EFFECT OF PHENYLEPHRINE BOLUS ADMINISTRATION ON GLOBAL LEFT-VENTRICULAR FUNCTION IN PATIENTS WITH CORONARY-ARTERY DISEASE AND PATIENTS WITHVALVULAR AORTIC-STENOSIS

Background. Although phenylephrine bolus administration is frequently used to increase coronary perfusion pressure in patients with coronary artery disease or valvular aortic stenosis, there are no data describ ing its effect on left ventricular function (LVF). Methods: Twenty pat ients scheduled for elective coronary artery bypass grafting (group 1) and 18 patients scheduled for elective aortic valve replacement (grou p 2) entered the study. The effect of phenylephrine was compared with that of norepinephrine in those patients who developed a defined degre e of arterial hypotension under general anesthesia. These patients wer e randomized to receive an initial bolus of either phenylephrine (1 mu g/kg) or norepinephrine (0.05 mug/kg) followed by a bolus of the other drug after arterial pressure and heart rate (HR) had returned to base line. Transesophageal echocardiography was used to evaluate LVF. Arter ial pressure, HR, ejection time, and LV diameter, area, and wall thick ness were recorded immediately before and for 3 min after bolus admini stration. Fractional diameter shortening, fractional area change, mean heart rate corrected velocity of circumferential fiber shortening (mV cf(c)), and LV meridional end-systolic walt stress (ESWS) were calcula ted. Results: Both substances effectively restored arterial pressure i n both groups. However, in group 1, phenylephrine administration resul ted in a reduction of fractional area change from 0.51 (median) to 0.3 9 (P = 0.0007) and a reduction of mVcf(c) from 1.16 to 0.61 circ/s (P = 0.0001). End-systolic wall stress increased from 98 to 186 10(3) dyn e.cm-2 (P = 0.0001). Administration of norepinephrine to group 1 and a dministration of either substance to the group 2 patients did not caus e any significant changes of LVF. Conclusions: The results indicate th at phenylephrine given as an intravenous bolus to patients with CAD an esthetized with fentanyl causes a transient impairment of LV global fu nction and that phenylephrine bolus administration is well tolerated i n patients with valvular aortic stenosis.