Potassium Disorders

A potassium result is both a laboratory value and a marker of electrical risk. Potassium is held mainly inside cells, so the serum concentration can change abruptly when potassium shifts across the cell membrane, even though total body potassium has not changed. Insulin and beta-2 agonists move potassium into cells; acidosis tends to move it out. These treatments buy time, but they do not remove potassium from the body. The practical sequence is therefore different for the two directions of imbalance. With hypokalaemia, identify the loss, check magnesium, and replace potassium safely—preferably by mouth when the patient is stable and able to absorb it. With hyperkalaemia, first decide whether the result is genuine and whether the myocardium is affected. If the ECG is abnormal, stabilize the cardiac membrane before relying on potassium-shifting or potassium-removing therapy. Recheck the concentration after treatment because a temporary intracellular shift can be followed by rebound. The sections that follow connect the number to its mechanism, the mechanism to the ECG and diagnostic workup, and the treatment to the monitoring that makes it safe.