Hemodynamic and Metabolic Determinants of End-Organ Perfusion and Microcirculation in an Animal Model of Thoracoabdominal Aortic Repair

Abstract

Introduction - Open repair of thoracoabdominal aorta (TAA) requires prolonged aortic crossclamping and extracorporeal circulation. Hybrid repair with proximal endovascular graft fixation can reduce ischemic time and eliminate the need for the pump. We measured the effects of hybrid approach on intraoperative and recovery hemodynamics in an experimental pig model. Methods - Four approaches were compared; group 1: open surgical TAA repair, group 2: 1st generation SPIDER graft, group 3: 2nd generation SPIDER with loop graft for implantation of lumbar arteries, and group 4: 3rd generation SPIDER graft with volume-based resuscitation. Hemodynamic variables, tissue perfusion, branch vessel flow, and clinical laboratory values were measured at baseline, at end-operation and at six hours (6H) postoperatively. Organ microperfusion was measured by gold-standard fluorescent microsphere (MS) technique. Data were analyzed by hierarchical linear mixed models to account for multilevel repeated measurements. Results - 27 pigs (75-85 kg) were studied. Total ischemic times were significantly longer for open grafts than SPIDER grafts for all branch vessels (p<0.0001). Branch vessel flows were not present in the OSR group during crossclamping, but recovered at clamp release and 6H postoperatively. Perfusion of the visceral organs measured by fluorescent microsphere varied significantly between baseline, post-implant and 6H postoperatively in all groups (p<0.0001). Between graft types, highly significant time-by-group interactions were observed for liver and bowel (all p<0.015). Hierarchical modeling demonstrated significant multilevel correlational influence of macro-hemodynamic changes (celiac or SMA flow and ischemic time) on microcirculation (end-organ perfusion) of hepatic and mesenteric beds (multilevel R2 0.61). Lactate levels were strongly correlated with bowel but not liver perfusion. Conclusion - Hybrid grafts significantly reduce intraoperative ischemia, end-organ perfusion abnormalities and metabolic derangements during thoracoabdominal aortic repair.