Abnormal serum chloride is associated with increased mortality among unselected cardiac intensive care unit patients

Abstract

Purpose: We sought to describe the association between serum chloride levels and mortality among unselected cardiac intensive care unit (CICU) patients.

Materials and methods: We retrospectively reviewed adult patients admitted to our CICU from 2007 to 2015. The association of dyschloremia and hospital mortality was assessed in a multiple variable model including additional confounders, and the association of dyschloremia and post-discharge mortality were assessed using Cox proportional-hazards analysis.

Results: 9,426 patients with a mean age of 67±15 years (37% females) were included. Admission hypochloremia was present in 1,384 (15%) patients, and hyperchloremia was present in 1,606 (17%) patients. There was a U-shaped relationship between admission chloride and unadjusted hospital mortality, with increased hospital mortality among patients with hypochloremia (unadjusted OR 3.0, 95% CI 2.5-3.6, p<0.001) or hyperchloremia (unadjusted OR 1.9, 95% CI 1.6-2.3, p<0.001). After multivariate adjustment, hypochloremia remained associated with higher hospital mortality (adjusted OR 2.1, 95% CI 1.6-2.9, p <0.001). Post-discharge mortality among hospital survivors was higher among patients with admission hypochloremia (adjusted HR 1.3, 95% CI 1.1-1.6; p<0.001).

Conclusion: Abnormal serum chloride on admission to the CICU is associated with increased short- and long-term mortality, with hypochloremia being a strong independent predictor.

Fig 1

CICU and hospital mortality and admission chloride level in the overall population, based on the presence of admission hypochloremia or hyperchloremia (A) or as a function of admission chloride level (B). Hypochloremia is defined as chloride <98 mEq/L and hyperchloremia is defined as chloride ≥108 mEq/L.

Fig 2. Hospital mortality and admission chloride level according to admission diagnosis.

Fig 3

Hospital mortality and admission chloride level in the overall population, based on the admission sodium (A), admission anion gap (B), and acid-base status (C). Hypochloremia is defined as chloride <98 mEq/L and hyperchloremia is defined as chloride ≥108 mEq/L. Hyponatremia is defined as sodium <135 and hypernatremia is defined as sodium ≥145. Metabolic acidosis is defined as bicarbonate <22 and metabolic alkalosis is defined as bicarbonate >26.

Fig 4. CICU and hospital mortality during hospitalization as a function of hypochloremia and hyperchloremia during the CICU stay.

Hypochloremia is defined as chloride <98 mEq/L and hyperchloremia is defined as chloride ≥108 mEq/L.

Fig 5

Kaplan-Meier curves demonstrating post-discharge survival among hospital survivor as a function of admission chloride (A) and minimum and maximum chloride during CICU stay (B). Hypochloremia is defined as chloride <98 mEq/L and hyperchloremia is defined as chloride ≥108 mEq/L.