Dissociative anesthesia

Another injectable anesthetic widely used in feline and primate practice is ketamine hydrochloride [1867-66-9]. Ketamine, a derivative of phencychdine, can be chemically classified as a cyclohexamine and pharmacologically as a dissociative agent. Analgesia is produced along with a state that resembles anesthesia but in humans has been associated with hallucinations and confusion. For these reasons, ketamine is often combined with a tranquilizer. The product is safe when used in accordance with label directions, but the recovery period may be as long as 12—24 h. 

Ketamine has analgesic activity that persists beyond the period of unconsciousness up to 1 h after injection. On regaining consciousness, the patient may experience a disconnection between outside reality and inner mental state (dissociative anesthesia). Frequently there is memory loss for the duration of the recovery period however, adults in particular complain about dis-Ltillmann, Color Atlas of Pharmacology... 

Ketamine is a specific drug for noninhalation narcosis that is used in brief surgical procedures. It causes a condition known as dissociative anesthesia, which ensures amnesia and analgesia, and preserves normal respiration and muscle tonicity in the patient. Ketamine is practically void of muscle relaxant capabilities. 

Ketamine and also tiletamine are structurally and pharmacologically related to phencyclidine. Its mechanism of action is not well understood. It has been suggested that it blocks the membrane effects of the excitatory neurotransmitter glutamic acid. Ketamine produces dissociative anesthesia, which means that the patient seems to be awake but there are no responses to sensory stimuli. Ketamine, which can be administered IV or IM, has strong analgesic activity. It is especially indicated for interventions of short duration without any need for skeletal... 

Ketamine is a cyclohexanone derivative whose pharmacological actions are quite different from those of the other IV anesthetics. The state of unconsciousness it produces is trancelike (i.e., eyes may remain open until deep anesthesia is obtained) and cataleptic it has frequently been characterized as dissociative (i.e., the patient may appear awake and reactive but does not respond to sensory stimuli). The term dissociative anesthesia is used to describe these qualities of profound analgesia, amnesia, and superficial level of sleep. 

Ketamine (Figure 25-2) produces dissociative anesthesia, which is characterized by catatonia, amnesia, and analgesia, with or without actual loss of consciousness. The drug is an arylcyclohexylamine chemically related to phencyclidine (PCP), a drug frequently abused because of its psychoactive properties. The mechanism of action of ketamine may involve blockade of the... 

All that we need to get on with the show is to develop a general model of dissociation and to create a do-it-yourself kit for the induction of desirable dissociations. In this view, Charcot s hysterical anesthesia becomes our way of cutting out the anesthetist and the novocaine injection. 

Like FCP, ketamine produces an unusual kind of anesthesia, called a dissociative state, in which the patient s awareness becomes detached from the body and from external reality. Like I CP, ketamine has produced a number of bad reactions, since many patients become frightened when they iind themselves in this unusual condition. So far, however, there has iuen no move to take ketamine off the market. 

Chander S. Isorhythmic atrioventricular dissociation during enflurane anesthesia. South Med J 1982 75(8) 945-50. 

Finally, a fourth class of hallucinogens includes phencyclidine (PCP or angel dust ) and the related compound ketamine. These are often referred to as the dissociative anesthetics because of their ability to produce surgical anesthesia while the individual remains at least semiconscious. Dissociative anesthetics arc thought to act through a receptor that influences activity of the excitatory amino acid ncurotransmittcr, glutamate (Balazs, Bridges, Cotman, 2006). 

Phencyclidine (PCP) and ketamine are classified as dissociative anesthetic hallucinogens. They produce a potent intoxication at moderate doses and complete surgical anesthesia at higher doses. Violent psychotic reactions appear to be fairly common with PCP. 

Affects the senses, and produces a dissociative anesthesia (catatonia, amnesia, analgesia) in which the patient may appear awake and reactive, but cannot respond to sensory stimuli. These properties make it especially useful for use in developing countries and during warfare medical treatment. Ketamine is frequently used in pediatric patients because anesthesia and analgesia can be achieved with an intramuscular injection. It is also used in high-risk geriatric patients and shock cases, because it also provides cardiac stimulation. 

Ketamine (Ketalar, others) has unique properties that make it useful for anesthetizing patients at risk for hypotension and bronchospasm and for certain pediatric procednres. However, significant side effects limit its rontine nse. Ketamine rapidly produces a hypnotic state qnite distinct from that of other anesthetics. Patients have profonnd analgesia, nnresponsiveness to commands, and amnesia bnt may have their eyes open, move their limbs involnntarily, and breathe spontaneously. This cataleptic state has been termed dissociative anesthesia. 

Fentanyl is used in combination with droperidol to produce dissociative anesthesia, or neuroleptanesthesia. 

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