Management of Severe Hypocalcemia and Hyponatremia in Critical Care

Acute Calcium Replacement

Administer an initial IV bolus of 10–20 mL of 10 % calcium gluconate diluted in 50–100 mL of 5 % dextrose, infused over 10–20 minutes while continuously monitoring the ECG. 1

Check serum calcium continuously during the acute phase and then at least weekly during dose‑adjustment periods. 1
Measure serum sodium every 2 hours in patients with severe hyponatremic symptoms, every 4 hours in mildly symptomatic patients, and weekly during long‑term adjustment. [2][4]
Assess serum phosphate and magnesium concurrently, correcting hypomagnesemia because it impairs parathyroid hormone secretion and calcium homeostasis. 1
Obtain a 24‑hour urine calcium collection after stabilization to screen for hypercalciuria. 1
Verify magnesium levels before initiating calcium therapy, as untreated hypomagnesemia prevents effective calcium correction. 1

Transfer the patient to an ICU and initiate sodium monitoring every 2 hours. [2][4]
Give 3 % hypertonic saline aiming to raise serum sodium by ≈6 mmol/L over the first 6 hours (or until severe symptoms resolve). [2][3]4
Limit total sodium correction to ≤8 mmol/L in the first 24 hours (if 6 mmol/L is corrected in the first 6 hours, allow ≤2 mmol/L additional rise in the next 18 hours). [2][3]4
Calculate the sodium deficit as: Desired increase in Na (mmol) × 0.5 × ideal body weight (kg). [2][4]
Prefer rapid intermittent boluses of 100–150 mL 3 % saline over continuous infusion for symptomatic hyponatremia.

Determine the underlying volume status (hypovolemic, euvolemic, hypervolemic) to guide therapy. 3
For SIADH, start with fluid restriction to ≤1 L/day as first‑line treatment. [2][5]6
For cerebral salt wasting (hypovolemic hyponatremia), replace volume and sodium with isotonic saline and consider fludrocortisone 0.1 mg three times daily for 7 days. [2][4]7

Do not restrict fluids in hypovolemic hyponatremia (e.g., cerebral salt wasting), as this raises the risk of cerebral infarction. [7][6]
Avoid correcting chronic hyponatremia faster than 8–10 mmol/L in any 24‑hour period to prevent osmotic demyelination syndrome. [2][4]8

For hypocalcemia, obtain serum PTH, 25‑hydroxyvitamin D, phosphate, and magnesium levels, and evaluate for postoperative hypoparathyroidism or vitamin D deficiency. 1
For hyponatremia, measure serum and urine osmolality, urine sodium, assess volume status, and rule out thyroid disease and adrenal insufficiency. 3