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NMDA Receptor Antagonist (Dissociative Anaesthetic / Analgesic) Pregnancy: Intraoperative use acceptable; CS induction agent of choice when thiopentone unavailable

Ketamine (Perioperative — Opioid-Sparing Analgesia)

Brand names: Ketalar

Adult dose

Dose: Sub-anaesthetic analgesia: 0.1–0.5 mg/kg IV bolus. Induction: 1–2 mg/kg IV. Intraoperative infusion: 0.1–0.5 mg/kg/hr IV. IM: 4–6 mg/kg for induction
Route: IV slow bolus or infusion; IM
Frequency: Bolus PRN or continuous infusion intraoperatively
Max: Titrate to response
Provides analgesia, sedation, and amnesia without significant respiratory depression. Maintains airway reflexes (relatively). Sub-anaesthetic dose (0.1–0.3 mg/kg) reduces intraoperative and post-operative opioid requirements. Avoid psychomimetic effects: co-administer midazolam 1–2 mg IV (reduces emergence reactions).

Paediatric dose

Dose: 1 mg/kg
Route: IV or IM
Frequency: Bolus; titrate
Max: IM: 6 mg/kg; IV: titrate to effect
Concentration: 10 mg/mL or 50 mg/mL mg/ml
Procedural sedation in children: 1–2 mg/kg IV or 4–6 mg/kg IM. Co-administer midazolam to reduce emergence phenomena. Widely used in paediatric A&E for fracture reduction.

Dose adjustments

Renal

No dose adjustment required

Hepatic

Caution in severe hepatic disease (prolonged action)

Paediatric weight-based calculator

Procedural sedation in children: 1–2 mg/kg IV or 4–6 mg/kg IM. Co-administer midazolam to reduce emergence phenomena. Widely used in paediatric A&E for fracture reduction.

Clinical pearls

  • Opioid-sparing: sub-anaesthetic ketamine (0.5 mg/kg IV at induction) reduces intraoperative and post-operative opioid consumption — recommended in Enhanced Recovery protocols
  • Maintains airway reflexes better than other agents — valuable in pre-hospital, emergency, and field anaesthesia
  • Bronchodilator: drug of choice for induction in severe asthmatics (bronchospasm protection)
  • Shock/trauma: ketamine maintains haemodynamics (sympathomimetic) — preferred induction agent in haemodynamically unstable patients
  • Co-administer midazolam 1–2 mg IV to reduce emergence hallucinations and dysphoria

Contraindications

  • Poorly controlled hypertension (increases BP and HR)
  • History of schizophrenia or psychosis
  • Raised intracranial pressure
  • Acute porphyria

Side effects

  • Hypertension and tachycardia (sympathomimetic — useful in shocked patients)
  • Emergence reactions / vivid dreams (reduce with benzodiazepine co-admin)
  • Hypersalivation
  • Laryngospasm (rare)
  • Nystagmus
  • Dysphoria (psychotomimetic effects)

Interactions

  • Benzodiazepines — reduce emergence reactions; co-prescribe routinely
  • Volatile anaesthetics — prolonged recovery
  • Antihypertensives — may unmask hypotension after stopping sympathomimetic effect

Monitoring

  • Blood pressure and HR (hypertension common)
  • Airway (secretions — may need suction)
  • Level of sedation
  • Emergence reactions on recovery

Reference: BNFc; BNF; RCoA Acute Pain Handbook; AAGBI Ketamine Guidelines; Cochrane Ketamine-PONV Review. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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