Treatment of traumatic brain edema by multiple doses of mannitol.

Mannitol is frequently used to reduce elevated intracranial pressure often associated with brain edema. In cases of a damaged blood-brain barrier, however, mannitol might aggravate vasogenic cerebral edema, as has recently been stressed. The aim of this study was to investigate whether multiple doses of mannitol administered during development of vasogenic brain edema following a cryogenic cortical injury affect hemispheric swelling and edema. Sprague-Dawley rats were anesthetized with ketamine and xylazine. A cortical freezing lesion was applied to the right parietal region. A first series of eight rats received four doses of 20% mannitol (0.4 g/kg within 10 minutes) thirty minutes, 3, 6 and 9 hours after trauma. Twelve hours after cryogenic injury, the brains were removed for determination of hemispheric swelling and cerebral water content. Eight control rats were infused with saline only. In a second series nine rats received eight doses of 20% mannitol 30 minutes, 3, 6, 9, 12, 15, 18 and 21 hours after trauma. In this series, the brains were removed 24 hours after freezing. Again respective control animals were infused with saline only. Hemispheric swelling was 7.2 +/- 0.5% after four doses of mannitol compared to 7.6 +/- 0.5% in control animals (n.s.). Following eight doses of mannitol hemispheric swelling was 8.9 +/- 0.4% compared to 10.1 +/- 0.4% in control rats (p < 0.05). Accordingly, the water content of traumatized hemispheres was lower following repeated mannitol treatment (80.5 versus 80.8%). Water content in control hemispheres was not affected by mannitol. Taken together, these results indicate that multiple doses of mannitol do not aggravate total hemispheric swelling, nor global water content following induction of vasogenic edema.(ABSTRACT TRUNCATED AT 250 WORDS)