Anesthesia and analgesia
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Anesthesia and analgesia · May 1996
Comparative StudyThe effect of thoracic epidural anesthesia on hypoxic pulmonary vasoconstriction in dogs: an analysis of the pressure-flow curve.
The aim of the present study was to examine whether hypoxic pulmonary vasoconstriction (HPV) is preserved during one-lung ventilation combined with thoracic epidural anesthesia (TEA) in dogs. Using a separately ventilated left lower lobe (LLL) in situ, the pressure-flow (P-Q) curve was obtained. The HPV response was assessed by the shift of the P-Q curve, changes in blood flow diversion rate (FDR) and decrease in PaO2 during hypoxic gas ventilation of LLL. ⋯ TEA reduced heart rate, cardiac output, mean arterial pressure, mean pulmonary arterial pressure, and mixed venous oxygen tension. Our results suggest that TEA did not affect the primary pulmonary vascular tone at baseline or during lobar hypoxia, but enhanced the diversion of blood flow and arterial blood oxygenation during lobar hypoxia. This enhanced HPV response probably reflects hemodynamic changes, such as decreased cardiac tension, due to sympathetic nerve activity blockade by TEA.
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Anesthesia and analgesia · May 1996
The effect of a cyclodextrin vehicle on the cardiovascular profile of propofol in rats.
We studied the aqueous solution of propofol dissolved in hydroxypropyl-beta-cyclodextrin (HP beta CD) 20% to determine whether the cardiovascular profile differed from that measured for propofol prepared in Intralipid 10% (Diprivan). Conscious male rats were given an intravenous bolus of propofol, 5.0 mg/kg, the minimum dose that induces a loss of righting. Immediately severe bradycardia occurred which was the result of a combination of sinus arrest and atrioventricular block; a significant decrease of blood pressure resulted. ⋯ The severe bradycardia produced by propofol in HP beta CD was blocked by both atropine and bilateral cervical vagotomy. Therefore, the effects of propofol in HP beta CD are cholinergic and neurally mediated. These results are consistent with the hypothesis that propofol reduces sympathetic tone prior to reduction in vagal tone, and thereby produces a period of time during which vagal tone is dominant.
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Anesthesia and analgesia · May 1996
Identification of cytochrome P450 3A1/2 as the major P450 isoform responsible for the metabolism of fentanyl by rat liver microsomes.
The metabolism of fentanyl was investigated using rat liver microsomes to determine whether fentanyl is metabolized by rat liver microsomal cytochrome P450 and, if so, which isoform is responsible for the metabolism. Microsomes isolated from rats pretreated with phenobarbital were more active in metabolizing fentanyl than were microsomes from saline controls. ⋯ Fentanyl metabolism was inhibited by antibodies specific for CYP3A1/2, as well as by chemical inhibitors specific for CYP3A. These results indicate that CYP3A1/2 plays a major role in the oxidation of fentanyl to norfentanyl by rat liver microsomes.