Effect of Low-Molecular-Weight Heparin on Potassium Homeostasis

Abstract

Background: Low-molecular-weight heparins (LMWHs) are being preferred to unfractionated heparin (UFH) because of their superior convenience and a comparable or slightly better toxicity profile. Whether LMWH has an inhibitory effect on aldosterone that causes hyperkalemia is yet uncertain. Methods: Twenty-eight patients (all male; mean age: 70 years, range 52–87 years) placed on LMWH therapy (40 mg subcutaneously every 12 h) for deep venous thrombosis prophylaxis after an operation were included in the study. Transtubular potassium concentration gradient (TTKG) was calculated 1 day prior to LMWH therapy and again after 4 days of treatment. Of the 28 patients enrolled in the study, we were able to calculate the TTKG in only 19 patients: 9 had a urinary osmolarity (either before or after LMWH therapy) less than the serum osmolarity, making the TTKG calculation unreliable. The Wilcoxon signed-rank test was used to analyze differences in the median serum potassium levels and TTKG before and after LMWH therapy. Results: All patients had adequate renal function (creatinine clearance >90 ml/min). Mean (± SD) serum potassium concentration before LMWH was 4.25 (± 0.40) mmol/dl. It increased to 4.35 (± 0.41) mmol/dl after initiating LMWH therapy (p = 0.09). Similarly, the mean (± SD) TKKG calculated was 5.52 (± 2.33) before and 5.97 (± 3.06) after 4 days of LMWH (p = 0.54). Conclusions: Unlike UFH, LMWH (Lovenox^®) in doses used for postoperative prophylaxis against deep venous thrombosis does not seem to have a significant effect on potassium homeostasis.