Hypomagnesaemia

“Electrolyte disturbance caused by serum magnesium levels less than 0.7mmol/L“

Risk Factors

• Alcoholism
• Congestive heart failure
• Diabetes
• Chronic diarrhoea
• Hypokalaemia
• Hypocalcaemia
• Malnutrition

Aetiology

• Decreased GI absorption:
  • Diarrhoea
  • Malabsorption
  • Inadequate dietary intake
• Increased renal loss
  • Diuresis secondary to alcohol
  • Glycosuria
  • Loop diuretic

Pathophysiology

• Decreased gastrointestinal absorption, increased renal loss of magnesium

Clinical Presentation

• Anorexia
• Nausea & vomiting
• Lethargy
• Weakness
• Personality change
• Tetany (positive Trousseau sign or Chvostek sign)
• Tremor and muscle fasciculations

Investigations

• Measurement of serum magnesium concentration in patients with risk factors and unexplained hypocalcaemia or hypokalaemia
• ECG

Management

• Oral magnesium salts such as magnesium gluconate
• IV or IM magnesium sulfate if severe (<0.5mmol/L) or cannot tolerate oral treatment

Complications

• Cardiac arrhythmia
• Seizures
• Coronary artery vasospasm