Retrograde perfusion of the spinal cord during aortic crossclamping: Initial observations in the swine model

Background: Retrograde perfusion has emerged as a useful technique for the preservation of the heart and brain when arterial circulation is interrupte d, Herein, this study was designed to test the hypothesis that retrograde p erfusion of the azygos vein is sufficient to maintain viability of the spin al cord during aortic occlusion in the swine model. Methods: Female swine, 17 to 22 kg, underwent left thoracotomy, creation of a shunt between the ao rtic arch and the azygos vein, and aortic crossclamping for 60 minutes: the shunt was open in the retrograde perfusion group (n = 5) and closed in the control group (n = 4). The animals were evaluated for neurologic function for 8 days and killed. Spinal cords were processed for histologic examinati on. Additional animals underwent left thoracotomy and injection of a castin g solution in the azygos vein (n = 2), left thoracotomy and angiography of the azygos vein (n = 2), and a compartmentalization procedure to separate t he azygos vein from the caval system followed by angiography (n = 2), Resul ts: Differences in the neurologic (2-sample t test, P = .11) and histologic (2-sample t test, P = .65) scores of retrograde perfusion and control grou ps n ere likely due to chance. Casting and angiography groups showed extens ive collaterals between azygos and caval systems, only partially interrupte d by compartmentalization. Conclusions: Retrograde perfusion does not prote ct the spinal cord from ischemic injury, The collateral network between the azygos and caval systems prevents the oxygenated blood from reaching the c ord. Surgical separation between the 2 systems was only partially successfu l in this study.