Ketamine

Ketamine is a unique intravenous or intramuscular agent used for both analgesia and anaesthesia. It is a phencyclidine derivative. It takes a longer period than other intravenous anaesthetics before its non-hypnotic effects are maximal. Similarly, recovery is delayed. Effects include:

• cardiovascular stimulation: arterial pressure can rise with tachycardia, making it good for battlefield analgesia in the presence of shock
• muscle tone is increased
• airway and laryngeal reflex tend to be maintained and less respiratory depression that other agents
• low incidence of emergence phenomena, e.g. hallucinations and other psychotic behaviour - worse if patient is disturbed or over-stimulated during recovery; it is commonly given with a small dose of benzodiazepines to reduce the chance of this occurring.
• antisialogue; less need for anti-secretory premedication.

It is contraindicated in those with hypertension, a history of stroke, or a significant psychiatric history, but it may be useful for uncooperative patients.