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Emergency And Acute Medicine: Hypocalcemia
Basics
Description Hypocalcemia is defined as a total plasma calcium level <8.7 mg/dL. Ionized calcium may be normal and therefore asymptomatic. Normal total serum calcium is 8.7–10.5 mg/dL.
Etiology Incidence is ~0.6% in the general population. Mechanisms include increased calcium loss from or decreased entry into the circulation. Circulating calcium exists as protein bound (45–50%, mainly albumin), complexed to anions (5–10%), and ionized free calcium (45–50%, physiologically active). Calcium homeostasis is regulated by parathyroid hormone, vitamin D (1,25-dihydroxyvitamin D), and calcitonin. Hypoalbuminemia is the most common cause; for each 1 g/dL decrease in albumin, total calcium decreases by ~0.8 mg/dL while ionized calcium remains unchanged.
Pediatric considerations Children have higher normal calcium levels (9.2–11 mg/dL). Neonatal hypocalcemia is defined as total calcium <7.5 mg/dL or ionized calcium <4 mg/dL and may present with jitteriness, tachypnea, apnea with cyanosis, and vomiting.
Diagnosis
Signs And Symptoms Occur when ionized calcium <3.2 mg/dL and depend on severity and rate of decline. Neuromuscular findings include paresthesias, hyperreflexia, muscle spasms, tetany, Chvostek sign, Trousseau sign, laryngeal stridor, seizures, and choreoathetosis. Cardiovascular effects include torsades de pointes, heart block, hypotension, impaired contractility, bradycardia, QT and ST prolongation, and T-wave abnormalities. Psychiatric manifestations include anxiety, irritability, depression, psychosis, confusion, and movement disorders. Ocular findings include papilledema and cataracts in acute cases.
Essential Workup Confirm diagnosis with serum ionized calcium level.
Diagnosis Tests And Interpretation
Lab ABG (pH changes affect ionized calcium), serum albumin, electrolytes, BUN/creatinine, glucose, magnesium, phosphate, PTH, and vitamin D metabolites as indicated.
ECG Prolonged QT interval and possible heart block.
Differential Diagnosis Impaired PTH secretion or action (post-surgical hypoparathyroidism, autoimmune or congenital hypoparathyroidism, pseudohypoparathyroidism), impaired vitamin D synthesis or action (malabsorption, renal disease), calcium sequestration or complexing (hyperphosphatemia, transfusion citrate, pancreatitis, rhabdomyolysis, alkalosis), hypomagnesemia, medications (bisphosphonates, calcitonin, phenytoin, cisplatin, PPIs), malignancy, sepsis, burns, and hungry bone syndrome after parathyroidectomy.
Treatment
Initial Stabilization/Therapy ABCs, IV access, and cardiac monitoring.
Emergency Department Treatment/Procedures Treat symptomatic hypocalcemia as an emergency. Give IV calcium gluconate 1–2 g in 50 mL D5W over 20 min. Faster infusion may cause dysrhythmias. Follow bolus with continuous infusion (0.5–1.5 mg/kg/hr elemental calcium). Do not mix calcium with bicarbonate or phosphate. Monitor calcium every 1–4 hr and titrate to symptoms or ECG changes. Correct hypomagnesemia if present (Mg 2 g IV). Use caution in patients on digoxin.
Chronic management Oral calcium 1.5–2 g/day (up to 4 g/day if malabsorption) plus vitamin D supplementation. Calcitriol is preferred for rapid onset.
Medications
IV calcium Calcium gluconate, calcium chloride, or calcium gluceptate (dose by elemental calcium).
Oral calcium Calcium carbonate, citrate, gluconate, lactate, or glubionate.
Vitamin D Calcitriol, ergocalciferol, or related preparations as indicated.
Follow-Up And Disposition
Admission Criteria Symptomatic hypocalcemia, ionized calcium <3.2 mg/dL, or need for continuous IV calcium.
Discharge Criteria Asymptomatic patients with ionized calcium >3.2 mg/dL and no significant comorbidities.
Follow-Up Recommendations Endocrinology follow-up for disorders of PTH or vitamin D metabolism.
Pearls And Pitfalls Hypocalcemia has multiple causes; treatment depends on severity and etiology. Severe symptoms require IV calcium. Hypocalcemia will not correct if magnesium deficiency is not treated first.
