Intrathecal analgesia and the cesarean rate

A POEM in your June issue (“Early intrathecal analgesia does not increase cesarean sections,” J Fam Pract 2005; 54:500) concludes that intrathecal analgesia does not increase the cesarean section rate. The reported New England Journal of Medicine study was of “neuraxial analgesia,” an obfuscating term. The author,¹ the editorialist,² and the press reported that women need not worry that an early epidural will lead to an increased likelihood of cesarean section.

This claim is unjustified by the research reported. This trial was not about early epidural use. It was about 2 methods of helping women with the pain of early labor. In the so-called epidural arm, at first request for analgesia, women got intrathecal fentanyl; in the narcotic arm, hydromorphone. And at that point women in both arms already had a 75% utilization rate of oxytocin augmentation—so high as to be non-generalizable to usual settings. On second request for pain relief, two thirds of the women in both arms were ≥4 cm dilated or in the active phase of labor. At this advanced state, in the intrathecal-“epidural” arm they received a low-dose epidural. In the narcotic arm, they got hydromorphone intramuscularly. This trial is misleading because it fails to emphasize that most women in were in the active phase of labor at randomization. This study, like the others randomizing late,^3,4 has shown only that when women’s early or latent phase pain is managed with intrathecal narcotic or other pharmacological or nonpharmacological means, an epidural in the active phase of labor does not increase the cesarean section rate. The role of intrathecal analgesia or early epidurals in contributing to cesarean increase has yet to be studied in a controlled trial, though when early epidurals are studied as a separate stratum from within the Cochrane meta-analysis of epidural vs narcotic,³ epidural given early (<4 cm) increase the cesarean section rate by an odds ratio of 2.59 (95% confidence interval, 1.29–5.23).

Michael C. Klein, MD
Professor Emeritus of Family Practice and Pediatrics,
Senior Scientist Emeritus, BC Research Institute for Children’s and Women’s Health