Hypocalcemia is defined as a total serum calcium concentration < 8.8 mg/dL (< 2.20 mmol/L) in the presence of normal plasma protein concentrations or as a serum ionized calcium concentration < 4.7 mg/dL (< 1.17 mmol/L). Reference ranges for serum calcium vary by age and sex. Hypocalcemia may be acquired or hereditary. Acquired causes include various illnesses, diet, medication, and surgery.
Hypoalbuminemia is the most common cause of hypocalcemia. Causes include cirrhosis, nephrosis, malnutrition, burns, chronic illness, and sepsis. This does not represent "true" hypocalcemia, because in most cases, ionized calcium is within normal ranges. In patients with hypoalbuminemia, the measured serum calcium concentration should be corrected for hypoalbuminemia.
The presentation of hypocalcemia varies widely, from asymptomatic to life-threatening. Hypocalcemia is frequently encountered in patients who are hospitalized. Depending on the cause, unrecognized or poorly treated hypocalcemic emergencies can lead to significant morbidity or death. Most cases of hypocalcemia are discovered by clinical suspicion and appropriate laboratory testing.
The treatment of hypocalcemia depends on the cause, severity, and presence of symptoms and how rapidly the hypocalcemia developed. Most cases of hypocalcemia are clinically mild and require only supportive treatment and further laboratory evaluation. Oral calcium repletion may be indicated for outpatient treatment of mild cases. On occasion, severe hypocalcemia may result in seizures; tetany; refractory hypotension; or arrhythmias that require a more aggressive approach, including intravenous infusions of calcium.
Hypercalcemia can result when too much calcium enters the extracellular fluid or when calcium excretion from the kidneys is insufficient. Approximately 90% of cases of hypercalcemia are caused by hyperparathyroidism or cancer. The remaining 10% of cases of hypercalcemia are caused by many different conditions, including vitamin D–related problems; disorders associated with rapid bone turnover; thiazide use; renal failure; and, in rare cases, familial disorders.
Treatment of hypercalcemia includes:
Volume repletion with isotonic sodium chloride solution
Peritoneal dialysis or hemodialysis
Surgical correction of hyperparathyroidism
This Fast Five Quiz was excerpted and adapted from the Medscape Drugs & Diseases articles Hyponatremia, Hypernatremia, Hypokalemia, Hyperkalemia, Hypocalcemia, and Hypercalcemia.
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Cite this: Vecihi Batuman. Fast Five Quiz: Electrolyte Disorders - Medscape - Mar 23, 2021.