Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Cardiovascular effects of sevoflurane compared with those of isoflurane in volunteers.
Sevoflurane is a new inhalational anesthetic with desirable clinical properties. In some clinical situations, an understanding of the detailed cardiovascular properties of an anesthetic is important, so the authors evaluated the hemodynamic effects of sevoflurane in healthy volunteers not undergoing surgery. ⋯ At 1.0 and 1.5 MAC, sevoflurane was well tolerated by healthy volunteers. At 2.0 MAC, in subjects with mean arterial pressure > or = 50 mmHg, no adverse cardiovascular properties were noted. Similar to other contemporary anesthetics, sevoflurane caused evidence of myocardial depression. Hemodynamic instability was noted in some subjects at high anesthetic concentrations in the absence of surgical stimulation. The incidence was similar to that with isoflurane. The cardiovascular effects of sevoflurane were similar to those of isoflurane, an anesthetic commonly used in clinical practice since 1981.
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Randomized Controlled Trial Comparative Study Clinical Trial
Direct cerebrovasodilatory effects of halothane, isoflurane, and desflurane during propofol-induced isoelectric electroencephalogram in humans.
The effect of volatile anesthetics on cerebral blood flow depends on the balance between the agent's direct vasodilatory action and the indirect vasoconstrictive action mediated by flow-metabolism coupling. To compare the intrinsic action of volatile anesthetics, the effect of halothane, isoflurane, and desflurane on flow velocity in the middle cerebral artery during propofol-induced isoelectricity of the electroencephalogram was examined. ⋯ Halothane, isoflurane, and desflurane have intrinsic, dose-related cerebral vasodilatory effects. Whereas all three agents are similar at 0.5 MAC, isoflurane and desflurane have greater vasodilatory effects than halothane at 1.5 MAC.
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Comparative Study
Intrathecal amitriptyline. Antinociceptive interactions with intravenous morphine and intrathecal clonidine, neostigmine, and carbamylcholine in rats.
Systemically administered opioids induce analgesia in part by spinal noradrenergic, serotonergic, and cholinergic mechanisms. The current study tested whether antinociception from systemically administered opioids could therefore be enhanced by intrathecal injection of a monoamine reuptake inhibitor to potentiate the action of spinally released norepinephrine and serotonin (amitriptyline) and intrathecal injection of a cholinesterase inhibitor to potentiate the action of spinally released acetylcholine (neostigmine). ⋯ These data suggest that intrathecal doses of amitriptyline resulting in potentiation of intravenous morphine antinociception may not be adequate to block muscarinic receptors, because they did not affect carbamylcholine-induced antinociception. These results further support the relevance of spinal monoamine reuptake and cholinesterase inhibition to synergistically enhance analgesia from systemic opioids.
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Comparative Study
Role of the vagus nerve in the antidysrhythmic effect of dexmedetomidine on halothane/epinephrine dysrhythmias in dogs.
Dexmedetomidine, an alpha 2-adrenergic agonist, can prevent the genesis of halothane/epinephrine dysrhythmias through the central nervous system. Because stimulation of alpha 2 adrenoceptors in the central nervous system enhances vagal neural activity and vagal stimulation is known to inhibit digitalis-induced dysrhythmias, dexmedetomidine may exert the antidysrhythmic property through vagal stimulation. To address this hypothesis, the effect of dexmedetomidine in vagotomized dogs was examined and compared with that in intact dogs. In addition, the effect of vagotomy on the antidysrhythmic action of doxazosin, an alpha 1 antagonist, was studied. ⋯ The vagus nerve plays an important role in the prevention of halothane/epinephrine dysrhythmias by dexmedetomidine in dogs. However, resting vagal tone neither modulates the onset of halothane/epinephrine dysrhythmias nor affects the antidysrhythmic action of doxazosin.