The effect of spinal analgesia on skin blood flow, evaluated by laser Doppler flowmetry

Changes in skin blood flow provoked by spinal analgesia were evaluated by laser Doppler flowmetry. This method permits a continuous and noninvasive measurement of the microvascular flow in the superficial skin layer. All recordings were made under control environmental conditions on 40 patients submitted to transurethral resection. During spinal analgesia a significant (P less than 0.001) reduction in skin blood flow was obtained in the shoulder and chest, while an increase (P less than 0.001) in skin blood flow was seen in the lower part of the body. In the postoperative period these changes still persisted, although they were less significant, indicating the individual duration of analgesia. The relations between intra-individual relative changes in skin blood flow and skin temperature during spinal analgesia were found to be virtually uncorrelated. Laser Doppler flowmetry seems to be a useful tool in the further evaluation of the influence of spinal analgesia on the extent of the associated sympathetic blockade.