EFFECT OF ANALGESIC TREATMENT ON THE PHYSIOLOGICAL CONSEQUENCES OF ACUTE PAIN

Physiological responses to acute pain are described, and the effects o f different analgesic techniques on these responses are discussed. The body's response to acute pain can cause adverse physiological effects . Pain can impede the return of normal pulmonary function, modify cert ain aspects of the stress response to injury, and alter hemodynamic va lues and cardiovascular function. It can produce immobility and contri bute to thromboembolic complications. In addition, pain can slow a pat ient's recovery from surgery and contribute to increased morbidity. Fe wer pulmonary complications occur when adequate analgesia is provided through the use of epidural narcotics and local anesthetics, particula rly if the injury or surgery involves the lower part of the body. Cont inuous morphine infusions, intercostal nerve blocks, and transcutaneou s electrical stimulation do not alter the frequency of pulmonary compl ications. The effectiveness of patient-controlled analgesia in reducin g postoperative pulmonary complications is still not known. Epidural l ocal anesthetic therapy inhibits the stress response, particularly in operations involving the lower abdomen or extremities; this technique is less effective during major abdominal procedures. Suppression of en docrine-metabolic changes following lower abdominal surgery requires n eural block to the fourth thoracic segment. Epidural narcotics partial ly inhibit the stress response after lower abdominal or extremity surg ery but not after upper abdominal or thoracic surgery. Local anestheti cs applied to the surgical site, intercostal nerve blocks, and intrapl eural and intraperitoneal administration also do not modify the stress response. Adequate analgesia through the use of local anesthetics and narcotics postoperatively generally results in improved cardiovascula r function, decreased pulmonary morbidity and mortality, earlier ambul ation, and decreased likelihood of deep vein thrombosis. Some data sug gest that improved patient outcome occurs with adequate analgesia. Blo ck of afferent and efferent neural pathways by local anesthetics seems to be the most effective analgesic modality in lessening the physiolo gic response to pain and injury.