Intermittent thoracic resuscitative endovascular balloon occlusion of the aorta improves renal function compared to 60 min continuous application after porcine class III hemorrhage.

BACKGROUND: Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) may be considered for stabilization of patients with hemorrhage from below the diaphragm. Occluding the aorta is a powerful means of hemorrhagic control but is also associated with acute kidney injury, which increases mortality in trauma patients. Allowing for intermittent distal blood flow during REBOA application (iREBOA) could decrease this risk, but circulatory consequences have not been sufficiently elucidated. Therefore, we investigated circulatory effects and the renal artery blood flow (RBF) in iREBOA versus continuous, complete aortic occlusion (cREBOA). METHODS: In a porcine model of uncontrolled class III hemorrhage (34% estimated total blood volume, mean 1360 mL), swine (n = 12, mean weight 60.3 kg) were randomly assigned to iREBOA: 3-min full deflation every 10 min (n = 6), or cREBOA (n = 6), for 60 min of thoracic (zone I) application. The animals then underwent 60 min of reperfusion (critical care phase). RESULTS: Survival was 100% in iREBOA and 83% in cREBOA. The intermittent balloon deflation protocol was hemodynamically tolerable in 63% of reperfusion intervals. Systolic blood pressure decreased during the reperfusion intervals in iREBOA animals (mean 108 mm Hg versus 169 mm Hg; p < 0.005). No differences were detected in heart rate, cardiac output or stroke volume between methods. Troponin I increased in cREBOA after 60 min (mean 666-187 ng/L, p < 0.05). The norepinephrine requirement increased in cREBOA during reperfusion (mean infusion time 12.5-5.5 min; p < 0.05). Total ischemic time decreased in iREBOA (60.0-48.6 min; p < 0.001). RBF increased in iREBOA during balloon deflations and after 60 min reperfusion (61%-39% of baseline RBF; p < 0.05). Urine output increased in iREBOA (mean 135-17 mL; p < 0.001). Nephronal osteopontin, a marker of ischemic injury, increased in cREBOA (p < 0.05). CONCLUSION: iREBOA was survivable, did not cause rebleeding, decreased the total ischemic time and increased the renal blood flow, urine output and decreased renal ischemic injury compared to cREBOA. Intermittent reperfusions during REBOA may be preferred to be continuous, complete occlusion in prolonged application to improve renal function.

Comparison of emergency surgical cricothyroidotomy and percutaneous cricothyroidotomy by experienced airway providers in an obese, in vivo porcine hemorrhage airway model.

BACKGROUND: Emergency front-of-neck airway (eFONA) is a life-saving procedure in "cannot intubate, cannot oxygenate" (CICO). The fastest and most reliable method of eFONA has not been determined. We compared two of the most advocated approaches: surgical cricothyroidotomy and percutaneous cricothyroidotomy, in an obese, in vivo porcine hemorrhage model, designed to introduce real-time physiological feedback, relevant and high provider stress. The primary aim was to determine the fastest method to secure airway. Secondary aims were arterial saturation and partial pressure of oxygen, proxy survival and influence of experience. METHODS: Twelve pigs, mean weight (standard deviation, SD) (60.3 ± 4.1) kg, were anesthetized and exposed to 25-35% total blood volume hemorrhage before extubation and randomization to Seldinger technique "percutaneous cricothyroidotomy" (n = 6) or scalpel-bougie-tube technique "surgical cricothyroidotomy" (n = 6). Specialists in anesthesia and intensive care in a tertiary referral hospital performed the eFONA, simulating an actual CICO-situation. RESULTS: In surgical cricothyroidotomy vs. percutaneous cricothyroidotomy, the median (interquartile range, IQR) times to secure airway were 109 (IQR 71-130) s and 298 (IQR 128-360) s (P = 0.0152), arterial blood saturation (SaO2) were 74.7 (IQR 46.6-84.2) % and 7.9 (IQR 4.1-15.6) % (P = 0.0167), pO2 were 7.0 (IQR 4.7-7.7) kPa and 2.0 (IQR 1.1-2.9) kPa (P = 0.0667), and times of cardiac arrest (proxy survival) were 137-233 s, 190 (IQR 143-229), from CICO. All six animals survived surgical cricothyroidotomy, and two of six (33%) animals survived percutaneous cricothyroidotomy. Years in anesthesia, 13.5 (IQR 7.5-21.3), did not influence time to secure airway. CONCLUSION: eFONA by surgical cricothyroidotomy was faster and had increased oxygenation and survival, when performed under stress by board certified anesthesiologists, and may be an indication of preferred method in situations with hemorrhage and CICO, in obese patients.

Blast polytrauma with hemodynamic shock, hypothermia, hypoventilation and systemic inflammatory response: description of a new porcine model.

