Critical levels of spinal cord blood flow and duration of ischemia for the acute recovery of segmental spinal cord responses in cats.
A broad range of residual lumbar spinal cord blood flows assessed by laser-Doppler flowmetry (rSCBF, 0-78%) was achieved by snare occlusion of the descending aorta and additional blood-volume reduction for 1-10 min in spinal cats (n = 30; 238 trials). The period of complete reflex suppression (delay until recovery) that revealed some correlation to duration (r = 0.72) and depth (r = -0.36) of ischemia showed comparable durations in mono- and polysynaptic reflexes, whereas it was significantly less for the cord dorsum potential (CDP). With rSCBF values > 50-60% reflexes and > 45%, the CDP was rarely abolished, irrespective of the duration of ischemia. The threshold of duration for a complete loss of reflex responses was found to be approximately 1 min of ischemia. The influence of rSCBF and duration of ischemia on the occurrence of incomplete recoveries of reflexes was assessed simultaneously in a logistic regression model. Compared with periods of ischemia of 3 min, all longer durations showed a steep risk gradient for incomplete recoveries; an increment of 10% in rSCBF led to a risk reduction for incomplete recoveries of nearly 25%. These findings were significant (p < 0.001) and indicated that blood-flow thresholds and limits for the development of neurologic deficits of the spinal cord are comparable to those of the brain, with the important difference that the blood-flow reserve of the spinal cord is smaller.
Kolenda
H
H
Institute of Physiology, University of Göttingen, Germany.
Steffens
H
H
Gefeller
O
O
Hagenah
J
J
Schomburg
E D
ED
D000818:Animals; D002415:Cats; D003655:Decerebrate State / Q000503:physiopathology; D004056:Differential Threshold; D004594:Electrophysiology; D007511:Ischemia / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D012018:Reflex / Q000502:physiology; D012023:Reflex, Monosynaptic / Q000502:physiology; D012039:Regional Blood Flow; D013116:Spinal Cord / Q000098:blood supply* / Q000503:physiopathology*; D013997:Time Factors