Validation of a novel partial resuscitative endovascular balloon occlusion of the aorta device in a swine hemorrhagic shock model: Fine tuning flow to optimize bleeding control and reperfusion injury.

OBJECTIVES: Partial restoration of aortic flow during resuscitative endovascular balloon occlusion of the aorta (REBOA) is advocated by some to mitigate distal ischemia. Our laboratory has validated the mechanics and optimal partial REBOA (pREBOA) flow rates using a prototype device. We hypothesize that pREBOA will increase survival when compared with full REBOA (fREBOA) in prolonged nonoperative management of hemorrhagic shock.
METHODS: Twenty swine underwent placement of aortic flow probes, zone 1 REBOA placement, and 20% blood volume hemorrhage. They were randomized to either solid organ or abdominal vascular injury. The pREBOA arm (10 swine) underwent full inflation for 10 minutes and then deflation to a flow rate of 0.5 L/min for 2 hours. The fREBOA arm (10 swine) underwent full inflation for 60 minutes, followed by deflation/resuscitation. The primary outcome is survival, and secondary outcomes are serologic/pathologic signs of ischemia-reperfusion injury and quantity of hemorrhage.
RESULTS: Two of 10 swine survived in the fREBOA group (2/5 solid organ injury; 0/5 abdominal vascular injury), whereas 7 of 10 swine survived in the pREBOA group (3/5 solid organ injury, 4/5 abdominal vascular injury). Survival was increased (p = 0.03) and hemorrhage was higher in the pREBOA group (solid organ injury, 1.36 ± 0.25 kg vs. 0.70 ± 0.33 kg, p = 0.007; 0.86 ± 0.22 kg vs. 0.71 ± 0.28 kg, not significant). Serum evidence of ischemia was greater with fREBOA, but this was not significant (e.g., lactate, 16.91 ± 3.87 mg/dL vs. 12.96 ± 2.48 mg/dL at 120 minutes, not significant). Swine treated with pREBOA that survived demonstrated trends toward lower alanine aminotransferase, lower potassium, and higher calcium. The potassium was significantly lower in survivors at 60 minutes and 90 minutes time points (5.97 ± 0.60 vs. 7.53 ± 0.90, p = 0.011; 6.67 ± 0.66 vs. 8.15 ± 0.78, p = 0.029). Calcium was significantly higher at 30 minutes, 60 minutes, and 90 minutes (8.56 ± 0.66 vs. 7.50 ± 0.40, p = 0.034; 8.63 ± 0.62 vs. 7.15 ± 0.49, p = 0.019; 8.96 ± 0.64 vs. 7.00, p = 0.028).
CONCLUSION: Prolonged pREBOA at a moderate distal flow rate provided adequate hemorrhage control, improved survival, and had evidence of decreased ischemic injury versus fREBOA. Prophylactic aggressive calcium supplementation may have utility before and during the reperfusion phase.