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INTRODUCTION: It is difficult to estimate the ischemic consequences when using partial resuscitative endovascular balloon occlusion of the aorta (REBOA). The aim was to investigate if end-tidal carbon dioxide (ETCO2) is correlated to degree of aortic occlusion, measured as distal aortic blood flow, and distal organ metabolism, estimated as systemic oxygen consumption (VO2), in a porcine model of normovolemia and hemorrhagic shock. MATERIALS AND METHODS: Nine anesthetized pigs (25-32 kg) were subjected to incremental steps of zone 1 aortic occlusion (reducing distal aortic blood flow by 33%, 66% and 100%) during normovolemia and hemorrhagic grade IV shock. Hemodynamic and respiratory variables, and blood samples, were measured. Systemic VO2 was correlated to ETCO2 and measures of partial occlusion previously described. RESULTS: Aortic occlusion gradually lowered distal blood flow and pressure, whereas ETCO2, VO2 and carbon dioxide production decreased at 66% and 100% aortic occlusion. Aortic blood flow correlated significantly to ETCO2 during both normovolemia and hemorrhage (R=0.84 and 0.83, respectively) and to femoral mean pressure (R = 0.92 and 0.83, respectively). Systemic VO2 correlated strongly to ETCO2 during both normovolemia and hemorrhage (R = 0.91 and 0.79, respectively), blood flow of the superior mesenteric artery (R = 0.77 and 0.85, respectively) and abdominal aorta (R = 0.78 and 0.78, respectively), but less to femoral blood pressure (R = 0.71 and 0.54, respectively). CONCLUSION: End-tidal carbon dioxide was correlated to distal aortic blood flow and VO2 during incremental degrees of aortic occlusion thereby potentially reflecting the degree of aortic occlusion and the ischemic consequences of partial REBOA. Further studies of ETCO2, and potential confounders, in partial REBOA are needed before clinical use., Funding Agencies:Nyckelfonden at Orebro University HospitalALF Grants

Background: Partial resuscitative endovascular balloon occlusion of the aorta (REBOA) is a concept of aortic occlusion to reduce ischemic organ injuries below the occlusion level. It is, however, difficult to determine when the occlusion is partial in clinical settings. End-tidal carbon dioxide (ETCO2) is an aerobic metabolite and its production is reduced during ischemia. The aim of this study was to investigate if ETCO2 can be used as an estimate of the degree of aortic occlusion and distal organ metabolism during normovolemia and hemorrhagic shock in a porcine model. Methods: Nine pigs (25-32 kg) were anesthetized and surgically prepared. Zone 1 aortic occlusion by 33%, 66% and 100% of aortic blood flow was induced during normovolemia and controlled hemorrhagic grade IV shock. Hemodynamic and respiratory variables including ETCO2, aortic and mesenteric blood flow, femoral arterial blood pressure and blood gases were measured. Oxygen consumption and carbon dioxide production were correlated to measures of partial occlusion used in previous studies. Results: Aortic occlusion gradually lowered distal blood flow and pressure, whereas ETCO2, oxygen consumption and carbon dioxide production decreased at 66 % and 100 % of aortic occlusion. End-tidal carbon dioxide, and blood flow of the superior mesenteric artery and abdominal aorta, strongly correlated to oxygen consumption and carbon dioxide production, whereas femoral blood pressure did not. Conclusion: End-tidal carbon dioxide may be used as an estimator of partial REBOA and distal organ metabolism in both normovolemia and hemorrhagic shock.