Background and Purpose--Mannitol is used worldwide to treat acute stroke, although its efficacy and safety have not been proven by randomized trials.

Methods--In a tricenter, prospective study, we analyzed the 30-day and 1-year case fatality with respect to mannitol treatment status in 805 patients consecutively admitted within 72 hours of stroke onset. Confounding factors were compared between treated and nontreated patients.

Results--Two thirds of the patients received intravenous mannitol as part of their routine treatment (mean dose, 47±22 g/d; mean duration, 6±3 days). The case fatality was 25% versus 16% (P=0.006) at 30 days and 38% versus 25% (P<0.001) at 1 year in the-mannitol treated and nontreated groups, respectively. Mannitol treatment effect was adjusted for age, stroke severity, fever in the first 3 days, and aspirin treatment (for ischemic strokes) in logistic regression models. Depending on the factors entered into the model, either no effect or harm could be attributed to mannitol. When the analysis was restricted to those admitted within 24 hours (n=568), case fatality differed significantly only at 1 year (35% in treated and 26% in nontreated patients, P=0.044). Although the prognostic scores of the Scandinavian Neurological Stroke Scale were similar in treated and nontreated patients, both in ischemic and hemorrhagic strokes, the patient groups differed in several factors that might also have influenced survival.

Conclusions--Based on the results of this study, no recommendations can be made on the use of mannitol in acute stroke, and properly randomized, controlled trials should be performed to come to a final conclusion.