EFFECT OF HYPOXIA OR HYPERBARIC-OXYGEN ON CEREBRAL EDEMA FOLLOWING MODERATE FLUID PERCUSSION OR CORTICAL IMPACT INJURY IN RATS

This study was designed to evaluate the production of cerebral edema [ as measured by tissue specific gravity (SpG)] following moderate fluid percussion (FP) and cortical impact (CI) injury in rodents. To determ ine the effects of a secondary systemic insult, hypoxia (13% oxygen fo r 30 min) was added to some experimental groups immediately after head injury. To determine the effects of hyperbaric oxygen (HBO) on injure d cortical tissue, additional animal groups were exposed to HBO (1.5 a tm, for 60 min), beginning 4 h after head trauma. Both injury models p roduced equal amounts of tissue edema at the site of injury (mean SpG +/- SEM = 1.035 +/- 0.001), when measured 6 h posttrauma. There was no significant edema at the tissue sites immediately adjacent to the tra uma sites. The addition of hypoxia to either injury system did not inc rease edema formation beyond that produced by injury alone. HBO reduce d the water content of the trauma site in animals that had received FP , but not in animals receiving CI. We conclude that with the injury pa rameters used in this protocol, both FP and CI appear to produce focal cerebral edema at the site of trauma. Hypoxia does not worsen edema. HBO appears to reduce edema produced by FP, but not by CI.