LOW HEMATOCRIT BUT NOT PERFUSION PRESSURE DURING CPB IS PREDICTIVE FOR RENAL FAILURE FOLLOWING CABG SURGERY

Abstract

Introduction. Acute renal failure (ARF) requiring dialysis occurs in 1% to 5% of patients following cardiac surgery, and remains a cause of major morbidity and mortality. While some preoperative risk factors have been characterized [1], the influence of intraoperative factors on the occurrence of ARF following cardiac surgery is less well understood. We examined the hypothesis that low hematocrit and low perfusion pressure during cardiopulmonary bypass (CPB) influence the development of ARF following coronary artery bypass graft (CABG) surgery. Methods. With IRB approval, perioperative data for 1404 first time CABG surgical patients from February 1st 1995 to February 1st 1997 was gathered from the Duke Heart Center and Anesthesia Databases including: age, sex, race, weight, history of stroke, peripheral vascular disease (PVD), congestive heart failure (CHF), diabetes (DM), obstructive lung disease (COPD), carotid bruit (PreCarBr), serum creatinine (PreCr), ejection fraction (PreEF), CPB duration, number of grafts, lowest CPB hematocrit (MinHct), lowest inflow (LowinflT) and nasopharyngeal (LowNpT) temperatures, and requirement for intraaortic balloon pump post CPB (IABP). Radial mean arterial pressure (MAP) was recorded automatically every minute using the Arkive Information Management System, and the time-pressure integral representing total MAP area <50mmHg during CPB (TM<50) was calculated. Postoperative ARF was identified as moderate (a rise of >or=to1.0mg/dl Cr) or severe (requiring dialysis). Association of variables with ARF was assessed by univariate and multivariate analysis, p<.05 was considered significant. Results. 95 of the 1404 CABG patients developed ARF (moderate-89, severe-6). MinHct was significantly lower, assessed by multivariate analysis, in the ARF group (18.8 +/- 3.6 vs 19.4 +/- 3.8%), while TM<50 was similar in both groups (ARF: 162 +/- 195 vs nonARF: 141 +/- 166 mmHg.min). Association of other variables is presented in Table 1.Table 1Discussion. We found the lowest hematocrit during CPB to be an independent predictor of ARF following CABG surgery, whereas an index of low perfusion pressure during CPB (TM<50) was not associated with post CABG ARF. Several previously reported perioperative risk factors [1] were also associated with ARF in our study. These data question the wisdom of tolerating severe anemia during CPB for CABG surgery.