An Intra-Aortic Shunt Prevents Paralysis During Aortic Surgery in Sheep

Abstract

Sheep are recommended by the United States Food and Drug Administration as a model for testing cardiovascular tissue, but are particularly prone to spinal cord ischemia and subsequent paralysis during aortic cross-clamping. A shunt consisting of a 9 cm long phosphorylcholine coated 1/4 in. (i.d.) polyvinylchloride tube was inserted through the aortotomy into the aorta to provide blood flow across the operative site. Blood pressure and flow in the distal aorta were measured continuously with an indwelling femoral artery catheter and an ultrasonic aortic flow probe. The hemodynamic effects were measured in seven 45 to 55 kg Suffolk sheep. This shunt was then used to implant decellularized pulmonary artery patches into 25 animals. Occlusion of the aorta reduced the distal mean aortic pressure from 86.4 +/- 4.6 mmHg to 1.79 +/- 0.4 mmHg (P < 0.001) and opening the intra-aortic shunt restored the distal mean aortic pressure to 67.9 +/- 7.3 mmHg (P = 0.053). Blood flow in the distal aorta was 2.35 +/- 0.37 L/min at baseline and was reduced to -0.01 +/- 0.01 L/min (P < 0.001) with the aorta cross-clamped and returned to 2.49 +/- 0.36 L/min (P = 0.945) when the shunt was opened. Use of this shunt prevented hind leg paralysis in all 24 animals surviving the procedure. A simple intra-aortic shunt was effective in restoring blood pressure and flow in the aorta distal to the operative site and prevented hind leg paralysis associated with aortic clamping.