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 < 0.05). Individual plasma
aldosterone values were found to be correlated to pRAs both during the UH period and the
LMWH period, and the slope of the positive linear relation between plasma
aldosterone and pRA was lower during the UH treatment period (63 versus 105 pg/ng/h). Finally, a negative linear correlation was found between the differences in individual predialysis plasma K+ observed during the 2 protocols and the differences in the corresponding plasma
aldosterone levels, suggesting a link between the higher kalemia and the lower
aldosterone responsiveness to
angiotensin with
unfractionated heparin. Although it cannot be concluded whether or not
LMWH inhibits
aldosterone synthesis, should
LMWH decrease
aldosterone production, this side effect
is 33% less marked than that of UH so that the predialysis plasma K+ levels are 10% lower. This property makes
LMWH use preferable to that of UH in patients with elevated predialysis kalemia.