BACKGROUND: Safe and effective labor analgesia is an important part of obstetric care. Intrathecally injected narcotics (ITN) are an effective alternative to epidural anesthesia, and are perceived less likely to interfere with the course and outcome of labor. Data on their effects, however, are sparse and contradictory.
METHODS: Our retrospective study compared labor length, oxytocin use, delivery type, maternal side effects, and neonatal outcomes among women who received ITN (n=100) and a group who received intravenous narcotics or no analgesia during labor (n=100). We randomly sampled medical records with stratification for parity and collected data through systematic chart review.
RESULTS: Women receiving ITN were more likely to be white. They experienced longer second-stage labors (73 minutes vs 40 minutes, P=.000) and used oxytocin twice as often. These differences remained significant after controlling for potential confounding factors. ITN use was also associated with a trend toward more cesarean sections (7% vs 1%, P=.06). More of the women receiving ITN required urinary catheterization (25% vs 5%, P=.000) and experienced significant pruritus (10% vs 0%, P=.001). Neonatal outcomes were similar for both groups.
CONCLUSIONS: In our retrospective study, ITN use was associated with a significant prolongation of second-stage labor, which may be clinically relevant for women having their first child. ITN were also associated with increased oxytocin use and a trend toward more cesarean births. Whether these relationships are causal or a proxy for more difficult labors is a question for future prospective studies.
Pain management during labor and delivery is an important issue affecting both the quality of the experience and its outcome. Early attempts at anesthesia with barbiturates, intravenous narcotics, or the combination of ether, morphine, and scopolamine (known as “twilight sleep”) were all associated with major side effects for mothers and infants.1 Contemporary emphasis has been on safer, more natural methods of pain management, including childbirth training, relaxation, and support from a labor companion. Though helpful, these approaches are not sufficiently effective for the majority of patients in labor.2 Recently, postpartum depression and posttraumatic stress disorder have been linked to difficult or painful deliveries,3,4 and good analgesia has been identified as a major determinant of women’s overall satisfaction with their birthing experiences.5 The need for safe, effective relief for labor pain was acknowledged directly by the medical community in 1992 in a joint statement issued by the American College of Obstetricians and Gynecologists and the American Society of Anesthesiologists: “Labor results in severe pain for many women. There is no other circumstance where it is considered acceptable for a person to experience severe pain amenable to safe intervention, while under a physician’s care.”6
In response to the need for effective labor pain management, neuraxial (spinal) analgesia has become increasingly popular in the United States. Three techniques are currently in use: epidural anesthesia (continuous infusion of local anesthetic with or without an adjuvant narcotic), intrathecally administered narcotics (ITN), and the combined spinal-epidural approach.7-10 Of the 3, the epidural is the most established and best studied method. According to a national survey published in 1986, epidural anesthesia was used for pain management for 16% of deliveries, while there was no reported use of ITN.11 Today, epidural analgesia is used for more than 60% of nulliparous labors in large urban hospitals in the United States and Canada.12,13
ITN were adapted to obstetric practice in the early 1980s, when it was demonstrated that a single subarachnoid injection of morphine sulfate could eliminate the pain of contractions in the first stage of labor.14,15 Since the initial reports, use of ITN has achieved increasing acceptance as a simple and effective technique for labor pain management. Its potential advantages include better pain control than parenteral narcotics16 and more rapid onset of analgesia with less intervention than an epidural.17 Because ITN do not involve a local anesthetic, they do not cause the sympathetic or motor blockade commonly observed with epidural anesthesia.10,17 Women receiving ITN retain sensation and motor control of pelvic musculature and lower extremities; thus, they are able to ambulate and change positions during labor and have essentially no blunting of the urge to push in the second stage.17,18 Although recent meta-analyses have found that epidurals are associated with a prolonged second stage of labor19 and a qualified decreased incidence in spontaneous vaginal deliveries,16,19 ITN have been characterized as not interfering with the natural progress of labor.8,20
ITN have been a particularly successful addition to labor services in community or military hospitals where anesthesiology services and access to epidurals are limited.19,21,22 Our hospital’s 15-year experience with ITN also supports their role in a busy, urban teaching hospital where health maintenance organizations influence the anesthesia standard toward a simple, low cost method. Typically, more than 4000 women deliver at our hospital each year, and approximately half receive ITN for their labor pain. Fewer than 5% receive epidurals; the rest deliver with parenteral narcotics or natural childbirth.