Mannitol is often used during intracranial surgery to improve surgical exposure. Furosemide is often added to mannitol to augment this effect. The concern exists, however, that the augmented diuresis caused by the addition of furosemide to mannitol may cause hypovolemia and hypoperfusion, hypokalemia, and hyponatremia. We examined the intraoperative safety of low-dose furosemide (0.3 mg/kg) combined with mannitol (1 g/kg).
We observed 23 patients in a double-blind, block randomized, placebo-controlled study to examine the effects of furosemide (0.3 mg/kg) when combined with mannitol (1 g/kg) on surgical brain relaxation for tumor surgery. Mannitol and the study drug (furosemide or placebo) were administered, and arterial blood gases with electrolytes (sodium, potassium, and lactic acid) and urine output volume were recorded every 30 minutes for 3 hours. Plasma sodium, potassium, and lactic acid concentrations, and interval urine outputs, were compared across time and between furosemide-placebo assignment groupings, with a P<0.01 considered significant.
Although mannitol produced a large volume of diuresis (1533±335 mL), the addition of a low dose of furosemide substantially increased both the rate of production of urine for the first 90 minutes after administration and the total volume of urine produced (2561±611 mL, P<0.001, compared with placebo group). The addition of furosemide did not produce a serum potassium level below 3.8±0.7 mEq/L, a serum sodium level below 128.3±3.4 mEq/L, or a serum lactic acid level above 2.4±0.9 mmol/L. There were no differences in the plasma potassium concentration, sodium concentration, or lactic acid concentration between the drug groups at any time point.
Despite an increase in urine output by as much as 67%, adding low-dose furosemide to mannitol does not seem to produce significant electrolyte derangements or hypovolemia compared with the administration of mannitol alone.
Departments of *Anesthesiology & Neurological Surgery
†Neuroanesthesiology, Northwestern University Feinberg School of Medicine
§Anesthesiology, Neurological Surgery, and Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
Present address: Vijay K. Ramaiah, MBBS, MD, University of Washington Harborview Medical Center, Washington, DC.
Present address: Carine Zeeni, MD, American University of Beirut, Beirut, Lebanon.
Funded by the Department of Anesthesiology, Northwestern University Feinberg School of Medicine.
Previously presented, partly, at the ASA 2011 & SNACC 2011.
The authors have no funding or conflicts of interest to disclose.
Reprints: Dhanesh K. Gupta, MD, Northwestern University Feinberg School of Medicine, Ward Memorial Building, #13-179, 303 East Chicago Ave. Chicago, IL 60611 (e-mail: firstname.lastname@example.org).
Received May 8, 2012
Accepted July 13, 2012