Treatment of Hypocalcemia

Classification by Severity

• Acute / symptomatic - medical emergency (tetany, seizures, laryngospasm, QT prolongation, cardiac arrhythmia)
• Chronic / asymptomatic - managed with oral supplementation

1. Acute Symptomatic Hypocalcemia (Emergency Treatment)

IV Calcium Options

Dosing Protocol

1. Initial bolus: Calcium gluconate 10-20 mL (10%) IV over 10 minutes with continuous ECG monitoring (watch QT interval).
   • In children: calcium gluconate 1-2 mL/kg at <1 mL/min
2. If symptoms persist (tetany, seizures): repeat the bolus as needed.
3. Maintenance infusion: Elemental calcium 1-2 mg/kg/hour (continuous IV infusion) until serum calcium normalizes.

Key Precautions

• Do not give IV calcium with bicarbonate- or phosphate-containing solutions (risk of precipitation).
• Do not give IV calcium in severe hyperphosphatemia (risk of ectopic calcium-phosphate deposition).
• Monitor serial ionized calcium levels throughout treatment.
• Watch for extravasation - calcium-containing fluids cause tissue necrosis.
• Avoid alkalosis - it further reduces ionized calcium.

2. Chronic / Asymptomatic Hypocalcemia

Oral Calcium

• Calcium carbonate is the most common oral supplement (1250 mg calcium carbonate = 500 mg elemental calcium).
• Start with 1-2 g of elemental calcium three times daily, given away from meals to maximize absorption.

Vitamin D / Calcitriol

• Calcitriol (active vitamin D) significantly improves calcium absorption from the gut.
• Start at 0.25 mcg twice daily and titrate up.
• For vitamin D deficiency (e.g., rickets), oral vitamin D 1000-2000 IU daily for 4 weeks with elemental calcium 40 mg/kg/day.

Diuretic Adjustment

• If the patient is on loop diuretics, consider switching to thiazide diuretics - thiazides reduce urinary calcium excretion, helping retain calcium.

3. Treat Underlying Causes

Important: Check serum magnesium in all cases of hypocalcemia. Hypomagnesemia impairs PTH secretion and causes PTH resistance - calcium will not rise until magnesium is corrected.

4. Monitoring During Treatment

• Fasting total and ionized serum calcium - check regularly
• Serum phosphate - monitor for reciprocal changes
• 24-hour urine calcium - keep below 4 mg/kg/day to prevent hypercalciuria and nephrocalcinosis
• Spot urine calcium-to-creatinine ratio - useful for outpatient monitoring
• PTH level - if hypocalcemia is not due to PTH deficiency
• Serum magnesium - at least annually in chronic cases

5. Anesthetic Considerations

• Correct significant hypocalcemia before elective surgery.
• Monitor ionized calcium intraoperatively in patients with known hypocalcemia.
• Avoid alkalosis intraoperatively (decreases ionized Ca²⁺).
• IV calcium may be needed after rapid transfusion of citrated blood products or large albumin volumes.
• Expect potentiation of negative inotropic effects of anesthetic agents.
• Responses to neuromuscular blocking agents are inconsistent - use nerve stimulator monitoring.

• Brenner and Rector's The Kidney, 2-Volume Set
• National Kidney Foundation Primer on Kidney Diseases, 8e
• Morgan and Mikhail's Clinical Anesthesiology, 7e

Oral Treatment of Hypocalcemia

Oral therapy is used for chronic or asymptomatic hypocalcemia. Symptomatic patients always need IV calcium first.

1. Oral Calcium Supplements

Calcium Carbonate (most common)

• Dose: 1-2 g of elemental calcium, 3 times daily
• Note: 1250 mg calcium carbonate = 500 mg elemental calcium
• Take away from meals to maximize absorption
• Preferred as first-line oral supplement

Calcium Chloride

• Generally not used orally - reserved for IV use only (causes vein sclerosis and pain even via IV peripheral routes)

2. Vitamin D Preparations (co-administered with calcium)

Calcitriol (1,25-dihydroxyvitamin D - active form)

• Dose: Start at 0.25 mcg twice daily, titrate up as needed
• Significantly increases gut calcium absorption
• Preferred in hypoparathyroidism and renal disease (kidney cannot activate vitamin D)

Cholecalciferol / Ergocalciferol (Vitamin D3 / D2)

• Used when the cause is nutritional vitamin D deficiency
• Dose: 1000-2000 IU daily for 4 weeks (for vitamin D deficiency rickets)
• Requires hepatic and renal activation - not suitable when these organs are impaired

