Anesthesiology
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The N1 and P3 waves of the auditory event-related potential provide information on consciousness and cortical function. The N1 wave is reduced during states of low vigilance. The P3 wave occurs only for stimuli that somehow capture the subject's attention. There are two types of P3:P3a and P3b. The P3a predominates frontally and probably occurs when the subject simply notices the stimulus. The P3b predominates parietally and indicates conscious awareness of the evoking stimulus. The N1 and P3 were recorded in 12 patients during cardiac surgery under sufentanil anesthesia to search for unintentional awareness. The study was limited to the period before cardiopulmonary bypass. ⋯ The attenuation of N1 from induction onward reflects a decrease in the level of arousal caused by sufentanil. A P3a during postintubation and precardiopulmonary bypass indicates that pitch discrimination at the cortical level occurs but does not prove that conscious awareness has occurred. Whether or not the P3a reflects the regaining of consciousness is not known.
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Drugs with a central alpha 2-adrenergic action can increase the threshold for halothane-epinephrine-induced arrhythmias. Recently, imidazoline-preferring receptors were shown to play a significant role in the hypotensive effect of alpha 2-adrenergic agonists containing an imidazole ring in their structure. To address the question of whether the antiarrhythmic property of the alpha 2-adrenergic agonists was caused by activation of alpha 2-adrenoceptors or imidazoline-preferring receptors in the central nervous system, the effect of an imidazoline (atipamezole) and a nonimidazoline (L-659,066 and yohimbine) alpha 2-adrenergic antagonist were examined as etiologic factors in the genesis of halothane-epinephrine-induced arrhythmias in dogs. ⋯ Because the imidazoline ring-containing alpha 2-adrenergic antagonist (atipamezole) potentiated the halothane-epinephrine-induced arrhythmias and the nonimidazole alpha 2-adrenergic antagonist (L-659,066 and yohimbine) did not, it is possible that the imidazoline-preferring, rather than the alpha 2-adrenergic, receptor is responsible for the antiarrhythmic property of alpha 2-adrenergic agonists.
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The effects of isoflurane on the transmural distribution of myocardial blood flow distal to an acute critical coronary stenosis and the relationship between the changes in regional blood flow and function were studied to determine whether isoflurane can produce a transmural "steal" phenomenon and to assess the role of this phenomenon in producing changes in regional myocardial function. ⋯ These results show that isoflurane is a coronary vasodilator able to induce a transmural redistribution of myocardial blood flow distal to an acute critical coronary stenosis. A true transmural steal, however, was not produced reliably in the absence of hemodynamic changes, suggesting that isoflurane either is only a moderate vasodilator, or that the decrease in subendocardial blood flow is offset by the negative inotropic action of the drug. When regional myocardial dysfunction distal to a severe coronary stenosis occurs, this correlates with decreasing subendocardial blood flow during isoflurane anesthesia, suggesting ischemia as the cause.