Effects of propofol, etomidate, and pentobarbital on critical oxygen delivery.

摘要: ome anesthetics currentlyavailable are specifically usedin intensive care units for se-dation, as well diagnosticand therapeutic bedside procedures.Propofol is largely appreciated (1, 2) forits favorable pharmacokinetic properties,allowing easy titration and rapid weaning(3). However, it produces dose-dependentcardiovascular depression similar to thatof barbiturates (4–6). Etomidate char-acterized by hemodynamic stability (4, 7),even in patients with cardiac disease (8),but etomidate can only be used shortdiagnostic or procedures (9)because its depressant properties on cor-tisol synthesis (10, 11) potentiallyharmful (12). Short-acting barbiturates,such pentobarbital, essentiallyused decrease refractory intracranialhypertension (13, 14); however, they havemarked cardiodepressant effects (5, 15,16). Although the effectsof these three agents character-ized, their balance betweenoxygen demand oxygen supply arenot defined.In critically ill patients, level ofsedation affect both deliveryand consumption a dose-dependent manner (17) result of thecombined usedto produce sedation cardiovascularsystem, sympathetic mediated stressresponse, muscular activity (18). An-esthetics may also alterthe extraction capabilities thetissues, reducing ability maintainoxygen availability at oxygendemand when acutelycurtailed. An alteration this protectivemechanism has been hy-pothesized several investigators inhigh-risk surgical (19, 20). How-ever, methodology did not allowdefinitive conclusion absence ofdeterminations individual ex-traction values.In experimental conditions, tissue ox-ygen evalu-ated measuring consumptionduring progressive oxygendelivery. Under normal whenoxygen delivery decreases, oxygenuptake remains constant systemicoxygen ratio increases propor-tionally. Below critical oxygendelivery, increase becomes insufficient tocompensate reduction oxygendelivery be-comes directly dependent de-livery (21). In presence stableoxygen demand, associated