Overview
The Clinical Problem
Potassium is the major intracellular cation, but the heart and skeletal muscles respond to its small extracellular changes.
Potassium is the major intracellular cation, but the heart and skeletal muscles respond to its small extracellular changes. A serum potassium concentration greater than 5.2 mmol/L is hyperkalemia; less than 3.5 mmol/L is hypokalemia. Either abnormality can impair conduction, produce weakness, and progress to a fatal dysrhythmia. The first nursing question is not simply, “Is the potassium high or low?” Ask, “Is the myocardium electrically unstable, and is the result credible?” A patient with hyperkalemia and peaked T waves needs immediate cardiac protection and potassium-lowering treatment. A patient with severe hypokalemia and ventricular ectopy needs monitored replacement. A stable patient with an unexpected, haemolysed specimen needs urgent confirmation—but not at the expense of delaying treatment when instability is already present. The two problems require opposite potassium movement. Hyperkalemia is managed by protecting the heart, shifting potassium into cells, and removing potassium from the body. Hypokalemia is managed by replacing potassium while preventing overcorrection and infusion-related arrhythmia.