Controversy exists about the effect of tissue
edema on cerebral microcirculation. High spatial resolution is required for observation of extravasation and microcirculation during focal vasogenic
edema formation. To study the relationship between tissue
edema and perfusion, we developed a technique for simultaneous visualization of extravasation and microvessel perfusion in rats. Focal intracortical microvascular injury was generated with a 1-sec
Nd-YAG laser pulse.
Evans blue albumin (EBA) was infused 30 min before
decapitation to study extravasation and
FITC-dextran was injected 30 sec prior to
decapitation to examine microvessel perfusion. Computerized scanning
laser-excited fluorescence microscopy followed by high resolution image analysis permitted quantitative assessment of both parameters on single fresh-frozen brain sections. Studied at 30 min (3.66 +/- 0.15 mm), 2 hr (4.14 +/- 0.08 mm, P < .05), and 8 hr (4.69 +/- 0.18 mm, P < .01) after injury, the diameter of the circular, sharply demarcated zone of EBA-extravasation increased progressively. At 30 min, microvessels at a zone surrounding the area of EBA-extravasation contained 69 +/- 14% (P < .05) more fluorescent
FITC-filling than in the control hemisphere, but the density of perfused microvessels was unchanged. At 2 hr, secondary tissue changes had already occurred in a zone surrounding the initial
laser lesion. While severe reduction in the density (-76 +/- 13%, P < .05) of perfused microvessels was observed within 400 to 240 microm inside the border of EBA extravasation, perfusion indexes were normal despite the presence of extravasated plasma constituents within 0-80 microm from the border. In a narrow zone (80 microm) outside the border of extravasation, individual microvessels contained 34 +/- 9% (P < .01) less
FITC-fluorescence than those in a homologous area of the uninjured contralateral hemisphere. This report demonstrates the feasibility of simultaneous measurement and high-resolution mapping of indices of microvascular perfusion (density, filling) and extravasated plasma constituents in damaged and intact brain areas. In this model, the presence of extravasated plasma constituents the size of
proteins did not immediately influence indices of cortical microcirculation. However, microvascular perfusion may be perturbed surrounding such an area of advancing vasogenic
edema formation.