[Disorders in plasmatic levels of potassium, magnesium, and calcium in elderly adults associated with colistin: time series].

Introduction: Water and electrolyte disturbances associated with colistin are understudied adverse effects in the medical literature. We aim to evaluate their incidence in hospitalized older adult patients.

Materials and methods: A longitudinal retrospective study of the interrupted time series type was conducted on patients admitted to Dr. César Milstein Hospital. We included adults aged 65 and older who received colistin with normal serum potassium, magnesium, and calcium at the outset. Electrolyte values were collected before, during and after suspending the antibiotic. Values were compared using non-parametric tests, and a multivariate linear regression model with robust intervals was performed to assess sociodemographic and clinical characteristics associated with serum concentrations.

Results: A total of 89 patients were included. The rate of hypokalemia was 77.5% (n=69), and factors associated with potassium decline included older age, increased creatinine levels, and longer colistin treatment duration. Serum magnesium disturbances were reported in 66 (79.5%) of the 83 patients evaluated. The decrease in both electrolytes was statistically significant in the measured times and both values normalized after 72 hours of stopping antibiotic therapy. The incidence of acute kidney injury during colistin treatment in patients with normal baseline creatinine was 63.6% (n = 42/66), and in those with abnormal baseline creatinine, it was 47.8% (n = 11/23).

Conclusion: We report high rates of electrolyte disturbances in patients treated with colistin, with hypokalemia being the most frequent, showing resolution following discontinuation of antibiotic therapy. Continuous monitoring of electrolyte levels and renal function during colistin treatment is crucial.