Surface dialysis after experimental brain injury: modification of edema fluid flow in the rat model

This study was undertaken to determine if dialysis of damaged brain surface can reduce cerebrospinal fluid (CSF) pressure and progressive brain edema. The authors secondarily determined if local brain cooling was simultaneously possible.

Telemetric pressure transmitters were implanted into the lumbar subarachnoid space of 58 young adult male rats. Cryogenic brain injury was created and 2 hours later decompressive craniectomy was performed. An osmotic cell with a semipermeable dialysis membrane placed on the damaged brain surface was perfused with dextran 15% solution for 2 or 4 hours. Water content was determined in the cerebral hemispheres using the wet-dry weight method. Evans blue-albumin spread was measured morphometrically. Brain temperature was measured bilaterally.

The CSF pressure increased after cryogenic injury and decreased after craniotomy. Two hours of brain dialysis significantly reduced CSF pressure in comparison with craniotomy alone and sham dialysis. Injured brain had higher water content, but this was not affected by dialysis. Spread of Evans blue-albumin, however, was significantly reduced by the treatment. Cooling of the dialysis solution caused significant local brain cooling.

Surface dialysis of cryogenically injured rat brain controls CSF pressure and reduces intraparenchymal spread of edema fluid in the acute period after injury. The authors postulate that edema fluid moves into the osmotic cell rather than spreading through the uninjured brain. Long-term experiments will be needed to prove that this combination therapy is effective.