Dissociative anesthetic
Ketamine
Ketalar Induction agent — yellow ⚠ 10 mg/mL⚠ 50 mg/mL⚠ 100 mg/mL
Dissociative anesthesia and analgesia that usually supports blood pressure and breathing.
Typical adult doses
| Indication | Dose | Onset | Duration |
|---|---|---|---|
| Induction | 1–2 mg/kg IV (label 1–4.5) | 30–60 s | 5–10 min |
| Induction, IM (label) | 6.5–13 mg/kg IM | 3–4 min | 12–25 min |
| Sub-anesthetic analgesia | 0.1–0.5 mg/kg IV | — | — |
Mechanism
NMDA receptor antagonist → dissociation, analgesia, amnesia.
Key effects
- Indirect sympathomimetic: ↑HR, ↑BP (catecholamine release/reuptake inhibition)
- Bronchodilation
- Relatively preserved respiratory drive and airway reflexes
- ↑ Secretions
Watch out for
- Direct myocardial depression is unmasked when catecholamines are depleted (prolonged shock) — BP may fall
- Emergence reactions (benzodiazepines reduce them)
- Label contraindication: where a significant BP rise would be hazardous
- Three concentrations exist — read the vial
Pimp questions
Pimp question 1
Why does ketamine usually raise blood pressure?
Answer
Sympathetic stimulation via catecholamine release and reuptake inhibition.
Pimp question 2
When might ketamine NOT raise blood pressure?
Answer
Catecholamine-depleted shock — its direct myocardial depression is unmasked.
Pimp question 3
Why add glycopyrrolate?
Answer
To reduce ketamine-induced secretions.