Experimental carbon dioxide laser brain lesions and intracranial dynamics: Part 2. Effect on brain water content and its response to acute therapy.

Experimental brain lesions were created over the left parietooccipital cortex of the albino rabbit through the intact dura mater with high radiating carbon dioxide laser energy (40-W impact, 0.5-second duration, for a total time of 4 seconds on a 12.5-mm surface). The brain water content was studied 2, 6, and 24 hours after the insult. Another two groups of animals received acute therapy with either dexamethasone (1 mg/kg) or furosemide (1 mg/kg). In all groups, Evans blue extravasation uniformly extended from the impact crater into the surrounding white matter. The brain water content in the gray matter was elevated from the control value by 2 hours after impact (P less than 0.005) and remained elevated at 6 and 24 hours. The white matter brain water content did not increase until 6 hours after impact and remained elevated in the 24-hour group (P less than 0.005). After dexamethasone treatment, there was a significant decrease of water in the gray matter (P less than 0.01), but not in the white matter. With furosemide therapy, there was no reduction of gray or white matter brain water.