PURPOSE: In the past decade blast injuries have become more prevalent. Blast trauma may cause extensive injuries requiring improved early resuscitation and prevention of haemorrhage. Randomized prospective trials are logistically and ethically challenging, and large animal models are important for further research efforts. Few severe blast trauma models have been described, which is why we aimed to establish a comprehensive polytrauma model in accordance with the criteria of the Berlin definition of polytrauma and with a survival time of > 2 h. Multiple blast injuries to the groin and abdomen were combined with hypoperfusion, respiratory and metabolic acidosis, hypoventilation, hypothermia and inflammatory response. The model was compared to lung contusion and haemorrhage. METHODS: 16 landrace swine (mean weight 60.5 kg) were randomized to "control" (n = 5), "chest trauma/hem" by lung contusion and class II haemorrhage (n = 5), and "blast polytrauma" caused by multiple blast injuries to the groin and abdomen, class II haemorrhage, lipopolysaccharide (LPS) infusion and hypothermia 32 °C (n = 6). RESULTS: The blast polytrauma group had an Injury Severity Score of 57 which resulted in haemodynamic shock, hypothermia, respiratory and metabolic acidosis and inflammatory response. The chest trauma/hem group had an Injury Severity Score of 9 and less profound physiologic effects. Physiologic parameters presented a dose-response relationship corresponding to the trauma levels. CONCLUSION: A comprehensive blast polytrauma model fulfilling the Berlin polytrauma criteria, with a high trauma load and a survival time of > 2 h was established. A severe, but consistent, injury profile was accomplished enabling the addition of experimental interventions in future studies, particularly of immediate resuscitation efforts including whole blood administration, trauma packing and haemostasis.

Increased crystalloid fluid requirements during zone 3 Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) versus Abdominal Aortic and Junctional Tourniquet (AAJT) after class II hemorrhage in swine.

PURPOSE: Pelvic and lower junctional hemorrhage result in a significant amount of trauma related deaths in military and rural civilian environments. The Abdominal Aortic and Junctional Tourniquet (AAJT) and infra-renal (zone 3) Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) are two options for resuscitation of patients with life threatening blood loss from and distal to the pelvis. Evidence suggest differences in the hemodynamic response between AAJT and zone 3 REBOA, but fluid management during resuscitation with the devices has not been fully elucidated. We compared crystalloid fluid requirements (Ringer's acetate) between these devices to maintain a carotid mean arterial pressure (MAP) > 60 mmHg. METHODS: 60 kg anesthetized and mechanically ventilated male pigs were subjected to a mean 1030 (range 900-1246) mL (25% of estimated total blood volume, class II) haemorrhage. AAJT (n = 6) or zone 3 REBOA (n = 6) were then applied for 240 min. Crystalloid fluids were administered to maintain carotid MAP. The animals were monitored for 30 min after reperfusion. RESULTS: Cumulative resuscitative fluid requirements increased 7.2 times (mean difference 2079 mL; 95% CI 627-3530 mL) in zone 3 REBOA (mean 2412; range 800-4871 mL) compared to AAJT (mean 333; range 0-1000 mL) to maintain target carotid MAP. Release of the AAJT required vasopressor support with norepinephrine infusion for a mean 9.6 min (0.1 µg/kg/min), while REBOA release required no vasopressor support. CONCLUSION: Zone 3 REBOA required 7.2 times more crystalloids to maintain the targeted MAP. The AAJT may therefore be considered in a situation of hemorrhagic shock to limit the need for crystalloid infusions, although removal of the AAJT caused more severe hemodynamic and metabolic effects which required vasopressor support.

The swine as a vehicle for research in trauma-induced coagulopathy: Introducing principal component analysis for viscoelastic coagulation tests.

BACKGROUND: Uncontrolled bleeding is the leading cause of potentially preventable deaths among trauma patients. Tissue injury and shock result in trauma-induced coagulopathy (TIC). There are still uncertainties regarding detection methods and best practice management for TIC, and a deeper understanding of the pathophysiology requires robust animal models. The applicability of swine in coagulation studies, particularly after trauma has not been sufficiently elucidated. We, therefore, evaluated the swine as a vehicle for TIC research in a selection of trauma modalities. METHODS: Twenty-six landrace swine (3 females/23 males) (mean weight, 60.0 kg) were anesthetized and randomized to negative controls, receiving no manipulation (n = 5), positive controls by hemodilution (n = 5), pulmonary contusion without hemorrhage (n = 5), pulmonary contusion with hemorrhage (n = 5), and blast polytrauma with hypothermia, hypoperfusion, hypoventilation, and systemic inflammation (n = 6). A comprehensive coagulation panel was analyzed at baseline, 20 minutes and 120 minutes after trauma. RESULTS: PT(INR), aPTT, thrombocytes, and fibrinogen did not change after trauma. D-dimer increased (p < 0.0001), prothrombin decreased (p < 0.05) and aPC decreased (p < 0.01) after polytrauma. PAI-1 decreased after pulmonary contusion with hemorrhage (p < 0.05). Positive controls displayed changes in PT(INR), thrombocytes, fibrinogen, prothrombin, aPC (p < 0.05). Principal Component Analysis of rotational thromboelastometry presented pathologic coagulation profiles in both polytrauma and positive control groups with vectors extending outside the 95% confidence interval, which were not detected in negative controls. CONCLUSION: Coagulopathy was induced after severe porcine blast polytrauma, specifically detected in rotational thromboelastometry. A novel method for principal component analysis of viscoelastic tests was introduced which may increase the detection sensitivity and differentiation of TIC phenotypes and should be further investigated in trauma populations.

