Association of Serum Anion Gap and Mortality in Critically Ill Patients Receiving Mechanical Circulatory Support

Background Mechanical circulatory support (MCS) devices are used to restore circulation in patients with end-stage heart failure. Serum anion gap is a marker of acid-base disorders. Objective To investigate whether serum anion gap is a predictor of hospital and intensive care unit mortality in patients receiving MCS and to compare its predictive utility with that of serum lactate level and Sequential Organ Failure Assessment (SOFA) score. Methods This retrospective analysis of data from Medical Information Mart for Intensive Care–IV database, 2008-2019, included adult patients receiving MCS. The Harrell C statistic was used to compare the predictive utility of serum anion gap with that of serum lactate level and SOFA score for hospital and intensive care unit mortality. Results Of 688 patients receiving MCS, 134 had an anion gap of less than 13 mEq/L; 139, of 13 to 14 mEq/L; 159, of 15 to 17 mEq/L; and 256, of greater than 17 mEq/L. The C statistic (95% CI) for hospital mortality was 0.632 (0.611-0.662) for serum anion gap, 0.684 (0.631-0.694) for lactate, and 0.689 (0.628-0.704) for SOFA score. The C statistic (95% CI) for intensive care unit mortality was 0.642 (0.623-0.662) for serum anion gap, 0.691 (0.646-0.702) for lactate, and 0.694 (0.668-0.711) for SOFA score. Conclusions Higher serum anion gaps were associated with greater levels of hospital and intensive care unit mortality among patients receiving MCS and had a low predictive utility for these outcomes.