Intraluminal papaverine with pH 3 doubles blood flow in the internal mammary artery

Seventy-five patients undergoing coronary artery bypass grafting were rando mized to receive injections of papaverine solution or isotonic saline or no injection into the left internal mammary artery (LIMA) used as graft. Bloo d flow in the LIMA was measured twice-after dissection of the pedicle and b efore anastomosis to the coronary artery. Blood flow increased significantl y in all three groups, but after papaverine injection it was twice as high as in the control groups, increasing by 285% (from 40 +/- 12 to 154 +/- 32 ml/min, p = < 0.0001). The pH of the papaverine solution was only 3, and we advise that surgeons check and correct pH in the papaverine solutions they use, in order to avoid endothelial damage to the LIMA. Based on these resu lts we can recommend papaverine injection into the arterial graft only if t he initial flow is low.