Hematocrit on Cardiopulmonary Bypass and Outcome after Coronary Surgery in Nontransfused Patients
Ranucci M, Conti D, Castelvecchio S, Menicanti L, Frigiola A, Ballotta A, Pelissero G. Annals of Thoracic Surgery 2010;89:11-18.
Reviewer: Nanhi Mitter, MD
Johns Hopkins Hospital
Excerpt from Paper’s Abstract
Ranucci et al. retrospectively analyzed 3003 patients at a single institution undergoing isolated coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) who did not receive a blood transfusion during their hospital stay. The outcome variables measured were major morbidity (mechanical ventilation longer than 48 hours, surgical reoperation, mediastinitis, renal dysfunction or failure, and stroke) and operative mortality (death within the hospital or 30 days after discharge). Patients were divided into four groups: group I – preoperative hematocrit (HCT) > 40% and lowest HCT on CPB > 28%, group II- preoperative HCT ≤ 40% and lowest HCT > 28%, group III – Preoperative HCT > 40% and lowest HCT on CPB ≤ 28%, and group IV – preoperative HCT ≤ 40% and lowest HCT on CPB ≤ 28%. There were no significant differences with respect to priming volume, use of ultrafiltration, and duration of CPB between the four groups. Preoperative HCT and the lowest HCT on CPB were found to be independent risk factors for major morbidity. Neither were independent risk factors for operative mortality, and a preoperative HCT of 40% or less was not found to be a risk factor for major morbidity if the lowest HCT on CPB was maintained above 28%.
This is a timely analysis that brings us one step closer to better understanding the complex subject of preoperative anemia and intraoperative HCT on outcomes after CABG. According to the results of the study, if the lowest HCT on CPB is maintained above 28%, patients with preoperative HCT below 40% can have similar outcomes to patients with a preoperative HCT > 40%. This has potential implications for hemodilution, priming volume, use of closed circuits, and fluid restriction prior to CPB. These results highlight the fundamental principle of poor oxygen carrying capacity and its contribution to end-organ dysfunction. Prior studies have evaluated perioperative anemia and postoperative outcomes however, they have included transfused patients which may be a confounding variable.
There are a few limitations to this study. Firstly, it is single center and retrospective in nature. Secondly, the proportion of patients is predominantly male (85%), therefore the results cannot be readily extrapolated to a diverse patient population. Furthermore, the anesthetic technique was not standardized. Anesthetic technique has been revealed to have a significant impact on outcomes after cardiac surgery. [1-3] It would be interesting to see how this data would be affected with a higher population of females, patients with lower left ventricular ejection fractions and renal dysfunction or in patients undergoing valvular or combination CABG and valvular surgery.
Although the management of anemia perioperatively is complex, this study sheds some light on the management of patients presenting for CABG surgery with a low preoperative HCT.
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3. Landoni G, B.-Z.G., Zangrillo A, et al, Desflurane and sevoflurane in cardiac surgery: A meta-analysis of randomized clinical trials. J Cardiothorac Vasc Anesth, 2007. 21: p. 502-511.