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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.

Hypokalemia is a common electrolyte abnormality. Intravenous repletion therapy with potassium chloride (KCl) in concentrations > 80-100 mEq/L is not recommended due to patient intolerance. Since this guideline at times may be clinically impractical, this study was designed to examine use of peripheral vein infusions of high concentration KCl therapy. Tolerance to KG 20 mEq/65 ml iv with and without lidocaine 50 mg was evaluated in 18 hypokalemic subjects in a randomized, placebo-controlled, double-blind study. Subjective and objective assessments of adverse effects were determined throughout the infusion period. Pain was assessed by both verbal descriptor and visual analog scales and correlated significantly following infusion of KCl with or without lidocaine. Multivariant analysis demonstrated differences in pain perception between solutions, with significantly less pain following KCl with lidocaine versus KCl infusions. Transient adverse effects occurred in both groups, but the incidence was not statistically different. Use of concentrated iv KCl infusions may benefit hypokalemic patients with hypervolemia and/or severe potassium deficits. Addition of lidocaine clearly improves patient tolerance to intravenous KCl replacement.

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Therapy with standard-dose TMP/SMX is associated with a slight increase in the serum potassium concentration. Routine monitoring of the serum potassium concentration in patients who are treated with standard-dose TMP/SMX therapy is unnecessary. However, TMP/SMX should be considered as a possible cause of unexplained hyperkalemia in elderly patients receiving TMP/SMX therapy.