Ketamine described

In overdose, ketamine may lead to hyperthermia, seizures, hypertensive crisis, coma, and even death. These symptoms are generally thought to be caused by ketamine s catecholaminergic effects (Reich and Silvay 1989). Ketamine is physically addicting, with a described withdrawal syndrome. 

The ion-channel blocking mechanism has been widely tested and found to be important in both pharmacology and physiology. Examples are the block of nerve and cardiac sodium channels by local anesthetics, or block of NMDA receptor channels by Mg2+ and the anesthetic ketamine. The channel-block mechanism was first used quantitatively to describe block of the squid axon K+ current by tetraethylammonium (TEA) ions. The effects of channel blockers on synaptic potentials and synaptic currents were investigated, particularly at the neuromuscular junction, and the development of the single-channel recording technique allowed channel blockages to be observed directly for the first time. 

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. 

Given the popularity of marijuana, LSD, mescaline, cocaine, and heroin, the use of ketamine in the 1970s and 1980s remained largely confined to either experimental therapeutic use, or what has been described by author Jay Stevens as the neuro-consciousness frontier, a small group of accredited and unaccredited individuals who experimented with the effects of hallucinogenic substances. 

Methods for evaluating postural hypotension were described in conscious dogs (Baum et al. 1981), conscious rabbits (Sponer et al. 1981), in rats (Lee et al. 1982) and in cynomolgus monkeys during ketamine anesthesia (Pals and Orley 1983). 

The title complex represents the parent compound of several known metalla-/3-iminoketone molecules.2 In each case a metalla-/3-diketone molecule is treated with a primary amine, affording the corresponding metalla-/3-imino-ketone derivative. The structure of the cis-tetracarbonylrhenium metalla analogue of N-phenylacetimidoylacetone has been determined.3 The structure of this complex confirms the formulation of these complexes as metalla analogues of the ketamine tautomer of /3-iminoketone molecules. However, the electronic structure is described best by the zwitterionic resonance form shown below. 

If the local tumor (sometimes called the primary tumor) is to be removed, the animals are anesthetized using the same Ketamine-Rompun solution described above. Adequate sedation is easily... 

Delayed acute intracranial hypertension has been described after ketamine anesthesia (18). 

There are reports that diazepam can produce paradoxical excitability immediately after i.v. administration to humans and small animals. Although this paradoxical effect is not well described in horses, diazepam should be administered with caution to mature horses when used as a sole agent. It can be used as the sole agent for sedation and restraint in young foals. Diazepam is recommended for i.v. use at doses of 0.02-0.1 mg/kg. Diazepam is primarily used in adult horses to provide muscle relaxation and for its anticonvulsant effect prior to anesthetic induction with ketamine. Diazepam (0.04 mg/kg) reduces the MAC of halothane by approximately 29% (Matthews et al 1990). Diazepam is considered the acute treatment of choice for status epilepticus in all species (see Ch. 9). Diazepam (0.02-0.04 mg/kg) is an appetite stimulant in horses, although its effect is of short duration (Brown et al 1976). 

Ketamine (special K, super K, vitamin K) is a shortacting general anesthetic producing what is described... 

On-line brain microdialysis in freely moving animals has previously been described.188 In brief, the rats were anaesthetised with midazolam (5 mg/kg s.c.), atropine nitrate (0.1 mg/kg s.c.), ketamine (50 mg/kg i.p.) and xylazine (8 mg/kg i.p.) 10% lidocaine was locally applied. The rats were then mounted into a stereotaxic frame (Kopf). The incisor bar was placed in position so that the skull was held horizontal. The skull was exposed and burr holes were drilled. A Y-shaped dialysis probe was used for the experiments, with an exposed tip length of 3 mm. The dialysis tube (ID 0.22 mm OD 0.31 mm) was prepared from... 

Kogan et al. described a method for simultaneous determination of nicotine and cotinine in plasma using ketamine as internal standard. After basification of the sample the alkaloids and the added internal standard were extracted with methylene chloride, back-extracted into... 

Much of the basic pharmacology of glutamate receptors was elucidated from these two spinal cord preparations in vivo or in vitro. Thus, the differential sensitivity of neurones to kainate, quisqualate and NMDA [3], the differential antagonistic effects of DAA, HA-966, GAMS, GDEE, D-AP5, Mg + and ketamine [6-9, 19] and the effects of these antagonists on S3maptic transmision [11-13, 95] were initially described in these spinal preparations. 

Ketamine typically is administered intravenonsly bnt also is effective by intramnscnlar, oral, and rectal rontes. The indnc-tion doses are 0.5 to 1.5 mg/kg IV, 4 to 6 mg/kg IM, and 8 to 10 mg/ml. Onset of action after an intravenous dose is similar to that of the other parenteral anesthetics, but the duration of anesthesia of a single dose is longer. For anesthetic maintenance, ketamine occasionally is continued as an infusion (25 to 100 (tg/kg per minute). Ketamine does not elicit pain on injection or true excitatory behavior as described for methohexital, although involuntary movements prodnced by ketamine can be mistaken for anesthetic excitement. 

Ketamine typically is administered intravenously but also is effective by intramuscular, oral, and rectal routes. Ketamine does not elicit pain on injection or true excitatory behavior as described for methohexital, although involuntary movements produced by ketamine can be mistaken for... 

The emergence phenomena described are adverse effects of ketamine. Administration of diazepam immediately prior to ketamine anesthesia reduces the incidence of these effects. The answer is (C). 

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