Time Course and Hemodynamic Effects of Alpha-1-Adrenergic Bolus Administration in Anesthetized Patients with Myocardial Disease

Phenylephrine (Phe) is frequently administered as an intravenous (IV) bolus to increase blood pressure, yet the acute time course and hemodynamic effects of bolus Phe in patients with myocardial disease have not been reported. Therefore 50 randomized IV bolus doses of Phe (50, 100, 150, or 200 micrograms) were given to 18 patients during anesthesia for elective coronary artery surgery. Esophageal Doppler techniques were used to continuously monitor cardiac output (CO); mean arterial pressure (MAP), CO, and calculated systemic vascular resistance (SVR) were recorded every 5 seconds for a total of 2 minutes. The hemodynamic changes (mean +/- SEM) for each of the four doses of Phe (50, 100, 150, 200 micrograms) were maximal at about 42 seconds after the drug was given. They consisted of an increase in MAP (11.6 +/- 2.1, 15.6 +/- 2.4, 14.7 +/- 2.4, 18.0 +/- 1.5 mm Hg); increase in SVR (766 +/- 190, 930 +/- 310, 950 +/- 344, 1732 +/- 824 dynes.sec.cm-5); and a decrease in CO (-.58 +/- .11, -.68 +/- .13, -.73 +/- .20, -.77 +/- .18 L.min-1). Hypertension, increased age, low preoperative ejection fraction, high baseline CO, and low baseline SVR significantly (P less than 0.05) decreased hemodynamic responses to Phe (see text). In conclusion, bolus IV Phe in patients with myocardial disease increases MAP and SVR and simultaneously decreases CO; these peak hemodynamic events occur approximately 42 seconds after Phe administration.