Changes in rat paw perfusion after experimental mononeuropathy: Assessmentby laser Doppler fluxmetry

This study was performed to determine the changes in perfusion that occur a fter chronic constriction injury (CCI). Male Sprague-Dawley rats weighing 2 75-300 g had loosely constricting ligatures placed around the left sciatic nerve. Paw withdrawal latency (PWL) to heat, skin temperature, and skin per fusion (laser Doppler) of the hind paws were measured before and for 30 day s after CCI. PWL, decreased significantly on the side of the CCI (maximum o f 34% decrease on Postoperative Day [POD] 3), then returned to normal over a 20-day period. Skin temperature initially increased on the side of CCI, t hen decreased with respect to the control limb on PODs 20-30. Despite the i nitial increase in skin temperature on the side of CCI, skin perfusion sign ificantly decreased immediately after CCI (maximum of 51% decrease on POD 6 ). The perfusion gradually returned to normal over 20 days. Because return to normal perfusion occurred while the skin temperature became colder than the control side, we conclude that there is no relationship between paw sur face temperature and perfusion. Implications: Our data suggest that loss of sympathetic tone in thermoregulatory arteriovenous anastomoses leads to de creased nutritional blood flow to the skin of the affected limb after chron ic constriction injury, which is consistent with the findings reported in h umans with reflex sympathetic dystrophy.