A Model of Acute Lung Injury Following Visceral Ischemia-Reperfusion by Supra-Coeliac Aortic Cross Clamping in Rats

Open surgery for abdominal aortic aneurysms requires transient interruption of blood circulation, causing ischemia-reperfusion of downstream organs. Renal, mesenteric, and splanchnic arteries may be involved. No therapy has proven effective in preventing remote lung injury caused by ischemia-reperfusion after supra-coeliac aortic clamping. To study the pathophysiological pathways of acute lung injury and pharmacological treatments, an experimental model of aortic clamping has been developed in rats. Subcutaneous analgesia with Buprenorphine (0.05 mg/kg) is administered before the procedure. General anesthesia with spontaneous ventilation is induced using halogen gas (Isoflurane 2.5%) via a mask. A xypho-pubic laparotomy is performed on a heated table (temperature monitored intrarectally). The gastro-splenic block and intestines are retracted to the right flank, and the liver is mobilized to the upper abdomen. The diaphragm and its pillars are identified to allow step-by-step release of the supra-coeliac aorta from its intradiaphragmatic passage. Dissection is performed gently to achieve circumferential control of the aorta between the diaphragm pillars. The underlying celiac trunk and superior mesenteric artery are carefully identified. A microvascular clamp may be used for aortic occlusion above the visceral arteries. Proper clamping is verified by the absence of aortic pulsatility, associated with pallor of the small intestine. The rat remains anesthetized throughout the ischemia duration. At the end of the ischemia duration, the microclamp is removed, and aortic pulsatility, as well as intestinal recoloration, are checked. The abdominal wall is closed with a suture, followed by closure of the rat's skin. At the end of the reperfusion period, the animal is anesthetized in the same manner. It is euthanized by exsanguination during blood sampling, and the lung can then be collected. Lung injury can be assessed through blood gas analysis, lung gravimetry, and histological examination. Lung samples can also be utilized for RT-PCR and Western blot analyses.