Effects of moderate acute isovolaemic haemodilution on myocardial function in patients undergoing coronary surgery under volatile inhalational anaesthesia.

Abstract

When myocardial oxygen demand is increased by elevated heart rate in patients undergoing coronary artery surgery under total intravenous anaesthesia, acute isovolaemic haemodilution may be associated with a deterioration of cardiac function. We investigated the effects of acute isovolaemic haemodilution during volatile inhalational anaesthesia. Forty patients undergoing coronary surgery were randomly assigned to two groups according to the rate of atrioventricular pacing (Group 70 at 70.min(-1) and Group 90 at 90.min(-1)). While paced at the fixed heart rate, acute isovolaemic haemodilution was performed before the start of cardiopulmonary bypass. In both groups mean (SD) stroke volume increased with haemodilution (from 65 (9) to 83 (10) ml.min(-1) (p < 0.01) in Group 70 and from 65 (9) to 81 (9) ml.min(-1) (p < 0.01) in Group 90) as a result of a decrease in systemic vascular resistance (from 1175 (231) to 869 (164) dynes.s.cm(-5) (p < 0.01) and from 1060 (185) to 849 (146) dynes.s.cm(-5) (p < 0.01), respectively) and an increase in end-diastolic volume (from 1049 (234) to 1405 (211) ml (p < 0.01) and from 1078 (106) to 1438 (246) ml (p < 0.01), respectively). Left ventricular pressure-derived data remained unchanged with acute isovolaemic haemodilution in both groups.