The effect of hypothermia on regional spinal cord blood flow in rats

Spinal cord ischemia may accompany surgical procedures on the aorta or vertebral column. Regional spinal cord blood flow (SCBF) was measured at five vertebral levels in the spinal cords of pentobarbital-anesthetized rats based on the distribution of intravenously injected carbon-14-labeled butanol. In seven normal rats, mean SCBF (+/- standard error of the mean) ranged from 52.7 +/- 5.4 to 68.5 +/- 4.9 ml.min-1.100 gm-1 (depending on the level, being lowest at the thoracic levels) and mean arterial blood pressure (MABP) was 126 mm Hg. Corporal hypothermia (mean rectal temperature 28.1 degrees +/- 0.6 degrees C) was induced by cold exposure in seven other rats, and SCBF, measured immediately thereafter, was significantly elevated at all five levels by 52% to 69% compared to the normal group. However, MABP was elevated in the hypothermic group to 165 +/- 4 mm Hg (p less than 0.0001). Therefore, in seven additional hypothermic rats, MABP was maintained at the control level by withdrawal of arterial blood as necessary. In these animals, SCBF at all levels was still significantly elevated compared with the normal group and the values were nearly identical to those measured in the hypertensive hypothermic rats. It was concluded that hemodynamic autoregulation of SCBF is impaired in the presence of moderate systemic hypothermia in pentobarbital-anesthetized rats.