Effects of pretreatment with different topical vasodilators on blood flow in the internal mammary artery: a prospective randomized study.

Background. This study was conducted to investigate how brief pretreatments with 4 different vasodilators applied topically at normal body temperature affect blood flow in the internal mammary artery.Methods. One hundred patients who had an internal mammary artery mobilized as a pedicle for coronary artery bypass grafting were randomly assigned to one of 5 groups of equal size (20 subjects in each). Each group of pedicles was treated with a different topical solution: normal saline (control), nitroglycerin, diltiazem, papaverine, or adenosine. Internal mammary artery flow and hemodynamic measurements were recorded immediately after harvesting and after 5 minutes of immersion in a tube filled with test solution (50 mL at 37°C). Results for each study variable were compared within and between groups, and posttreatment-to-pretreatment ratios were also calculated and compared.Results. All 4 vasodilator groups showed a significant increase in internal mammary artery flow rate from pretreatment to posttreatment, whereas the saline group did not. There were no significant differences among the 5 groups' pretreatment flow rates (P = .526) or posttreatment flow rates (P = .194). The mean ratio values (posttreatmentto-pretreatment) for flow rate were 1.08 ± 0.17 in the saline group, 1.74 ± 0.17 with nitroglycerin, 1.77 ± 0.49 with diltiazem, 1.82 ± 0.59 with papaverine, and 1.57 ± 0.54 with adenosine. Post hoc analysis revealed that the mean ratio values for flow rate in the 4 vasodilator groups were significantly higher than the corresponding ratio in the saline group.Conclusions. Brief treatment of the internal mammary artery with topical vasodilators at normal body temperature significantly increases blood flow in this vessel. The data from this study are particularly valuable in relation to off-pump surgery, in which this vessel is usually anastomosed soon after it is harvested.