Accreditation of Healthcare Organizations recently declared pain to be the "fifth vital sign," thus underscoring the importance of proper and timely pain management.14
Women in labor deserve to have as many options as possible at their disposal to ensure a safe and satisfying birth experience both for themselves and for their infants. For women who wish to experience an unmedicated (i.e., natural) childbirth, an increasingly wide variety of nonpharmacologic methods of support are available.15 However, for those who experience severe pain in early labor and desire analgesia, the findings reported by Wong et al. make it clear that safe, effective pain relief with the use of regional anesthetics should not be withheld simply because an arbitrary degree of cervical dilatation has not yet been achieved.
Source Information
From Brigham and Women's Hospital, Boston.
References
Cohen J. Doctor James Young Simpson, Rabbi Abraham De Sola, and Genesis chapter 3, verse 16. Obstet Gynecol 1996;88:895-898.
Lurie S. Euphemia Maclean, Agnes Sampson, and pain relief during labour in 16th century Edinburgh. Anaesthesia 2004;59:834-835.
Caton D. What a blessing she had chloroform: the medical and social response to the pain of childbirth from 1800 to the present. New Haven, Conn.: Yale University Press, 1999.
Simpson W. The works of JY Simpson. Edinburgh: Adam and Charles Black, 1871.
Eltzschig HK, Lieberman ES, Camann WR. Regional anesthesia and analgesia for labor and delivery. N Engl J Med 2003;348:319-332.
Hess PE, Pratt SD, Soni AK, Sarna MC, Oriol NE. An association between severe labor pain and cesarean delivery. Anesth Analg 2000;90:881-886.
Panni MK, Segal S. Local anesthetic requirements are greater in dystocia than in normal labor. Anesthesiology 2003;98:957-963.
Alexander JM, Sharma SK, McIntire DD, Wiley J, Leveno KJ. Intensity of labor pain and cesarean delivery. Anesth Analg 2001;92:1524-1528.
Comparative Obstetric Mobile Epidural Trial (COMET) Study Group UK. Effect of low-dose mobile versus traditional techniques on mode of delivery: a randomised controlled trial. Lancet 2001;358:19-23.
Sharma SK, McIntire DD, Wiley J, Leveno KJ. Labor analgesia and cesarean delivery: an individual patient meta-analysis of nulliparous women. Anesthesiology 2004;100:142-148.
Segal S, Su M, Gilbert P. The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis. Am J Obstet Gynecol 2000;183:974-978.
Wong CA, Scavone BM, Peaceman AM, et al. The risk of cesarean delivery with neuraxial analgesia given early versus late in labor. N Engl J Med 2005;352:655-665.
Pain relief during labor. ACOG committee opinion no. 295. Washington, D.C.: American College of Obstetricians and Gynecologists, July 2004.
Improving the quality of pain management through measurement and action. Oakbrook Terrace, Ill.: Joint Commission on Accreditation of Healthcare Organizations, March 2003 (monograph). (Accessed January 28, 2005, at http://www.jcaho.org/news+room/health+care+issues/pain+mono_jc.pdf.)
Simkin PP, O'Hara M. Nonpharmacologic relief of pain during labor: systematic review of five methods. Am J Obstet Gynecol 2002;186:Suppl:S131-S159.(William Camann, M.D.)