DEXMEDETOMIDINE AS AN ANESTHETIC ADJUNCT IN CORONARY-ARTERY BYPASS-GRAFTING

Background: alpha(2)-Adrenergic agonists decrease sympathetic tone wit h ensuing attenuation of neuroendocrine and hemodynamic responses to a nesthesia and surgery, The effects of dexmedetomidine, a highly specif ic alpha(2)-adrenergic agonist, on these responses have not been repor ted in patients undergoing coronary artery bypass grafting. Methods: E ighty patients scheduled for elective coronary artery bypass grafting received, in a double-blind manner, either a saline placebo or a dexme detomidine infusion, initially 50 ng . kg(-1) . min(-1) for 30 min bef ore induction of anesthesia with fentanyl, and then 7 ng . kg(-1) . mi n(-1) until the end of surgery, Filling pressures, blood pressure, and heart rate were controlled by intravenous fluid and by supplemental a nesthetics and vasoactive drugs. Results: Compared with placebo, dexme detomidine decreased plasma norepinephrine concentrations by 90%, atte nuated the increase of blood pressure during anesthesia (3 vs, 24 mmHg ) and surgery (2 vs. 14 mmHg), but increased slightly the need for int ravenous fluid challenge (29 vs. 20 patients) and induced more hypoten sion during cardiopulmonary bypass (9 vs. 0 patients), Dexmedetomidine decreased the incidence of intraoperative (2 vs. 13 patients) and pos toperative (5 vs. 16 patients) tachycardia, Dexmedetomidine also decre ased the need for additional doses of fentanyl (3.1 vs. 5.4), the incr ements of enflurane (4.4 vs, 5.6), the need for beta blockers (3 vs. 1 1 patients), and the incidence of fentanyl-induced muscle rigidity (15 vs. 33 patients) and postoperative shivering (13 vs. 23 patients). Co nclusions: Intraoperative intravenous infusion of dexmedetomidine to p atients undergoing coronary artery revascularization decreased intraop erative sympathetic tone and attenuated hyperdynamic responses to anes thesia and surgery bur increased the propensity toward hypotension.