Resolution of experimental vasogenic brain edema at different intracranial pressures

Resolution of vasogenic brain edema was examined using the infusion edema model in rabbits. Texas Red-albumin (MW 66,000 D) and sodium fluorescein (MW 376 D) dissolved in artificial cerebrospinal fluid (aCSF) were infused into the white matter of the left frontal lobe of the brain. To quantify the edema fluid cleared by the ventricular system, ventriculo-cisternal perfusion was performed with aCSF. A closed cranial window, implanted above the left parietal brain, served for studying resolution of the artificial edema fluid via the subarachnoid space. CSF-samples were collected in 30 minutes-intervals and analysed with a spectrophotometer. Clearance of edema fluid was examined under low (2-5 mm Hg), medium (9-12 mm Hg), or high (14-17 mm Hg) intracranial pressures (ICP). In the low pressure-group, both edema fluid markers were found in the ventriculo-cisternal and subarachnoid perfusate at 60 and 90 min, in the group with moderately increased ICP at 90 and 120 min, respectively. In the high ICP-group both fluorescence dyes appeared not less than 90 min in the ventricular system, while no increase at all could be found in the subarachnoid space. Our results imply that resolution of edema fluid via both the ventricular system and the subarachnoid space depends on the actual ICP level.