Potassium imbalance: causes and prevention.

The amount of potassium normally found in the serum is less than 2% of the total body amount. Thus, the serum potassium level is not the ideal indicator of potassium activity in the body. Potassium homeostasis or imbalance is a function of changes in input, changes in output, and shifts of potassium between the serum and the intracellular fluid. Most significant hyperkalemia is associated with renal impairment, either glomerular or tubular; hypokalemia in many instances is causally related to increased renal potassium losses. Such losses can be sequentially measured and the information used to prevent potassium depletion. The key to understanding and treating potassium imbalance is to know which patients are at risk, what the physiologic consequences of hypokalemia and hyperkalemia are, and how to use urinary potassium measurements and the ECG for prevention rather than relying on the serum potassium level only.