In order to investigate haemodynamic response and catecholamine release during anaesthesia with xenon, we conducted a study on 28 pigs which were allocated randomly to one of four groups: total i.v. anaesthesia with pentobarbitone and buprenorphine, and xenon anaesthesia with inspiratory concentrations of 30%, 50% or 70%, respectively, supplemented with pentobarbitone. Haemodynamic variables were measured using arterial and Swan Ganz catheters. Depth of anaesthesia was monitored using spectral edge frequency analysis. Plasma concentrations of dopamine, noradrenaline and adrenaline were measured by high pressure liquid chromatography. All haemodynamic variables and plasma concentrations of dopamine and noradrenaline remained within normal limits. Adrenaline concentrations were reduced significantly in all groups. Xenon anaesthesia was associated with a high degree of cardiovascular stability. Significant reduction in adrenaline concentrations at inspiratory xenon concentrations of 30% and 50% can be explained by analgesic effects of xenon below its MAC value.
We investigated the effects of the carotid sinus baroreflex on coupling of the left ventricle (LV) and the arterial system in twelve anesthetized dogs, with all nerves and carotid sinus circulation intact and instrumented to measure LV pressure and volume. The Rheos(R) device was used to directly electrically stimulate the carotid sinus baroreceptors. Stimulation resulted in a significant reduction in systolic blood pressure (SBP), 95.6+/-8.1 to 77.3+/-5.3 mmHg (p<0.0001) and heart rate (HR), 85+/-13.2 to 67.2+/-18.8 (p<.001). Cardiac output was unchanged. Ventricular-vascular coupling was determined by the ratio of arterial and ventricular elastance (Ea/Ees). At baseline, Ea/Ees was 1.26+/-0.27 and after stimulation decreased to 0.51+/-0.16 (p<0.001), favoring optimization of metabolic efficiency. This decrease was entirely due to a reduction in Ea while Ees was unchanged. The maintenance of end-diastolic volume (EDV) during stimulation allowed stroke work (SW) to remain unchanged as arterial pressure decreased. Thus mechanical efficiency, described as the ratio of stroke work to pressure-volume area (SW/PVA) increased from baseline of 0.51+/-0.05 to 0.69+/-0.04 (p<0.0001) during baroreceptor stimulation. We conclude that electrical activation of the carotid sinus baroreceptors results in optimization of both energetic and mechanical efficiency and has no acute effect on LV Ees. These novel findings await confirmation in chronically instrumented animals.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.