Hypothermic retrograde venous perfusion with adenosine cools the spinel cord and reduces the risk of paraplegia after thoracic aortic clamping

Objective: We evaluated the utility of retrograde venous perfusion to cool the spinal cord and protect neurologic function during aortic clamping. We hypothesized that hypothermic adenosine would preserve the spinal cord duri ng ischemia. Methods: Six swine (group I) underwent thoracic aortic occlusi on for 30 minutes at normothermia. Group II animals underwent spinal coolin g by retrograde perfusion of the paravertebral veins with hypothermic (4 de grees C) saline solution during aortic occlusion. The spinal cords of group III animals were cooled with a hypothermic adenosine solution in a similar fashion. Intrathecal temperature was monitored and somatosensory evoked po tentials assessed the functional status of spinal pathways. Results: Spinal cooling without systemic hypothermia significantly improved neurologic Tar lov scores in group III (4.8 +/- 0.2) and group II (3.8 +/- 0.4) when compa red with group I scores (1.3 +/- 0.6) (P <.001), Furthermore, 5 of the 6 an imals in group III displayed completely normal neurologic function, whereas only one animal in group II and no animals in group I did (P =.005). Somat osensory evoked potentials mere lost 10.6 +/- 1.4 minutes after ischemia in group I. In contrast, spinal cooling caused rapid cessation of neural tran smission with loss of somatosensory evoked potentials at 6.9 +/- 1.2 minute s in group EI and 7.0 +/- 0.8 minutes in group III (P =.06), Somatosensory evoked potential amplitudes returned to 85% of baseline in group III and 90 % of baseline in group II compared with only 10% of baseline in group I (P =.01). Conclusions: We conclude that retrograde cooling of the spinal cord is possible and protects against ischemic injury and that adenosine enhance s this effect. The efficacy of this method may be at least partly attribute d to a more rapid reduction in metabolic and electrical activity of the spi nal cord during ischemia.