Cerebral Oximetry Monitoring During Preoperative Phlebotomy to Limit Allogeneic Blood Use in Patients Undergoing Cardiac Surgery

Preoperative phlebotomy can minimize the need for allogenic blood products. Frequently, removed blood is replaced with intravenous fluids to maintain euvolemia (acute normovolemic hemodilution [ANH]). During cardiopulmonary bypass (CPB), ANH may present problems when the circuit prime causes further hemodilution and unacceptably low hemoglobin. This investigation aimed to demonstrate that minimum volume replacement after preoperative phlebotomy can be used safely when guided by cerebral oxygenation (rSO(2)) measured by near-infrared spectroscopy (NIRS). This prospective study included patients undergoing surgery for congenital heart disease. After preoperative phlebotomy, fluid replacement was guided by mean arterial pressure (MAP), heart rate, and rSO(2), which were measured at baseline, immediately after phlebotomy, and 15 and 30 min after phlebotomy. This study enrolled 38 patients ages 3 months to 50 years. Preoperative phlebotomy removed 9.3 ± 2.9 mL/kg of blood, and 5.6 ± 5.1 mL/kg of crystalloid was administered intraoperatively. Within 30 min after phlebotomy, 23 patients had a MAP decrease of 20 % or more from baseline. This fall in MAP coincided with a decrease in rSO(2) of 20 or more at 2 of 114 measured points. Initially, rSO(2) decreased from 74 ± 9 to 68 ± 10 but thereafter remained constant. On five occasions, rSO(2) decreased 20 or more from baseline, but no patient’s NIRS value was less than 45. A decrease in rSO(2) occurred more commonly in younger patients and those who had a larger volume of blood removed. Preoperative phlebotomy without significant volume replacement can be performed safely before CPB. Volume replacement may be more appropriately guided by rSO(2) than by hemodynamic variables.