Treatment of Abnormal Ionized Calcium Levels
The treatment of abnormal ionized calcium levels depends on the direction and severity of the abnormality, with hypocalcemia requiring calcium supplementation and hypercalcemia requiring hydration and possibly bisphosphonates.
Hypocalcemia Management
Post-Parathyroidectomy Hypocalcemia
- If ionized calcium falls below normal (<0.9 mmol/L or <3.6 mg/dL), initiate calcium gluconate infusion at 1-2 mg elemental calcium per kg body weight per hour 1, 2
- A 10-mL ampule of 10% calcium gluconate contains 90 mg of elemental calcium 2
- Monitor ionized calcium every 4-6 hours for the first 48-72 hours after parathyroidectomy, then twice daily until stable 1
- Gradually reduce calcium infusion when ionized calcium reaches normal range (1.15-1.36 mmol/L) and remains stable 1
- When oral intake is possible, transition to oral calcium carbonate 1-2 g three times daily, plus calcitriol up to 2 g/day 1
Administration Considerations
- For emergency situations (severe symptomatic hypocalcemia), administer calcium gluconate 10% 15-30 mL IV over 2-5 minutes 3
- For patients with renal impairment, start at the lowest dose of the recommended range and monitor serum calcium levels every 4 hours 4
- Administer through a central venous catheter when possible to prevent tissue injury from extravasation 3
Hypercalcemia Management
Mild to Moderate Hypercalcemia
- Mild hypercalcemia (total calcium <12 mg/dL or ionized calcium 5.6-8.0 mg/dL) is often asymptomatic and may not require acute intervention 5
- For primary hyperparathyroidism with mild hypercalcemia, consider parathyroidectomy based on age, calcium level, and evidence of kidney or skeletal involvement 5
- In patients >50 years with serum calcium <1 mg/dL above upper normal limit and no evidence of skeletal or kidney disease, observation may be appropriate 5
Severe Hypercalcemia
- For symptomatic or severe hypercalcemia (total calcium ≥14 mg/dL or ionized calcium ≥10 mg/dL), initial therapy consists of:
- For patients with kidney failure, consider denosumab and dialysis 5
- Glucocorticoids may be used when hypercalcemia is due to excessive intestinal calcium absorption (vitamin D intoxication, granulomatous disorders) 5
Special Considerations
Adynamic Bone Disease in CKD
- For adynamic bone disease in Stage 5 CKD (determined by bone biopsy or intact PTH <100 pg/mL), allow plasma PTH levels to rise to increase bone turnover 1
- This can be accomplished by decreasing doses of calcium-based phosphate binders and vitamin D or eliminating such therapy 1
- Lowering dialysate calcium (1.0-2.0 mEq/L) has been suggested but remains experimental 1
Severe Hyperparathyroidism
- Parathyroidectomy is recommended for severe hyperparathyroidism (persistent intact PTH >800 pg/mL) with hypercalcemia and/or hyperphosphatemia refractory to medical therapy 1
- Effective surgical options include subtotal parathyroidectomy or total parathyroidectomy with parathyroid tissue autotransplantation 1
Monitoring in Critical Illness
- Extreme abnormalities of ionized calcium (<0.8 mmol/L or >1.4 mmol/L) are independently associated with increased ICU and hospital mortality 6
- However, within a broad range of values, ionized calcium concentration has no independent association with mortality 6
- Widespread, protocolized measurement and correction of ionized calcium with the goal of normalizing values should be discouraged in critically ill patients without specific indications 7
Complications to Watch For
- Overdosage of calcium can result in hypercalcemia, with symptoms including depression, weakness, fatigue, confusion, hallucinations, disorientation, seizures, and coma 4
- After parathyroidectomy, patients may develop hungry bone syndrome requiring vigorous calcium replacement 8
- If phosphate binders were used pre-surgery, they may need to be discontinued or reduced based on serum phosphorus levels 1