Pathophysiology and clinical management of hyperkalemia in chronic kidney disease.

Adaptive increases in kidney and gastrointestinal excretion of K help to prevent hyperkalemia in patients with chronic kidney disease (CKD) as long as the glomerular filtration rate (GFR) remains >15-20 mL/min. K balance is maintained by increased secretion per functioning nephron, which is mediated by elevated plasma K concentration, aldosterone, increased flow rate, and enhanced Na-K-ATPase activity. Fecal losses of potassium also increase in CKD. These mechanisms are effective in preventing hyperkalemia if urine output is in excess of 600 mL/day and the GFR exceeds 15 mL/min. Development of hyperkalemia with only mild to moderate reductions in GFR should prompt a search for intrinsic disease of the collecting duct, disturbances in mineralocorticoid activity, and/or decreased delivery of sodium to the distal nephron. The initial approach to treatment is to review the patient's medication profile and whenever possible discontinue drugs that impair kidney K excretion. Patients should be educated on sources of K in the diet and should be strongly encouraged to avoid the use of K containing salt substitutes as well as herbal remedies since herbs may be a hidden source of dietary K. Effective diuretic therapy and correction of metabolic acidosis are effective strategies to minimize the potential for hyperkalemia. Discontinuation or use of submaximal doses of renin-angiotensin blockers should be discouraged given the cardiovascular protective effect these drugs provide. Potassium binding drugs can be useful to enable use of these drugs and potentially allow liberalization of the diet in CKD patients.