Metabolic alkalosis acquired in intensive care: A retrospective cohort study

Introduction

Alkalosis is a common acid-base disturbance in intensive care unit (ICU) patients. We evaluated the epidemiology of metabolic alkalosis developing during admission to the ICU and its relationship with outcome.

Methods

Multicentre, retrospective cohort study of admissions to 12 ICUs in Queensland, Australia from January 1st, 2015 to December 31st, 2021. We excluded readmissions, patients with metabolic alkalosis within the first 24 h and those with ICU length of stay (LOS) ≤48 h. The primary outcome was the cumulative incidence of metabolic alkalosis during admission, and secondary outcomes were the frequency of potential underlying causes. Multivariable analyses, including adjustment for immortal time bias, were used to explore its relationship with mortality.

Results

Of 24,676 eligible admissions, 8889 (36%) developed metabolic alkalosis during their stay in the ICU. The median time to first development was four days in the ICU (interquartile range 3–6 days). The most common potential causes were diuretics (28%) and steroids (24%), but no cause could be identified in more than 40% of cases. After adjustment for immortal time bias, patients with metabolic alkalosis were seen to have increased mortality rates. However, it was not an independent predictor of outcome after adjusting for disease severity and comorbidities using multivariable analysis.

Conclusion

Metabolic alkalosis develops commonly in the ICU, but its association with increased mortality may be attributable to other confounding factors. Further research is required to elucidate its underlying causes and whether treatments to correct alkalosis improve outcomes.