Experimental carbon dioxide laser brain lesions and intracranial dynamics: Part 1. Effect on intracranial pressure, systemic arterial pressure, central venous pressure, electroencephalography, and gross pathology.

Experimental brain lesions were created in the left parietooccipital cortex of the albino rabbit through the intact dura mater with high radiating carbon dioxide laser energy (40-watt impacts of 0.5-second duration for a total of 4 seconds on a 12.5-mm surface). Behavior, intracranial pressure (ICP), systolic arterial pressure (SAP), central venous pressure (CVP), electroencephalography (EEG), and gross pathology were studied at 2, 6, and 24 hours after the insult at a constant PaCO2 (38-42 torr). Disruption of the blood-brain barrier (Evans blue extravasation) was uniformly seen extending from the impact crater into the surrounding white matter in all groups. The ICP was elevated in sham-operated animals at 2 hours after the impact, and it remained elevated at 6 and 24 hours. The EEG revealed severe slowing with high voltage waves in the insulted left hemisphere. There was no change in mean SAP or CVP when compared to the sham-operated group. In the dexamethasone-pretreated group, there was a reduction of ICP when compared to the untreated group at 24 hours after the insult (P less than 0.005), but no changes in the gross pathology were noted.