Surgical sealant in the prevention of early vein graft injury in an ex vivo model.

BACKGROUND: The amelioration of the adaptation process (arterialisation) of the vein graft wall to the arterial circulation in coronary artery bypass surgery by using extravascular support is clearly established in animal models and in in vitro and ex vivo set-ups. This support consists of some form of external graft-supporting modality like a prosthetic graft of stent. The clinical application of perivenous support, however, is hampered due to the fact that no easy applicable external support is available. Considering that application in the form of a spray is the most convenient modality, we evaluated whether polyethylene glycol is capable of providing adequate perivenous support. Polyethylene glycol is a synthetic, biodegradable product, used in cardiac surgery as a sealant, and is commercially available in the form of a spray. METHODS: Segments of human saphenous vein graft obtained during coronary artery bypass graft (CABG) procedures were placed in an ex vivo model, a side loop of the extracorporeal perfusion circuit, and perfused with autologous blood, making the circumstances identical to the implanted saphenous vein grafts concerning pressure, temperature, level of complement and leukocyte activation and blood pressure. Alternately around every other study vein graft segment polyethylene glycol was applied. Unsupported grafts served as control. After 1 min of solidification, perfusion was started with a pressure of about 60 mmHg (nonpulsatile flow). Perfusion was maintained for 60 min, after which the grafts were collected for light microscopy and electron microscopy. RESULTS: Light microscopy and electron microscopy showed remarkable attenuation of endothelial cell loss and less injury of smooth muscle cells of the circular and longitudinal layer of the media in the supported group compared to the nonsupported vein graft segments. CONCLUSION: Polyethylene glycol is able to provide adequate external vein graft support, preventing overdistension, in an ex vivo model. This provides a basis for clinical application. Further investigation is warranted to evaluate long-term effects.

Perivenous application of fibrin glue reduces early injury to the human saphenous vein graft wall in an ex vivo model.

OBJECTIVES: From animal and clinical studies it is known that prevention of 'over-distention' of vein grafts by using extravascular support ameliorates the arterialization process in vein grafts with subsequent more favorable patency. The most ideal support is a biodegradable, porous, elastic graft (Biomaterials, 15 (1994) 83). However, a specific graft meeting these criteria is not available yet. Fibrin glue on the other hand, although used for other purposes in cardiac surgery, theoretically meets the criteria for ideal extravascular support. In this ex vivo study, we evaluated the possible beneficial effect of perivenous application of fibrin glue. METHODS: Segments of human vein graft obtained during CABG procedures in 14 consecutive patients were placed in a side loop of the extracorporeal perfusion circuit. In this way the study vein grafts did meet identical circumstances as the vein grafts implanted. Perfusion in the loop was started with a flow just enough to counteract the collapse of the vein, usually about 8 mm Hg, and alternately around the segments fibrin glue was applied or no perivenous support was administered as control. After 1 min of soldification, perfusion was started with a pressure of about 60 mm Hg (non-pulsatile flow). Perfusion was maintained for 60 min, after which the grafts were collected for light microscopic and electron microscopic assessment. RESULTS: Light microscopy and electron microscopy showed remarkable attenuation of endothelial cell loss and less injury of smooth muscle cells of the circular muscle layer of the media in the fibrin glue supported vein grafts compared to the non-supported group. CONCLUSION: Fibrin glue is able to accomplish adequate external vein graft support, preventing overdistention, in an ex vivo model. This provides a basis for clinical application. Further investigation is necessary to evaluate long-term effects.

Induction and detection of disturbed homeostasis in cardiopulmonary bypass.

During cardiopulmonary bypass (CPB) haemodynamic alterations, haemostasis and the inflammatory response are the main causes of homeostatic disruption. Even with CPB procedures of short duration, the homeostasis of a patient is disrupted and, in many cases, requires intensive postoperative treatment to re-establish the physiological state of the patient. Although mortality is low, disruption of homeostasis may contribute to increased morbidity, particularly in high-risk patients. Over the past decades, considerable technical improvements in CPB equipment have been made to prevent the development of the systemic inflammatory response syndrome (SIRS). Despite all these improvements, only the inflammatory response, to some extent, has been reduced. The microcirculation is still impaired, as measured by tissue degradation products of various organs, indicating that CPB may still be considered as an unphysiological procedure. The question is, therefore, whether we can detect the pathophysiological consequences of CPB in each individual patient with valid bedside markers, and whether we can relate this to determinant factors in the CPB procedure in order to assist the perfusionist in improving the adequacy of CPB. The use of these markers could play a pivotal role in decision making by providing an immediate feedback on the determinant quality of perfusion. Therefore, we suggest validating the proposed markers in a nomogram to optimize not only the CPB procedure, but also the patient's safety.