Furosemide vs Placebo for Brain Relaxation

Increased brain bulk may be problematic during brain surgery for tumors because it may limit surgical exposure and access to the surgical site. Mannitol, an osmotic diuretic, is commonly given to alleviate brain bulk, and sometimes furosemide in a small dose is added if mannitol alone is insufficient. It is unclear if adding this furosemide truly helps to diminish brain bulk, and it is possible that furosemide may cause too much diuresis, leading to dehydration and its side effects (e.g., low blood pressure). Our purpose is to investigate what the effects of furosemide are in the setting of brain surgery for tumors, specifically with regards to decreasing brain bulk and/or causing dehydration. Study Hypothesis: The addition of furosemide to mannitol will result in improved brain relaxation in human subjects undergoing craniotomy for brain tumor resection than that seen with mannitol alone. However, the combination of mannitol and furosemide will also lead to more significant intravascular volume depletion than that seen with mannitol alone.