The effects of mannitol on cerebral edema after large hemispheric cerebralinfarct

Objective: To evaluate the effect of a single large dose of mannitol on mid line tissue shifts after a large cerebral infarction. Background: Theoretic ally, mannitol use in the largest cerebral infarctions may preferentially s hrink noninfarcted cerebral. tissue, thereby aggravating midline tissue shi fts and worsening neurologic status. To test this theory, we studied patien ts with hemispheric infarctions using continuous and sequential MRI during administration of a single dose of mannitol. Methods: Patients with neurolo gic deterioration from complete middle cerebral artery (MCA) infarctions an d CT evidence of at least 3 mm of midline shift were studied using T1-weigh ted three-dimensional multiplanar rapid acquisition gradient echo image dat a sets acquired at 5- to 10-minute intervals before, during, and after a 1. 5 gm/kg bolus infusion of mannitol. Horizontal and vertical displacements w ere calculated by previously described methods. Glasgow Coma Scale (GCS) an d MCA Stroke Scale (MCASS) were measured before and after mannitol administ ration. Mean changes in tissue shifts were compared using repeated measures analysis of valiance. Clinical variables were compared using paired t-test s. Results: Seven patients were enrolled. The final average change in midli ne shift compared with the initial displacement was 0.0 +/- 1 mm for horizo ntal (F = 0.06, p = 0.99) and 0.25 +/- 1.3 mm for vertical displacement (F = 0.06, p = 0.99). Whereas average scores for the group did not change, MCA SS improved in two, GCS improved in three, and pupillary light reactivity r eturned in two patients. No patient worsened. Conclusions: Acute mannitol u sed in patients with cerebral edema after a large hemispheric infarction do es not alter midline tissue shifts or worsen neurologic status.