Effects of vasoactive drugs on flows through left internal mammary artery and saphenous vein grafts in man

Vasoactive agents are commonly used in the postcardiopulmonary bypass period to elevate the mean arterial pressure of myocardial revascularization patients. Concern exists that administration of vasoactive agents in this setting may affect flow through saphenous vein and internal mammary artery grafts. Twenty-eight patients were randomly assigned to receive one of the six two-drug combinations of phenylephrine, norepinephrine, and epinephrine. After termination of cardiopulmonary bypass baseline, hemodynamic measurements and electromagnetic flow probe measurements of saphenous vein and internal mammary artery graft flow were made. The first agent was then infused to elevate mean arterial pressure 20 mm Hg. After 5 minutes of stability, hemodynamic and graft flow measurements were repeated. The infusion was terminated, 5 minutes of stability were obtained, and baseline measurements were repeated. The second agent was then infused, and measurements were repeated after a 5-minute stabilization period. Phenylephrine induced a nonsignificant increase in saphenous vein graft flow (68 ± 31 versus 81 ± 49 ml/min) and a significant decrease in internal mammary artery graft flow (40 ± 16 versus 32 ± 12 ml/min). Norepinephrine induced a significant increase in saphenous vein graft flow (80 ± 39 versus 97 ± 39 ml/min) and no significant change in internal mammary artery graft flow (44 ± 20 versus 45 ± 20 ml/min). Epinephrine induced a significant increase in both saphenous vein (82 ± 38 versus 96 ± 40 ml/min) and internal mammary artery (38 ± 12 versus 55 ± 24 ml/min) graft flows. We conclude that administration of vasoactive agents in the postcardiopulmonary bypass period may significantly affect saphenous vein and internal mammary artery graft flows.