A loss of taurine and other amino acids from ventricles of patients undergoing bypass surgery.

OBJECTIVE--To study the changes in amino acid content of left ventricles of patients during cardiac surgery that involves cardiopulmonary bypass and cold cardioplegia. DESIGN--Biopsy specimens (up to 10 mg wet weight) from the left ventricle of 30 patients undergoing coronary artery bypass graft and valve replacement surgery on cardiopulmonary bypass (protected by cold cardioplegia with St Thomas' solution) were taken immediately before the infusion of the cardioplegic solution and just before the removal of the cross clamp, and were analysed for their amino acid content. RESULTS--Of the most abundant cellular amino acids in the left ventricle taurine, glutamine, glutamate, and aspartate, but not alanine, showed a significant fall during the period of cross clamping. A rise in intracellular sodium (Na) is known to occur during cold cardioplegic arrest so that an activation of an amino acid/Na efflux, similar to that seen in animal experiments, seems a likely mechanism. The anomalous behaviour of alanine suggests some recovery of metabolism. CONCLUSIONS--The loss of alpha amino acids (by contrast with the loss of taurine) will depress protein synthesis and reduce energy reserves after cardiac surgery. Attempts to preserve the concentrations of intracellular alpha amino acids must be balanced against the need to regulate intracellular Na concentration and hence intracellular pH and calcium ions. The presence of alpha amino acids in the cardioplegic solution (or in a resuscitation solution) should maintain the intracellular concentrations and favour activation of the taurine/Na symport to oppose the rise in intracellular Na concentration. Because the reservoir of tissue taurine is limited, the potential benefits of increasing the concentration of taurine in the heart by diet before surgery and addition of alpha amino acids to the cardioplegic solution merits further assessment

A Reappraisal of Saphenous Vein Grafting

Autologous saphenous vein grafting has been broadly used as a bypass conduit, interposition graft, and patch graft in a variety of operations in cardiac, thoracic, neurovascular, general vascular, vascular access, and urology surgeries, since they are superior to prosthetic veins. Modified saphenous vein grafts (SVG), including spiral and cylindrical grafts, and vein cuffs or patches, are employed in vascular revascularization to satisfy the large size of the receipt vessels or to obtain a better patency. A loop SVG helps flap survival in a muscle flap transfer in plastic and reconstructive surgery. For dialysis or transfusion purposes, a straight or loop arteriovenous fistula created in the forearm or the thigh with an SVG has acceptable patency. The saphenous vein has even been used as a stent cover to minimize the potential complications of standard angioplasty technique. However, the use of saphenous vein grafting is now largely diminished in treating cerebrovascular disorders, superior vena cava syndrome, and visceral revascularization due to the introduction of angioplasty and stenting techniques. The SVG remains the preferable biomaterial in coronary artery bypass, coronary ostioplasty, free flap transfer, and surgical treatment of Peyronie disease. Implications associated with saphenous vein grafting in vascular access surgery for the purpose of dialysis and chemotherapy are considerable. Vascular cuffs and patches have been developed as an important and effective means of enhancing the patency rates of the grafts by linking the synthetic material to the receipt vessel. In addition, saphenous veins can be a cell source for tissue engineering. We review the versatile roles that saphenous vein grafting has played as well as its current status in therapy