Ketamine
An NMDA-blocking anesthetic, given IV or IM, that gives dissociative anesthesia with strong pain relief while supporting blood pressure.
Drug card
- Class
- Intravenous anesthetic, and an NMDA receptor antagonist
- How it works
- Blocking NMDA glutamate receptors, producing dissociative anesthesia
- Used for
- Sole anesthetic for procedures not needing muscle relaxation
- Inducing anesthesia, or adding to other anesthetics
- Known for
- Emergence delirium: confusion and agitation on waking
- Vivid dreams and hallucinations
- Raised blood pressure
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does ketamine work?
Ketamine, a racemic mixture, is a non-competitive NMDA receptor antagonist; its metabolite norketamine acts weakly at the same site. It produces dissociative anesthesia: deep analgesia, with throat reflexes and muscle tone kept and the heart and breathing stimulated, and only brief, mild respiratory depression. It can be given IV or IM.
Like other intravenous anesthetics: Given IV, these drugs reach the brain fast and switch off consciousness, so they are used to start (induce) anesthesia and for sedation; propofol works within about 40 seconds. Their targets differ: propofol enhances inhibitory GABA-A receptor signaling, while ketamine blocks excitatory NMDA glutamate receptors. As with all general anesthetics, how they cause unconsciousness is not fully understood.
Uses
What is ketamine used for?
- Sole anesthetic for procedures not needing muscle relaxation
- Inducing anesthesia, or adding to other anesthetics
Side effects
Side effects of ketamine
- Emergence delirium: confusion and agitation on wakingKnown for
- Vivid dreams and hallucinationsKnown for
- Raised blood pressureKnown for
- Fast heart rate
- Increased saliva
- Raised pressure inside the skullSerious
- Raised eye pressure, double vision and nystagmus
- Breathing depression with rapid high dosesSerious
- LaryngospasmSerious
- Bladder damage (cystitis, can bleed) with long-term misuseSerious
- Liver and bile duct injury with repeated useSerious
- Dependence and misuseSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated where a rise in blood pressure would be dangerous.
- Throat reflexes stay active, so it is not used alone for procedures on the throat or airways.
- Benzodiazepines, opioids and alcohol add to sedation and breathing depression; theophylline lowers the seizure threshold.
- Little stimulation during recovery reduces emergence reactions; monitor people with raised intracranial pressure.
Good to know: Unlike propofol, it tends to keep up blood pressure and breathing and gives strong analgesia, but emergence reactions and misuse limit it; it is a controlled drug.
Remember it
A way to remember it
Propofol is the milk of amnesia; ketamine keeps the pressure up.
Propofol is a milky-white oil-in-water emulsion, made with soybean oil and egg lecithin, that switches off consciousness and lowers blood pressure. Ketamine, which blocks NMDA receptors, tends to raise blood pressure and heart rate instead.
Written for biofideX
Its class
Intravenous anesthetics
Other intravenous anesthetics with a card:
Easily mixed up with inhaled anesthetics, benzodiazepines and local anesthetics.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Anesthesia and muscle relaxants
Ketamine is one of 8 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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