Barbiturate Induction Agent
Pregnancy: Compatible for anaesthetic induction — used extensively in obstetric anaesthesia (rapidly crosses placenta but short duration)
Thiopental Sodium
Brand names: Intraval Sodium
Adult dose
Dose: Induction: 3–5 mg/kg IV (reduce to 1–2 mg/kg in shocked/elderly/debilitated patients). Raised ICP/status epilepticus: 3–5 mg/kg loading, then 0.5–5 mg/kg/h infusion
Route: IV
Frequency: Single dose for induction; infusion for SE/ICP
Max: 7 mg/kg per induction dose
Preferred induction agent for RSI in raised ICP (reduces cerebral O2 demand and ICP). Causes dose-dependent cardiovascular depression. Strongly alkaline solution (pH 10.5) — extravasation causes tissue necrosis.
Paediatric dose
Dose: 5 mg/kg
Route: IV
Frequency: Single induction dose
Max: 7 mg/kg
Concentration: 25 mg/mL or 50 mg/mL (reconstituted) mg/ml
Neonates and infants require lower doses (2–3 mg/kg). Reconstitute with water for injection to 25 mg/mL. Yellow powder — reconstitute freshly.
Dose adjustments
Renal
No dose adjustment; elimination not significantly renally dependent
Hepatic
Caution in severe hepatic impairment — prolonged effect due to reduced metabolism
Paediatric weight-based calculator
Neonates and infants require lower doses (2–3 mg/kg). Reconstitute with water for injection to 25 mg/mL. Yellow powder — reconstitute freshly.
Clinical pearls
- Porphyria absolute contraindication — thiopental can trigger acute porphyric crisis, potentially fatal
- Remains preferred over propofol for raised ICP induction in some centres due to ICP-lowering effect
- Extravasation or intra-arterial injection: causes severe tissue necrosis and ischaemia — verify IV placement before injection
- Check patency and confirm IV before injecting — if in artery, patient feels immediate burning; papaverine 40 mg may be injected intra-arterially
Contraindications
- Porphyria (absolute — causes porphyric crisis)
- Absence of resuscitation facilities
- Inability to secure airway
Side effects
- Hypotension (significant — especially with hypovolaemia)
- Apnoea/respiratory depression
- Laryngospasm
- Extravasation necrosis (very alkaline)
- Anaphylaxis (rare)
- Tachycardia (reflex)
Interactions
- Opioids — additive CNS and respiratory depression
- Antihypertensives — enhanced hypotension
- Atropine — often given prophylactically to prevent bradycardia
Monitoring
- Blood pressure (continuous)
- ECG
- SpO2/respiratory function
- BIS or other depth of anaesthesia monitoring (infusion use)
Reference: BNFc; BNF; Stoelting's Pharmacology and Physiology in Anaesthetic Practice; RCoA Guidelines. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.