Perineural injection to nerve root and radicular blood flow: a clinical study during spinal surgery

Background and objective To investigate the effects of the perineural injec tion of lidocaine or corticosteroids on radicular blood flow during spinal surgery. Methods After lumbar discectomy, a probe for laser Doppler flowmetry was pl aced directly on the 4th or 5th lumbar nerve root. Thirty patients undergoi ng lumbar discectomy were randomly assigned to one of three groups. Each gr oup received one of three protocols for a perineural injection to the nerve root: 1.6 mt 0.9% saline in group A, 1.0 mt 1% lidocaine in group B or 1.6 mt dexamethasone (4 mg) in group C. Measurements included radicular blood flow, mean arterial pressure, haemoglobin concentration, percutaneous oxyge n saturation and end-tidal carbon dioxide tension. Radicular blood flow was measured by laser Doppler flowmetry before the injection and 15 min after these injections. The three groups were similar with respect to mean arteri al pressure, haemoglobin concentration, percutaneous oxygen saturation and end-tidal carbon dioxide tension. Results Radicular blood flow did not change after the injection in any of t he groups. Conclusions The results suggest that the perineural injection of 1% lidocai ne or dexamethasone does not affect radicular blood flow during lumbar disc ectomy.