VASOACTIVE EFFECTS OF KETAMINE ON ISOLATED RABBIT PULMONARY-ARTERIES

Ketamine has been used in patients with congenital heart disease and p ulmonary hypertension with hypothetical controversy. Its direct effect on pulmonary arteries has not yet been clearly characterized, This in vitro study was performed to determine the direct vasoactive effects of ketamine on isolated rabbit pulmonary arteries, Responses of pulmon ary artery rings from New Zealand white rabbits were assessed in the p resence and absence of intact endothelium and with or without precontr action by norepinephrine (NE, 3X 10(-6)M) or potassium chloride (KCI, 3x10(-2)M). Using a preparatory tissue bath, cumulative concentration response curves of ketamine were obtained at different concentrations (0.03, 0.1, 0.3, 1, 3 mM) after a period of stabilization, Ketamine ca used a dose-related vasodilation on KCl-precontracted pulmonary arteri es, It elicited almost 100%, relaxation at a concentration of 3 mM. Ke tamine also induced a dose-related vasodilation on NE-precontracted pu lmonary arteries at a lesser degree, All of the effects were endotheli um independent. In conclusion, ketamine has strong endothelium-indepen dent, direct vasodilatory effects on isolated rabbit pulmonary arterie s. Ketamine may act through Ca++ channel-blocking effect as well as in hibition of Ca++ release from sarcoplasmic reticulum.