Investigation of a method for long-term preservation of the vascular allograft.

BACKGROUND/OBJECTIVE: During multiple organ procurement, blood vessels are routinely retrieved and stored in University of Wisconsin solution and then discarded after two weeks, if not used at organ transplantation owing to lack of a method for long-term preservation. Therefore, the aim of this study is to investigate a method for long-term preservation of vascular allografts in ethanol. METHODS: Aorta and vena cava allografts were retrieved and stored in 75% ethanol solution for 12 months at 4°C. Four pigs were divided into two groups. A segment of aorta was excised and replaced by insertion of preserved aorta graft (Group A) or vena cava graft (Group V). The pigs were observed for six weeks. A laparotomy was performed and the vascular graft was harvested for histopathology followed by euthanasia at the end of study. RESULTS: Three pigs recovered uneventfully, while one pig died from venous graft rupture in the third week after surgery. There was no aneurysmal formation or thrombosis in the grafts. Some calcification was seen over aorta allograft. On histopathology, the elastic pattern was almost normal, although the endothelial cells degenerated after preservation. After implantation, the formation of the endothelium cell-like layer was seen in both aorta and vena cava allografts. CONCLUSION: Vascular allografts were functional after preservation for 12 months. The vena cava grafts had much less wall calcification than the aorta grafts. Further studies are necessary to investigate vascular graft remodelling with a longer observation period after implantation.

Computed tomographic assessment of lung aeration at different positive end-expiratory pressures in a porcine model of intra-abdominal hypertension and lung injury.

BACKGROUND: Intra-abdominal hypertension (IAH) is common in critically ill patients and is associated with increased morbidity and mortality. High positive end-expiratory pressures (PEEP) can reverse lung volume and oxygenation decline caused by IAH, but its impact on alveolar overdistension is less clear. We aimed to find a PEEP range that would be high enough to reduce atelectasis, while low enough to minimize alveolar overdistention in the presence of IAH and lung injury. METHODS: Five anesthetized pigs received standardized anesthesia and mechanical ventilation. Peritoneal insufflation of air was used to generate intra-abdominal pressure of 27 cmH2O. Lung injury was created by intravenous oleic acid. PEEP levels of 5, 12, 17, 22, and 27 cmH2O were applied. We performed computed tomography and measured arterial oxygen levels, respiratory mechanics, and cardiac output 5 min after each new PEEP level. The proportion of overdistended, normally aerated, poorly aerated, and non-aerated atelectatic lung tissue was calculated based on Hounsfield units. RESULTS: PEEP decreased the proportion of poorly aerated and atelectatic lung, while increasing normally aerated lung. Overdistension increased with each incremental increase in applied PEEP. "Best PEEP" (respiratory mechanics or oxygenation) was higher than the "optimal CT inflation PEEP range" (difference between lower inflection points of atelectatic and overdistended lung) in healthy and injured lungs. CONCLUSIONS: Our findings in a large animal model suggest that titrating a PEEP to respiratory mechanics or oxygenation in the presence of IAH is associated with increased alveolar overdistension.