A new protective solution for hypothermic storage of free vein grafts in cardiovascular surgery

In order to reduce the operative injury of the endothelium in free reversed vein grafts, cultured human endothelial cells were used to test the optimal concentration of the constituents of a flushing solution for improved protection of the endothelium. The following solution proved to be the most suitable when tested at 20 degrees C; mannitol 160 mmol l-1, glucose 15 mmol l-1, NaCl 30 mmol l-1, KHCO3 5 mmol l-1, K2SO4 10 mmol l-1, KH2PO4 4 mmol l-1, MgSO4 20 mmol l-1, CaCl2 1.5 mmol l-1, potassium citrate 1.0 mmol l-1, Pluronic F-68 20 mg l-1, HEPES 4 mmol l-1, HEPES-Na 6 mmol l-1, pH 7.25, osmolality 325 mosmol kg-1 H2O. When endothelial cell injury was measured by a 51Cr-release assay, the new solution protected human endothelial cells in culture during hypothermic incubation better than isotonic NaCl, St Thomas' cardioplegic solution or Krebs-Henseleit's buffer. Transmission and scanning electron microscopy showed that the endothelium of human saphenous vein grafts was well preserved following 6 h of incubation at 20 degrees C with the new solution. As determined by morphometry using scanning electron microscopy, the endothelium of free porcine vein grafts was better preserved after incubation for 2 h at 20 degrees C with the new solution than with either isotonic NaCl (p = 0.02) or diluted, heparinized blood (p = 0.02) as the incubation medium, all cases observed following 2 h of subsequent arterial flow. The present study indicates that the endothelium of free vein grafts can be well protected against hypothermia when the flushing and irrigation fluid has a composition favouring endothelial protection. It appears likely that such treatment of vein grafts will reduce the frequency of vein graft narrowing and occlusion, post-operatively.