II. Definitions
- Hypermagnesemia
- Serum Magnesium over 2.5 meq/L
- Typically asymptomatic until Serum Magnesium >4-5 mg/dl
III. Symptoms
- Muscle Weakness
- Headache
- Excessive thirst
IV. Signs
- Hyporeflexia
- Clonus
- Severe findings (Serum Magnesium >10 mEq/dl)
- Bradyarrhythmia
- Hypotension
- Respiratory depression
- Pulmonary Edema
V. Causes
- Renal Failure
- Medication overuse
- Adrenal Insufficiency (Addison's Disease)
- Hypothyroidism (Myxedema)
- Massive Magnesium dosing or intake
- Preeclampsia or Eclampsia management
- Tissue breakdown
VI. Labs
- See Serum Magnesium
- Serum Magnesium level is reliable in Hypermagnesemia (contrast with Hypomagnesemia)
-
Serum Magnesium Interpretation
- Normal in pregnancy: 1.3 to 2.6 mg/dl
- Therapeutic in Preeclampsia: 5.5-7.5 mg/dl
- Loss of Patellar Reflex: 10-12 mg/dl
- Respiratory depression: 15-17 mg/dl
- Paralysis: 15-17 mg/dl
- Cardiac Arrest: 30-35 mg/dl
VII. Management
- Stop all Magnesium Sources
- Supportive Care with ABC Management
-
Hemodialysis
- Indicated in End Stage Renal Disease and severe, refractory signs
- Cardiotoxicity Management: Calcium
- Calcium Chloride (1.4 mEq/ml)
- Dose: 5 ml over 10 minutes
- May repeat second dose in 5 minutes if EKG not improved
- Preferred historically for shock or cardiac instability (especially if central access)
- However Calcium Gluconate likely has same efficacy with better peripheral IV safety
- See Intravenous Calcium for differences between Calcium preparations
- Calcium Gluconate 10% (0.4 mEq/ml)
- Preferred agent if only peripheral IV available (Decreased venous sclerosis with infusion)
- Initial dose: 10 ml over 2-5 minutes (10 minutes is lower risk if time allows)
- Second dose after 5 minutes if EKG not improved
- Advantages over Calcium Chloride
- Calcium Chloride (1.4 mEq/ml)
VIII. References
- Willis and Swaminathan in Swadron (2023) EM:Rap 23(6): 4-5