Experimental carbon dioxide laser brain lesions and intracranial dynamics: Part 3. Effect on cerebral blood flow.

Experimental carbon dioxide brain lesions were created over the intact dura mater of the left parietooccipital region of the anesthetized albino rabbit (40-watt impacts of 0.5-second duration, for a total of 4 seconds, with 0.5-second intervals between impacts), and cerebral blood flow (CBF) studies were performed with the hydrogen clearance technique. The animals were mechanically ventilated to maintain a constant PaCO2. Blood pressure, central venous pressure, electroencephalogram, and intracranial pressure were continuously monitored. The control CBF before lesion was 64.1 +/- 15.8 and 70.9 +/- 13.4 ml/100 g/minute for the left and the right hemispheres, respectively. CBF studies at 2, 4, 6, 8, and 24 hours after the lesion did not significantly change from the control values, save for a trend to increase over the right hemisphere only at 2 hours (range 106.0 +/- 55.4 to 41.6 +/- 9.3). It is concluded that in this model the changes in intracranial pressure and brain edema that are seen and have been previously reported are not due to change in cerebral circulation. The brain edema that results probably has characteristics similar to those seen in the cryogenic lesion (vasogenic) model, and this could account for the rise in intracranial pressure.