EFFECT OF DEXAMETHASONE, BARBITURATE AND HYPOTHERMY ON EDEMA INDUCED BY CO2-LASER BRAIN LESION IN THE DOG - LIGHT AND ELECTRON-MICROSCOPIC STUDY

Experiments were carried out to compare the effectiveness of dexametha sone, a barbiturate, and hypothermy on experimental cerebral edema cau sed by CO2 laser in dogs. Experimental brain lesions were created over the right frontal cortex of the dogs through the intact dura mater wi th CO2 laser energy (40 W impact, 0,5 second duration, for a total tim e of 4 seconds on a 12.5 mm surface). Animals were divided into four g roups and treated with dexamethasone, a barbiturate, hypothermy, and a crystalloid (control group). The brains were examined 48 hours after injury. Histologically all brain lesions showed three distinct layers with a vaporized center bordered by a zone of coagulation necrosis sur rounded by edema. The main finding in the surrounding coagulation and edematous layers was dilatation of the vessels. Hemorrhage was sometim es observed mainly in the edematous layer. The effect of these therapi es on the laser lesion and the effectiveness of these therapies on sur rounding cerebral edema were evaluated by both light and electron micr oscopy. The control group showed significantly greater edema than the dexamethasone group. There was only a minimal difference between the c ontrol group and the barbiturate group, and there was no significant d ifference in amount of edema between control group and the hypothermy group. There was less edema in the dexamethasone group than in the oth er ones. These data suggest that dexamethasone inhibits edema in CO2 l aser lesions with the same efficacy as shown in the treatment of vasog enic edema.