Protective effects of steroids on the cortico-microcirculation injured by cold

Abstract

✓ Early microcirculatory changes after focal cold injury of the cerebral cortex were examined in dogs with and without steroids by serial fluorescein angiography of the brain (FAB), by measurement of the diameter of epicerebral vessels, and by measurement of cerebral blood flow with the clearance method using krypton-85 and xenon-133. Changes in the transcerebral vessels were examined by x-ray projection microangiography. Within 30 minutes of the injury, the cortical area injured by a temperature of −65° C showed a reduction in blood flow of 60%. When treated with steroids and while still at the same temperature, blood flow was reduced by only 35%. Serial FAB revealed slowing and arrest of flow in the epicerebral microcirculation which could be noted first in the small veins, then in the medium-sized veins and small arteries. Fluorescein dye leaked from the epicerebral vessels, around the small veins, then around larger veins and small arteries. Some leakage of dye from medium-sized arteries was noted 2 hours after injury. This sequence of slowing and arrest of the microcirculation, with exit of dye from intact arterial vessels, identified here for the first time in relation to a cortical freezing lesion, may help to explain the development of later brain edema which spreads widely in the subcortical white matter. After steroids, improvement of the microcirculation was present as defined by cortical blood flow, fluorescein angiography, and x-ray projection microangiography.