Analgesia epidural

Epidural Analgesia for Labor and Delivery
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 unableto 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.
The Clinical Problem
For most women labor causes severe pain, similar in degree to that causedby complex regional pain syndromes or the amputation of a finger.
Although severe pain is not life-threatening in healthy parturient women, it can have neuropsychological consequences. Postnatal depression may be more common when analgesia is not used, and pain during labor has been correlated with the development of post-traumatic stress disorder. In addition, one study suggested that theimpairment of cognitive function in the postpartum period can be mitigated by the use of any form of intrapartum analgesia. Men are also affected by severe labor pain. A survey of first-time fathers showed that the men whose partners received an epidural felt three times as helpful and involved during labor and delivery and had less anxiety and stress, as compared with men whose partners did not receivean epidural.
Pathophysiology and the Effect of Therapy
The 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. Later in labor, perineal stretching transmits painful stimuli through the pudendal nerve and sacral nerves S2 through S4. The maternal stress response can leadto increased release of corticotrophin and cortisol. 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% and decreased uterine blood flow by 50%. Catecholamine release is also accompanied by increased maternal cardiac output, systemic vascularresistance, and oxygen consumption. For women with preexisting cardiac or respiratory compromise, such increases may be difficult to sustain
Epidural analgesia for labor and delivery involves the injection of a local anesthetic agent as lidocaine or bupivacaine and an opioid analgesic agent like morphine or fentanyl into the lumbar epidural space. The injected agent gradually diffuses across thedura into the subarachnoid space, where it acts primarily on the spinal nerve roots and to a lesser degree on the spinal cord and paravertebral nerves. In spinal analgesia, which is often combined with epidural analgesia, the analgesic agent is injected directly into the subarachnoid space, resulting in a more rapid onset of effect.
Adverse Effects
There has been a good deal of concern, basedon older observational studies, that women who have epidural analgesia during labor are more likely to require a cesarean delivery. However, the preponderance of evidence now supports the conclusion that the use of epidural analgesia during labor does not have a significant effect on rates of cesarean delivery. A Cochrane review of 20 trials involving a total of 6534 women estimated that therelative risk of cesarean delivery with epidural analgesia as compared with other methods or with no analgesia was 1.07 (95% confidence interval, 0.93 to 1.23). Epidural analgesia does increase the duration of the second stage of labor by 15 to 30 minutes and may increase the rate of instrument-assisted vaginal deliveries as well as that of oxytocin administration. Clinicians and patients have also...