Haemodynamic effects of leg raising in patients undergoing coronary artery bypass grafting

Twenty patients undergoing elective coronary artery bypass grafting were studied prospectively to evaluate the haemodynamic effects of passive leg raising. The patients were divided into two groups: those having good left ventricular function with ejection fraction of 0.50 or more (group I, n=10) and those having poor left ventricular function with ejection fraction of upto 0.35 (group II, n=10). Morphine-based anaesthetic technique was used and standard haemodynamic measurements were obtained at following stages: (1) control - 20 to 30 min after induction of anaesthesia; (2) one minute, and (3) five min after raising both the legs; (4) one min, and (5) five min after the legs were repositioned. In group I, heart rate decreased from 71±9 to 66±8 beats/min (p<0.001) at stage 1 and persisted throughout the study period. This was accompanied by a decrease in cardiac index, although, the statistical significance was achieved at stage 3 and 4 only. The haemodynamic changes observed in group II were of more severe magnitude. The heart rate decreased from 90±13 to 84±13 beats/min at stage 1 (p<0.05) and persisted throughout the study with maximum decrease of 14 percent occurring at stage 3. The cardiac index decreased significantly from 2.4±0.3 to 2.0±0.5 L/min/m² (p<0.05) at stage 1. This persisted throughout the study except that it recovered at stage 4. The maximum decrease in cardiac index (20%) occurred at stage 2. In addition, systemic vascular resistance increased significantly from 1458±255 to 1830±420 dyne.sec.cm^-5 (p<0.05) at stage 1 and persisted throughout the study period. We conclude that passive leg raising should be undertaken with caution in patients with coronary artery disease especially in those who have poor left ventricular function.