Anaesthetic of choice in asthma patients: March 2007

Ans. C: Ketamine Ketamine is classified as an NMDA (N-methyl-D-aspaate) receptor antagonist, and at high, fully anesthetic level doses, ketamine has also been found to bind to opioid (mu) receptors and sigma receptors. Like other drugs of this class such as tiletamine and phencyclidine (PCP), it induces a state referred to as "dissociative anaesthesia" and is used as a recreational drug. Ketamine has a wide range of effects in humans, including analgesia, anaesthesia, hallucinations, elevated blood pressure, and bronchodilation. It is primarily used for the induction and maintenance of general anaesthesia, usually in combination with some sedative drug. Ketamine is usually injected intravenously or intramuscularly, but it is also effective when insufflated, smoked, or taken orally. When used at anaesthetic doses, it will usually stimulate rather than depress the circulatory system, so I/ V anaesthetic of choice for shock. Ketainine produces a dissociative state, characterised by a sense of detachment from one's physical body and the external world which is known as depersonalization and derealization. At sufficiently high doses users may experience what is coined the "K-hole", a state of dissociation whose effects are thought to mimic the phenomenology of schizophrenia.