Unexpected impact of preoperative anemia in low-risk isolated coronary artery bypass grafting or single-valve surgical patients: Do not overlook these patients in anemia management!

Preoperative anemia is prevalent in cardiac surgery and independently associated with increased risk for short-term and long-term mortality. The purpose of this study was to examine the effect of preoperative hematocrit (Hct) on outcomes in cardiac surgical patients and whether the effect is comparable across levels of Society of Thoracic Surgeons predicted risk of mortality (STS PROM).The study consisted of adult, isolated coronary bypass grafting (CABG) or single valve surgical patients in a statewide registry from 2011-2022 (N=29,828). Regressions were used to assess effect of preoperative Hct on STS-defined major morbidity/mortality including the interaction of Hct and STS PROM as continuous variables.Median age was 66 (58-73) yrs, STS PROM was 1.02% (0.58%-1.99%), and preoperative Hct was 39.5% (35.8%-42.8%). The sample consisted of 78% isolated CABG (n=23,261), 10% isolated mitral valve repair/replacement (n=3,119), 12% isolated aortic valve replacement (n=3,448), and 29% were female (n=8,646). Multivariable analyses found that higher Hct was associated with reduced risk of STS-defined morbidity/mortality (OR=0.96, P<0.001). These effects for Hct persisted even after adjustment for intraoperative blood transfusion. The interaction of Hct and STS PROM was significant for morbidity/mortality (OR=1.01, P<0.001). There was a stronger association between Hct levels and morbidity/mortality risk in the lowest STS risk patients compared to the highest STS risk patients.Lower risk patients had a greater association between preoperative Hct and major morbidity and mortality compared to higher risk patients. Preoperative anemia management is essential across all risk groups for improved outcomes.