ROLE OF THE ENDOTHELIUM IN THE RELAXATION INDUCED BY PROPOFOL AND THIOPENTAL IN ISOLATED ARTERIES FROM MAN

Induction of anaesthesia with intravenous propofol and thiopental is o ften accompanied by hypotension. This study evaluates whether propofol and thiopental induce relaxation of isolated arteries from man and wh ether this effect is modulated by the endothelium. Mesenteric artery r ings (with and without endothelium) from 12 patients were placed in or gan baths and precontracted with phenylephrine before addition of prop ofol (10(-3) M) or thiopental (10(-3) M). Relaxation induced by propof ol and thiopental was evaluated for rings with intact endothelium in t he presence of the nitric oxide synthase inhibitor N-G-nitro-L-arginin e methyl ester (L-NAME; 10(-4) M) or the cyclooxygenase inhibitor indo methacin (10(-5) M). The vasodilator effect of propofol was similar fo r intact and denuded endothelium rings whereas the relaxation induced by thiopental was significantly attenuated in denuded-rings. In intact endothelium rings, L-NAME and indomethacin caused marked inhibition o f the relaxation induced by thiopental, but not that induced by propof ol. These results suggest that propofol induces endothelium-independen t relaxation of isolated mesenteric arteries in man, whereas thiopenta l causes endothelium-dependent relaxation mediated by nitric oxide and prostaglandins.