Aortic haemostasis and resuscitation: advanced resuscitative endovascular balloon occlusion of the aorta for non-compressible torso haemorrhage and reversal of haemorrhage-induced traumatic cardiac arrest in a swine model

Trauma is the leading cause of death in young people in the UK and US. Non-compressible torso haemorrhage (NCTH) is a major cause of potentially survivable trauma death. A large proportion of these patients are in traumatic cardiac arrest (TCA) on arrival at hospital, and survival rates after haemorrhagic TCA are extremely low. The limited data available suggest that closed chest compressions (CPR) are ineffective, and may be harmful, in haemorrhagic TCA. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) has shown promise in the setting of NCTH, although its utility in haemorrhagic TCA is unknown. Selective Aortic Arch Perfusion (SAAP) is an experimental intervention that has the potential to resuscitate haemorrhagic TCA, but it has not been compared to CPR or REBOA. The aim of this research was to evaluate SAAP against other interventions for the management of haemorrhagic TCA. A large swine (70-90 kg) translational model of TCA secondary to NCTH and a controlled arterial haemorrhage was developed to answer hypotheses in three parts. First, a comparison of 60 minute survival between CPR, REBOA, SAAP with oxygenated lactated Ringer’s solution (SAAP-LR), and SAAP with oxygenated fresh whole blood (SAAP-FWB), followed by surgical control and a three-hour critical care period; second, in a more severe model of TCA, comparison of SAAP-LR and SAAP-FWB, and an evaluation of extra-corporeal life support (ECLS) to mitigate the effects of aortic occlusion; and third, a translational paradigm of escalating endovascular intervention, from REBOA to SAAP, to ECLS. In Part One, 40 animals were allocated to four groups; SAAP-FWB inferred a significant 60 minute survival advantage (90.0%, 95%CI 59.6-99.5) over CPR (10.0%, 95%CI 0.5-40.4), REBOA (0.0%, 95%CI 0.0-27.8), and SAAP-LR (30.0%, 95%CI 10.8-60.3), p<0.001. SAAP-FWB and CPR were observed to resuscitate cardiac electrical asystole; both of these are novel findings, but no asystolic animals survived to the end of the protocol. In Part Two, ECLS after SAAP catheter removal demonstrated a significant three-hour survival advantage over non-ECLS historical controls, p<0.05. The translational paradigm of escalating endovascular intervention was shown to be a feasible and efficacious method of resuscitating swine in haemorrhagic TCA in Part Three. A novel swine donor pool supplied >700 units of FWB for the experiments, and was an effective way of obtaining large volumes of blood product whilst reducing overall animal use. Ventricular fibrillation was observed in animals in the SAAP-FWB group, and further development of the technique is needed prior to clinical implementation. SAAP-FWB is capable of resuscitating swine in haemorrhagic cardiac electrical asystole, and infers a superior short-term survival compared to intervention with CPR, REBOA, and SAAP-LR, but further data are needed to ensure normocalcaemia during infusion of citrated blood products. ECLS has been demonstrated to prolong survival in the setting of cardiopulmonary dysfunction secondary to TCA and intra-aortic balloon occlusion. An escalating paradigm of endovascular intervention is a feasible and efficacious method of resuscitating large swine in haemorrhagic TCA that is translatable to clinical practice