Ketamine is a dissociative anesthetic characterized by the maintenance of reflexes and a catatonic state. It is routinely administered with a benzodiazepine because, on its own, it can induce seizures. In veterinary medicine, the ketamine-benzodiazepine combination can be used for chemical restraint. Induction of dissociative anesthesia as well as use at sub-anesthetic doses as a constant rate infusion provides somatic analgesia42 that can also decrease or prevent central sensitization43.
Unlike most other induction agents, ketamine causes indirect stimulation of the sympathetic system causing increases in heart rate and arterial blood pressure44. As this results in an increase in myocardial oxygen consumption and cardiac work, clinical recommendations suggest reducing or avoiding its use in cardiovascular compromised patients.
High doses of ketamine, such as those used for induction when premedication is not utilized, can cause an apneustic breathing pattern45. Without the concomitant use of sedatives and muscle relaxants, recoveries can be rough, characterized by disorientation, vocalizing and thrashing. Ketamine and other dissociatives provide predictable quick inductions by various routes of administration.