Physiopathology and control of postoperative pain

Potent systemic (narcotic) analgesics, when given in doses sufficient to produce ample pain relief, usually also produce mental and respiratory depression and, at times, circulatory impairment, that prolong postoperative morbidity. Complications due to morphine sulfate or meperidine hydrochloride can be minimized by titrating the patient's pain with small intravenous doses of narcotics (morphine sulfate, 2 to 3 mg, or meperidine hydrochloride, 15 to 25 mg) administered slowly at 15- to 20-minute intervals until the pain is relieved. On the third or fourth postoperative day, acetaminophen tablets usually suffice to provide relief of pain with little or no risk to patients. Continuous segmental epidural block or intercostal block, with or without splanchnic block, provide excellent pain relief that, in contrast to the narcotic, is complete. These are especially useful after operations on the chest or abdomen or the lower extremity. Regional analgesia is especially indicated in patients not adequately relieved from severe postoperative pain with narcotics, or when these drugs are contraindicated by advanced pulmonary, renal, or hepatic disease. Continuous caudal analgesia is also effective to completely releive severe postoperative pain in the lower limbs and perineum.