OBJECTIVE Surgical trauma results in diffuse sympathoadrenal activation which is thought to contribute to perioperative cardiovascular complications in high-risk patients. Regional anesthetic and analgesic techniques can attenuate this "stress response" and reduce the occurrence rate of adverse perioperative events; however, their use in the postoperative period is logistically difficult and costly. The present study was undertaken to evaluate whether transdermal administration of the alpha2 adrenergic-receptor agonist, clonidine, can be used as a pharmacologic means of blunting the stress response throughout the perioperative period. METHODS Double-blind, placebo-controlled clinical trial in patients undergoing pancreatico-biliary surgery. METHODS Operating rooms and surgical intensive care unit of a major university teaching hospital. METHODS Forty patients scheduled for major upper abdominal surgery. METHODS Patients received either clonidine (0.2 mg orally and a clonidine TTS-3 patch the evening before surgery and 0.3 mg orally on call to the operating room) or matched oral and transdermal placebo. RESULTS Heart rate, systemic arterial blood pressure, plasma catecholamine, clonidine, interleukin-6 concentrations, and 24-hr urine cortisol and nitrogen excretion were measured the day before surgery and daily thereafter for 72 hrs postoperatively. Preoperative transdermal (and oral) clonidine administration resulted in therapeutic plasma clonidine concentrations throughout the perioperative period (1.54 +/- .07 [SEM] microg/mL). Clonidine reduced preoperative epinephrine and norepinephrine concentrations by 65%. Plasma catecholamine concentrations increased in both groups following surgery but were markedly lower throughout the postoperative period in patients receiving clonidine. Patients receiving clonidine had a reduced frequency rate of postoperative hypertension. Clonidine had no effect on plasma interleukin-6 concentration, urine cortisol excretion, or urine nitrogen excretion. No adverse effects of clonidine administration were observed. CONCLUSIONS The combined administration of oral and transdermal clonidine effectively attenuated the catecholamine response to surgical stress throughout the postoperative study period. Clonidine administration produced specific sympatholytic effects, since other elements of the stress response were not attenuated. Undesirable side effects were not noted. The sustained sympatholytic effects we observed suggest that alpha2 adrenergic-receptor agonists may offer a pharmacologic means of modifying the sympathoadrenal response to injury, and may be useful in reducing perioperative complications.