Magnesium Sulphate

Question 1

What is magnesium sulphate?

Answer 1

Magnesium sulphate (10 mmol ampule (2.5g)/5mL) is an electrolyte and important cofactor in multiple processes. It causes vasodilation & bronchospasm through the inhibition of smooth muscle contraction. Magnesium also produces anticonvulsant and anti-dysrhythmic properties.

Filtered in the kidneys and excreted predominantly in the urine with small amounts in the faces & saliva.

Onset: immediate
Duration: 30 min
Half-life: varies

Question 2

Indications for magnesium sulphate?

Answer 2

ACP2:

1. Box jellyfish envenomation
2. Irukandji syndrome (with intractable pain unrelieved by narcotic analgesia AND/OR systolic BP >160 mmHg)

CCP:

3. Eclampsia
4. Torsades de Pointes
5. Severe life-threatening asthma (only in patient who have required IM/IV adrenaline)

Question 3

Contraindications for magnesium sulphate?

Answer 3

1. Allergy/ADR
2. Atrioventricular (AV) block
3. Renal failure

Question 4

Precautions for magnesium sulphate?

Answer 4

1. Renal impairment

Question 5

Side effects of magnesium sulphate?

Answer 5

1. Pain at the cannulation site

2. Magnesium toxicity: hypotension/resp depression, loss of deep tendon reflexes

Question 6

What is the dose of magnesium sulphate for an adult with box jellyfish envenomation or irukandji syndrome?

Answer 6

10 mmol over 20 min IV
Repeated once at 20 min

Administered via a SPRINGFUSOR 30 mL
- mix 10 mmol (5 mL) of magnesium sulphate with 15 mL sodium chloride 0.9% in the 30 mL syringe to achieve a final concentration of 10 mmol/20 mL

Question 7

What is the dose of magnesium sulphate for a paediatric with box jellyfish envenomation or irukandji syndrome?

Answer 7

0.1 mmol/kg (rounded up to nearest 0.5 mmol) over 15 min IV
Single dose must not exceed 5 mmol
Repeated once at 10 min
Total max dose 10 mmol

Administered via a SPRINGFUSOR 30 mL
- mix 0.1 mmol/kg of magnesium sulphate with sodium chloride 0.9% in the 30 mL syringe to achieve a final concentration of 0.1 mmol/kg in 15 mL