Urgent considerations
See Differentials for more details
Any patient presenting with symptoms and signs of hypocalcaemia, or found to have low serum calcium levels, should have a thorough evaluation for the causes of hypocalcaemia. Acute hypocalcaemia can be seen in patients postoperatively after parathyroid surgery due to the 'hungry bone syndrome' or iatrogenic hypoparathyroidism.
The main aim of acute management of hypocalcaemia is to improve the acute clinical features, including cardiac hyperexcitability, tetany, hypotension, seizures, mental confusion, and carpopedal spasms, and not necessarily to return the calcium level to normal.[1]
Depending on the urgency (e.g., tetany, respiratory failure, arrhythmia, or seizure) and magnitude of hypocalcaemia (e.g., acute drop to <1.9 mmol/L [<7.5 mg/dL]), calcium replacement can be given by intravenous infusion or intravenous push.
Calcium gluconate is the preferred form of intravenous calcium because calcium chloride is more likely to cause local irritation.[1] Electrocardiographic monitoring is recommended because dysrhythmias can occur if correction is too rapid.
Calcium, particularly when given rapidly by the intravenous route, may produce serious arrhythmias in patients taking digitalis, as hypercalcaemia can worsen digitalis toxicity. Conversely, hypocalcaemia can nullify the effects of digoxin; thus, digoxin may be ineffective until serum calcium is restored to normal. Continuous ECG monitoring during intravenous calcium replacement is mandated in patients receiving digoxin therapy.[2] After the calcium level has been adjusted, the possible causes of hypocalcaemia should be investigated.
Magnesium levels (especially hypomagnesaemia) should be checked and adjusted; an imbalance can be associated with hypocalcaemia because of its effect on parathyroid hormone secretion and action. Any cause of hypomagnesaemia (e.g., use of proton pump inhibitors [PPIs]) can result in hypocalcaemia.[12][29] It is important to identify hypomagnesaemia, because calcium cannot be adequately adjusted unless magnesium has first been replaced. Hypomagnesaemia secondary to a PPI will recur if the PPI is re-started.[29][30]
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