THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES Spinal Cord Blood Flow Measured with Microspheres Following Spinal Cord Injury in the Rat

A decrease in spinal cord blood flow (SCBF) is a known sequela of spinal cord injury. The radioactive microsphere technique permits repeated measurement of spinal cord blood flow (SCBF) and cardiac output (CO) in the same experimental animal. The purpose of this study was to adapt the radioactive microsphere technique for use in the rat extradural clip compression injury model used in our laboratory. Thirteen adult Wistar rats were anaesthetized and ventilated. Mean systemic arterial pressure (MSAP) was recorded continuously. Control animals (n = 8) did not have a surgical procedure whereas the injured animals (n = 5) underwent a C7-T1 laminectomy followed by a one minute, 50 gram extradural clip compression injury at Tl. Radioactive microspheres were used for two blood flow and CO determinations in both groups. MSAPfell 59% in the injured animals (p<0.01), but this was not accompanied by significant changes in heart rate or CO. There was a 50% reduction in SCBF in the injured cord (p<0.02), and there were significant reductions in cerebral blood flow (p<0.05) and cerebellar blood flow (p<0.02) following spinal cord injury. RESUME: Le flot sanguin medullaire mesure aux microspheres a la suite d'une blessure de la moelle epiniere chez le rat Une diminution du flot sanguin medullaire est une sequelle bien connue de traumatisme a la moelle Epiniere. La technique utilisaht des microspheres radioactives permet des mesures repetees du flot sanguin medullaire et du debit cardiaque chez le meme animal d'experimentation. Le but de cette etude etait d'adapter la technique utilisant des microspheres radioactives, pour l'appliquer chez le rat utilise dans notre laboratoire comme modele animal de traumatisme par compression au moyen d'une pince extra durale. Treize rats Wistar adultes furent anesthesies et ventiles. La tension arterielle systemique moyenne fut enregistree de fagon continue. Les animaux controles (n = 8) n'eurent pas d'intervention chirurgicale, alors que les cas subirent une laminectomie au niveau de C7-T1, suivie d'une traumatisme par compression au moyen d'une pince extradurale exercant une pression de 50 gm pendant 1 minute au niveau de Tl. Deux determinations du flot sanguin et du d6bit cardiaque furent faites dans les deux groupes au moyen de microspheres radioactives. La tension arterielle systemique moyenne chuta de 59% chez les animaux traumatisms, mais ceci ne fut pas accompagne de changements significatifs du rythme ou du debit cardiaque. Le flot sanguin medullaire fut reduit de 50% dans la moelle traumatisee (p<0.02) et le flot sanguin cerebral (p<0.05) et cerebelleux (p<0.02) furent reduits de fagon significative a la suite du traumatisme medullaire. Can. J. Neurol. Sci. 1986; 13:91-96 A number of techniques have been utilized to measure spinal cord blood flow (SCBF) in experimental spinal cord injury.'" Techniques used in larger animals include the C-antipyrene method,the hydrogen clearance technique,' and radioactive microspheres." The majority of investigations have demonstrated a drop in SCBF following experimental cord injury,'" although hyperemia following cord injury has also been reported. In our laboratory, the experimental model has been clip compression injury in the rat, and SCBF was measured before and after injury by C-antipyrene autoradiography.'' Although very accurate, this blood flow technique allows only one flow study per animal. In contrast, the radioactive microsphere method used by other investigators allows multiple studies per animal,' although only large animals such as dogs have been studied. Microspheres also allow measurement of regional organ blood flow, cardiac output (CO), From the Division of Neurosurgery and Playfair Neuroscience Unit, Toronto Western Hospital. University of Toronto. Toronto. Ontario Received August 15. 1985. Accepted February II, 1986. Reprints requests to: C.H.Tator.M.D., Division of Neurosurgery, Playfair Neuroscience Unit. Toronto Western Hospital, 399 Bathurst Street. Toronto, Ontario, Canada M5T 2S8