Comparison of systemic vasodilators: effects on flow in internal mammary and radial arteries

BACKGROUND: Spasm is a major concern with the use of arterial conduits in coronary artery bypass surgery (CABG). We evaluated the effect of systemic vasodilators on in vivo radial artery flow compared with internal mammary artery (IMA) flow. METHODS: Fifty patients undergoing primary CABG with a mean age of 69 +/- 5 years enrolled in this study and were randomized to 1 of 5 groups based on the vasodilating agent administered (nitroglycerin, nitroprusside, dobutamine, milrinone, and normal saline as control group). Radial artery and IMA flows, blood pressure, central venous pressure, and heart rate were measured before and 10 minutes after drug administration. RESULTS: Mean arterial pressure decreased significantly after drug administration in both the nitroglycerin (p = 0.007) and nitroprusside (p < 0.001) groups and increased in the dobutamine group (p < 0.001). There were no significant differences between IMA flow or radial flow among the groups before drug administration. A multivariate general linear model was created and revealed drug (specifically nitroglycerin) as the only predictor to increase flow in the IMA (p < 0.001) or the radial artery (p = 0.009). CONCLUSIONS: We conclude that intravenous nitroglycerin causes in vivo vasodilatation of both the IMA and radial artery and is a good systemic vasodilator to be given when harvesting these two conduits.