Quantitative analysis of brain edema resolution into the cerebral ventricles and subarachnoid space

Resolution of vasogenic brain edema was examined using a model of infusion of fluid into the brain of rabbits. For this purpose infusion of Texas Red-albumin (MW 67.000 D) and sodium fluorescein (MW 376 D) dissolved in artificial cerebrospinal fluid (mock CSF) was made into the white matter of the left frontal lobe of the brain. In order to quantify the portion of edema fluid which was cleared by the ventricular system, a ventriculo-cisternal perfusion was performed with mock CSF. A closed cranial window was implanted above the left parietal brain for superfusion of the cerebral cortex with mock CSF, in order to study resolution of the artificial edema fluid via the subarachnoid space. CSF-samples were collected in 30 minutes-intervals and analysed with a spectrophotometer. The clearance of edema fluid was examined under low (2-5 mmHg) and medium (9-12 mmHg) intracranial pressure (ICP). In the low-pressure group both edema fluid markers were found in the ventriculo-cisternal and subarachnoid perfusate at 60 min and 90 min, respectively, after start of infusion. In the group with moderately increased ICP the markers appeared at 90 min and 120 min, respectively. The amount of clearance of fluorescent dye via the subarachnoid space was the same in both groups and independent of the intracranial pressure.