Quantitative CT assessment of furosemide- and mannitol-induced changes in brain water content

We studied the effects of two commonly employed antiedema agents, mannitol and furosemide, on CT brain density in eight patients with primary and metastatic brain tumors. Noncontrast CTs were performed before and after IV furosemide or IV mannitol, and serial blood samples were analyzed for osmolality. Computer-generated frequency histograms of CT numbers from "before-and-after" brain slices were using quantile-quantile (QQ) plots and the Kruskal-Wallis statistic. After IV mannitol, there was a progressive increase in CT brain density, which corresponded to an upward shift in the QQ plot over the range 0 to 70 Hounsfield units. The differences between baseline and posttreatment histograms for mannitol patients were significantly different from controls, and maximum differences coincided with peak serum osmolality. No statistically significant effects were observed in the furosemide group despite maximal diuresis. The relative magnitude of the quantitative changes observed after mannitol and furosemide administration are consistent with anticipated changes in brain water content.