DOES URAPIDIL INDUCE VENODILATION

This study aimed to assess and compare the effects of urapidil and clo nidine on right ventricular volumes and function in 20 physical status ASA III patients, with a bordeline untreated essential hypertension a nd with or without chronic coronary artery disease. The patients were randomly assigned to two equal groups to receive either urapidil (0.4 mg . kg-1) or clonidine (2.5 mug . kg-1). Neither patient had congesti ve heart failure, valvular heart disease, previous myocardial infarcti on, nor was any being treated with beta-blocking agents or with amioda rone. Usual anti-anginal medication (nifedipine and isosorbide) was ma intained up to the time of the procedure. Monitoring was obtained from ECG, Swan-Ganz catheter fitted out with a fast response-thermistor, a nd radial artery cannula. Blood samples were withdrawn for plasma atri al natriuretic factor determination. Thirty minutes after catheter ins ertion, baseline data were collected in supine and 45-degrees head-up tilt positions. Following urapidil or clonidine i.v. injection, three series of measurements (3, 8 and 13 min) were made in supine and tilt positions according to a randomized sequence. The two groups were simi lar with regard to age, weight, height, coronary artery disease and tr eatment. Urapidil and clonidine elicited a similar decrease in mean ar terial pressure of 14 % in supine position and 20 % in head-up tilt po sition, combined with an exclusive decrease in systolic index i.e. not associated with a change in peripheral vascular resistances. Despite the decrease in arterial pressure, heart rate remained unchanged. Righ t ventricular ejection fraction was maintained after both urapidil and clonidine, however end-diastolic and end-systolic volumes decreased, with no modification by tilting. Atrial natriuretic factor decreased a fter - both urapidil and clonidine injection. This study substantiates the decrease of venous return elicited by the peripheral venodilation and blood pooling following the i.v. injection of urapidil,