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Am Fam Physician. 1998;57(4):640-646

to the editor: As Navy family physicians, we devote a great deal of time to the care of our pregnant patients. We therefore appreciated Drs. Stephens and Ford's1 excellent outline of the advantages and disadvantages of intrathecal narcotics compared with epidural analgesia, as well as the differences in the effectiveness of both in the first and second stages of labor. We do feel that one point in the article needs clarification, however.

Drs. Stephens and Ford write, “The relationship between epidural analgesia and rates of cesarean delivery remains controversial.”1 However, published studies actually indicate a significant increase in cesarean deliveries associated with epidural analgesia. A randomized, controlled, prospective trial conducted from 1990 to 1992 found that 25 percent of patients who received epidural analgesia required cesarean delivery, compared with 2.2 percent of those who received intravenous narcotics.2 In fact, this result was deemed so significant that after only 93 of a planned 200 patients were observed, the study was terminated because it would have been “unethical to continue randomization.”2 A meta-analysis of six studies conducted from 1989 to 1993 found significantly higher rates of cesarean deliveries under epidural analgesia in five of the six studies.3 From this literature, it seems clear that the woman undergoing labor with epidural analgesia faces a higher risk of cesarean section.

Unfortunately, there is little in the literature about the relative risks of cesarean section and operative vaginal delivery with each of the three common modes of analgesia—intrathecal narcotic analgesia, epidural analgesia and intravenous narcotic analgesia. Intrathecal narcotic analgesia is a promising tool of family-centered maternity care that warrants further research. Patient-oriented outcomes of great interest to us would be maternal and infant morbidity and mortality, risk of cesarean section and other operative interventions, quality of pain relief when compared to epidural analgesia in labor, costs and patient experience of the birth process. However, until outcomes-based studies are conducted, we can only say that intrathecal narcotic analgesia may offer a safe, effective alternative to epidural analgesia without the increased risk of cesarean section.

to the editor: We find several points in the article on intrathecal narcotics that are controversial and a few other points that could arguably result in patient death.

On page 463 the authors mention that epidural analgesia is unique in providing pain relief that blocks both visceral and somatic pain stimuli. The epidural is not unique, however; a somatic, visceral and sympathetic blockade also occurs with a subarachnoid block. The innervation of the birth process involves the sacral somatic nerves of the perineum, sympathetic afferent T10 through L1 for pain of uterine contractions and sympathetic efferent T6 through T10 to trigger and maintain uterine contractions. The early regional anesthesia for obstetrics was aimed toward getting anesthesia from T10 caudally and avoiding anesthesia above T10, to maintain good contractions. This was the principle of the “saddle block” spinal; sensory level to the umbilicus gave a painless delivery yet maintained contractions and the mother's ability to push and strain for a vaginal delivery.

On page 465 the article says in both Table 1 and in the text that a prolongation of labor can occur with continuous epidural placement. This statement is not proven, is extremely controversial and was debated recently at a meeting of the Society of Obstetric Anesthesia and Perinatology by Dr. David Chestnut (a board certified OB/GYN and anesthesiologist).1

Under the subtitle “Combined Spinal-Epidural Analgesia,” the authors do not mention that the epidural catheter needs to be tested. The epidural catheter must be tested prior to starting a continuous epidural infusion or before performing epidural intermittent bolus. Any epidural catheter has the potential for migration, especially when the dura is punctured, as in the combined spinal-epidural technique.

Under the subtitle “Intrathecal Narcotics,” the statement “any woman who has reached the active phase of labor is a potential candidate for intrathecal narcotics” is inaccurate. A woman who is morbidly obese with a potential for difficult intubation is not a candidate because of the risk of respiratory depression. On the subject of respiratory depression, Table 2 has the dose of sufentanil (Sufenta) as 7.5 to 12.5 μg. The anesthesia literature has several case reports24 that show 10 μg of sufentanil given intrathecally to cause maternal respiratory depression and a decrease in fetal heart rate.

Although the article says that no specific position is required after application of intrathecal narcotics, it should be emphasized that the supine position should be avoided, due to aortocaval compression leading to maternal hypotension syndrome, a decrease in uteroplacental blood flow and a possible decrease in fetal heart rate. A left uterine displacement is recommended to prevent maternal-hypotension syndrome.

in reply: The comments of Drs. Sheldon and Taylor and Drs. Miller and Jacoby are appreciated. Again, the aim of the treatise on intrathecal narcotics was not to settle the debate about epidural anesthesia and mode of delivery. While the studies cited by Drs. Sheldon and Taylor suggest an increase in cesarean deliveries associated with epidural anesthesia, there is ample data to refute this view.1,2 Additional outcomes-based data implicated with the use of epidural anesthesia include increased rates of maternal fever and intrapartum hemorrhage.3 Data have demonstrated a normal increase in maternal temperature following administration of epidural anesthetic, particularly in primiparous patients.4 This physiologic hyperthermia is not associated with an infectious process, and if interpreted in isolation, may lead to inappropriate use of antibiotic therapy.

An important issue raised by Drs. Sheldon and Taylor is the lack of prospective data delineating the association, if any, between the use of intrathecal narcotics and mode of delivery. To date, no such data has been published.

In regard to the letter from Drs. Miller and Jacoby, we would like to offer several points of clarification. The focus on intrathecal narcotic application was intended to broaden physician awareness, not to promote unqualified use of the procedure.

The saddle block described in the letter uses subarachnoid anesthetic agents rather than pure narcotics. The use of epidural or subarachnoid anesthetics should be attempted only with proper training.

The issue of prolongation of labor, increased instrumented or operative delivery rates and increased incidence of maternal fever with the application of epidural anesthesia is controversial, and will remain so pending definitive research data. Studies have indeed shown a prolongation of labor subsequent to epidural use.5 Other studies have shown no relationship between length of labor and epidural anesthesia.2 Physicians caring for laboring patients need to be aware of the data so that patients can make informed decisions regarding their choices of labor analgesia.

The epidural catheter used with the combined spinal-epidural technique should indeed be tested prior to infusing or bolusing epidural anesthetic agents.

Data on sufentanil dosing is taken directly from the American Society of Anesthesiologists.6 Case reports noting adverse reactions with sufentanil were appropriately referenced in the article.710 As a matter of preference, we use fentanyl at our facility because more reports of adverse reactions with sufentanil have been published.

The selection of a “morbidly obese” patient as an absolute contraindication to intrathecal narcotics is a poor one. Such a patient would potentially have complications whatever the analgesia. The selection of labor analgesia must be carefully tailored to each patient.

The procedure is typically performed in the seated or left lateral decubitus position. Following the procedure, the supine position should indeed be avoided to prevent aortocaval compression and uteroplacental compromise.

I appreciate the comments of Drs. Miller and Jacoby, as they highlight the importance of careful patient screening, meticulous counseling and patient education. Armed with such information, family physicians, obstetricians and anesthesiologists form a collaborative team to provide safe and effective comfort for laboring patients.

Email letter submissions to Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors. Letters submitted for publication in AFP must not be submitted to any other publication. Letters may be edited to meet style and space requirements.

This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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