Effects of isovolemic hemodilution on abdominal aortic aneurysmectomy in high risk patients.

Intraoperative isovolemic hemodilution might increase blood flow and tissue oxygenation in the periphery but there is concern that acute anemia may have deleterious effects on myocardium in patients with coronary artery disease. This study investigates the effects of intraoperative isovolemic hemodilution on morbidity, mortality and hemodynamics in 32 patients with significant cardiovascular disease undergoing elective abdominal aortic aneurysmectomy. The average hematocrit was lowered intraoperatively from 43% to 31% by withdrawing blood and replacing volumes with 1:3 Ringer's lactate. In ten patients myocardial function was evaluated during aortic cross-clamping and declamping in the face of hemodilution. There were two deaths: one myocardial infarction and one multiple organ failure. Aortic cross clamping did not change heart rate, vascular pressures (VP), vascular resistance (SVR), cardiac output (CO), and left ventricular stroke work (LVSW). Following declamping, VP, CO and LVSW decreased and SVR increased momentarily (p less than 0.05), but the myocardial function did not change. Isovolemic hemodilution had no apparent adverse effects on morbidity, mortality and cardiovascular performance in these patients.