Effects of fluid management on edema volume and midline shift in a rat model of ischemic stroke

Background and Purpose-The purpose of this study was to investigate the eff ects of fluid management on brain water content (BW) and midline shift (MLS ) after a focal cerebral ischemic insult. Methods: A suture model was used to induce focal cerebral ischemia for 90 m inutes (n = 44). The rats were randomly assigned to 3 groups 2.5 hours afte r reperfusion: dehydration (n = 24), control (n = 8), or hydration (n = 12) . BW was obtained with the wet-dry weight method 24 hours after middle cere bral artery (MCA) occlusion. In addition, MRI were obtained (n = 31) 24 hou rs after the onset of ischemia so that the ratio of hemispheric volumes ips ilateral (IH) and contralateral (CH) to the infarct and the extent of MLS c ould be obtained. Results-Across the range from moderate dehydration to intravascular volume expansion with isotonic saline, BW of the IH increased linearly as a functi on of change in body weight (r(2) = 0.89), whereas few changes in relation to body weight were observed; in CH, indicating a preferential effect of fl uid management on the infarcted hemisphere. Furthermore, the hemispheric vo lume ratio (IH/CH) and MLS also increased in relation to changes in body we ight. However, paradoxical increases in BW, IH/CH, and extent of MLS were o bserved in comparison with controls when severe dehydration was produced wi th high-dose mannitol. Conclusions-Changes in ischemic BW by fluid management correlated closely w ith changes in body weight except when high-dose mannitol was used. Mannito l, as a dehydrating agent, may be associated with bimodal effects, with a h igh dose aggravating ischemic BW.