Resuscitative endovascular balloon occlusion of the aorta : Physiology and clinical aspects of an emerging technique

Sammanfattning: Traumatic hemorrhagic shock is a major cause of death worldwide. Patients enter the fatal triad of hypothermia, acidosis and coagulopathy and die quickly due to cardiovascular collapse. Ideally, procedures should be performed at the injury scene to prevent this fatal event. Unfortunately, intervention cannot be performed as soon as is needed and time to intervention becomes the enemy of survival. Hemorrhage control until definitive repair can possibly save lives. Hemorrhage from the extremities can be controlled by external pressure but severe hemorrhage from thoracic, abdominal or pelvic cavities, called non-compressible torso hemorrhage, requires internal hemorrhage control. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) uses an endovascular balloon that is inserted into the aorta using minimally invasive methods and is inflated to increase perfusion pressure and avoid cardiovascular collapse, providing a bridge to intervention. REBOA is hypothetised to increase central blood pressure but cause ischemia reperfusion injury below the occlusion level. The purpose of this thesis was to investigate the general impact of REBOA on physiology, metabolism, inflammatory response in normovolemia and hemorrhage. Investigation was conducted through clinical and experimental models.Study I was a multicentre cohort study of patients with traumatic hemorrhagic shock who received REBOA. Ninety-six patients were included, with an overall mortality of 56% and with no major complications from REBOA use. REBOA was used in a continuous and non-continuous fashion depending on the patients’ level of hypovolemia.Study II and the following three studies were animal experimental studies. Study II was a randomized control study in pigs to evaluate physiological, metabolic, inflammatory and end-organ function in a normovolemic state. It was demonstrated that REBOA increased central blood pressure but caused ischemic insult.Study III, a randomised controlled experimental model in pigs. Investigation was made to examine the possibility of titrating blood pressure with partial occlusion and investigate if partial occlusion reduced the ischemic insult. Partial REBOA could be achieved in this study and the ischemia reperfusion injury was less pronounced in partial occlusion than total. However, the difficulty regarding how to determine partial occlusion in a clinical setting remained.Study IV was therefore an experimental study conducted to compare the different methods of determining partial occlusion and detect the best correlation to organ perfusion. The following variables were compared to oxygen consumption: end-tidal carbon dioxide, aortic blood flow, superior mesenteric blood flow and femoral mean pressure. The study revealed that end-tidal carbon dioxide correlates best to organ perfusion.