Spinal cord blood flow and conduction during experimental cord compression in normotensive and hypotensive dogs

Spinal cord blood flow (SCBF) and dorsal column conduction, as assessed by the dorsal column evoked potential (DCEP), were measured during subacute cord compression in dogs. Ventral, midline balloons were used to produce compression and a dorsally situated strain gauge transducer measured the cord pressure. In normotensive animals there was autoregulation of SCBF to perfusion pressures (PP) of 65 to 70 mm Hg, and up to cord pressures of 55 to 60 mm Hg. The DCEP amplitude was significantly decreased even during this autoregulatory period. Conduction failure occurred at PP of 20 to 30 mm Hg. Chemically produced hypotension (74 mm Hg) did not affect either SCBF or DCEP. Minimal compression superimposed on hypotension decreased both flow and DCEP amplitude. The results indicate that ischemia is probably not the cause of the impaired conduction although, as the degree of compression increases, the cord will become ischemic once the autoregulatory limit is passed.