General - Magnesium

Question 1

Hypermagnesemia is considered when there’s a serum magnesium concentration of what?

Answer 1

> 2.6mg/dL

Question 2

1) What is hypermagnesemia usually caused by?
2) Name 2 other causes

Answer 2

1) Renal failure
2) Hypothyroidism, Addison’s disease, drugs containing magnesium i.e. laxatives or antacids, familial hypocalciuric hypercalcaemia, Milk-alkali syndrome which causes metabolic alkalosis

Question 3

What can be given to increase magnesium excretion?

Answer 3

• Diuretics
• IV calcium

Question 4

Hypomagnesaemia is when serum magnesium concentration is below what?

Answer 4

1.8mg/dL

Question 5

Name 3 causes of hypomagnesaemia

Answer 5

• Decreased gut absorption (PPIs, insufficient dietary intake, alcoholism, total parenteral nutrition, malabsorption, diarrhoea)
  disease, vomiting, short bowel syndrome or fistulae)
• Redistribution from extracellular to intracellular space (refeeding syndrome, insulin administration, acute pancreatitis, alcohol withdrawal, hypokalaemia, hypercalcaemia)
• Increased renal excretion (loop and thiazide diuretics, digoxin, gentamicin, chemotherapy)

Question 6

Name 2 complications of hypomagnesaemia

Answer 6

• Weakness
• Paraesthesia
• Seizures
• Coma
• Hypocalcaemia
• Hypokalaemia
• Ventricular arrhythmias
• Chondrocalcinosis

Question 7

1) If magnesium concentration is <0.4mmol/L, or there’s tetany, arrhythmias or seizures - what is the treatment?
2) If magnesium concentration is >0.4mmol/L, what is the treatment?

Answer 7

1) IV magnesium replacement i.e. magnesium sulphate
2) Oral magnesium salts