Analysis of the acid-base disorders of critically ill patients in the medical intensive care unit

Lee, Seong Geun; Cheong, Jae Hoon; Kim, Ji Eun; Song, Sang Heon; An, Seoung Jae; Lee, Dong Won; Lee, Soo Bong; Kwak, Ihm Soo

Abstract

BACKGROUND: Acid-base imbalances are common in critically ill patients; however, the incidence of acid-base imbalances in the medical intensive care units has not been fully determined. In this study, we investigated the incidence and the type of acid-base imbalances in critically ill patients and we assessed which variables were associated with the patients' outcome.
METHODS
One hundred eighty-seven patients (122 men, age: 61.2+/-12.8 years) were enrolled. All the patients were admitted to the medical intensive care unit between January 2005 and December 2005. All the data sets included simultaneous measurements of an arterial blood gas with base excess, the serum electrolytes, the anion gap and the APACHE II scores.
RESULTS
The mortality rate was 56.7%. The incidence of acid-base imbalances was as follows: 25.1% were single disorders that existed with only a single primary acid-base imbalance, 48.7% were double disorders, 13.4% were triple disorders and 12.8% were normal (no disorders). The incidence of metabolic acidosis was 57.8% and the mortality rate was not different according to the type of acid-base imbalances. There were significant differences between the nonsurvivors and survivors according to the pH (7.34 vs. 7.41, respectively), HCO(-)3 (20.68 mmol/L vs. 25.90 mmol/L, respectively), ECF base excess (-5.19 vs. 1.19, respectively), the anion gap (18.57 mmol/L vs. 13.77 mmol/L, respectively), the corrected anion gap (23.63 mmol/L vs. 17.96 mmol/L, respectively), the serum albumin (2.37 g/dL vs. 2.74 g/dL, respectively), and the APACHE II scores (20.7 vs 17.2, respectively). However, on the Cox proportional hazard regression analysis, only the APAHCE II scores affected the patients' outcome.
CONCLUSIONS
There were diverse acid-base imbalances in the critically ill patients and the incidence of metabolic acidosis was highest among the acid-base imbalances. The best predictor of the patients' outcome was the APACHE II scores.