The influence of isoflurane on blood flow in coronary bypass grafts

The effects of isoflurane on graft blood flow, central hemodynamics and ECG were evaluated in 20 patients during coronary artery surgery in the period immediately after cardiopulmonary bypass (CPB). Intravenous anesthesia with thiopentone, diazepam, fentanyl (continuous infusion), droperidol and pancuronium supplemented with nitrous oxide was used before, and thiopentone and fentanyl were used during CPB. A first measurement of graft flow was performed during fentanyl infusion and the patients were randomly allocated to a control (n = 10) and a study (n = 10) group. In the study group isoflurane was administered in a dose that reduced systolic arterial blood pressure (SAP) to approximately 100 mmHg (13.3 kPa) (inspired concentration 0.5-1.5%) and a second measurement was performed after 30 min. In the control group the infusion of fentanyl was continued. Isoflurane reduced graft blood flow from 52 +/- 5 (mean and s.e. mean) to 40 +/- 5 ml . min-1 (P less than 0.01) concomitant with reductions in SAP, cardiac index, stroke index, left ventricular stroke work index and power index, while these parameters as well as graft flow remained unchanged in the control group. Isoflurane did not produce any change in the degree of ischemia as judged from the ECG. A high blood flow in recently established coronary artery bypass grafts is essential for the prevention of early graft occlusion; therefore the graft-flow-reducing effect of isoflurane has to be taken into consideration when evaluating different anesthetic regimens in the period after CPB.