Thiopentone

ADMINISTRATION ROUTES:

IV

ALTERNATIVE NAMES:

Sodium thiopental

ICU INDICATIONS:

1. Induction of anaesthesia
2. Treatment of status epilepticus refractory to other measures
3. Treatment of refractory raised intracranial pressure after traumatic brain injury

PRESENTATION AND ADMINISTRATION:

IV:

500 mg vials for reconstitution

Reconstitute with Water for Injection

For IV injection dilute 500 mg to a total of 20 mL using Water for Injection (makes a solution with a concentration of 25 mg/mL)

Store at room temperature

Note: Section 29 drug when administered IV (requires specific notification to Director-General of Health as unapproved route of administration)

DOSAGE:

IV:

2 - 5 mg/kg slow push

In unstable patients (i.e. most ICU patients) administer 75 mg at a time then assess effect on blood pressure and conscious state before administering more.

IV Infusion:

3 - 5 mg/kg/hour

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose as in normal renal function

DOSAGE IN PAEDIATRICS:

IV:

2 - 5 mg/kg slow push

CLINICAL PHARMACOLOGY:

Thiopentone is a short-acting CNS depressant which induces hypnosis and anaesthesia. It has no analgesic effect. It produces hypnosis within 30 seconds of intravenous injection. Repeated intravenous doses lead to prolonged anaesthesia as fatty tissues act as a reservoir & accumulate thiopentone in concentrations 6 - 12 times greater than the plasma concentration. This depot is then slowly released which prolongs anaesthesia. Recovery from bolus dose may be rapid (5 - 10 minutes) and is due to redistribution into body tissues rather than hepatic metabolism, which is slow.

CONTRAINDICATIONS:

1. Hypersensitivity to thiopentone
2. Acute intermittent porphyria

WARNINGS:

Administer with caution in haemodynamically unstable patients as rapid injection may cause profound hypotension. Extravasation can cause significant tissue necrosis due to a high pH (10.6) so reliable intravenous access is required for injection.

Risks of infusion:

If given by infusion over longer periods of time, there is an increased risk of infection due to an immunosuppressive effect. Thiopentone can also cause hyponatraemia and hypokalaemia. Stopping the infusion may result in rebound hyperkalaemia which should be closely monitored for. Emergence from infusion may take many hours or even days (depending on amount & duration of administration) due to fatty tissue deposition as previously described.

PRECAUTIONS:

General:

Use with care in patients with reduced left ventricular function

Laboratory Tests:

No tests additional to routine ICU tests are required

Drug/Laboratory Test Interactions:

None known

IMPORTANT DRUG INTERACTIONS IN ICU:

Thiopentone has a synergistic action with other CNS depressant drugs.

ADVERSE REACTIONS:

General:

Anaphylactic and anaphylactoid reactions

Cardiovascular:

Hypotension, myocardial depression, arrhythmias

Respiratory:

Respiratory depression, coughing, bronchospasm and laryngospasm

Dermatological:

Urticaria