Calcium and Tetany

Tetany is the bedside expression of increased neuromuscular excitability, usually from a critically low ionized calcium concentration. The patient may first report tingling around the mouth or in the fingers, but the dangerous progression is muscle spasm involving the hands, larynx, respiratory muscles, or heart. A nurse who recognizes that progression acts on airway, breathing, circulation, and cardiac rhythm rather than treating the tingling as an isolated complaint. Chronic kidney disease creates a characteristic setting for hypocalcemia: impaired renal activation of vitamin D reduces intestinal calcium absorption, phosphate retention binds calcium and disrupts mineral balance, and secondary hyperparathyroidism increases bone turnover. The result may be gradual and relatively subtle, or it may become clinically urgent when the ionized calcium falls enough to produce tetany. The priority changes with the patient's presentation. An asymptomatic patient with a mildly low total calcium requires confirmation and cause-directed evaluation. A patient with carpopedal spasm, stridor, a seizure, hypotension, or a prolonged QT interval needs immediate escalation and carefully administered intravenous calcium according to the emergency order or protocol.