Changes in skin blood flow and temperature during spinal analgesia evaluated by laser Doppler flowmetry and infrared thermography.

Changes in skin blood flow and skin temperature during spinal analgesia and "sham" spinal analgesia were studied using laser Doppler flowmetry and skin temperature measurements on patients scheduled for transurethral resection. Infrared thermography was also used. During "sham" spinal analgesia skin blood flow decreased 17.7% +/- 37% (s.d.) and skin temperature fell 0.05 degrees C +/- 0.6 (s.d.) degree C. The height of the blockade was T10 or above in all cases. Using the laser Doppler technique with measuring points from the clavicle to T12, a tendency towards increased skin blood flow was seen in six cases out of 20 at T10 (significant elevations in 3/20) and in 14 cases out of 20 at T12 (significant elevations in 7/20). Skin temperature measurements and thermography showed a tendency towards cooling in the thoraco-abdominal region in the vast majority of the cases and a marked temperature elevation in the foot only. No differences between hyperbaric and glucose-free solutions for spinal analgesia were noticed. The conclusion of this study is that during spinal analgesia the extent of sympathetic blockade is less than the extent of analgesia.