Differences in acid-base behavior between intensive care unit survivors and nonsurvivors using both a physicochemical and a standard base excess approach: a prospective, observational study.

PURPOSE: This study aimed to test the hypothesis that intensive care unit survivors and nonsurvivors differ with regard to type and severity of acid-base disorders.
MATERIALS AND METHODS: Prospective, observational, cohort study of 107 consecutive patients admitted in a 7-bed intensive care unit during a 6-month period that stayed at least 4 days. All acid-base variables for the first 3 days and the day of discharge were analyzed.
RESULTS: Survivors had significant metabolic acidosis upon admission, which was due to hyperlactatemia, an excess of unmeasured anions, and principally, hyperchloremia. A progressive decrease in these anions in the presence of constant hypoalbuminemia led to normal standard base excess at discharge. Nonsurvivors had greater metabolic acidosis upon admission with acidifying variables in similar proportions to that of the survivors. On the day of death, nonsurvivors had a similar degree of metabolic acidosis but a different proportion of the anions (less chloride and more lactate) compared with the day of admission. Unmeasured anions were greater in nonsurvivors both on the day of admission and on the day of death.
CONCLUSIONS: Intensive care unit survivors and nonsurvivors differed in the severity of metabolic acidosis; however, the proportion of the different anions causing the acidosis on admission was similar between these 2 groups.