Anesthetic effects

Use of isopropyl alcohol in industrial appHcations does not present a health hazard. The alcohol produces anesthetic effects in high vapor concentration. Consequently, the OSHA permissible exposure limit (PEL) and the ACGIH threshold limit value (TLV) have been estabUshed at 400 ppm (0.098 mg/L) for an 8-h exposure (TWA) (138). This level causes a mild irritation of the eyes, nose, and throat (139). However, the TLV level does not produce symptoms of anesthesia (140). The OSHA and ACGIH short-term exposure limits (STELs) are 500 ppm. The odor threshold for isopropyl alcohol ranges from 3 to 200 ppm, which is the minimum concentration having identifiable odor (141). 

In other applications of CT, orally administered barium sulfate or a water-soluble iodinated CM is used to opacify the GI tract. Xenon, atomic number 54, exhibits similar x-ray absorption properties to those of iodine. It rapidly diffuses across the blood brain barrier after inhalation to saturate different tissues of brain as a function of its lipid solubility. In preliminary investigations (99), xenon gas inhalation prior to brain CT has provided useful information for evaluations of local cerebral blood flow and cerebral tissue abnormalities. Xenon exhibits an anesthetic effect at high concentrations but otherwise is free of physiological effects because of its nonreactive nature. 

The Class I antiarrhythmic agents inactivate the fast sodium channel, thereby slowing the movement of Na" across the cell membrane (1,2). This is reflected as a decrease in the rate of development of phase 0 (upstroke) depolarization of the action potential (1,2). The Class I agents have potent local anesthetic effects. These compounds have been further subdivided into Classes lA, IB, and IC based on recovery time from blockade of sodium channels (11). Class IB agents have the shortest recovery times (t1 ) Class lA compounds have moderate recovery times (t 2 usually <9 s) and Class IC have the longest recovery times (t 2 usually >9 s). 

Glass IG Antiarrhythmic Agents. Class IC antiarrhythmic agents have marked local anesthetic effects. They slow the rapid inward sodium current producing marked phase 0 depression and slow conduction. Action potential duration of ventricular muscle is increased, ie, prolonged repolarization, but decreased in the His-Purkinie system by these agents. The effects on the ECG are increased PR interval, marked prolongation of the... 

Propranolol. Propranolol hydrochloride, considered the prototype of the P-adrenoceptor blocking agents, has been in use since 1964. It is a nonselective, highly Hpid-soluble P-adrenoceptor blocker having no ISA. It is a mixture of (+) and (—) enantiomers, and the (—) enantiomer is the active moiety. The local anesthetic effects of propranolol are equipotent to those of Hdocaine [137-58-6] C 4H22N20, (see Anesthetics). Therapeutic effects include termination of catecholamine-induced arrhythmias, conversion of SA nodal tachycardias (including flutter and fibrillation) and AV nodal tachyarrhythmias to normal sinus rhythm, digitahs-induced arrhythmias, and ventricular arrhythmias (1,2). The dmg also has cardioprotective properties (37,39). 

Carbon tetrachloride is toxic by inhalation of its vapor and oral intake of the Hquid. Inhalation of the vapor constitutes the principal ha2ard. Exposure to excessive levels of vapor is characterized by two types of response an anesthetic effect similar to that caused by compounds such as diethyl ether and chloroform and organic injury to the tissues of certain organs, in particular the Hver and kidneys. This type of injury may not become evident until 1—10 days after exposure. The nature of the effect is deterrnined largely by the vapor concentration but the extent or severity of the effect is deterrnined principaHy by the duration of exposure (38). 

Toxicity. 1,1-Dichloroethane, like all volatile chlorinated solvents, has an anesthetic effect and depresses the central nervous system at high vapor concentrations. The 1991 American Conference of Governmental Industrial Hygienists (ACGIH) recommends a time-weighted average (TWA) solvent vapor concentration of 200 ppm and a permissible short term exposure level (STEL) of 250 ppm for worker exposure. The oral LD q of... 

Trichloroethylene is acutely toxic, primarily because of its anesthetic effect on the central nervous system. Exposure to high vapor concentrations is likely to cause headache, vertigo, tremors, nausea and vomiting, fatigue, intoxication, unconsciousness, and even death. Because it is widely used, its physiological effects have been extensively studied. 

