Articles: anesthetics.
-
Anesthesia and analgesia · Aug 1989
Solubility of I-653, sevoflurane, isoflurane, and halothane in plastics and rubber composing a conventional anesthetic circuit.
This study defines some characteristics of a standard anesthetic circuit that may impede anesthetic induction and recovery with I-653, sevoflurane, isoflurane, and halothane. Partition coefficients for anesthetic circuit components (masks, bellows, bags, airways, and circuit tubes) consistently ranked halothane greater than isoflurane greater than sevoflurane greater than I-653, suggesting a reverse order of washin and washout rates for an anesthetic circuit constructed from similar components. ⋯ The rates of change in I-653 concentration closely approximated the maximal possible theoretical rates. Our results suggest that absorption of I-653 by circuit components or soda lime should not hinder induction of or recovery from anesthesia.
-
This study was designed to investigate if propofol produced cardiovascular effects by direct actions or by indirect actions secondary to depression of the central nervous system. Experiments were performed on chloralose anaesthetized dogs in which all neurogenic cardiovascular reflexes were abolished by bilateral vagotomy and common carotid ligatures, in combination with i.v. bretylium and propranolol. Bolus doses of propofol followed by infusions at rates up to 160 mg kg-1 h-1 produced blood concentrations of propofol from 1.99 to 112 micrograms ml-1. ⋯ Blood concentrations of propofol less than 10 micrograms ml-1 caused an increase in mean capacitance of 8.0 (SEM 1) ml kg-1 with no significant changes in systemic vascular resistance, pulmonary vascular resistance or inotropic state of the heart. We conclude that anaesthesia with propofol may be accompanied by decreased cardiac output secondary to reduction in preload by a direct venodilator effect. Our experiments indicate that cardiac output and arterial pressure are preserved well at normal anaesthetic blood concentrations of propofol if the preload is maintained.
-
J. Pharmacol. Exp. Ther. · Jul 1989
Quantitative histologic analysis of local anesthetic-induced injury to rat sciatic nerve.
Quantitative measurements of endoneurial edema, cytoplasmic lipid droplets, nerve fiber injury and Schwann cell damage were used to elucidate the pathogenesis of local anesthetic-induced injury to sciatic nerve in the rat. All histopathologic measurements were conducted on rat sciatic nerves removed at 48 hr after the extraneural injection of one of three concentrations of the local anesthetic 2-chloroprocaine, procaine, etidocaine or lidocaine. ⋯ Quantitative electron microscopic evaluation of Schwann cell injury indicated that the Schwann cells of unmyelinated fibers were more likely to undergo lysis after exposure to local anesthetics, whereas those of myelinated fibers were more likely to accumulate cytoplasmic lipid droplets. These quantitative data on the specificity of the regional distribution of nerve injury and of Schwann cell effects are consistent with a direct cellular toxicity of the local anesthetics; however, these results do not preclude a role for toxicity mediated indirectly by changes in the endoneurial environment.
-
Dexmedetomidine, a highly selective and potent alpha-2 adrenoceptor agonist, reduces halothane anesthetic requirements by over 90% in rats. The present study examined whether dexmedetomidine produces a hypnotic-anesthetic action in rats. Dexmedetomidine induced a hypnotic-anesthetic state in rats characterized by loss of righting reflex at doses greater than or equal to 0.1 mg/kg. ⋯ Antagonists with beta-2 receptor blocking properties also enhanced dexmedetomidine-induced hypnosis. Selective beta-1 receptor antagonists did not affect the hypnotic action of dexmedetomidine. These results suggest that dexmedetomidine produces a hypnotic-anesthetic action in rats via activation of central alpha-2 adrenoceptors.