Serum potassium variability is associated with increased mortality in a large cohort of hospitalized patients.

BACKGROUND: Few studies have examined that the role of serum potassium concentration [K+] variability on clinical outcomes is still poorly investigated. The aim of our study was to analyse the association between serum ([K+]) disorders, with focus on [K+] variability and mortality in a large, unselected cohort of hospitalized patients.

METHODS: We performed a retrospective observational cohort study on the inpatient population admitted to Fondazione Policlinico Universitario A. Gemelli IRCCS between 1 January 2010 and 31 December 2014 with inclusion of adult patients with ≥2 [K+] measurements. The outcome of interest was in-hospital mortality. The exposures of interest were [K+] fluctuations, hypohyperkalaemia and mixed dyskalaemia during hospital stay. [K+] variability was evaluated using the coefficient of variation (CV). Logistic regression models were fitted to obtain odds ratios (ORs) and 95% confidence intervals (CIs) for the association between the exposures of interest and in-hospital death.

RESULTS: Overall, 64 507 patients met our inclusion criteria. During a median follow-up of 8 days, 965 patients (1.5%) died. Multivariable adjusted logistic models suggested a higher risk for death in patients in the third (OR = 1.45, 95% CI 1.13-1.88; P = 0.003) and fourth (OR = 3.30, 95% CI 2.64-4.16; P < 0.001) highest quartiles of [K+] CV compared with those in the lowest quartile with a significant linear trend across quartiles (P-trend <0.001). Results did not change after restricting the analyses to patients with normokalaemia (NK). All [K+] disorders were independently associated with an increased risk of in-hospital death compared with NK.

CONCLUSIONS: High [K+] variability is an independent risk factor of in-hospital mortality, even within the normal [K+] range.