Emergence from ketamine anaesthesia in the postoperative period may be associated with audiovisual ketamine hallucinations , confusional state, which may progress to delirium, proprioceptive disturbances (feelings of detachment from the body) and slightly reduced ability to recall objects seen after administration of the drugs.
The ability to recall objects seen immediately before drug exposure remains unaffected. The psychological effects produced by S- ketamine resemble negative symptoms of schizophrenia, attention deficits, body perception disturbances and catatonia-like motor phenomena.
In addition to schizophrenia-like and dissociative symptoms, ketamine hallucinations produces a dose-dependent impairment to episodic and working memory and a slowing of semantic processing. ketamine hallucinations also impairs recognition memory and procedural learning; however, attention, perceptual priming and executive functioning are usually not affected.
The inhibition of sensory perception by ketamine in subanaesthetic concentrations is due to N-methyl-D-aspartate receptor blockade. Binding to kappa and muscarinic receptors may contribute to the psychotomimetic side effects seen during recovery from ketamine hallucinations anaesthesia.
Dreams and hallucinations usually disappear within a few hours. However, they can occur up to 24 hours of post-administration. The dreams frequently have a morbid content and are often experienced in vivid colour.
Some ketamine effects may be mediated through increased glutamate release which is effectively blocked by glutamate release-inhibiting drugs such as lamotrigine.88 Benzodiazepines are most effective in prevention as well as treatment of this phenomenon, with midazolam being more effective than diazepam.
Inclusion of thiopental or inhaled anaesthetics decreases the incidence of emergence delirium due to ketamine hallucinations