Symptoms of Hypermagnesemia
Hypermagnesemia causes a spectrum of symptoms ranging from neurological manifestations to cardiovascular complications, with severe cases leading to respiratory depression and cardiac arrest. 1, 2
Clinical Manifestations by Severity
Neurological Symptoms
- Weakness and fatigue
- Muscle paralysis
- Ataxia (impaired coordination)
- Somnolence and confusion
- Altered mental status progressing to coma in severe cases 2, 3
- Decreased deep tendon reflexes 1
Cardiovascular Manifestations
- Vasodilation
- Hypotension (potentially refractory)
- Bradycardia
- Conduction abnormalities:
- Prolonged PR interval
- Widened QRS complex
- Prolonged QT interval 2
- Heart blocks
- Cardiac arrest in severe cases 1, 2
Respiratory Effects
Correlation with Magnesium Levels
- Mild hypermagnesemia (2.2-2.5 mEq/L): Often asymptomatic or mild symptoms
- Moderate hypermagnesemia (2.5-5.0 mEq/L): Hyporeflexia, nausea, vomiting, facial flushing, lethargy
- Severe hypermagnesemia (>5.0 mEq/L): Complete loss of deep tendon reflexes, severe hypotension, respiratory depression, heart blocks, coma 2
High-Risk Populations
Hypermagnesemia symptoms are most commonly seen in:
- Patients with renal insufficiency receiving magnesium-containing medications 2, 5
- Obstetric patients receiving magnesium sulfate for preeclampsia or preterm labor 1, 2
- Patients with bowel obstruction taking magnesium-containing laxatives or antacids 6, 5
Clinical Pitfalls
- Hypermagnesemia is often overlooked as a cause of altered mental status and hemodynamic instability 4
- Symptoms may be mistaken for other conditions such as stroke, sedative overdose, or sepsis
- Retained magnesium-containing medications in the GI tract can cause rebound hypermagnesemia even after initial treatment 6
- ECG changes may be subtle in early stages but can rapidly progress to life-threatening arrhythmias 2
Emergency Management
For cardiac arrest with suspected hypermagnesemia:
- Administer intravenous calcium (calcium chloride 10% 5-10 mL or calcium gluconate 10% 15-30 mL) over 2-5 minutes as a physiological antagonist 1, 2
- In severe cases with inadequate response to conservative measures, hemodialysis should be considered for rapid correction of magnesium levels 4, 6
Early recognition of hypermagnesemia symptoms is crucial as prompt intervention can prevent progression to life-threatening complications and improve outcomes.