The Long-Term Effects of Mild to Moderate Hypothermia on Gray and White Matter Injury After Spinal Cord Ischemia in Rats

BACKGROUND: The short-term effects of hypothermia on gray matter injury after spinal cord ischemia (SCI) have been established. We sought to investigate the long-term effects of mild to moderate hypothermia on gray and white matter injury after SCI. METHODS: Ninety-five rats were randomly divided into eight groups according to body temperature during SCI (32 degrees C, 35 degrees C, or 38 degrees C) and reperfusion interval (2 or 28 days). SCI was conducted for 15 min using a balloon catheter and blood withdrawal. After assessing the hindlimb motor function, gray and white matter injury was assessed using the number of normal neurons and the extent of vacuolation, respectively. RESULTS: Hindlimb motor function at 2 and 28 days was significantly better in hypothermic groups of 32 degrees C and 35 degrees C than in the normothermic group. The number of normal neurons at 2 and 28 days was significantly higher in the hypothermic group of 32 degrees C than in the normothermic group. The percentage areas of vacuolation at 2 and 28 days were significantly lower in hypothermic groups of 32 degrees C and 35 degrees C than in the normothermic group. CONCLUSIONS: The neuroprotective effects of intraischemic mild to moderate hypothermia on gray and white matter injury are mostly sustained for a long-term period of 28 days after SCI. (Anesth Analg 2009;109:559-66)