Halothane physiological effects

The induction of unconsciousness may be the result of exposure to excessive concentrations of toxic solvents such as carbon tetrachloride or vinyl chloride, as occasionally occurs in industrial situations (solvent narcosis). Also, volatile and nonvolatile anesthetic drugs such as halothane and thiopental, respectively, cause the same physiological effect. The mechanism(s) underlying anesthesia is not fully understood, although various theories have been proposed. Many of these have centered on the correlation between certain physicochemical properties and anesthetic potency. Thus, the oil/water partition coefficient, the ability to reduce surface tension, and the ability to induce the formation of clathrate compounds with water are all correlated with anesthetic potency. It seems that each of these characteristics are all connected to hydrophobicity, and so the site of action may be a hydrophobic region in a membrane or protein. Thus, again, physicochemical properties determine biological activity. 

The studied molecules include such diverse compounds as volatile anesthetics (halothane), local anesthetics of the cocaine type, calcium channel-blocking agents such as verapamil, antidepressants (chlorpromazine), and anti cancer drugs such as adriamycin. It is argued that the factor of interest to the physiological effect may not... 

In a double-blind, randomized, controlled study of 77 children undergoing halothane anesthesia for adenoidect-omy, the effects of atropine 0.02 mg/kg, glycopyrrolate 0.04 mg/kg, and physiological saline were compared (9). There was no difference in the incidence of ventricular dysrhythmias. Atropine prevented bradycardia but was associated with sinus tachycardia in most patients. The bradycardias that occurred in the groups that received glycopyrrolate or placebo were short-lived and resolved spontaneously. 

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