Effects of surgical sympathectomy on skin blood flow in a rat model of chronic limb ischemia.

The role of lumbar sympathectomy in the treatment of limb ischemia secondary to arteriosclerosis obliterans has been controversial. Increased temperature and rubor of the skin, which usually follow sympathectomy, have generally been interpreted as indicative of improved nutritive skin blood flow. However, the existence of a (nonnutritive) thermoregulatory level of skin microcirculation makes such an extrapolation questionable. We investigated the total (mainly thermoregulatory) skin blood flow (TSBF) in the hindlimb of 15 male Lewis rats by means of laser Doppler flowmetry and the nutritive skin blood flow (NSBF) by means of capillary microscopy (red blood cell velocity). Transcutaneous oximetry was used to assess skin oxygenation (SO). Measurements were performed before and 2 and 28 days after ligation of the common iliac and iliolumbar artery. Subsequently, either a surgical resection of the sympathetic chain (L2-L6) was performed or a sham operation. Measurements were repeated 2 and 28 days later. For the group of 15 rats as a whole, TSBF (p < 0.05), NSBF (p < 0.05), and SO (p < 0.05) were found to be drastically reduced at day 2 after litigation compared to preligation values. This reduction partially recovered during the following weeks. TSBF (p < 0.05) and NSBF (p < 0.05), however were still reduced at day 28 after ligation compared to preligation values, whereas the SO at this time tended to be lower (p = 0.11). In the sympathectomy group the TSBF was found to be increased at day 2 (p < 0.05) and day 28 (p < 0.05) after sympathectomy, both compared to values obtained at day 28 after ligation. Sympathectomy did not have an effect on NSFB and SO. The sham procedure had no effect on the TSBF, NSBF, or SO. These results indicate that in case of lower limb ischemia, sympathectomy improves skin blood flow at the thermoregulatory but not the nutritive level of skin microcirculation. This may be related to the fact that the thermoregulatory vessels are mainly sympathetically controlled, whereas the nutritive capillaries are mainly controlled by local (nonneural) factors.