Development of an ovine model of occlusive arterial injury for the evaluation of endovascular interventions

Ovine Iliac Vein Model for Endovascular Thrombectomy of Acute Deep Venous Thrombosis

An ovine iliac vein thrombosis model was devised to test a wall-contacting rotational thrombectomy device. Thrombosis was successfully induced in 9 sheep with an average clot length of 31 mm ± 12 and >60% vessel occlusion on angiography. The thrombus was subsequently removed, maintaining normal intraoperative pulmonary arterial pressure (5.9 mm Hg ± 3.6) and complete distal reperfusion after thrombectomy. Additionally, the sheep were without signs of vascular trauma or embolic complications on gross necropsy and histopathologic analysis. The findings from this study support the use of an ovine iliac deep vein thrombosis model for testing of a lower extremity thrombectomy device.

Resuscitative endovascular balloon occlusion of the aorta: what is the optimum occlusion time in an ovine model of hemorrhagic shock?

PURPOSE

The aim of this study is to evaluate the early survival and organ damage following 30 and 60 min of thoracic resuscitative endovascular balloon occlusion of the aorta (REBOA) in an ovine model of severe hemorrhagic shock.

METHODS

Eighteen sheep were induced into shock by undergoing a 35 % controlled exsanguination over 30 min. Animals were randomized into three groups: 60-min REBOA 30 min after the bleeding (60-REBOA), 30-min REBOA 60 min after the bleeding (30-REBOA) and no-REBOA control (n-REBOA). Resuscitation with crystalloids and whole blood was initiated 20 and 80 min after the induction of shock. Animals were observed for 24 h with serial potassium and lactate measurements. Autopsy was performed to evaluate organ damage.

RESULTS

Two animals of the n-REBOA group died within 90 min of shock induction; no hemorrhagic deaths were observed in the REBOA groups. Twenty-four-hour survival for the 60-, 30-, and n-REBOA groups was 0/6, 5/6, and 4/6 (P = 0.002). In 60-REBOA, potassium and lactate were increased at 270-min time point: from 4.3 to 5.1 mEq/l and from 3.7 to 5.1 mmol/L, respectively. Both these values were significantly higher than in the n-REBOA group (P = 0.029 for potassium and P = 0.039 for lactate). Autopsy revealed acute tubular necrosis in all died REBOA group animals.

CONCLUSIONS

In this ovine model of severe hemorrhagic shock, REBOA can be used to prevent early death from hemorrhage; however, 60 min of occlusion results in significant metabolic derangement and organ damage that offsets this gain.