clinical therapeuticsT h e ne w e ngl a nd jou r na l o f m e dic i ne n engl j med 362;16 nejm.org april 22, 2010
1503This Journal feature begins with a case vignette that includes a therapeutic recommendation. A discussion of the clinical problem and the mechanism of benefit of this form of therapy follows. Major clinical studies, the clinical use of this therapy, and potential adverse effects are reviewed. Relevant formal guidelines, if they exist, are presented. The article ends with the author's clinical recommendations.A 30-year-old nulliparous woman at 39 weeks' gestation is undergoing induction of labor because of premature rupture of membranes. She is currently receiving an oxytocin infusion, and her cervical dilatation is 1 cm. Her obstetrician has ordered intermittent intravenous administration of fentanyl for pain relief, but she feels nauseated, has been unable to rest, and describes her pain as 9 on a scale of 10. The patient strongly prefers a vaginal delivery to cesarean delivery and is concerned that epidural analgesia may alter the progress of labor. The anesthesiologist is consulted to discuss the use of epidural analgesia during labor and delivery.
Pathoph ysiol ogy a nd the Effec t of Ther a pyThe pain of labor, caused by uterine contractions and cervical dilatation, is transmitted through visceral afferent (sympathetic) nerves entering the spinal cord from T10 through L1 (Fig. 1). Later in labor, perineal stretching transmits painful stimuli through the pudendal nerve and sacral nerves S2 through S4. The maternal stress response can lead to increased release of corticotropin, cortisol, norepinephrine, β-endorphins, and epinephrine. Epinephrine can have relaxant effects on the uterus that may prolong labor. Studies in healthy pregnant ewes showed that psychological stress or pain increased maternal plasma levels of norepinephrine by 25%
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