Acid–base disorders evaluation in critically ill patients: hyperchloremia is associated with mortality

Introduction

Acid–base disorders are common in critically ill patients, and they are generally associated with greater morbidity and mortality. The objectives of this study are to find out whether the diagnostic evaluation of acid–base disorders in a population of critically ill patients can be improved using Stewart's method compared with the traditional model, and whether acid–base variables are associated with hospital mortality.

Methods

This prospective observational study took place in a university-affiliated hospital in Porto Alegre, Brazil, during the period of February to May 2007. We recorded clinical data and acid–base variables from 175 patients at ICU admission.

Results

The evaluation according to Stewart's method would allow an additional diagnosis of metabolic disorder in 59 (33.7%) patients. Individually, none of the variables appear to be good predictors of hospital mortality. However, using the multivariate stepwise logistic regression, we had a model with good discrimination containing the SOFA score, age, chloride and albumin (area under receiver operating characteristic curve = 0.80; 95% CI = 0.73 to 0.87). See Figure 1.

Figure 1

ROC curves for the models including SOFA, age, albumin and chloride.

Conclusion

The Stewart approach, compared with the traditional evaluation, allows identifying more patients with major acid–base disturbances. Hypoalbuminemia and hyperchloremia were associated with mortality.