[Temporary extracorporeal perfusion - an alternative technique for maintaining limb viability in case of arterial...

Acute limb ischemia often leads to disability and death of patients with vascular trauma, which is especially important in difficult conditions of limited resources, with the necessity of long-distance transportation of patients, with the absence of vascular surgeons. 'Non-operative' methods of extracorporeal perfusion of the limb, such as passive arterio-arterial shunting (PassS) and active veno-arterial shunting (ActS), using the extracorporeal membrane oxygenation technology potentially can reduce the number of complications and poor outcomes in such patients.

This study aimed to investigate the effectiveness of modern methods of temporary extracorporeal restoration of limb perfusion in an animal experiment.

22 sheep weighing 36.6 (34.0-44.0) kg were enrolled into the study. Acute arterial obstruction was modeled by endovascular balloon occlusion of the distal aorta for 30 minutes. After that, the animals were randomized into 3 groups: the control group (CG, n=7), the PassS group (n=8), and the ActS group (n=7). During the next 6 hours, the CG animals were monitored without intervention; The PassS group animals underwent extracorporeal shunting from the carotid to the femoral artery sheaths by means of a connecting line; the ActS group animals underwent extracorporeal shunting from the inferior vena cava via a centrifuge pump and an oxygenator to the femoral artery (flow rate 0.5-0.7 l/min). All animals received identical anticoagulant therapy. The total experimental time was 24 hours.

During aortic occlusion, the blood flow rate in the extremity arteries decreased to zero. Passive shunting led to a significant increase of the blood flow rate to 15.5 (8.2-19.5) cm/s (p=0.036 compared to the CG), and active shunting led to an increase to 26.5 (12.5-62.5) cm/s (p=0.014 compared to the CG). During ActS, the values of tissue oximetry increased significantly (above 40%), and non-significantly - in the PassS group (at the level of 40%). During blood shunting in the ActS group, a progressive decrease of blood pressure was noted due to venous 'stealing', thus requiring vasopressor support of 1.6 (0.0-8.0) mg (p = 0.016 compared to the PassS). As a result, a significantly higher mortality rate was observed in the ActS group: only 2 out of 7 animals in the ActS group survived, while 4 out of 7 animals in the CG group and 7 out of 8 animals in the PassS group survived by the end of the experiment (p=0.041).

Extracorporeal limb perfusion is an effective tool for temporary restoration of blood flow in the injured limb. At the same time, PassS provides low blood flow without affecting systemic hemodynamics, while ActS provides better perfusion of limb tissues, but at the cost of impaired systemic hemodynamics.