End-tidal Carbon Dioxide as an Indicator of Partial REBOA and Distal Organ Metabolism in Normovolemia and Hemorrhagic Shock in Anesthetized Pigs

Abstract

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 (ETCO 2 ) is correlated to degree of aortic occlusion, measured as distal aortic blood flow, and distal organ metabolism, estimated as systemic oxygen consumption (VO 2 ), 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 VO 2 was correlated to ETCO 2 and measures of partial occlusion previously described. Results: Aortic occlusion gradually lowered distal blood flow and pressure, whereas ETCO 2 , VO 2 and carbon dioxide production decreased at 66% and 100% aortic occlusion. Aortic blood flow correlated significantly to ETCO 2 during both normovolemia and hemorrhage (R ¼ 0.84 and 0.83, respectively) and to femoral mean pressure (R ¼ 0.92 and 0.83, respectively). Systemic VO 2 correlated strongly to ETCO 2 during both normovolemia and hemorrhage (R ¼ 0.91 and 0.79, respectively), blood flow of the superior mesenteric artery (R ¼ 0.77 and 0.85, respectively) and abdominal aorta (R ¼ 0.78 and 0.78, respectively), but less to femoral blood pressure (R ¼ 0.71 and 0.54, respectively). Conclusion: ETCO 2 was correlated to distal aortic blood flow and VO 2 during incremental degrees of aortic occlusion thereby potentially reflecting the degree of aortic occlusion and the ischemic consequences of partial REBOA. Further studies of ETCO 2 , and potential confounders, in partial REBOA are needed before clinical use.

A randomized porcine study of hemorrhagic shock comparing end-tidal carbon dioxide targeted and proximal systolic blood pressure targeted partial resuscitative endovascular balloon occlusion of the aorta in the mitigation of metabolic injury

“…In a previous study by our group [ 31 ], aortic blood flow correlated well to ETCO 2 and also to overall VO 2 and VCO 2 in a porcine study during normovolemia and during hemorrhage. As a result of hypoperfusion and maximum oxygen extraction, VO 2 becomes oxygen delivery dependent and eventually drops below the critical oxygen delivery level.…”

“…Consequently, this group tended to be more acidotic, an aspect that affects the maintenance of vital organ function during shock. The targeted ETCO 2 level used in this study was based on a prior study by our group in an attempt to maintain overall aerobic metabolism [ 31 ]. The targeted SBP level was based on clinically accepted permissive hypotension in trauma situations.…”

“…The animals were premedicated with azaperone and anesthetized with tiletamine/zolazepam ± propofol as previously described as previously described [ 20 , 31 ]. Anesthesia was maintained by Propofol 10 mg kg −1 h −1 (Fresenius Kabi, Uppsala Sweden) and Remifentanil 40 µg kg −1 h −1 (Actavis, Dublin, Irland) using infusion pumps (Alaris GP; Cardinal Health Care, Rolle, Switzerland).…”

What's New in Shock, October 2021?

“…Another translational approach is reported in this issue by Sadeghi and colleagues (9). Resuscitative endovascular balloon occlusion of the aorta (REBOA) has been shown to be potentially lifesaving in exsanguinating torso hemorrhage, but ischemia distal to the occlusion and subsequent ischemia-reperfusion injury are serious complications.…”