Incremental balloon deflation following complete resuscitative endovascular balloon occlusion of the aorta results in steep inflection of flow and rapid reperfusion in a large animal model of hemorrhagic shock

Abstract

Introduction To avoid potential cardiovascular collapse after Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA), current guidelines recommend methodically deflating the balloon over 5 minutes to gradually reperfuse distal tissue beds. However, anecdotal evidence suggests that this approach may still result in unpredictable aortic flow rates and hemodynamic instability. We sought to characterize aortic flow dynamics following REBOA as the balloon is deflated in accordance with current practice guidelines. Methods Eight Yorkshire-cross swine were splenectomized, instrumented, and subjected to rapid 25% total blood volume hemorrhage. After 30 minutes of shock, animals received 60 minutes of zone 1 REBOA with a low-profile REBOA catheter. During subsequent resuscitation with shed blood, the aortic occlusion balloon was gradually deflated in stepwise fashion at the rate of 0.5 mL every 30 seconds until completely deflated. Aortic flow rate and proximal mean arterial pressure (MAP) were measured continuously over the period of balloon deflation. Results Graded balloon deflation resulted in variable initial return of aortic flow (median 78 seconds, IQR 68–105sec). A rapid increase in aortic flow during a single balloon deflation step was observed in all animals (Median 819 mL/min IQR 664-1241mL/min) and corresponded with an immediate decrease in proximal MAP (Median 30 mmHg IQR 14.5–37mmHg). Total balloon volume and time to return of flow demonstrated no correlation (r2=0.016). Conclusion This study is the first to characterize aortic flow during balloon deflation following REBOA. A steep inflection point occurs during balloon deflation that results in an abrupt increase in aortic flow and a concomitant decrease in MAP. Furthermore, the onset of distal aortic flow was inconsistent across study animals and did not correlate with initial balloon volume or relative deflation volume. Future studies to define the factors that impact aortic flow during balloon deflation are needed to facilitate controlled reperfusion following REBOA.

Three cases of resuscitative endovascular balloon occlusion of the aorta (REBOA) in austere pre-hospital environment—technical and methodological aspects

“…The biggest impact of AO on SBP for patient 2 was noticed when the last milliliter was removed from the balloon, suggesting first an important role of partial AO on the stability of the patient and second a nonlinear correlation between AO and SBP. This observation has actually been described by Davidson et al [ 38 ] in a swine model where a steep inflection point occurs during balloon deflation that results in an abrupt increase in aortic flow and a concomitant decrease in mean arterial pressure. Furthermore, the onset of distal aortic flow was inconsistent across study animals and did not correlate with initial balloon volume or relative deflation volume.…”

A Novel Automated Endovascular Variable Aortic Control Device to Expand Function of Standard REBOA Catheters

“…These changes are too precise to be performed manually with any manner of fidelity or consistency, thereby necessitating robotic control. As we have demonstrated in prior experiments and again in the present experiment, very small adjustments in the degree of aortic occlusion translate into large variations in aortic flow rate [12,15]. Hyperemic aortic flow was again observed during the balloon deflation phase of this experiment and likely reflects the hyperdynamic cardiac state induced by aortic occlusion, combined with low systemic vascular resistance from vasodilated distal tissue beds.…”

“…Hyperemic aortic flow was again observed during the balloon deflation phase of this experiment and likely reflects the hyperdynamic cardiac state induced by aortic occlusion, combined with low systemic vascular resistance from vasodilated distal tissue beds. This hyperemic flow is fairly unpredictable in its onset and occurs at different balloon volumes depending on the individual animal [12]. Therefore, establishing clinical guidelines for manual balloon deflation based on a prescribed volume is not practical.…”

“…Because of this, manual titration of partial flow requires very subtle changes in balloon volume to maintain stable flow, which is not possible with current REBOA balloon technology. Even small occlusion balloon volume shifts can result in rapid changes in aortic blood flow and pressure, creating significant challenges for medical providers trying to stabilize a critically ill patient [11,12]. Future balloon technology aimed at decreasing the wide swings in blood flow in response to changes in balloon volume may be able to improve manual control of P-REBOA.…”

The complications associated with Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA)

“…However, an animal study conducted on eight swine models of hemorrhage found that graded balloon deflation still led to a rapid increase in aortic flow followed by a decrease in proximal mean arterial pressure. Furthermore, the time required for return of distal aortic flow was variable and inconsistent across the subjects [ 27 ].…”