Laser Doppler evaluation of microcirculation behaviour during an ischaemia-reperfusion injury.

Laser Doppler flowmetry (LDF) was tested in an experimental ischaemic model on rat limbs to evaluate the degree of ischaemia and to find a possible correlation with values obtained with this device and prognosis. Under general anaesthesia, 40 Wistar rats were submitted to 4 h and 30 min of ischaemia of the left hind limb. Ten rats formed the control group (group 1). Two enzymes, native superoxide dismutase (SOD) and SOD modified with polyethylene glycol, were employed in 15 rats each (groups 2 and 3). Data were collected by means of LDF both in the sole and muscles before ischaemia (steady state), during ischaemia and at the beginning of reperfusion, and only in the sole after 1 h of reperfusion. A range of predictive (95%) perfusion values (PU) for limb healing or necrosis was identified at the beginning of reperfusion. During ischaemia, PU changed from 0 to 10, both in the sole and in the muscle. A three-factor ANOVA (site, group, time) did not show interaction of these factors with PU (F = 1.655; p = 0.195), even if every single effect was significant (p < 0.0005). A two-factor ANOVA (group, time) showed a significant interaction of these factors with PU (F = 4.079; p = 0.019). The logistic regression between the reperfusion PU of each site and the survival of the limb was observed at the beginning and after 1 h of reperfusion in the sole only. Furthermore, a correlation between sole and muscle PU at the steady state and at the beginning of the reperfusion period was observed. The results showed the effectiveness of LDF, which can be considered a quite reliable tool to evaluate the degree of ischaemia and to have a good correlation with prognosis in this kind of experiments.