Heparin-induced hyperkalemia in chronic hemodialysis patients: Comparison of low molecular weight and unfractionated heparin

Aldosterone suppression and subsequent hyperkalemia are well described reversible side effects of prolonged treatment with heparin. This study was designed to examine whether the discontinuous use of heparin three times a week to prevent thrombosis formation during hemodialysis sessions could also induce hypoaldosteronism and might contribute to increased predialysis kalemia in hemodialysis patients. Two different heparinization regimens were prospectively compared in a crossover study of 11 chronic hemodialysis patients. During 2 consecutive weeks, the patients were dialyzed each week with either their usual doses of unfractionated heparin (UH) (6,160 IU ± 1,350 IU) or low molecular weight heparin (LMWH) (15 anti-Xa activity [aXa] U/kg ± 5 aXa U/kg/h). In all but 2 patients, the predialysis level of plasma K± was higher with UH than with LMWH, and the mean value was higher (5.66 ± 0.83 versus 5.15 ± 0.68 mM, p = 0.01) while no differences in the predialysis plasma concentrations of creatinine, phosphate, urea, and bicarbonate were observed, excluding the potential role of differences in diet and dialysis efficacy in explaining the higher plasma K± concentration with UH. The mean plasma aldosterone to plasma renin activity (pRA) ratio was higher with LMWH than with UH (149.54 ± 123.1 versus 111.91 ± 86.22 pg/ng/h, p + levels are 10% lower. This property makes LMWH use preferable to that of UH in patients with elevated predialysis kalemia.