Transition from abdominal aortic and junctional tourniquet to zone 3 resuscitative endovascular balloon occlusion of the aorta is feasible with hemodynamic support after porcine class IV hemorrhage.

BACKGROUND: Traumatic hemorrhage remains a major cause of death in rural civilian and combat environments. Potential interventions to control hemorrhage from the pelvis and lower junctional regions include the abdominal aortic and junctional tourniquet (AAJT) and resuscitative endovascular balloon occlusion of the aorta (REBOA). The AAJT requires low technical skills and may thus be used by nonmedical professionals, but is associated with time-dependent ischemic complications. In combination with delayed patient evacuation, it may therefore be deleterious. Transition to zone 3 REBOA in higher levels of care may be a possibility to maintain hemostasis, mitigate adverse effects and enable surgery in patients resuscitated with the AAJT. It is possible that a transition between the interventions could lead to hemodynamic penalties. Therefore, we investigated the feasibility of replacing the AAJT with zone 3 REBOA in a porcine model of uncontrolled femoral hemorrhage. METHODS: Domestic pigs (n = 12) averaging 57 kg were exposed to a class IV uncontrolled hemorrhage from the common femoral artery. The animals were randomized to 60-minute AAJT (n = 6) or 30-minute AAJT with transition to 30-minute zone 3 REBOA. Hemodynamic and metabolic parameters and ultrasonographic measurements of the common femoral artery were collected. RESULTS: Transition from AAJT to zone 3 REBOA caused a significant decrease in mean arterial pressure (25 mm Hg). Hemostasis was maintained. The common femoral artery diameter decreased by 1.8 mm (38%) after hemorrhage and further 0.7 mm (23%) after aortic occlusion. CONCLUSION: Transition from AAJT to zone 3 REBOA after a class IV bleeding is feasible with hemodynamic support. Vascular access to the femoral artery for REBOA insertion poses a technical challenge after hemorrhage and AAJT application. LEVEL OF EVIDENCE: Laboratory animal study, level IV.

Abdominal Aortic and Junctional Tourniquet release after 240 minutes is survivable and associated with small intestine and liver ischemia after porcine class II hemorrhage.

BACKGROUND: Uncontrolled hemorrhage is a leading cause of tactical trauma-related deaths. Hemorrhage from the pelvis and junctional regions are particularly difficult to control due to the inability of focal compression. The Abdominal Aortic and Junctional Tourniquet (AAJT) occludes aortic blood flow by compression of the abdomen. The survivability of tourniquet release beyond 120 minutes is unknown and fluid requirements to maintain sufficient blood pressure during prolonged application are undetermined. We therefore compared 60-minute and 240-minute applications and release of the AAJT for 30 minutes, with crystalloid fluid therapy, after a Class II hemorrhage. METHODS: Sixty-kilogram anesthetized pigs were subjected to 900-mL hemorrhage and AAJT application for 60 minutes (n = 5), 240 minutes (n = 5), and fluid therapy only for 240 minutes (n = 5) and reperfusion for 30 minutes. RESULTS: The AAJT application was hemodynamically and respiratory tolerable for 60 minutes and 240 minutes. Cumulative fluid requirements decreased by 64%, comparable to 3000 mL of crystalloids. Mechanical ventilation was impaired. AAJT increased the core temperature by 0.9°C compared with fluid therapy. Reperfusion consequences were reversible after 60 minutes but not after 240 minutes. A 240-minute application resulted in small intestine and liver ischemia, persisting hyperkalemia, metabolic acidosis, and myoglobinemia, suggesting rhabdomyolysis. CONCLUSION: The AAJT application for 240 minutes with reperfusion was survivable in an intensive care setting and associated with abdominal organ damage. Long time consequences and spinal cord effects was not assessed. We propose an application time limit within 60 minutes to 240 minutes, though further studies are needed to increase the temporal resolution. The AAJT application may be considered as a rescue option to maintain central blood pressure and core temperature in cases of hemorrhagic shock from extremity bleedings, if fluid therapy is unavailable or if the supply is limited. LEVEL OF EVIDENCE: Therapeutic study, level II.