Effect of hyperglycemia on serum sodium concentration and tonicity in outpatients on chronic dialysis

When serum glucose concentration is nearly normal, serum sodium concentration and tonicity are usually normal in ambulatory outpatient diabetics on chronic hemodialysis or peritoneal dialysis. In hyperglycemia, patients on hemodialysis do not undergo osmotic diuresis and are able to nearly normalize their serum tonicity by increasing the intake of water. Patients on peritoneal dialysis differ from hemodialysis patients because of continued loss of water in the peritoneal dialysate and achieve only partial correction of tonicity by water consumption. The model currently used to predict changes in serum sodium concentration and in tonicity from hyperglycemia assumes no changes in external balance of body water or solute during development of hyperglycemia and, therefore, is not applicable in ambulatory dialysis patients with intact thirst mechanism, because of water retention. In ambulatory patients on chronic dialysis, clinical manifestations of hyperglycemia include thirst, water intake, and weight gain. Neurologic manifestations due to hypertonicity are usually absent.