BACKGROUND: The goal of this study was to demonstrate the effect of esmolol to prevent reflex tachycardia occurred during sodium nitroprusside(SNP) induced hypotension. METHODS: Thirty patients were randomly assigned to the SNP group(n=15) received continuous infusion of SNP at 2.72±0.56 mcg/kg/min or combined SNP and esmolol(SNP-ESM) group(n=l5) received combined continuous infusion of SNP at 1.54±0.34 mcg/kg/min and esmolol at 200 mcg/kg/min for 1 hour to maintain a 20~25% reduction of mean arterial pressure(MAP) from baseline. Heart rate(HR) and MAP were measured at baseline, during hypotensive period(5, 10, 20, 30, 60 min) and after hypotensive period(70, 80, 90,1 20 min). RESULTS: SNP-induced hypotension resulted in significant(P<0.001) increases in heart rate during hypotensive period and MAP after the end of SNP infusion. However, infusion of SNP-ESM resulted in significant(p<0.05) reduction in heart rate and SNP requirement during hypotensive period, and rebound hypertension was not observed after the end of induced hypotension. CONCLUSIONS: SNP-ESM infusion is a safe and effective pharmacologic means and provides several advantages over single SNP that include reduction in SNP requirement, no reflex tachycardia during induced hypotension and no rebound hypertension following hypotensive period.