# ๐Ÿ“‰ Hypocalcemia ## ๐Ÿ”ฌ Calcium-Phosphate Homeostasis Overview **Understanding the System:** Hypocalcemia results from disruption of the regulatory pathways shown above. The kidneys (red) are crucial for calcium reabsorption and calcitriol synthesis. Loss of PTH, vitamin D deficiency, or kidney disease commonly cause hypocalcemia. ## ๐Ÿšจ EMERGENCY PROTOCOL: Symptomatic Hypocalcemia 1 **IV Calcium Gluconate:** 1-2 ampules (90-180 mg elemental Ca) in 50-100 mL NS over 10-20 min 2 **Continuous Infusion:** 50-100 mg elemental Ca/hr in NS or D5W 3 **Check & Replace Magnesium:** IV MgSOโ‚„ 2-4 g over 20 min if low 4 **Cardiac Monitoring:** Essential, especially if on digoxin 5 **Avoid Bicarbonate:** Worsens hypocalcemia by โ†‘Ca-albumin binding **โš ๏ธ Warning Signs:** Tetany, seizures, laryngospasm, QT prolongation โ†’ TREAT IMMEDIATELY! ## ๐Ÿ“Š Clinical Presentation ### Neuromuscular Manifestations (Most Common) #### Chvostek's Sign Facial twitch with tapping #### Trousseau's Sign Carpopedal spasm with BP cuff #### Paresthesias Perioral, fingers, toes #### Tetany Muscle cramps, spasms #### Seizures Generalized tonic-clonic #### Laryngospasm Life-threatening stridor ### Cardiovascular - **QT prolongation** (most important ECG finding) - Heart failure (reversible) - Hypotension - Torsades de pointes (rare) ### Chronic Manifestations - Basal ganglia calcification - Cataracts - Dental abnormalities - Dry skin, brittle nails ## ๐Ÿ” Etiology and Pathophysiology [TABLE] ## ๐Ÿ”ฌ Diagnostic Approach ### Systematic Evaluation 1 **Confirm True Hypocalcemia:** - Albumin-corrected Ca or ionized Ca - Rule out lab error, EDTA contamination 2 **Essential Labs:** - **PTH:** Key branch point - **Phosphate:** High in hypoparathyroidism, low in vitamin D deficiency - **Magnesium:** MUST check and replace - **25-OH Vitamin D:** Screen for deficiency - **Creatinine:** Assess kidney function 3 **Interpretation by PTH Level:** - **Low/Undetectable PTH:** Hypoparathyroidism - **High PTH:** Secondary hyperparathyroidism (vitamin D deficiency, CKD, pseudohypoparathyroidism) - **Normal PTH:** Inappropriately normal = partial hypoparathyroidism or hypomagnesemia 4 **Additional Testing (as indicated):** - 1,25(OH)โ‚‚ Vitamin D (if 25-OH D normal) - 24-hour urine calcium - Genetic testing (DiGeorge, CaSR mutations) - ECG (QT interval) ## ๐Ÿงฎ Calcium Replacement Calculator Current Calcium (mg/dL): 6.5 Patient Weight (kg): 70 **Calcium Deficit: 140 mg elemental calcium**\ IV Calcium Gluconate 10%: ~1.5 ampules\ IV Calcium Chloride 10%: ~0.5 ampules ## ๐Ÿ’Š Treatment Strategies ### ๐Ÿ“Œ Acute Management #### IV Calcium Administration - **Calcium Gluconate 10%:** Preferred (less tissue necrosis if extravasates) - 1 ampule = 10 mL = 90 mg elemental calcium - **Calcium Chloride 10%:** 3ร— more elemental Ca but caustic - 1 ampule = 10 mL = 270 mg elemental calcium - **Rate:** 50-100 mg elemental Ca/hour - **Dilution:** In NS or D5W (NOT in bicarb or phosphate) **โš ๏ธ Critical:** MUST replace magnesium concurrently or calcium won't correct! ### ๐Ÿ“Œ Chronic Management by Etiology #### Hypoparathyroidism [TABLE] #### Vitamin D Deficiency **Replacement Protocol:** - **Loading:** 50,000 IU weekly ร— 8 weeks - **Maintenance:** 1,500-2,000 IU daily - **Obesity/Malabsorption:** 2-3ร— higher doses - **Goal:** 25-OH Vitamin D \>30 ng/mL #### CKD-Related - Phosphate control first (prevents Ca ร— POโ‚„ precipitation) - Calcitriol or vitamin D analogs - Calcium-based phosphate binders (if Ca low) - Careful monitoring to avoid vascular calcification ## ๐ŸŽฏ Key Clinical Pearls - Hypomagnesemia MUST be corrected first - Ca won't normalize otherwise - Check phosphate: High = hypoparathyroidism, Low = vitamin D deficiency - QT prolongation is the most important ECG finding - risk of torsades - Chvostek's sign: 10% false positives in normal patients - Trousseau's sign: More specific than Chvostek's - Post-thyroidectomy: Check Ca daily ร— 48-72 hours - Hungry bone syndrome: Severe hypocalcemia post-parathyroidectomy - IV calcium + digoxin = โ†‘โ†‘risk of toxicity (slow infusion, cardiac monitoring) - Alkalosis worsens symptoms by โ†“ionized Ca (avoid hyperventilation) - Vitamin D deficiency is pandemic - check in all hypocalcemia patients - PPIs can cause hypomagnesemia โ†’ secondary hypocalcemia - Critical illness hypocalcemia often doesn't need treatment unless symptomatic ## ๐Ÿ“š Special Considerations ### Post-Surgical - Risk after thyroid/parathyroid surgery - Check Ca q6h ร— 48-72h post-op - Prophylactic Ca + calcitriol if high risk - Permanent in 1-5% of total thyroidectomies ### Pregnancy/Lactation - โ†‘Ca demands (fetal skeleton, breast milk) - May unmask subclinical hypoparathyroidism - Increase Ca + vitamin D supplementation - Monitor closely postpartum ### Neonates - Early: Maternal hyperparathyroidism โ†’ suppressed fetal PTH - Late: DiGeorge, vitamin D deficiency - Check maternal history - Consider 22q11 deletion testing ## ๐Ÿ”„ Monitoring and Follow-up ### Outpatient Monitoring Schedule **Initial (Weekly ร— 1 month):** Ca, POโ‚„, Mg, Cr **Stable (q3-6 months):** Ca, POโ‚„, Cr, 25-OH Vitamin D **Annual:** 24hr urine Ca, renal imaging if hypercalciuria **Dose Adjustments:** Based on symptoms and Ca levels, not just labs --- [Website version](https://urinenephrology.org/2025_UDPA_Lectures_Live/electrolytes/calcium/hypocalcemia.html) ยท Markdown synchronized October 3, 2026.