Effects of anesthesia and laminectomy on regional spinal cord blood flow in conscious sheep

Blood flow for the whole spinal cord (SCBF), central cord (largely gray matter), and peripheral cord (largely white matter) has been measured at all segmental levels using radioactive microspheres in conscious sheep. Whole SCBF was greatest in the lower cervical and lumbar enlargements and least in the upper cervical and thoracic regions. This was attributable partly to regional variations in gray-matter blood flow but principally to regional variations in the proportion of gray and white matter present. Whole SCBF for the total cord was 14.5 +/- 0.8 ml/100 gm/min, central cord flow was 40.6 +/- 3.5 ml/100 gm/min, and peripheral cord flow was 9.7 +/- 1.9 ml/100 gm/min. Blood flow was not affected by sodium pentobarbital provided the level of anesthesia, arterial pressure, and blood gases was carefully regulated. Laminectomy usually resulted in a marked increase in central cord blood flow at the site of cord exposure, lasting about 90 minutes; this increase was not necessarily reflected in whole SCBF because of the absence of any change in blood flow in the relatively large proportion of peripheral cord. This effect of laminectomy could adversely influence results obtained from studies using invasive techniques to measure SCBF.