Comparison of hydrogen clearance and 14C-antipyrine autoradiography in the measurement of spinal cord blood flow after severe impact injury.

Spinal cord blood flow was measured by two different techniques in normal and traumatized cat spinal cord. Flow was measured in the thoracic cord after severe (500-gm-cm) impact injury at T-6. Blood flow was measured sequentially at two sites for 7 hours after trauma using the hydrogen clearance technique, and spatially at many sites but at selected times by means of the 14C-antipyrine autoradiographic method. The two techniques gave similar results. Control white-matter blood flow in the lateral funiculus was 11.13 +/- 1.29 ml/min/100 gm in the hydrogen clearance series, and 11.07 +/- 3.16 gm blood/min/100 gmin the antipyrine series. Following injury, blood flow remained in the control range until 1 hour after trauma, when ischemia became the major pattern. From 4 to 8 hours following trauma, several categories of flow patterns emerged. In one group of animals, white-matter blood flow returned to control levels at some points along the length of cord surveyed, but remained depressed at adjacent cord levels. In another category of animals, most sites in the white matter had flows approaching control levels by 7 to 8 hours. In yet another group, all sites examined, although a limited number, showed ischemia. In contrast, gray-matter ischemia appeared earlier (25% of control levels at 1 hour), had a sharper focus, and persisted in the period examined. The differences in blood flow between gray and white matter and the longitudinal variation in white-matter flow suggested that the hydrogen clearance method should be verified by autoradiography for accuracy of spatial flow patterns.