Suxamethonium

ADMINISTRATION ROUTES:

IV, IM

ALTERNATIVE NAMES:

Succinyl Choline

ICU INDICATIONS:

1. Muscle relaxant used in rapid sequence induction

Note: Rocuronium is the preferred muscle relaxant for use in rapid sequence induction in Wellington ICU. Suxamethonium is only listed here for the very rare occasion when rocuronium may be contraindicated.

PRESENTATION AND ADMINISTRATION:

IV:

Suxamethonium 100 mg/2 mL

Administer neat

Refrigerate - stable at room temperature for 14 days

DOSAGE:

IV:

1 mg/kg

IM:

3 mg/kg

Note: Intramuscular is NOT the preferred route of use in ICU & should only be used in an emergency when intravenous/intraosseous access cannot be established

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose as in normal renal function. Avoid if there is hyperkalaemia

DOSAGE IN PAEDIATRICS:

IV:

Neonate:

3 mg/kg

Child:

2 mg/kg

Note: in children, there is a risk of bradycardia and asystole particularly if there is hypoxia. Suxamethonium should be given with atropine.

CLINICAL PHARMACOLOGY:

Suxamethonium is a depolarising skeletal muscle relaxant

CONTRAINDICATIONS:

1. Muscular dystrophy or other skeletal myopathies (including critical illness myopathy)
2. Personal or family history of malignant hyperthermia
3. Hypersensitivity to suxamethonium
4. Acute phase of injury following major burns, extensive denervation of skeletal muscle, or upper motor neuron injury. Risk of hyperkalaemia in these patients increases over time (peak 7 - 10 days after injury). Risk is dependent on the extent and location of injury. Precise time of onset and the duration of risk period is unknown

WARNINGS:

Cardiac arrest in children

Suxamethonium has been very rarely reported to cause acute rhabdomyolysis with hyperkalaemia followed by ventricular dysrhythmias, cardiac arrest and death in apparently healthy children. They were subsequently found to have undiagnosed skeletal muscle myopathy, most frequently Duchenne's muscular dystrophy. When a healthy infant or child develops cardiac arrest soon after administration of suxamethonium not felt to be due to inadequate ventilation, oxygenation or anaesthetic overdose, immediate treatment for hyperkalaemia should be instituted.

Electrolyte disturbances & digoxin toxicity

Suxamethonium should not be administered with to patients suffering from electrolyte abnormalities or those who may have digitalis toxicity. under these circumstances suxamethonium may induce serious cardiac arrhythmias or cardiac arrest due to hyperkalaemia.

Malignant hyperthermia

Suxamethonium administration has been associated with acute onset of malignant hyperthermia, a potentially fatal hypermetabolic state of skeletal muscle.

Suxamethonium apnoea

Prolonged muscle paralyis may occur after administration due to an abnormality or deficiency in plasma cholinesterase which is responsible for drug offset by metabolism. This may be caused by a genetically mediated enzyme deficiency or aquired due to certain diseases, physiological states (including pregnancy) or other medications. In such situations, the patient should be re-anaesthetised to avoid awareness. Resolution may take several hours. If administered elsewhere, admission to ICU for sedation and ongoing ventilation, awaiting resolution, may be required.

PRECAUTIONS:

General:

Suxamethonium may cause raised intraocular pressure & raised intracranial pressure

Laboratory Tests:

No tests additional to routine ICU tests are required

Drug/Laboratory Test Interactions:

None known

IMPORTANT DRUG INTERACTIONS IN ICU:

Drugs which may enhance the neuromuscular blocking action of suxamethonium include:

• gentamicin
• lithium carbonate
• magnesium salt
• metoclopramide

The neuromuscular blocking effect of suxamethonium may be enhanced by drugs that reduce plasma cholinesterase activity:

• oral contraceptives
• glucocorticoids
• monoamine oxidase inhibitors

ADVERSE REACTIONS:

General:

Allergic reactions (anaphylactic or anaphylactoid responses), malignant hyperthermia

Musculoskeletal:

Inadequate block, prolonged block

Cardiovascular:

Hypotension, hypertension, vasodilatation (flushing), tachycardia, bradycardia

Respiratory:

Respiratory arrest, dyspnoea, bronchospasm, laryngospasm

Renal:

Rhabdomyolysis with possible myoglobinuric acute renal failure