DOES HEMOGLOBIN CONCENTRATION AFFECT PERIOPERATIVE MYOCARDIAL LACTATEFLUX IN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-SURGERY

Increasing concern over complications related to blood transfusions ha s prompted a reevaluation of what constitutes an ''adequate'' perioper ative hemoglobin concentration, particularly in patients undergoing co ronary artery bypass graft (CABG) surgery. Data from 224 patients with preserved ventricular function (ejection fraction > 50%), undergoing CABG surgery, previously studied under a variety of anesthetic protoco ls, were reexamined to determine the effect of hemoglobin (HGB) concen tration on myocardial lactate flux (MLF) (as an index of ischemia). Th e interaction of MLF and HGB concentration, anesthetic technique (ANES ), and hemodynamic variables (including systemic and pulmonary arteria l pressures (SAP and PAP), cardiac output (CO), and myocardial oxygen consumption (MVO(2)) was determined from a pool of 1598 data sets obta ined from 224 patients. Data were collected from just prior to inducti on of anesthesia until 24 h postoperatively. Univariate analysis revea led a statistically significant relationship between MLF and HGB conce ntration (P < 0.001) but the correlation coefficient was only 0.09. Mu ltiple regression analysis did not determine HGB concentration to be a significant independent term affecting MLF in either the overall grou p or in a subgroup of 22 patients having an adverse outcome (myocardia l infarction, stroke, or death). For patients undergoing CABG surgery, HGB concentrations within the range of 58-172 g/L were not a signific ant variable in production of global myocardial ischemia as evidenced by MLF. This suggests that HGB concentrations as low as 60-70 g/L in t he perioperative period are well tolerated and are not associated with an increased incidence of myocardial ischemia.