Association of hyperkalemia with clinical outcomes in advanced chronic kidney disease. / Asociación entre hiperkaliemia y evolución clínica en la enfermedad renal crónica avanzada.

ABSTRACT

INTRODUCTION: Patients with advanced chronic kidney disease (CKD) are at greatest risk of hyperkalemia (HK). The relationship between HK and negative outcomes (mortality or progression of renal insufficiency) in non-dialysis dependent CKD patients is controversial. AIMS: To determine the incidence, prevalence, and factors related with HK in a cohort of CKD patients, and its relationship with mortality, hospitalization rate, CKD progression, and dialysis initiation. MATERIAL AND METHODS: A retrospective, observational study in an incident cohort of adult patients with stage 4 or 5 CKD not on dialysis. Inclusion criteria were having at least three consecutive estimated glomerular filtration rate (eGFR) measurements in a follow-up period >3 months. Decline in renal function was estimated as the slope of the individual linear regression line of eGFR over follow-up time. HK was defined as serum K levels ≥5.5 meq/l. Associations of HK with outcomes were adjusted for major confounding variables in the multivariate analysis. RESULTS: The study group consisted of 1079 patients (574 males, mean age 65±14 years) with mean baseline eGFR 14.8±4.5 ml/min/1,73 m2. Mean follow-up time was 15 months with a median of 7 serum sample determinations per patient. HK was observed at baseline in 26% of patients; in at least one serum sample during the individual follow-up period in 68%; or chronically (>50% of samples) in 33% of patients. By multivariate logistic regression, the best determinants of chronic HK were male sex (OR = 1.529; 95% CI [1.154-2.025], p = .003), serum bicarbonate (OR = 0.863 [0.829-0.900], p <.0001), diuretic treatment (OR = 0.743 [0.556-0.992], p = .044), and angiotensin converting enzyme inhibitor and/or angiotensin receptor blockers (OR = 4.412 [2.915-6.678], p <.0001). Patients whose serum K levels were in the upper quartile showed a significantly faster CKD progression (-4.05±5.22 vs. -2.69±5.61 ml/min/1.73 m2/year, p <.0001), and more frequent dialysis initiation (63% vs. 57%, p = .115), though lower mortality (9% vs. 17%, p = .003) and hospitalization rates (2.68±5.94 vs. 3.16±6.77 days per year, p = .301) than the other study patients. However, in the multivariate analysis, average serum K levels were not independently associated with the clinical outcomes investigated. CONCLUSION: HK is a common biochemical finding in non-dialysis dependent CKD patients, mainly associated with prescribed medication. However, HK was not independently associated with major negative clinical outcomes.