The Forgotten Electrolyte
Magnesium serves as cofactor for >300 enzymatic reactions
Total Body Content
25g (1,000 mmol)
25g (1,000 mmol)
Intracellular
99% of total body Mg++
99% of total body Mg++
Normal Range
1.8-2.4 mg/dL
1.8-2.4 mg/dL
🎯 Clinical Significance and Homeostasis
Physiologic Roles
- Energy Metabolism: Mg-ATP complex formation
- Protein Synthesis: Ribosomal RNA binding
- Ion Channel Function: Na-K-ATPase, Ca++ channels
- Cardiac Conduction: Membrane stability
- Neuromuscular: Excitation-contraction coupling
Renal Handling
- Filtered Daily: 2,400 mg
- Reabsorbed: 95% total
- Proximal Tubule: 20%
- Thick Ascending Limb: 60% (key site)
- Distal Tubule: 10% (TRPM6 channels)
Critical Interactions
- Potassium: Mg++ required for K+ repletion
- Calcium: PTH synthesis and action
- Phosphate: Vitamin D metabolism
- Digitalis: Enhanced toxicity in deficiency
- Arrhythmias: Torsades de pointes risk
Magnesium Disorder Modules
📉 Hypomagnesemia
Mg++ < 1.8 mg/dL - Recognition and Management
🚨 Emergency Recognition:
- Tetany, seizures, torsades de pointes
- Refractory hypokalemia or hypocalcemia
- High-risk patients: alcohol use, PPI therapy
Key Causes:
- Chronic alcohol use disorder
- PPI therapy (>1 year)
- Loop/thiazide diuretics
- Malabsorption syndromes
Treatment Priorities:
- IV: 1-2g loading, 6g/24h
- PO: Citrate/gluconate forms
- Correct BEFORE K+ or Ca++
- Monitor DTRs, symptoms
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📈 Hypermagnesemia
Mg++ > 2.6 mg/dL - Rare but Life-Threatening
🚨 Emergency Recognition:
- Absent deep tendon reflexes (>7-10 mg/dL)
- Respiratory depression, cardiac arrest risk
- Almost always requires renal dysfunction
Key Risk Factors:
- CKD stages 4-5
- Mg-containing antacids/laxatives
- IV magnesium overdose
- Epsom salt ingestion
Emergency Treatment:
- IV Calcium (functional antagonist)
- Saline diuresis (if GFR adequate)
- Emergency dialysis (renal failure)
- Respiratory/cardiac support
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🧮 Magnesium Level Interpreter
Interpretation: Normal magnesium level
💎 Essential Clinical Pearls
Hypomagnesemia Pearls
- 30% total body depletion may occur before serum levels drop
- 60% of hypomagnesemic patients have concurrent hypokalemia
- PPI-induced deficiency usually requires >1 year of therapy
- Alcohol withdrawal increases Mg++ requirements substantially
- Magnesium citrate/gluconate preferred over oxide (better absorption)
Hypermagnesemia Pearls
- Rare with normal kidney function - always suspect renal dysfunction
- Deep tendon reflexes disappear at 7-10 mg/dL (reliable marker)
- Calcium provides immediate functional antagonism while definitive therapy initiated
- Magnesium citrate contains 1.75g elemental Mg - dangerous in CKD
- Hemodialysis clearance ~100 mL/min - very effective removal
🛡️ Prevention and Risk Mitigation
High-Risk Patient Identification and Monitoring
🔍 Hypomagnesemia Risk:
- Chronic alcohol use disorder
- Long-term PPI therapy (>1 year)
- Loop or thiazide diuretics
- Inflammatory bowel disease
- Diabetes with poor control
⚠️ Hypermagnesemia Risk:
- CKD stages 4-5 (eGFR <30)
- Elderly patients with constipation
- Patients using Mg-based laxatives
- Post-operative bowel preparation
- Traditional remedy users
🎯 Chapter Learning Objectives
Upon completion of this module, students will be able to:
- Recognize the clinical presentations of both hypo- and hypermagnesemia
- Identify high-risk patients and common causes of magnesium disorders
- Understand the critical interactions between magnesium, potassium, and calcium
- Apply evidence-based treatment protocols for both conditions
- Implement appropriate monitoring strategies during acute management
- Prevent magnesium disorders through risk stratification and patient education
- Integrate magnesium assessment into routine electrolyte evaluation
🚀 Ready to Master Magnesium Disorders?
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