Retrograde venous perfusion with hypothermic saline and adenosine for protection of the ischemic spinal cord

Purpose: Spinal cord injury and the resultant postoperative paraplegia are devastating complications of thoracic aortic surgery, for which no widely a ccepted protective interventions exist. We hypothesized that retrograde ven ous perfusion-cooling of the spinal cord with a hypothermic saline and aden osine solution would protect it from ischemic injury caused by thoracic aor tic occlusion. Methods: Adult domestic swine of either sex (weight range, 20 to 30 kg) wer e intubated and ventilated. A left thoracotomy was performed. The accessory hemiazygous vein was divided, and a catheter was inserted distally. The ao rta was clamped at the left subclavian artery The venous catheter was not u sed in the animals in the control group (n = 7); in the animals in the expe rimental group (n = 7), a cold (4 degrees C) saline and adenosine solution was infused into the accessory hemiazygous vein. After 30 minutes, the damp and catheter were removed, and the chest was dosed. A blinded observer eva luated the animals' hind-leg motor activity 24 hours later. The Tarlov scal e was used: 0, complete paralysis; 1, minimal movement; 2, stands with assi stance; 3, stands alone; 4, weak walk; 5, normal gait. The animals' rectal temperatures were measured at the end of the experiment, and blood pressure was measured throughout. Two other groups were studied to assess the effec t of the intervention on spinal cord temperature. Results: The animals in the control group had a mean Tarlov score of 1.7 +/ - 0.6; the animals in the experimental group had a mean Tarlov score of 4.9 +/- 0.1 (P < .01). The animals in the experimental group had a significant ly greater drop in spinal cord temperature than those in the control group (4.05 +/- 0.6 degrees C vs 0.58 +/- 0.12 degrees C; P < .01). No significan t difference in rectal temperatures was found, nor did any arrhythmias or h ypotensive episodes occur in either group. Perfusion of the spinal cord was confirmed with angiography by using this approach. Conclusion: Retrograde venous perfusion-cooling of the spinal cord with a h ypothermic saline and adenosine solution protects the cord from ischemic in jury caused by damping of the thoracic aorta.