Effects of treatment with dexamethasone on recovery from experimental cerebral arterial gas embolism

Dexamethasone is often recommended as an adjunct to recompression in the treatment of serious central nervous system decompression accidents. We studied the effects of prophylactic and therapeutic administration of dexamethasone combined with hyperbaric treatment in anesthetized dogs that were subjected to carotid air embolism and a brief episode of arterial hypertension. To assess recovery we measured somatosensory evoked potential (SSEP) amplitude, intracranial pressure, brain water, and cerebral blood flow. Three groups were studied: pre-air treatment (dexamethasone 1 mg/kg 3-4 h before carotid air embolism, and 1 mg/kg immediately after air embolism); post-air treatment (2 mg/kg immediately after air embolism); and control (equivalent volumes of saline pre- and post-air). There was a slight improvement in SSEP early in the course of hyperbaric therapy in the pre-air treated group; the post-air group never differed from control. No differences in intracranial pressure or brain water were found among groups. No blood flows below those lethal to neurons occurred in treated animals but 4 of 7 control animals had low flows. Although prophylactic treatment with dexamethasone produces some improvement in recovery, we cannot confirm that dexamethasone is an effective adjunct to recompression when administered therapeutically.