It is estimated that concentrations of 3000 ppm cause unconsciousness in less than 10 minutes (39). Anesthetic effects have been reported at concentrations of 400 ppm after 20-min exposure. Decrease in psychomotor performance at a trichloroethylene concentration of 110 ppm has been reported in one study (33), whereas other studies find no neurotoxic effects at concentrations of 200 ppm (40—43). 

Ethylene is an anesthetic gas with a rapid onset of action and a rapid recovery from its anesthetic effects. It provides adequate analgesia but has poor muscle-relaxant properties. The advantages of ethylene include minimal bronchospasm, laryngospasm, and postanesthesia vomiting. A disadvantage of ethylene is hypoxia. This gas is supplied in red cylinders. Mixtures of ethylene and oxygen are flammable and explosive. 

Dimethyl ether is used as a propellant in aerosols. It is also a solvent, a fuel used in welding, and a refrigerant. In high concentrations, it has an anesthetic effect. 

After several minutes the peel can induce an anesthetic effect whereby increasing patient tolerance... 

The discharging is closely related to the most optimum anesthetic effect. For strong and efficient anesthetic potency, the neutral forms of the drugs are suitable because they... 

Menthol 1.25-16% BenGay Patch Icy Hot fetch Mineral Ice Sensation of heat follows cooling Mild anesthetic effects at low concentrations... 

Used medicinally as a short-acting general anesthetic. Effects dissipate after approximately 20 min. 

Further, the removal of benzodiazepine sensitivity in a selective a subunit in a mouse using the gene knockin technique has established that the al subunit plays a major role in the sedative and amnesiac effects of benzodiazepines, part of the anticonvulsant effect and little of the anxiolytic effect the latter effects are more importantly mediated by the a2 subunit [5, 6], The 0 subunit selectivity for the drugs loreclezole (an anxiolytic) and etomidate (an anesthetic) allowed determination that a single residue in the M2 domain could account for this selectivity (02 = 03 >01). When a mouse knockin selectively removed the etomidate sensitivity of the 02 subunit, the animals showed reduced sensitivity to sedative effects of etomidate but no reduction of the true anesthetic effects. In contrast, mutation of the 03 subunit to negate etomidate sensitivity of that subunit alone resulted in a mouse with no sensitivity to the anesthesia produced by etomidate. This proved that the GABA receptor is the target of at least this one anesthetic (etomidate) and, furthermore, that the specific locations in the brain of 03 subunits are important for anesthetic action, while the... 

At high concentrations, HFC-134a has anesthetic and narcotic properties cardiac sensitization may also occur. The biochemical mechanism(s) of action of these two effects is not well understood. The anesthetic effect was fully reversible. 

The halogenated hydrocarbons are generally of low acute toxicity, but several are associated with anesthetic effects and cardiac sensitization. Cardiac sensitization to halogenated alkanes appears related to the number of chlorine or fluorine substitutions. Halogenated alkanes in which >75% of the... 

End point/Concentration/Rationale The highest no-effect concentration of 8,000 ppm for 1 h was used as the basis for the AEGL-1. This concentration is considerably below the threshold for effects in animal studies. For example, anesthetic effects occur at a concentration of approximately 200,000 ppm. 

Davies et al. (1976) reported a 30-min anesthetic effective concentration (EC50) of... 

The attenuated clearance of BSP observed in MCB or CCI4 treated fish may be due to factors unrelated to liver dysfunction. For example, anesthetic effects associated with CCI4 or MCB intoxication may have influenced plasma clearance of BSP... 

Thus, there are numerous neurochemical systems that participate in pain transmission and analgesia systems in the brain. Potentially, any drug that interferes with any of these systems could have analgesic effects. As will be demonstrated in this chapter, there are many plants with analgesic and anesthetic effects, working through a variety of pharmacological mechanisms (table 8.4). 

Interestingly, one study has shown that cocaine may be a direct antagonist at nicotinic receptors (Damaj et al. 1999). Cocaine blocks several of nicotine s effects, including analgesia on the tail-flick test, independent of its monoamine activity or local anesthetic effects. 

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