Comparison between the effects of pentobarbital or ketamine/nitrous oxide anesthesia on metabolic and endothelial components of coronary reactive hyperemia

Barbiturates induce reduction of myocardial contractility and metabolism, w hereas ketamine exerts a sympathomimetic effect that can mask its direct de pressant effect on contractility. However, it is un clear whether barbitura tes, which interfere with the cytochrome P-450 pathway, or ketamine, which inhibits nitric oxide synthesis, also alter the responsiveness of the coron ary vessels to vasodilator stimuli. We hypothesized that the parameters of coronary reactive hyperemia (CRH), which reflect both the degree of myocard ial metabolism and vascular reactivity, could be modified by the type of an esthesia used. In two groups of goats, anesthesia was induced either using ketamine plus nitrous oxide or pentobarbital alone. To record coronary flow an electromagnetic flow-probe was placed around the left circumflex corona ry artery. In the ketamine group(n= 14) and in the pentobarbital group (n = 16) CRH was studied using the indices of myocardial metabolism and vascula r dilator responsiveness. In the pentobarbital group all of the indices of myocardial metabolism were lower than in the ketamine group (i.e, the exces s to debt flow ratio was 2.3+/-0.8 vs. 4.6+/-2.4: p<0.001). Yet, some indic es of vascular responsiveness (time derivative of coronary flow and the pea k to basal flow ratio) were not different in the two groups. Moreover, the duration of the reactive hyperemia was shorter in the ketamine than in the pentobarbital group (118+/-47 vs.153+/-45 s, p<0.05). It is suggested that pentobarbital decreases the indices of CRH related to metabolic activity, w hereas ketamine reduces the duration of the hyperemic response, which sugge sts an impairment of endothelial function. (C) 2001 Elsevier Science Inc. A ll rights reserved.