IMPACT OF MINIMUM HEMATOCRIT DURING CARDIOPULMONARY BYPASS ON MORTALITY IN PATIENTS UNDERGOING CORONARY-ARTERY SURGERY

Background The hematocrit on cardiopulmonary bypass (CPB) frequently f alls to a low level during many cardiac surgical procedures. This stud y was designed to explore the impact on mortality of minimum hematocri t level achieved during the CPB after coronary artery surgery. Methods and Results Two thousand seven hundred thirty-eight sequential isolat ed coronary artery surgery patients during a 42-month period at a tert iary academic center were included in this study. Thirty-one standardi zed preoperative risk factors used in a multiple logistic regression r evealed eight statistically significant independent predictors for pos toperative mortality. Minimum hematocrit level during CPB was then add ed to the regression model and was found to be an independent risk fac tor for mortality. The entire patient population was divided into dich otomous groups using different minimum hematocrit levels on CPB for th e determination of cutoff points by multiple logistic regression. Afte r adjusting for other risk factors, the minimum hematocrit level of 14 % was found to be a statistically significant cutoff point. Patients w ith minimum hematocrit levels less than or equal to 14% were found to have an increased probability of risk-adjusted mortality (odds ratio, 2.70; P=.002). A subgroup analysis revealed that high-risk patients wi th minimum hematocrit levels less than or equal to 17% were found to h ave a significantly increased probability of postoperative mortality ( odds ratio, 2.20; P=.017). Conclusions Minimum hematocrit level during CPB is an independent risk factor for mortality after coronary artery surgery. There is a significantly increased risk of mortality for hem atocrit levels less than or equal to 14%. For high-risk patients, ther e is a significantly increased risk of mortality for hematocrit levels less than or equal to 17%.