3. Diuretic Adjustment

• Switch from loop diuretics (furosemide - increases urinary Ca²⁺ loss) to thiazide diuretics (reduce urinary calcium excretion)
• This is an adjunct measure, not a direct calcium supplement

4. Oral Magnesium (if hypomagnesemia is present)

• Hypomagnesemia must be corrected alongside calcium - oral or IV magnesium sulfate
• Without correcting Mg²⁺, calcium levels will not normalize regardless of supplementation

Quick Reference Table

Treatment of Urticaria

Step 1 - Identify and Remove the Trigger

Treatment Algorithm (EAACI & American Guidelines)

A. Mild to Moderate Acute Urticaria

First-Generation H1 Antihistamines (sedating)

Second-Generation H1 Antihistamines (non-sedating - preferred)

Second-generation antihistamines are preferred for long-term use due to better tolerability and no sedation.

B. Severe Urticaria with or without Angioedema

• H1 antihistamines: Diphenhydramine 25-50 mg PO q4-6h, or 10-50 mg IV/IM q4-6h (max 400 mg/24 hours)
• Corticosteroids:
  • Prednisone 10-60 mg PO every morning with taper over 2 weeks
  • Triamcinolone 40-60 mg IM single dose
  • Dexamethasone 4-20 mg/day IV or IM

C. Anaphylaxis (most severe)

• Airway: Intubation if needed
• Breathing: Supplemental oxygen
• Circulation: Epinephrine 1:1000 IV + volume expanders (saline)
• IV methylprednisolone 1-2 mg/kg/day
• H1 + H2 antagonists IV: Diphenhydramine 25-50 mg + Famotidine 20 mg IV

D. Chronic Idiopathic / Spontaneous Urticaria (CSU) - Stepwise Approach

Step 1 - Monotherapy

• Second-generation antihistamine (cetirizine 10 mg/day or fexofenadine 60-180 mg once or twice daily)
• Avoid known triggers (NSAIDs, physical factors)

Step 2 - If inadequate control after 2-4 weeks

• Increase dose of second-generation antihistamine (up to 4x standard dose)
• Add a second-generation antihistamine
• Add an H2 antagonist: Famotidine 20 mg twice daily or Cimetidine 400 mg twice daily
• Add a leukotriene receptor antagonist: Montelukast 10 mg/day
• Add a first-generation antihistamine at bedtime

Step 3 - If still inadequate (after another 2-4 weeks)

• Dose advancement of a more potent antihistamine: Hydroxyzine or Doxepin as tolerated

Step 4 - Refractory / Specialist-managed

• Omalizumab (anti-IgE monoclonal antibody): 150-300 mg subcutaneously once monthly
• Cyclosporine: 3 mg/kg/day or higher for 8-16 weeks (added to background antihistamine)

E. Refractory and Special Cases

• Systemic corticosteroids
• Dapsone
• Antifibrinolytics (tranexamic acid or epsilon-aminocaproic acid) - especially useful with angioedema
• Methotrexate
• Tacrolimus
• Hydroxychloroquine
• IV immunoglobulin (IVIG)
• Plasmapheresis
• Narrow-band UVB phototherapy

Note: Evidence for these agents is limited and mostly anecdotal. Risks vs. symptom burden must be weighed carefully.

F. Hereditary Angioedema (Bradykinin-mediated)

• Acute attacks: Icatibant, Ecallantide, or purified/recombinant C1-inhibitor
• Prophylaxis: C1-inhibitor, Lanadelumab

Special Populations

Pregnancy / Lactating Women

• Avoid systemic treatment in the first trimester if possible
• Chlorphenamine preferred (long safety record)
• Cetirizine and loratadine acceptable, preferably after first trimester, when benefits outweigh risks

Pediatric Patients

• Same treatment principles as adults
• Doses follow manufacturer's weight-based recommendations

Quick Summary Table

• Goldman-Cecil Medicine, International Edition
• Fitzpatrick's Dermatology, Volumes 1 & 2
• EAACI/GA²LEN/EDF/WAO Guideline 2018; AAAAI/ACAAI 2014 Guidelines

Recent evidence (PubMed 2024-2026): A systematic review (PMID 38420865) on acute urticaria treatment and a network meta-analysis (PMID 39673624) on omalizumab dosing for chronic urticaria are available - these are broadly consistent with the stepwise approach above.