Effects of lidocaine infusion on the sympathetic response to abdominal surgery

Activation of afferent nerves in the area of surgery is a cause for surgical pain and stress. Intravenous (IV) lidocaine has been shown to inhibit postoperative pain. In the present double-blind study, the effects of a continuous IV infusion of lidocaine (2 mg/min) on the sympathoadrenal stress response to surgery were evaluated in 38 patients scheduled for elective cholecystectomy who were randomly assigned to two groups. In one group, lidocaine infusion was started 30 min before the operation and continued for 24 hr after surgery (n = 18). In the second group (n = 20), saline was infused. The increases in heart rate and blood pressure after tracheal intubation were not significantly different between the groups, but tachycardia and hypertension associated with extubation was prevented in patients given lidocaine. Differences in blood pressure and heart rate between the two groups were otherwise not significant intra- or postoperatively, nor were differences in blood glucose or plasma catecholamine concentrations during the first 24 hr after skin incision. Urinary catecholamine concentrations did not differ significantly in the two groups during the first postoperative day, but during the second postoperative day urinary output of epinephrine and norepinephrine were significantly less in the group of patients receiving lidocaine infusion. It was concluded that the IV infusion of lidocaine during and after major abdominal surgery suppresses extubation-induced hypertension and tachycardia but does not inhibit the general sympathetic response during the first postoperative day. However, lidocaine infusion reduces urinary output of catecholamines during the second postoperative day, suggesting a more rapid decline in the sympathoadrenal response postoperatively in the experimental group.