Comparison of saphenous vein graft relaxation between Plasma-Lyte solution and normal saline solution

Venospasm of saphenous vein grafts may damage endothelial cells and compromise early and late graft performance. Hence it is desirable to identify and use storage solutions that minimize vascular spasm during vein preparation. In view of this, we initiated isometric tension-recording studies in isolated canine and human saphenous vein to evaluate the acute, vasoactive effects of two storage solutions, Plasma-Lyte solution and normal saline solution. In initial experiments, canine saphenous veins were mounted in tissue baths containing physiologic salt solution and tonically constricted by 2 x 10(-6) mol/L norepinephrine. The physiologic salt solution in the bath was then replaced by Plasma-Lyte solution or normal saline solution containing the same norepinephrine concentration, and changes in contraction amplitude were recorded for 90 minutes. Storage in Plasma-Lyte solution at 37 degrees C completely relaxed norepinephrine-activated canine saphenous vein within 20 minutes, whereas veins remained partially constricted in normal saline solution. Both Plasma-Lyte solution and normal saline solution relaxed canine saphenous vein less at room temperature (25 degrees C) than at 37 degrees C, implying that warming of storage solutions in the operating room may promote graft dilation. To identify the mechanism by which Plasma-Lyte solution induced relaxation, we replaced its putative vasodilator components of gluconate and acetate with NaCl, but this alteration did not reduce relaxation induced by Plasma-Lyte solution. However, adding 1.6 mmol/L CaCl2 to Plasma-Lyte solution completely reversed the venodilation, suggesting that the low Ca2+ content of Plasma-Lyte solution confers its relaxant action. Finally, we tested the vasoactive effect of Plasma-Lyte solution on human saphenous vein obtained by discard from coronary bypass operations. Plasma-Lyte solution at 37 degrees C effectively dilated norepinephrine-activated human saphenous vein, inducing complete relaxation within 20 minutes. On this basis, we recommend the use of Plasma-Lyte solution as a venodilating storage solution during coronary bypass operations to optimize vein graft relaxation before implantation.