Ketamine

Ketamine In Dogs & Cats: Uses, Dosage and Side Effects

Overview

• It antagonises glutamate at N-methyl-d-aspartate (NMDA) receptors in the CNS.
• It interacts complexly with opioid receptors and antagonises mu receptors.
• It is exhibiting agonist activity at the delta and kappa receptors.
• It has no effect on GABA receptors.

Uses of Ketamine

• Provision of chemical restraint or dissociative anaesthesia.
• Ketamine may also provide profound visceral and somatic analgesia and inhibits central sensitization via NMDA receptor blockade.
• Used to provide perioperative analgesia as an adjunctive agent, although optimal doses for analgesia have not been determined.

Dose of Ketamine in Dogs and Cats

Dogs:

• Perioperative analgesia:
• Intraoperatively: 10 μg (micrograms)/kg/min.
• Postoperatively: 2–5 μg/kg/min.
• Both are preceded by a 250–500 μg/kg loading dose.
• There is some evidence to suggest that a 10 μg/kg/min dose may be too low to provide
  adequate analgesia continuously, although other evidence-based dose recommendations are lacking.
• Induction of anaesthesia (combined with diazepam or midazolam) as part of a volatile anaesthetic technique: 2 mg/kg i.v.
• Induction of general anaesthesia combined with medetomidine or dexmedetomidine to provide a total injectable combination: ketamine (5–7 mg/kg i.m.) combined with medetomidine (40 μg/kg i.m.) or dexmedetomidine (20 μg/kg i.m.).

Cats:

• General anaesthesia: combinations of ketamine (5–7.5 mg/kg i.m.) combined with medetomidine (80 μg (micrograms)/kg i.m.) or dexmedetomidine (40 μg/kg i.m.) will provide 20–30 min general anaesthesia.
• Reduce the doses of both drugs when given i.v.
• Perioperative analgesia: doses are the same as those for dogs.

Side Effects of Ketamine in Dogs and Cats

• Cardiovascular depression.
• Arrhythmias may arise in animals with a high sympathetic nervous system tone.
• Tachycardias can also arise after administration of high i.v. doses.
• Respiratory depression may be marked in some animals.
• Ketamine may result in spacey, abnormal behaviour for 1–2 hours during recovery.
• Prolonged administration of ketamine by infusion may result in drug accumulation and
  prolonged recovery.

Contraindications of Ketamine in Dogs and Cats

• Not recommended for animals whose eyes are at risk of perforation or who have raised intraocular pressure.
• Not recommended in animals with raised intracranial pressure