To meet these goals, 24-hour, in-house anesthesia coverage is usually necessary. Providing such service in smaller facilities is more challenging-a problem underscored by the fact that approximately a third of all hospitals providing obstetrical care perform fewer than 500 deliveries per year. The financial burden incurred to provide 24/7 obstetrical anesthesia coverage may result in cost deicits (Bell, 2000). Compounding this burden, some third-party payers have denied reimbursement for epidural analgesia in the absence of a specific medical indication-an approach repudiated by the American College of Obstetricians and Gynecologists (2017a).
Regarding obstetricians, they should be proficient in local and pudendal analgesia. These may be administered in appropriately selected circumstances described on page 489.
Hawkins (2010) emphasized that labor pain is a highly individual response to variable stimuli that are uniquely received and interpreted (Fig.
These stimuli are modified by emotional, motivational, cognitive, social, and cultural circumstances. Labor pain caused by uterine contractions and cervical dilation is transmitted through visceral aferent sympathetic nerves entering the spinal cord from Tto through Lt. Later in labor, perineal stretching transmits painful stimuli through the pudendal nerve and sacral nerves S2 through 54' Cortical responses to pain and anxiety during labor are complex and may be inluenced by maternal expectations for childbirth, her age, preparation through education, emotional support, and other factors. Pain perception is heightened by fear and the need to move into various positions. A woman may be motivated to have a certain type of birthing experience, and these opinions will influence her judgment regarding pain management.
Maternal physiological responses to labor pain can influence maternal and fetal well-being and labor progress. For example, hyperventilation may induce hypocarbia. A greater metabolic rate augments oxygen consumption. Increases in cardiac output and vascular resistance may raise maternal blood pressure. Pain, stress, and anxiety trigger release of stress hormones such as
Cortical responses to pain pain, anxle y, age,
FIGURE 25-' Sources of pain during labor and maternal physiological responses. (Reproduced with permission from Hawkins JL: Epidural analgesia for labor and delivery, N Engl J Med. 2010 Apr 22;362(16):1503-1510.) cortisol and �-endorphins. The sympathetic nervous system response to pain leads to a marked elevation in circulating catecholamines that can adversely afect uterine activity and uteroplacental blood low. Efective analgesia attenuates or eliminates these responses.
If uterine contractions and cervical dilatation cause discomfort, pain relief is ofered. If neuraxial analgesia is contraindicated or unavailable or is declined, a narcotic from Table 25-3 plus one of the tranquilizer-antiemetic drugs such as promethazine (Phenergan) is usually appropriate. With a successful program of analgesia and sedation, the mother ideally rests quietly between contractions. In this circumstance, discomfort usually is felt at the acme of an efective uterine contraction.
Meperidine, 50 to 100 mg, with promethazine, 25 mg, may be administered intramuscularly at intervals of 2 to 4 hours. A more rapid efect is achieved by giving meperidine intravenously in doses of 25 to 50 mg every 1 to 2 hours. Whereas analgesia is mximal 30 to 45 minutes after an intramuscular injection, it develops almost immediately following intravenous administration. Meperidine readily crosses the placenta and can have a prolonged half-life in the newborn (American College of Obstetricians and Gynecologists, 20l7a). Its depressant efect in the fetus follows closely behind the peak maternal analgesic efect.