Ketamine is a medication mainly used for starting and maintaining anesthesia. It induces a trance-like state while providing pain relief, sedation, and memory loss. Other uses include for chronic pain, sedation in intensive care, and depression. Heart function, breathing, and airway reflexes generally remain functional. Effects typically begin within five minutes when given by injection, and last up to about 25 minutes.
Common side effects include agitation, confusion, or hallucinations as the medication wears off. Elevated blood pressure and muscle tremors are relatively common. Spasms of the larynx may rarely occur. Ketamine is an NMDA receptor antagonist, but it may also have other actions.
Ketamine was discovered in 1962, first tested in humans in 1964, and approved for use in the United States in 1970. It was extensively used for surgical anesthesia in the Vietnam War due to its safety. It is on the World Health Organization’s List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication. The wholesale price in the developing world is between US$0.84 and US$3.22 per vial. Ketamine is also used as a recreational drug for its hallucinogenic and dissociative effects
Uses as an anesthetic:
- Anesthesia in children, as the sole anesthetic for minor procedures or as an induction agent followed by muscle relaxant and tracheal intubation
- Asthmatics or people with chronic obstructive airway disease
- As a sedative for physically painful procedures in emergency departments
- Emergency surgery in field conditions in war zones
- To supplement spinal or epidural anesthesia/analgesia using low doses
Since it suppresses breathing much less than most other available anesthetics, ketamine is used in medicine as an anesthetic; however, due to the hallucinations it may cause, it is not typically used as a primary anesthetic, although it is the anesthetic of choice when reliable ventilation equipment is not available.
Ketamine is frequently used in severely injured people and appears to be safe in this group. A 2011 clinical practice guideline supports the use of ketamine as a dissociative sedative in emergency medicine. It is the drug of choice for people in traumatic shock who are at risk of hypotension. Low blood pressure is harmful in people with severe head injury and ketamine is least likely to cause low blood pressure, often even able to prevent it.
The effect of ketamine on the respiratory and circulatory systems is different from that of other anesthetics. When used at anesthetic doses, it will usually stimulate rather than depress the circulatory system. It is sometimes possible to perform ketamine anesthesia without protective measures to the airways. Ketamine is considered relatively safe because protective airway reflexes are preserved.