EFFECTS OF SEVOFLURANE AND ISOFLURANE ON SYSTEMIC VASCULAR-RESISTANCE- USE OF CARDIOPULMONARY BYPASS AS A STUDY MODEL

We have examined the dose-related effects of sevoflurane and isofluran e on systemic vascular resistance (SVR) during cardiopulmonary bypass (CPB) in patients undergoing elective coronary artery surgery. Fifty-t wo patients were allocated randomly to one of six groups to receive 1. 0, 2.0 or 3.0 vol% (inspiratory) sevoflurane or 0.6, 1.2 or 1.8 vol% i soflurane, or to a control group. During hypothermic (32-33 degrees C) non-pulsatile CPB, systemic vascular resistance index (SVRI) was reco rded before administration of volatile anaesthetics and every 5 min fo r 20 min. Sevoflurane and isoflurane concentrations were measured next to the gas inlet port and at the gas outlet port of the oxygenator. W ash-in of sevoflurane occurred more rapidly than that of isoflurane, r eaching a relatively steady state for both agents from the 10th to the 20th min. There was no significant change in SVRI in patients receivi ng 1.0 and 2.0 vol% sevoflurane, and 0.6 and 1.2 vol% isoflurane, comp ared with baseline values. However, 3 vol% sevoflurane decreased SVRI at 10, 15 and 20 min, and 1.8 vol% isoflurane decreased SVRI significa ntly at 15 and 20 min, whereas SVRI increased at 15 and 20 min in the control group. Thus during CPB, sevoflurane had similar vasodilator ef fects on SVRI as isoflurane.