Comparison of Isoflurane and Halothane When Used to Control Intraoperative Hypertension in Patients Undergoing Coronary Artery Bypass Surgery

Abstract

The hemodynamic effects of isoflurane and halothane when used to control intraoperative hypertension were evaluated in 20 patients undergoing coronary artery bypass grafting. The patients were anesthetized with flunitrazepam, fentanyl, pancuronium, and N2O-O2. Control measurements were made after skin incision. When mean arterial pressure increased to 110 mm Hg due to sternal spread or surgical manipulation of the aorta, isoflurane or halothane were used to return arterial pressure to control levels. Using a non-rebreathing system, inspired isoflurane concentrations of 1.5-2.0 vol% or halothane concentrations of 1.0-1.5 vol% were necessary. Measurements were repeated during the hypertensive episode and after treatment with isoflurane or halothane while surgical stimulation continued. Both inhalation anesthetics decreased arterial pressure to baseline values within 5-10 min. The lowering of arterial pressure with halothane was not accompanied by significant decreases in the elevated systemic vascular resistance and pulmonary capillary wedge pressure. Cardiac index and stroke volume index decreased markedly when halothane was used (18% and 25%, respectively). In contrast, isoflurane significantly decreased systemic vascular resistance (42%). This reduction of left ventricular afterload was associated with an increase in cardiac index (22%) and a decrease in left ventricular filling pressure. Heart rate did not change significantly. These findings indicate that isoflurane is superior to halothane for controlling intraoperative hypertension during coronary artery bypass surgery.