ESMOLOL REDUCES ANESTHETIC REQUIREMENT FOR SKIN INCISION DURING PROPOFOL NITROUS-OXIDE MORPHINE ANESTHESIA

Background: Although beta blockers have been used primarily to decreas e unwanted perioperative hemodynamic responses, the sedative propertie s of these compounds might decrease anesthetic requirements. This stud y was designed to determine whether esmolol, a short-acting beta(1)-re ceptor antagonist, could reduce the propofol concentration required to prevent movement at skin incision. Methods: Sixty consenting patients were premedicated with morphine, and then propofol was delivered by c omputer-assisted continuous infusion along with 60% nitrous oxide. Pat ients were randomly divided into three groups, propofol alone, propofo l plus low-dose esmolol (bolus of 0.5 mg/kg, then 50 mu g . kg(-1). mi n(-1)), and propofol plus high-dose esmolol (bolus of 1 mg/kg, then 25 0 mu g . kg(-1). min(-1)). Two venous blood samples were drawn at equi librium. The serum propofol concentration that prevented movement to i ncision in 50% of patients (Cp(50)) was calculated by logistic regress ion. Results: The propofol Cp(50) with nitrous oxide was 3.85 mu g/ml, High-dose esmolol infusion was associated with a significant reductio n in the Cp(50) to 2.80 mu g/ml (P < 0.04). Propofol computer-assisted continuous infusion produced stable serum concentrations with a sligh t positive bias, Esmolol did not alter the serum propofol concentratio n, No intergroup differences in heart rate or blood pressure response to intubation or incision were found. Conclusions: Esmolol significant ly decreased the anesthetic requirement for skin incision. The compone nts and mechanism of this interaction remain unclear, A simple pharmac okinetic interaction bem een esmolol and propofol does not explain the Cp(50) reduction. These results demonstrate an anesthetic-sparing eff ect of a beta-adrenerqic antagonist in humans under clinically relevan t conditions.