Validation of laser-Doppler flowmetry in measurement of spinal cord blood flow

Laser-Doppler flowmetry (LDF) is a non-invasive method for continuous on-line monitoring of microvascular blood flow. LDF has previously been validated with established methods in various tissues, yet its validity and resolution in the central nervous system (CNS) remain unclear. We compared LDF with the microsphere method (MS) using two independent laser probes placed on the dorsal lumbar spinal cord (L5 laminectomy) of anesthetized rabbits (n = 9). After base-line flow measurements, spinal cord blood flow (SCBF) was increased (up to 50%) with phenylephrine (10-80 micrograms.kg-1.min-1 iv) and decreased (up to 50%) with chlorisondamine (10 mg/kg iv) or other stimuli. The percentage changes of lumbar SCBF and vascular resistance (VR) from the base line obtained by LDF and MS excellently agreed (rBF = 0.86, rVR = 0.94, P less than 0.0001). LDF estimated also the absolute SCBF values parallel to MS (r = 0.77, P less than 0.001). In conclusion, the validity of LDF in estimating the SCBF and dynamic changes of BF and VR is confirmed. Therefore, LDF may prove useful for monitoring CNS microcirculation in normal or pathophysiological states.