To Örebro University

OBJECTIVE: Induced hypothermia improves outcome in aortic arch surgery, neonatal neurointensive care, and transplant surgery for example. In contrast, spontaneous hypothermia has been associated with worse outcomes in patients suffering from hemorrhagic shock, mostly explained by its adverse effects on the coagulation system. We investigated if induced hypothermia would impair short-term survival in experimental aortic rupture with retroperitoneal bleeding.

METHODS: Anesthetized pigs were randomized into 2 groups: hypothermia by peritoneal lavage of ice-cold Ringer's acetate and external cooling (n = 10) and normothermia (n = 10). Aortic rupture with retroperitoneal bleeding was induced by endovascular means creating a 6 mm hole in the retroperitoneal portion of abdominal aorta. Survival (primary outcome), hemodynamics, and arterial blood gases including lactate were collected and analyzed up to 180 min after aortic rupture.

RESULTS: The body temperature (mean ± standard deviation) in the hypothermic group was 31.5 ± 1.0 °C and 38.7 ± 0.4 °C in the normothermic group at the time for aortic rupture. Survival up to 180 min after the retroperitoneal bleeding was significantly higher in the hypothermic compared with the normothermic group (P = 0.023).

CONCLUSIONS: Induced hypothermia did not impair survival in this experimental retroperitoneal aortic bleeding model in anesthetized pigs. This finding may indicate a minor role for the coagulation system in this type of bleeding.

Juxtahepatic venous injuries often cause life-threatening hemorrhagic shock, the mortality is high and new management methods are needed. The aims were to explore endovascular methods for retrohepatic vascu-lar isolation, their effects on survival, hemodynamics, metabolism, end-organ damage and bleeding, and if ultrasound and anatomical land-marks could be used to guide placement of resuscitative endovascular balloon occlusion of the inferior vena cava (REBOVC). Study I ex-plored the effects of different combinations of REBOVC +/- endovascu-lar aortic balloon occlusion (REBOA) +/- the Pringle maneuver (PM) for 5 minutes in anesthetized pigs (n=9). REBOVC was found to be tol-erated hemodynamically if combined with REBOA whereas REBOVC alone or combined with PM was not. In study II, REBOA was com-pared to REBOA + REBOVC in normovolemia and in hemorrhagic shock in anesthetized pigs (n=6-7/group). REBOA + REBOVC was tol-erated for 45 minutes, but negative hemodynamic and metabolic ef-fects in hemorrhagic shock must be considered. In Study III, the effects in anesthetized pigs of different combinations of balloon occlusion (REBOA vs REBOA + REBOVC vs REBOA + infra- and suprahepatic REBOVC + portal vein occlusion) on survival, hemodynamics, retrohe-patic bleeding, metabolism, and collateral flow were compared to no occlusion. REBOA was found to most efficiently stabilize hemodynam-ics and prolong survival despite larger collateral flow and retrohepatic bleeding. The inability of venous occlusion to stabilize hemodynamics as efficiently as REBOA was probably due to a combination of arterial collateral flow combined with reduced venous return. Studies IV + V examined if ultrasound (in anesthetized pigs, n=9) and anatomical landmarks (computerized tomography images from 50 humans) could be used to position REBOVC and found that subxiphoidal ultrasound and external landmarks can be useful tools to adequately position RE-BOVC in the inferior vena cava.

PURPOSE: Combining resuscitative endovascular balloon occlusion of the aorta (REBOA) and the inferior vena cava (REBOVC) with open surgery is a new hybrid approach for treating retrohepatic vena caval injuries. We compared endovascular total hepatic isolation with supraceliac REBOA ± suprahepatic REBOVC and no occlusion in experimental retrohepatic vena cava bleeding regarding survival, bleeding volume, hemodynamic stability, and arterial collateral blood flow.

METHODS: Twenty-five anesthetized pigs (n = 6-7/group) were randomized to REBOA; REBOA + REBOVC; REBOA + infra and suprahepatic REBOVC + portal vein occlusion (endovascular Heaney maneuver, four-balloon-occlusion, 4BO) or no occlusion. After balloon inflation, free bleeding was initiated from an open sheath in the retrohepatic vena cava. Bleeding volume, right internal thoracic artery (RITA) blood flow, hemodynamics, and arterial blood variables were measured until death or up to 90 min.

RESULTS: The REBOA group had a longer median survival time (63 min) compared with the 4BO (24 min, P = 0.02) and no occlusion (30 min, P = 0.02) groups, not versus the REBOA + REBOVC group (49 min, P > 0.05). The first 15 min accumulated bleeding was comparable in all groups (P > 0.05); Thereafter, bleeding volume was higher in the REBOA group versus the 4BO group (P < 0.05), not versus the other groups. RITA blood flow and MAP were higher in the REBOA group versus the other groups after 10 min of bleeding (P < 0.05).

CONCLUSIONS: Endovascular Heaney maneuver was not beneficial for survival or hemodynamic stability in this porcine model, whereas supraceliac REBOA was. Anatomical differences in thoracoabdominal collaterals between pigs and humans must be considered when interpreting these results.

