✓ Posttraumatic spinal cord blood flow (SCBF) was assessed after elevating the mean systemic arterial pressure (mSAP) with a blood transfusion, or with an infusion of dopamine. The effect of the anesthetic agent, gamma hydroxybutyrate, was also assessed. Flows were measured using the 14C-antipyrine autoradiographic method. Animals were injured at T-1 by acute compression of the spinal cord with a clip exerting a pressure of 175 gm. Uninjured animals, with mSAP's of 120.0 ± 17.0 mm Hg, had gray and white matter flows of 74.2 ± 22.3 and 18.7 ± 6.7 ml/100 gm/min, respectively, while injured untreated animals had mSAP's of 82.5 ± 14.1 mm Hg and gray and white matter flows of 13.3 ± 12.1 and 3.9 ± 3.9 ml/100 gm/min, respectively, at the injury site. Blood transfusion raised the mSAP's to 127.5 ± 13.7 mm Hg in the injured animals and doubled the flows in gray and white matter to 25.6 ± 30.2 and 6.3 ± 6.4 ml/100 gm/min, respectively. Dopamine did not have as beneficial an effect as blood transfusion on either the mSAP (101.0 ± 16.7 mm Hg) or the SCBF (gray and white matter flows of 18.4 ± 12.4 and 5.8 ± 5.9 ml/100 gm/min). Gamma hydroxybutyrate (GHB) had almost no effect on the mSAP or SCBF of normal animals, and in injured animals produced only a unilateral increase in flow on the less severely injured side, without affecting the mSAP.
Eugen J. Dolan and Charles H. Tator
Eugen J. Dolan, Ensor E. Transfeldt, Charles H. Tator, Edward H. Simmons and Kenneth F. Hughes
✓ Distraction is considered to be a factor in many spinal cord injuries. With a specially designed distraction apparatus and the 14C-antipyrine autoradiographic technique, the effect of distraction on spinal cord blood flow (SCBF) in cats was studied. Distraction was performed at L2–3 at a rate of 0.25 cm/10 min, and the spinal evoked response (SER) was monitored by stimulating the sciatic nerve and recording at T-13. The SCBF was assessed in five control animals, four animals in whom the SER was markedly altered by distraction, and five animals after the SER had been abolished and an additional 0.5 cm distraction applied. Control cats had gray- and white-matter flows of 44.5 ± 1.4 (SEM) and 10.5 ± 0.4 ml/100 gm/min, respectively. Distraction to the point of marked SER alteration caused a 50% loss of SCBF at and caudal to the distraction site. An additional 0.5 cm distraction produced total abolition of SCBF at the distraction site and for a considerable distance rostral and caudal to it. Thus, it is shown that spinal distraction causes cord ischemia similar to that seen with other types of spinal cord injury. In addition, distraction severe enough to cause loss of the SER has already produced severe cord ischemia.
Eugen J. Dolan, Charles H. Tator and Laszlo Endrenyi
✓ A clip compression method was used to produce acute spinal cord compression injury in rats. The force and duration of the spinal cord compression were independently varied, and functional recovery of the cord was assessed using the inclined plane technique. Mathematical modeling produced a curve defining the relationship between force, duration, and functional recovery for each week after injury. The study clearly showed the beneficial effect of decompression and that increasing either the force or duration of compression, or both, caused a reduction in recovery.
Eugen J. Dolan and Charles H. Tator
✓ A new method is described for the determination of force-distance curves for aneurysm clips. A dissecting microscope with a goniometer eyepiece was used to determine the angle between the clip blades as various forces were applied to open the clip. The cosine law was then used to calculate the force-distance curves. The method allows accurate characterization of different clips and is especially useful for the early detection of clip weakening.