Determinants of renal potassium excretion in critically ill patients

Abstract

Insulin administration lowers plasma potassium concentration by augmenting intracellular uptake of potassium. The effect of insulin administration on renal potassium excretion is unclear. Some studies suggest that insulin has an antikaliuretic effect although plasma potassium levels were poorly controlled. Since the introduction of glycemic control in the intensive care unit, insulin use has increased. We examined the relation between administered insulin and renal potassium excretion in critically ill patients under computer-assisted glucose and potassium regulation. Prospective observational study. Twelve-bed surgical intensive care unit of a university teaching hospital. Consecutive intensive care unit patients. Potassium and glucose levels were regulated by a computer-assisted decision support system. Both potassium and insulin were continuously administered by syringe pump. Renal potassium excretion was measured daily in the 24-hr urine collections. The 24-hr urinary samples of patients with kidney failure or on renal replacement therapy were excluded. Multivariate analysis with potassium excretion as the dependent variable was performed. In 178 consecutive patients, 1,456 24-hr urinary samples, were analyzed. Mean ± SD plasma potassium was 4.2 ± 0.3 mmol/L, with 79 ± 46 mmol/d of potassium administered and a mean insulin dose of 53 ± 38 U/day. Renal potassium excretion was 126 ± 51 mmol/day. After multivariate analysis correcting for relevant variables (including diuretics, pH, potassium levels and renal sodium excretion), insulin administration was independently and positively associated with renal potassium excretion. Other significant variables were potassium levels, potassium administration, renal sodium and chloride excretion, creatinine clearance, diuretic therapy, pH, known diabetes and intensive care unit admission day (R = .52; p <. 001). Insulin administration is associated with an increase in the renal potassium excretion in critically ill patients.