The hemodynamics and clinical effects of labetalol in hypotensive anesthesia

Labetalol is a relatively new and unique hypotensive agent that has both alpha- and beta-adrenoceptor blocking properties. 12 patients in fit physical condition who underwent elective oral surgery were subject to hypotensive anesthesia with labetalol to assess the hemodynamic aspects and clinical effects of the drug. All of them had their anesthesia maintained with halothane and N2O in 50% O2 supplemented by fentanyl and vecuronium. Initiation of deliberate hypotension was made with intravenous bolus of labetalol at 0.5 mg/kg and the ideal level of mean arterial pressure at 55 +/- 5 mm Hg was maintained with adjustment of the concentration of halothane. At the termination of deliberate hypotension, the blood pressure was recuperated to the baseline level by lowering the concentration of halothane and administration of 0.5-0.6 mg intravenous atropine. Our results showed that the total dose of labetalol used was 44 +/- 13 mg and blood loss amounted to 354 +/- 136 ml. Important changes of hemodynamic parameters before and after labetalol included the fall of mean BP, HR, mean PAP, CI, LVSWI, SVRI, PVRI and O2 delivery and the increasing of O2 extraction. As to CVP, PCWP, SVI, O2 consumption and shunting the alterations were minimal. Blood gas analysis showed that, save a slight fall of pH indicating mild metabolic acidosis, the PaO2 and PaCO2 remained unchanged following the use of labetalol. Labetalol-induced hypotension could be effectively reversed by using of atropine as shown in our study and all the patients recovered uneventfully from hypotensive anesthesia. They were entirely free from any complication or sequela relevant to the deliberate hypotension after one year's follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)