Effect of oral glucose administration on serum potassium concentration in hemodialysis patients.

BACKGROUND: Extrarenal potassium disposal is particularly critical in patients with end-stage renal disease. Exogenous insulin stimulates this disposal by enhancing potassium uptake into cells in hemodialysis (HD) patients and healthy subjects. However, the effect of physiological levels of endogenous insulin on this disposal in these patients or healthy subjects is unknown. METHODS: Effects of an oral glucose tolerance test (37.5, 75, and 150 g) on serum potassium levels were determined in 13 HD patients and 7 healthy controls. Serum potassium and insulin levels and plasma aldosterone and epinephrine levels were measured before and after glucose loads. RESULTS: In HD patients and controls, serum insulin levels increased to a similar magnitude in parallel with increased serum glucose levels, but serum potassium levels decreased significantly only in HD patients. In HD patients, plasma aldosterone or epinephrine levels were not changed significantly after a glucose load. In HD patients, the decrease in serum potassium levels was dependent on the increase in serum insulin levels and was more prominent when 150 g of glucose was administered. In HD patients, the decrease in serum potassium levels correlated negatively (r = -0.45; P < 0.001) with the increase in serum insulin levels, and maximal decrease in serum potassium levels correlated negatively (r = -0.54; P < 0.001) with maximal increase in serum insulin levels. CONCLUSION: Endogenous production of physiological concentrations of insulin in response to exogenous glucose administration decreases serum potassium levels only in HD patients, independently of plasma aldosterone and epinephrine levels.

Serum potassium handling at pre- and posthemodialysis in patients with end-stage renal disease.

The current study simultaneously measured serum and red blood cell (RBC) K+ as well as plasma pH, bicarbonate, serum insulin, and aldosterone at pre-, end-, and at 5, 11, and 19 hours posthemodialysis in 25 patients with end-stage renal disease and evaluated the factors influencing serum K+ levels during those periods. Our patients were studied under their current dietary conditions. At end-dialysis, serum K+ levels decreased, but RBC K+ levels were not changed. At this time point, the decrease in serum K+ levels was exclusively caused by removal of K+ by dialysis. At 5 hours postdialysis, serum K+ rapidly increased, whereas RBC K+ decreased. The 5 hour postdialysis serum K+ increase negatively correlated with the decrease in serum insulin levels. At 11 hours postdialysis, serum K+ slowly but significantly increased, and RBC K+ increased to those levels at pre- and end-dialysis. At 19 hours postdialysis, serum K+ further increased, but RBC K+ remained stable. From 5 to 19 hours postdialysis, the increase in serum K+ was independent of changes in plasma pH, bicarbonate, insulin, and aldosterone but was associated with both the predialysis serum K+ levels and the magnitude of the decrease in serum K+ at end-dialysis.