Ketamine delirium

Phencyclidine (l-[l-phenylcyclohexyl] piperidine, PCP) was originally developed as an intravenous anesthetic in the 1950s. Used for this indication, it causes a trance-like state without loss of consciousness and was hence classified as a dissociative anesthetic. However, it was soon withdrawn from human use because it produced unpleasant hallucinations, agitation, and delirium. The product was later used in veterinary medicine. Ketamine, a chemically closely related substance, was developed to replace PCP and is stiU in use as a dissociative anesthetic in children. Ketamine is less potent than PCP, and its effects are of shorter duration. However, it may also cause hallucinations (see the section on ketamine in Chapter 7, Club Drugs ). Much of the ketamine sold on the street (special K, cat Valium) has been diverted from veterinarians offices. 

At low doses, ketamine may result in impairment of attention, learning ability, and memory, and at high doses it has been associated with delirium, amnesia, impaired motor function, hypertension, depression, and respiratory depression (Krystal et al. 1994). Another mechanism of action appears to be a blocking of the reuptake of catecholamines. This effect leads to an increase in heart rate and blood pressure (Reich and Silvay 1989). 

Ketamine (special K, jet, green), chemically related to PCP, is a veterinary anesthetic that can cause hallucinations, delirium, and vivid dreams. 

Acute phencyclidine intoxication can proceed through stages from stupor to coma with unresponsiveness to pain. Delirium lasting several days is common during recovery from coma and may occur transiently as the final phase of an episode of intoxication (Gorelick Balster, 1995). Ketamine has similar effects when abused recreationally. When used as an anaesthetic in adults, it... 

The mechanisms of action of phencyclidine and ketamine are complex (Gorelick Balster, 1995). The drugs are non-competitive antagonists at NMDA receptors, and also bind to associated phencyclidine/sigma opioid receptors. They also have agonist actions at dopamine receptors, complex interactions with both nicotinic and muscarinic acetylcholine receptors and poorly understood interactions with noradrenergic and serotonergic systems. These multiple actions may combine to produce delirium and psychotic reactions. 

Other hallucinogenic drugs including substances related to LSD are mentioned under delirium. Phencyclidine and ketamine can also produce similar hallucinatory states without delirium including time distortion, distortion of body image, synaesthesia, visual hallucinations, depersonalisation, derealisation, paranoid ideation and a schizophreniform psychosis which includes the negative symptoms of schizophrenia (Gorelick Balster, 1995). 

Ketamine <1 Dissociative Yes No Slight Minimal emergence delirium IM or IV... 

Emergence delirium with restlessness, disorientation and unpleasant dreams or hallucinations may occur for up 24 hours following ketamine administration. Their incidence is reduced by psychological preparation of the patient, avoidance of verbal and tactile stimulation during the recovery period, or by concomitant administration of opioids, benzodiazepines, propofol or physostigmine. However, unpleasant dreams may persist. 

Phencyclidine, PCP, or l-(l-phenylcyclohexyl) piperidine, is an arylcyclohexamine with structural similarities to ketamine. It is a lipophilic weak base with a pKa of 8.5. Phencyclidine was originally synthesized and marketed under the trade name Semyl by Parke-Davis for use as an intravenously administered anesthetic agent in humans. Distribution began in 1963 but was discontinued in 1965 due to a high incidence (10 to 20%) of post-operative delirium and psychoses. However, its use continued as a veterinary tranquilizer for large animals until 1978, when all manufacture was prohibited and PCP was placed in Schedule II of the federal Controlled Substances Act (1970). 

The duration of the drug s action depends on the method of administration. Upon recovery from ketamine, the patient or user may be agitated, disoriented, restless, and tearful. This is called emergence delirium. Patients may continue to experience unpleasant dreams up to 24 hours after the drug has been taken. Flashbacks have been reported, and their incidence may be higher than with many hallucinogens.55... 

People who use ketamine regularly can suffer psychological problems. Paranoia and delirium are the main difficulties.59 There are many reports of regular ketamine users starting to see patterns and coincidences (synchronicities) in the world around them. To users, these patterns indicate that they are somehow more important or integral to the world than other people, and this can also contribute to their feelings of paranoia. 

Subanesthetic low-dose ketamine is thought to cause delirium and disturbing dreaming. A systematic review of NMDA receptor antagonists in preventive analgesia has shown that only one of 20 studies documented adverse psychotomimetic effects attributable to ketamine (435). In that study, ketamine was given by the epidural route in a relatively high dose. 

Ketamine often causes emergence delirium and disturbing dreaming. Benzodiazepines are often co-adminis-tered to attempt to manage this. The optimal dose of diazepam to add to ketamine-fentanyl field anaesthesia has been assessed in a randomized double-blind study in 400 patients from Vanuatu the optimal dose was 0.1 mg/ kg (436). 

Ketamine, a compound chemically related to PCP, is used primarily as a veterinary anesthetic but has gained popularity recently as a recreational drug Once used extensively in human medicine, it has fallen out of favor because of emergence delirium, characterized by hallucinations, delirium, vivid dreams, and other psychiatric effects. This untoward effect as a medicinal agent is precisely the effect that recreational users are seeking. 

Ketamine is a phencyclidine derivative and as such has abuse potential. Phencyclidine was developed in the 1950s as an anaesthetic, but its use was abandoned because it caused hallucinations and delirium. It became popular as PCP (phenylcyclohexylpiperidine), a drug of abuse, in the 1970s. 

Ketamine is a potent analgesic-anesthetic that is also effective intramuscularly. One particular property, production of cardiovascular stimulation, is of special advantage in elderly patients and those in shock (e.g., from bums). However, its propensity to precipitate hallucinations, delirium, disorientation, and other perceptual illusions postoperatively in about 12% of patients has led to its infrequent use in the United States. Ketamine s close structural analogy to the notorious and dangerous hallucinogen, phencyclidine (PCP, angel dust ), should be noted. This drug, which was first also introduced as an... 

Ketamine can cause attention deficits and memory problems. At higher doses, users may experience symptoms similar to those seen with phencyclidine (PCP) use, such as hallucinations, dream-like states, or delirium. Even higher doses of Ketamine may cause high blood pressure, depression, and severe breathing problems, which may lead to death. 

Emergence from ketamine s anesthesia may be associated with psychological manifestations such as pleasant dream-like states, vivid imagery, hallucinations and emergence delirium, sometimes accompanied by confusion, excitement, and irrational behavior. The duration is ordinarily a few hours however, recurrences have been seen up to 24 hours postoperatively. No residual psychological... 

Unlike other parenteral anesthetics, ketamine increases cerebral blood flow and ICP with minimal alteration of cerebral metabolism. These effects can be attenuated by concurrent administration of thiopental and/or benzodiazepines along with hyperventilation. However, given that other anesthetics actually reduce ICP and cerebral metabohsm, ketamine is relatively contraindicated for patients with increased ICP or those at risk for cerebral ischemia. The effects of ketamine on seizure activity are mixed. Emergence dehrium characterized by hallucinations is a frequent comphcation of ketamine that can result in serious patient dissatisfaction and can complicate postoperative management. Delirium is most frequent in the first hour after emergence and appear to occur less frequently in children benzodiazepines reduce the incidence of emergence delirium. 

Psychological The incidences of different types of emergence phenomena after intravenous ketamine, mean dose 1.15 mg/kg, for procedural sedation have been investigated in children [40 ]. Of 745 patients, 93 (13%) cried on awakening from sedation, of whom 84 were consoled by their parents. The rest were defined as having emergence delirium. Another seven children were... 

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