Postoperative hemoglobin levels and its association with myocardial ischemia in non-cardiac surgical patients

Background. Low hemoglobin (Hb) levels as well as cardiac complications are common conditions in postoperative surgical patients and both are associated with poor outcome. The aim of this study was to determine the influence of postoperative Hb levels on myocardial ischemia in high-risk patients who underwent non-cardiac surgery. Methods. In this retrospective observational cohort study, we evaluated 3638 consecutive patients admitted to the 24-hour postoperative anesthesia care unit between 2006 and 2010; 273 (8%) high-risk patients, defined as three or more cardiac risk factors, were selected for analyses. Postoperative Hb levels were divided into tertiles (low, intermediate and high). The endpoint of this study was myocardial ischemia which was defined as new electrocardiographic abnormalities and/or elevated levels of troponin-T. The relationship between postoperative Hb levels and myocardial ischemia was assessed using logistic regression analyses stratified by gender. Results. Postoperative myocardial ischemia was present in 73 (27%) of the 273 patients. After adjustment for significant pre-, intra- and postoperative risk factors, 4 independent risk factors remained for postoperative myocardial ischemia in male patients: age (OR 1.1; 95% CI: 1.0-1.1), a history of ischemic heart diseases (OR 4.2; 95% CI: 1.0-17.8), renal failure (OR 5.4; 95% CI: 2.1-13.9) and postoperative Hb levels: intermediate tertile (10.3-11.6 g/dL) (OR 5.8; 95% CI: 1.6-20.9) and lowest tertile (7.9-10.2 g/dL) (OR 12.9; 95% CI: 3.0-55.5). Conclusion. Postoperative Hb levels are independently associated with postoperative myocardial ischemia in high-risk patients undergoing non-cardiac surgery.