Impact of Preoperative Anemia on Outcome in Adult Cardiac Surgery: A Propensity-Matched Analysis

Abstract

Preoperative anemia is not considered an operative mortality risk factor by the majority of the risk stratification tools used in cardiac surgery. However, retrospective studies have found associations between preoperative anemia and morbidity and mortality in cardiac operations. The present study compares the postoperative outcome of a group of moderate-to-severe anemic patients with a propensity-matched group of nonanemic patients undergoing cardiac operations. This is a retrospective study based on 17,056 consecutive patients included in our Institutional Database. A total of 13,843 adult patients with preoperative hematocrit value available were selected for this study; 401 patients had a severe anemia (hematocrit<30%). From the remaining patients, a control group of 401 non-severely anemic patients was selected with a propensity-based matching. Postoperative morbidity and mortality were compared between the 2 groups. The 2 groups were comparable for preoperative comorbidities and operative details. Anemic patients had a significantly (p=0.045) higher rate of stroke (1% vs 0%), major morbidity (27.4% vs 17.5%, p=0.001), and a significantly higher (0.014) operative mortality rate (12.7% vs 7.5%). An additional analysis, inclusive of patients with moderate preoperative anemia, confirmed these results. Moderate-to-severe preoperative anemia is a risk factor for major morbidity and operative mortality in adult cardiac operations. This finding is confirmative of the role of preoperative anemia in determining adverse events in major noncardiac operations. The exclusion of preoperative anemia from the existing risk scores is probably a statistical consequence of the associated comorbid conditions that confound the specific role of anemia as a risk factor.