[Evaluation of scanning laser Doppler flowmetry in anesthetized cats]

The aim of this work was to evaluate the reliability of scanning laser Doppler flowmetry (SLDF) developed by Michelson (Heidelberg retina flowmeter) as compared to fundus camera based laser Doppler flowmetry (FLDF). Blood flow was measured on several occasions by SLDF in the optic nerve head (ONH) and in retinal capillaries of the intervascular area (IV A) in four immobilized anesthetized cats. The circulation was stimulated with pure oxygen breathing, and intravenous infusion of noradrenalin or papaverine. Blood flow was also monitored during euthanasia. The two techniques were compared in repeated successful experiments. In the ONH and IV A, mean values of blood flow were 20-1600 (arbitrary units, AU), and 400-1700 AU respectively. The mean coefficient of variance was 9.1% in the ONH and 8.0% in the IV A in five consecutive measurements. The relative change in IV A blood flow between SLDF and FLDF during noradrenalin infusion were similar over time, although the values of the changes were not significantly correlated (n = 15 r = 0. 489 p = 0.064). Papaverine infusion showed various responses in the ONH except one point where FLDF showed an increase in blood flow. During euthanasia, the SLDF revealed an increase in ONH blood flow temporally in some animals, but not in IV A. A Value of 100-200 AU for both ONH and IV A remained even after euthanasia. The FLDF, however, showed a decrease in ONH blood flow with systemic blood pressure. Measurement of IV A blood flow appears more reliable than that of ONH blood flow. The characteristics of SLDF should be considered when we interpret the blood flow value.