Acute effect of angiographic contrast medium on cortical specific gravity after middle cerebral artery occlusion in rats.

Early angiography after cerebral arterial occlusion has been cited as potentially detrimental. This investigation evaluates the effect of acute angiographic contrast medium administration on the cortical edema induced by middle cerebral artery (MCA) occlusion. Sixteen rats underwent MCA occlusion, and after 1 hour half the rats underwent ipsilateral internal carotid injection of meglumine diatrizoate, whereas the remainder underwent cervical internal carotid exposure only. Six rats had only sham operations on the MCA and internal carotid, and 4 other rats served as normal controls. Cortical specific gravity was measured to reflect cerebral edema 4 hours after occlusion or sham operation. Specific gravity of the lateral frontal cortex in the hemisphere ipsilateral to occlusion was 1.0396 +/- 0.0011 (mean +/- SEM) when no angiographic contrast medium was administered, significantly less (p less than 0.01) than in rats exposed to contrast medium (specific gravity 1.0442 +/- 0.0005). The latter value was not significantly different from normal. Other cortical areas on the side of the contrast medium injection were also relatively dehydrated compared with normal controls. Early meglumine diatrizoate administration after MCA occlusion results in a decrease in cerebral cortical edema, possible by inducing an osmotic gradient that draws water from the extravascular space.