EFFECT OF TOPICAL VASODILATORS ON INTERNAL MAMMARY ARTERIES

The internal mammary artery (IMA) is the conduit of choice for graftin g the left anterior descending artery. However, arterial spasm and red uced early now has been a cause of postoperative morbidity. The purpos e of this study is to evaluate the effect of vasodilators on IMA flow. Fifty patients who had the IMA harvested in preparation for bypass gr afting were studied. The IMA was mobilized from the subclavian vein to below the bifurcation of the IMA. The artery was prepared for graftin g at least 3 cm proximal to the bifurcation. The IMA was allowed to bl eed freely, and now was determined (now 1). The patients were divided into five groups: group I (n = 10) had 10 mi of saline solution applie d topically to the IMA; group II had topical papaverine (5 mg/10 mi no rmal saline solution) applied to the IMA; group III had nitroglycerin (5 mg/10 mi normal saline solution) applied to the IMA, group IV had s odium nitroprusside (2.5 mg/10 mi) applied to the pedicle, and group V had 5 mi of papaverine mixed in 5 mi of saline solution injected into the periarterial tissues of the IMA pedicle. Before cardiopulmonary b ypass, the flows were remeasured (flow 2). With each measurement, hemo dynamic parameters were recorded. The time between measurements was re corded. There was no difference in blood pressure or pulse at the time of measurement. Each group showed a significant increase in now from now 1 to now 2 (group I, 59 +/- 20.7 versus 72.8 +/- 17 mL/min, p 0.03 5; group II, 85.5 +/- 25.4 versus 118.5 +/- 53 mL/min, p = 0.014; grou p III, 70.55 +/- 24.4 versus 90.1 +/- 30.1 mL/min, p = 0.014; group IV , 43.0 +/- 27.2 versus 67.2 +/- 27.38 mL/min, p = 0.044; and group V, 57.6 +/- 33.3 versus 83.2 +/- 48.9 mL/min, p = 0.029). Comparing the i ncrease in IMA now between the groups from now 1 to flow 2, there were no differences in the absolute increase of now (p = 0.836) or in the percent change from baseline (p = 0.896). After the IMA was prepared f or grafting, there was a reduction in flow that resolved with time. Th us, if the artery is fashioned proximally and has adequate early now ( >40 mL/min), topical vasodilators are not warranted.