Effect of mannitol and furosemide on blood-brain osmotic gradient and intracranial pressure
ABSTRACT The effect of mannitol (1.0 gm/kg) and furosemide (0.7 mg/kg), alone and in combination, on the blood-brain extracellular fluid and cerebrospinal fluid (CSF) osmotic gradient, elevated intracranial pressure (ICP), CSF and serum osmolality, and urine output was studied in 26 mongrel dogs. Mannitol and furosemide, when used together, produced a greater (62.4% versus 56.6%) and more sustained (5 hours versus 2 hours) fall in ICP than mannitol alone. This correlated with a prolongation of the reversal of the blood-brain osmotic gradient (-3.4 to + 38.5 mOsm/kg) and a rate of urine formation 15 times control values. There was a transient but not significant fall in serum Na+ with the combined treatment, but the arterial pressure did not vary from pretreatment levels. The results from this present study suggest that the distal loop diuretics in a dose of less than 1.0 mg/kg act synergistically with mannitol by causing preferential excretion of water over solute in the renal distal tubule, and thereby sustaining the osmotic gradient initially established by the mannitol infusion. It is possible, but unlikely in the doses used, that the additive effect of furosemide on reducing ICP in the presence of mannitol is due to interference with CSF formation or Na+ and H2O movement across the blood-brain barrier.
- SourceAvailable from: Concezione Tommasino
- "Furosemide and similar drugs may also act primarily by reducing cell swelling, rather than by changing extracellular fluid volume. In several studies it has been demonstrated that furosemide decreases CSF production, and this effect can explain the synergism between mannitol and furosemide on intracranial compliance . Furosemide's maximal effect is delayed compared with mannitol  . "
Article: Fluids and the neurosurgical patient[Show abstract] [Hide abstract]
ABSTRACT: Few human data exist concerning the impact of fluid administration on brain pathophysiology. Those factors that influence water movement into the brain are examined, in order to provide reasonable recommendations for peri-operative fluid management in the patients with brain pathology.Anesthesiology Clinics of North America 07/2002; 20(2):329-46, vi. DOI:10.1016/S0889-8537(01)00013-X