The value of anion gap for predicting the short-term all-cause mortality of critically ill patients with cardiac diseases, based on MIMIC-III database.

BACKGROUND

The association of anion gap (AG) with short-term mortality in the critically ill patients with cardiac diseases is still not well understood.

OBJECTIVE

To evaluate the association of AG with short-term mortality, and the predictive ability of AG for short-term mortality in critically ill patients with cardiac diseases.

METHODS

This retrospective cohort study enrolled 9104 critically ill patients with cardiac diseases from the Medical Information Mart for Intensive Care III (MIMIC III) database. The restricted cubic spline models were used to evaluate the nonlinear relationship between AG and short-term mortality. Cox proportional hazards regression models and subgroup analysis were applied to assess the association of AG with short-term mortality.

RESULTS

The data were divided into three groups by AG tertiles: tertile I (AG <12, n = 2095), tertile II (12 ≤ AG < 15, n = 3195), and tertile III (15 ≤ AG, n = 3814). The restricted cubic spline models revealed continuous AG was non-linearly related to short-term mortality. The elevated AG tertiles were strongly associated with higher in-hospital, 30-day and 90-day mortality (all P for trend < 0.001). After adding AG to traditional severity scores, the area under curves (AUCs) elevated significantly compared to severity scores alone (all DeLong's test: P < 0.001). Subgroup analysis did not indicate significant interaction in most diverse subgroups.

CONCLUSION

AG was an independent risk factor for short-term all-cause mortality in critically ill patients with cardiac diseases. AG improved significantly the mortality predictive abilities of traditional severity scores when AG was added to these scores.