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 dexamethasone, a barbiturate, and hypothermy on experimental cerebral edema caused by CO2 laser in dogs. Experimental brain lesions were created over the right frontal cortex of the dogs through the intact dura mater with CO2 laser energy (40 W impact, 0.5 second duration, for a total time of 4 seconds on a 12.5 mm surface). Animals were divided into four groups 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 surrounded by edema. The main finding in the surrounding coagulation and edematous layers was dilatation of the vessels. Hemorrhage was sometimes observed mainly in the edematous layer. The effect of these therapies on the laser lesion and the effectiveness of these therapies on surrounding cerebral edema were evaluated by both light and electron microscopy. The control group showed significantly greater edema than the dexamethasone group. There was only a minimal difference between the control group and the barbiturate group, and there was no significant difference in amount of edema between control group and the hypothermy group. There was less edema in the dexamethasone group than in the other ones. These data suggest that dexamethasone inhibits edema in CO2 laser lesions with the same efficacy as shown in the treatment of vasogenic edema.