Hemorrhage continues to be the dominant cause of preventable deaths in patients undergoing traumatic events, accounting for 90% of trauma-related deaths in the military setting and 40% of post-traumatic deaths in the civilian population1,2. Although direct pressure can treat compressible hemorrhage, non-compressible torso hemorrhage remains difficult to treat and can be lethal without prompt hemostatic control. The historical approach of resuscitative thoracotomy or laparotomy with aortic cross-clamping has proved to be extremely invasive3,4. This intervention also requires a complex selection algorithm to determine the candidacy of patients that have undergone traumatic insults5.
In recent years, there has been a resurgence of interest in a previously described approach—resuscitative endovascular balloon occlusion of the aorta (REBOA)6,7,8. Although REBOA has conferred a short-term survival advantages in hemorrhage, a prolonged complete occlusion of the aorta during balloon inflation poses serious concerns that include irreversible end-organ ischemia9,10. In an attempt to overcome this potential morbidity, alternative endovascular strategies to manage hemorrhage are being devised. One such strategy that has seen a growing attention is a partial occlusion of the aorta11,12. The idea of partial aortic balloon occlusion affords the perfusion of vascular beds distal to the site of occlusion, improved physiologic proximal aortic MAPs, and a gradual afterload reduction following the balloon deflation. These changes in parameters are desired modifications to the physiological characteristics of a bleeding animal. Prior to this method's translation to humans, complete and partial aortic balloon occlusion catheters have been heavily tested in swine models of hemorrhagic shock11,12,13.
Swine have been used in studies entailing hemorrhagic shock for many years. Most of the current understanding of the pathophysiology of hemorrhagic shock is derived from studies that have utilized animal models, including swine. Their physiology and homeostatic responses in the setting of pathologic volume depletion following hemorrhage, especially those pertaining to blood clotting and cardiovascular responses, have been well-documented and are like those in humans14. Swine models of hemorrhagic shock also provide opportunities to investigate treatment strategies for hemorrhagic shock and other traumatic injuries.
In this study, we demonstrate a clinically realistic model of hemorrhagic shock in swine to evaluate endovascular treatment strategies, including complete and partial aortic balloon occlusion. We hypothesize that a partial occlusion of the aorta results in a better physiologic and laboratory profile compared to a complete occlusion of the aorta in swine undergoing a controlled fixed-volume hemorrhage.
We aimed to compare the physiologic effects of partial and complete aortic occlusion as a treatment for hemorrhagic shock in a swine model. Partial aortic occlusion was achieved using a selective aortic balloon occlusion in trauma (SABOT) catheter (Figure 1). The SABOT catheter is a two-balloon system that allows intra-luminal blood flow, thereby providing a partial aortic flow to the vascular beds distal to the occlusion. Complete aortic occlusion was achieved using a single-balloon aortic occlusion catheter (e.g.,CODA) (Figure 1). Treatment groups were randomized to undergo resuscitative aortic occlusion either with the complete or with the partial aortic balloon occlusion catheters (n = 2/group).
The major steps of the model include the induction of anesthesia and intubation, the maintenance of anesthesia, instrumentation, 35% TBV hemorrhage (20 min total; half over the first 7 min, and half over the remaining 13 min), aortic balloon occlusion and whole-blood resuscitation (60 min of occlusion; 20% whole-blood resuscitation during the last 20 min of the occlusion), critical care monitoring (240 min) with hemodynamic observation, and euthanasia with tissue harvesting. Figure 2 demonstrates the model utilized in this experiment.