Hall Anesthesia Practice Test

When potassium is high, the heart becomes at risk for dangerous electrical disturbances. The immediate problem is the effect on cardiac membranes, which hyperkalemia makes more excitable and prone to conduction abnormalities. Giving calcium IV stabilizes the myocardial cell membranes by raising the threshold potential, so the cells are less likely to depolarize in response to the excess extracellular potassium. This quickly reduces the likelihood of arrhythmias and buys time to lower or redistribute potassium with other measures. Importantly, calcium does not lower potassium levels itself; it simply protects the heart while you address the underlying potassium excess. After stabilization, you would use therapies that shift potassium into cells or remove it from the body, such as insulin with glucose, bicarbonate in appropriate cases, beta-agonists, diuretics, or dialysis, depending on the clinical context.