What is the most appropriate next step in management for a patient with hypocalcemia and mild hyponatremia presenting with central nervous system (CNS) symptoms such as agitation?

Management of Hypocalcemia with CNS Symptoms in the Presence of Mild Hyponatremia

The most appropriate next step is immediate administration of intravenous calcium gluconate (Option B), as symptomatic hypocalcemia with CNS manifestations represents a medical emergency requiring urgent correction regardless of concurrent mild hyponatremia.

Rationale for Immediate Calcium Correction

Symptomatic hypocalcemia (calcium 1.92 mmol/L, approximately 7.7 mg/dL) with agitation constitutes acute symptomatic hypocalcemia requiring immediate IV calcium gluconate administration. 1 The patient's calcium level is below the critical threshold of 7.5 mg/dL where urgent correction is mandated, and CNS symptoms (agitation) indicate cerebral dysfunction from hypocalcemia. 1, 2

• Administer calcium gluconate 50-100 mg/kg IV slowly with continuous ECG monitoring as the first-line intervention for symptomatic hypocalcemia. 3, 1, 4
• Calcium gluconate is preferred over calcium chloride for IV administration, containing 90 mg elemental calcium per 10 mL of 10% solution (9.3 mg or 0.465 mEq per mL). 1, 4
• Do NOT exceed an infusion rate of 200 mg/minute in adults to avoid hypotension, bradycardia, and cardiac arrhythmias. 4

Why Hyponatremia Correction is NOT the Priority

The sodium level of 132 mmol/L represents mild hyponatremia that is not severe enough to cause CNS symptoms on its own. 3

• Severe CNS symptoms from hyponatremia (seizures, coma) typically occur with sodium levels below 120 mmol/L, not at 132 mmol/L. 3
• The agitation is far more likely attributable to the severe hypocalcemia (1.92 mmol/L) than to mild hyponatremia. 1, 5
• Correcting hyponatremia first while ignoring symptomatic hypocalcemia could lead to life-threatening cardiac arrhythmias, seizures, or laryngospasm. 1, 5

Critical Monitoring During Calcium Administration

Continuous ECG monitoring is mandatory during calcium gluconate infusion due to risk of cardiac arrhythmias, particularly prolonged QT interval correction and potential for dysrhythmias. 1, 5, 4

• Measure serum calcium every 4-6 hours during intermittent infusions and every 1-4 hours during continuous infusion. 4
• Check magnesium levels immediately - hypomagnesemia (<1.0 mg/dL) will prevent successful calcium correction and must be repleted concurrently with IV magnesium sulfate. 1, 2
• Assess for Chvostek's sign (facial twitching with facial nerve tapping) and Trousseau's sign (carpopedal spasm with BP cuff inflation) to gauge neuromuscular irritability. 1

Essential Concurrent Investigations

While administering calcium, obtain:

• Ionized calcium, magnesium, PTH, phosphorus, creatinine, and 25-hydroxyvitamin D to determine the underlying etiology. 1, 5
• 12-lead ECG to assess for prolonged QT interval and cardiac manifestations. 1, 5
• Magnesium is particularly critical as severe hypomagnesemia causes functional hypoparathyroidism and hypocalcemia will not correct until magnesium is repleted. 2

Common Pitfalls to Avoid

Never delay calcium administration to correct mild hyponatremia first - this represents a dangerous misunderstanding of priorities in symptomatic hypocalcemia. 1

• Avoid rapid IV administration - infuse slowly to prevent hypotension, bradycardia, syncope, and cardiac arrest. 4
• Use a secure IV line to prevent extravasation, which causes calcinosis cutis, tissue necrosis, and ulceration. 4
• Do not mix calcium gluconate with fluids containing bicarbonate or phosphate (precipitation occurs), or with ceftriaxone (fatal precipitates can form, especially in neonates). 4
• Never overlook magnesium deficiency - this is the most commonly missed reversible cause of refractory hypocalcemia. 2

Addressing the Hyponatremia Subsequently

Once the life-threatening hypocalcemia is corrected and the patient is stabilized:

• The mild hyponatremia (132 mmol/L) can be addressed with fluid restriction (1 L/day) if SIADH is suspected, or with appropriate treatment based on volume status assessment. 3
• Rapid correction of chronic hyponatremia should be avoided (not exceeding 8 mmol/L over 24 hours) to prevent osmotic demyelination syndrome. 3

1, 5, 2, 4