Sun28November0628PM 40

What is the single most likely side effect resulting from the administration of 1 mg/kg suxamethonium to an adult patient?

(Please select 1 option)

Malignant hyperpyrexia

Myalgia Correct

Prolonged block

Hyperkalaemia

Anaphylaxis

Explanation

The incidence of suxamethonium induced myalgia ranges from 1.5 - 85% and is the commonest adverse effect of administration.

It occurs more commonly in females, ambulatory surgery and resembles the aches experienced after unaccustomed exercise. Majority studies reveal absence of correlation between fasciculations and muscle

pain. Also there is no correlation between fasciculations and muscle damage as evidenced by CK changes. However the pain is thought to be due to microfibrillar rupture.

Attempts at attenuating the severity of postoperative pain have focused on pre-treatment with a number of drugs. These include small doses of non-depolarising neuromuscular blocking agent, phenytoin, lidocaine, vitamin C, calcium gluconate, dantrolene, magnesium, aspirin/NSAIDs and chlorpromazine.

The administration of suxamethonium normally leads to a transient rise in serum potassium in the order of 0.2-0.4 mmol/L but is not sufficient to cause hyperkalaemia unless of course the serum potassium concentration is already at the upper limit of normal.

The rises in K+ can be dangerously high following burns and spinal cord injury. This is thought to be due to proliferation of extra-junctional receptors. Suxamethonium is thought to be safe in the early stages of these injuries (less than 48 hours).

Prolonged block from suxamethonium may result from a phase II block or a genetic/acquired deficiency of plasma cholinesterase.

The incidence of suxamethonium apnoea is quoted as approximately 1 in 1,800.

The incidence of malignant hyperthermia is between 1 in 45,000 - 1 in 100,000 general anaesthetics with known trigger agents.

The incidence of anaphylaxis to suxamethonium is approximately 1 in 1,000.

Answer Statistics

1

2%

2

76%

3

6%

4

16%

5

3%

Times answered: 253