Basics
Description Hypocalcemia is defined as a total plasma calcium level <8.7 mg/dL. Ionized calcium may be normal and therefore asymptomatic. Normal total serum calcium is 8.7–10.5 mg/dL.
Etiology Incidence is ~0.6% in the general population. Mechanisms include increased calcium loss from or decreased entry into the circulation. Circulating calcium exists as protein bound (45–50%, mainly albumin), complexed to anions (5–10%), and ionized free calcium (45–50%, physiologically active). Calcium homeostasis is regulated by parathyroid hormone, vitamin D (1,25-dihydroxyvitamin D), and calcitonin. Hypoalbuminemia is the most common cause; for each 1 g/dL decrease in albumin, total calcium decreases by ~0.8 mg/dL while ionized calcium remains unchanged.
Pediatric considerations Children have higher normal calcium levels (9.2–11 mg/dL). Neonatal hypocalcemia is defined as total calcium <7.5 mg/dL or ionized calcium <4 mg/dL and may present with jitteriness, tachypnea, apnea with cyanosis, and vomiting.
Diagnosis
Signs And Symptoms Occur when ionized calcium <3.2 mg/dL and depend on severity and rate of decline. Neuromuscular findings include paresthesias, hyperreflexia, muscle spasms, tetany, Chvostek sign, Trousseau sign, laryngeal stridor, seizures, and choreoathetosis. Cardiovascular effects include torsades de pointes, heart block, hypotension, impaired contractility, bradycardia, QT and ST prolongation, and T-wave abnormalities. Psychiatric manifestations include anxiety, irritability, depression, psychosis, confusion, and movement disorders. Ocular findings include papilledema and cataracts in acute cases.
Essential Workup Confirm diagnosis with serum ionized calcium level.
Diagnosis Tests And Interpretation
Lab ABG (pH changes affect ionized calcium), serum albumin, electrolytes, BUN/creatinine, glucose, magnesium, phosphate, PTH, and vitamin D metabolites as indicated.
ECG Prolonged QT interval and possible heart block.
Differential Diagnosis Impaired PTH secretion or action (post-surgical hypoparathyroidism, autoimmune or congenital hypoparathyroidism, pseudohypoparathyroidism), impaired vitamin D synthesis or action (malabsorption, renal disease), calcium sequestration or complexing (hyperphosphatemia, transfusion citrate, pancreatitis, rhabdomyolysis, alkalosis), hypomagnesemia, medications (bisphosphonates, calcitonin, phenytoin, cisplatin, PPIs), malignancy, sepsis, burns, and hungry bone syndrome after parathyroidectomy.
Treatment
Initial Stabilization/Therapy ABCs, IV access, and cardiac monitoring.
Emergency Department Treatment/Procedures Treat symptomatic hypocalcemia as an emergency. Give IV calcium gluconate 1–2 g in 50 mL D5W over 20 min. Faster infusion may cause dysrhythmias. Follow bolus with continuous infusion (0.5–1.5 mg/kg/hr elemental calcium). Do not mix calcium with bicarbonate or phosphate. Monitor calcium every 1–4 hr and titrate to symptoms or ECG changes. Correct hypomagnesemia if present (Mg 2 g IV). Use caution in patients on digoxin.
Chronic management Oral calcium 1.5–2 g/day (up to 4 g/day if malabsorption) plus vitamin D supplementation. Calcitriol is preferred for rapid onset.
Medications
IV calcium Calcium gluconate, calcium chloride, or calcium gluceptate (dose by elemental calcium).
Oral calcium Calcium carbonate, citrate, gluconate, lactate, or glubionate.
Vitamin D Calcitriol, ergocalciferol, or related preparations as indicated.
Follow-Up And Disposition
Admission Criteria Symptomatic hypocalcemia, ionized calcium <3.2 mg/dL, or need for continuous IV calcium.
Discharge Criteria Asymptomatic patients with ionized calcium >3.2 mg/dL and no significant comorbidities.
Follow-Up Recommendations Endocrinology follow-up for disorders of PTH or vitamin D metabolism.
Pearls And Pitfalls Hypocalcemia has multiple causes; treatment depends on severity and etiology. Severe symptoms require IV calcium. Hypocalcemia will not correct if magnesium deficiency is not treated first.
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