EFFECT OF HYPOTHERMIA AND LEFT-HEART BYPASS ON SPINAL ISCHEMIA IN THEDOG

Objective: To test the hypothesis that systemic hypothermia (SH) to 30 degrees C in combination with partial left heart bypass (PLHB) at eit her a high or low distal arterial perfusion pressure (DAPP) following 45 minutes of crossclamp (XC) occlusion of the thoracic aorta will pro tect against clinical and histological spinal cord ischemia in the dog . Design: A blinded, prospective, randomized, and controlled experimen tal trial.Setting: Tertiary care center animal laboratory. Participant s: Seventeen adult mongrel dogs. Interventions: The animals were rando mized into 5 groups: control group 1: XC plus no protection (n=3); con trol group 2: XC plus systemic normothermia plus PLHB, with a DAPP les s than 20 mm Hg (n=3); treatment group 1. XC plus systemic normothermi a plus PLHB, with a DAPP greater than 20 mm Hg (n=3); treatment group 2: XC plus SH plus PLHB, with a DAPP greater than 20 mm Hg (n=3); trea tment group 3: XC plus SH plus PLHB, with a DAPP less than 20 mm Hg (n =5). Main Outcome Measures: Clinical and histological neurological inj ury evaluation by separate blinded observers. Results: Control animals were neurologically and histologically ischemic. Treatment animals we re neurologically and histologically normal. Partial left heart bypass with a DAPP greater than 20 mm Hg prevented paraplegia, with either s ystemic normothermia or SH. Systemic hypothermia plus PLHB, even with a DAPP less than 20 mm Hg, protected against spinal cord ischemia duri ng thoracic aortic occlusion Conclusion: Systemic hypothermia to 30 de grees C combined with PLHB at either a high or low DAPP prevented spin al cord ischemia following thoracic aortic XC occlusion in our canine model and merits clinical trial in patients.