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 describing its effect on left ventricular function (LVF).
Methods: Twenty patients scheduled for elective coronary artery bypass grafting (group 1) and 18 patients scheduled for elective aortic valve replacement (group 2) entered the study. The effect of phenylephrine was compared with that of norepinephrine in those patients who developed a defined degree of arterial hypotension under general anesthesia. These patients were randomized to receive an initial bolus of either phenylephrine (1 micrograms/kg) or norepinephrine (0.05 micrograms/kg) followed by a bolus of the other drug after arterial pressure and heart rate (HR) had returned to baseline. Transesophageal echocardiography was used to evaluate LVF. Arterial pressure, HR, ejection time, and LV diameter, area, and wall thickness were recorded immediately before and for 3 min after bolus administration. Fractional diameter shortening, fractional area change, mean heart rate corrected velocity of circumferential fiber shortening (mVcfc), and LV meridional end-systolic wall stress (ESWS) were calculated.
Results: Both substances effectively restored arterial pressure in both groups. However, in group 1, phenylephrine administration resulted in a reduction of fractional area change from 0.51 (median) to 0.39 (P = 0.0007) and a reduction of mVcfc from 1.16 to 0.61 circ/s (P = 0.0001). End-systolic wall stress increased from 98 to 186 10(3) dyne-cm-2 (P = 0.0001). Administration of norepinephrine to group 1 and administration of either substance to the group 2 patients did not cause any significant changes of LVF.
Conclusions: The results indicate that phenylephrine given as an intravenous bolus to patients with CAD anesthetized with fentanyl causes a transient impairment of LV global function and that phenylephrine bolus administration is well tolerated in patients with valvular aortic stenosis.