OBJECTIVES: In fluoroscopy-free settings, alternative safe and quick methods for placing resuscitative endovascular balloon occlusion of the aorta (REBOA) and resuscitative endovascular balloon occlusion of the inferior vena cava (REBOVC) are needed. Ultrasound is being increasingly used to guide the placement of REBOA in the absence of fluoroscopy. Our hypothesis was that ultrasound could be used to adequately visualize the suprahepatic vena cava and guide REBOVC positioning, without significant time-delay, when compared with fluoroscopic guidance, and compared with the corresponding REBOA placement.

METHODS: Nine anesthetized pigs were used to compare ultrasound-guided placement of supraceliac REBOA and suprahepatic REBOVC with corresponding fluoroscopic guidance, in terms of correct placement and speed. Accuracy was controlled by fluoroscopy. Four intervention groups: (1) fluoroscopy REBOA, (2) fluoroscopy REBOVC, (3) ultrasound REBOA and (4) ultrasound REBOVC. The aim was to carry out the four interventions in all animals. Randomization was performed to either fluoroscopic or ultrasound guidance being used first. The time required to position the balloons in the supraceliac aorta or in the suprahepatic inferior vena cava was recorded and compared between the four intervention groups.

RESULTS: Ultrasound-guided REBOA and REBOVC placement was completed in eight animals, respectively. All eight had correctly positioned REBOA and REBOVC on fluoroscopic verification. Fluoroscopy-guided REBOA placement was slightly faster (median 14 s, IQR 13-17 s) than ultrasound-guided REBOA (median 22 s, IQR 21-25 s, p=0.024). The corresponding comparisons of the REBOVC groups were not statistically significant, with fluoroscopy-guided REBOVC taking 19 s, median (IQR 11-22 s) and ultrasound-guided REBOVC taking 28 s, median (IQR 20-34 s, p=0.19).

CONCLUSION: Ultrasound adequately and quickly guide the placement of supraceliac REBOA and suprahepatic REBOVC in a porcine laboratory model, however, safety issues must be considered before use in trauma patients.

LEVEL OF EVIDENCE: Prospective, experimental, animal study. Basic science study.

BACKGROUND: Mortality from traumatic retrohepatic venous injuries is high and methods for temporary circulatory stabilization are needed. We investigated survival, and hemodynamic and metabolic effects of resuscitative endovascular balloon occlusion of the aorta (REBOA) and vena cava inferior (REBOVC) in anesthetized pigs.

METHODS: Twenty-five anesthetized pigs in normovolemia or severe hemorrhagic shock (controlled arterial bleeding in blood bags targeting systolic arterial pressure of 50 mmHg, corresponding to 40-50% of the blood volume) were randomized to REBOA zone 1 or REBOA+REBOVC zone 1 (n=6-7/group) for 45 minutes occlusion, followed by 3-hour resuscitation and reperfusion. Hemodynamic and metabolic variables and markers of end-organ damage were measured regularly.

RESULTS: During occlusion, both the REBOA groups had higher systemic mean arterial pressure (MAP) and cardiac output (P<0.05) compared to the two REBOA+REBOVC groups. After 60 minutes reperfusion, there were no statistically significant differences between the two REBOA groups and the two REBOA+REBOVC groups in MAP and cardiac output. The two REBOA+REBOVC groups had higher arterial lactate and potassium concentrations during reperfusion, compared to the two REBOA groups (P<0.05). There was no major difference in end-organ damage markers between REBOA and REBOA+REBOVC. Survival after one-hour reperfusion was 86% and 100% respectively in the normovolemic REBOA and REBOA+REBOVC groups, and 67% and 83% respectively in the corresponding hemorrhagic shock REBOA and REBOA+REBOVC groups.

CONCLUSION: Acceptable hemodynamic stability during occlusion and short-term survival can be achieved by REBOA+REBOVC with adequate resuscitation; however, the more severe hemodynamic and metabolic impacts of REBOA+REBOVC compared to REBOA must be considered.

LEVEL OF EVIDENCE: Prospective, randomized, experimental animal study. Basic science study, therapeutic.

BACKGROUND: Resuscitative endovascular balloon occlusion of the vena cava inferior (REBOVC) may provide a minimal invasive alternative for hepatic vascular and inferior vena cava isolation in severe retrohepatic bleeding. However, circulatory stability may be compromised by the obstruction of venous return. The aim was to explore which combinations of arterial and venous endovascular balloon occlusions, and the Pringle maneuver, are hemodynamically possible in a normovolemic pig model. The hypothesis was that lower body venous blood pooling from REBOVC can be avoided by prior resuscitative endovascular aortic balloon occlusion (REBOA).

METHODS: Nine anesthetized, ventilated, instrumented and normovolemic pigs were used to explore the hemodynamic effects of eleven combinations of REBOA and REBOVC, with or without the Pringle maneuver, in randomized order. The occlusions were performed for 5 minutes but interrupted if systolic blood pressure dropped below 40 mmHg. Hemodynamic variables were measured.

RESULTS: Proximal REBOVC, isolated or in combination with other methods of occlusion, caused severely decreased systemic blood pressure and cardiac output, and had to be terminated before 5 min. The decreases in systemic blood pressure and cardiac output were avoided by REBOA at the same or a more proximal level. The Pringle maneuver had similar hemodynamic effects to proximal REBOVC.

CONCLUSIONS: A combination of REBOA and REBOVC provides hemodynamic stability, in contrast to REBOVC alone or with the Pringle maneuver, and may be a possible adjunct in severe retrohepatic venous bleedings.Level of evidenceBasic science study, therapeutic.