The Value of Hypertonic Mannitol Solution in Decreasing Brain Mass and Lowering Cerebrospinal-Fluid Pressure

Abstract

T HE value of a chemical or pharmacological agent that temporarily would lower cerebrospinal-fluid pressure and decrease the mass of the brain is apparent to neurosurgeons. Since Weed and 1VfcKibben 4e,47 demonstrated that various hypertonic solutions could accomplish these effects, many agents have been tested. 6,14,17,22,29,45,49,55 Each of these substances has been found to have certain disadvantages or toxic effects. The use of hypertonic urea for these purposes originally was proposed by FremontSmith and Forbes, 15 and Wolff and Forbes, 64 and was restudied by Fremont-Smith eta/., ~3 Smythe et a/., 39 and Javid and Settlage. ~5 This material was difficult to prepare for sterile intravenous injection, but when lyophilized urea and invert sugar became available it found wide acceptance. ~4,42,44 While hypertonic urea frequently is effective in lowering cerebrospinal-fluid pressure and decreasing the mass of the brain, there are certain theoretical and practical objections to its use. Urea is distributed throughout total body water, n.4~ although it does equilibrate relatively slowly with brain water and cerebrospinal fluid, s.33 Thus, unless the urea administered were excreted fairly rapidly, one would expect dissipation of its osmotic gradient as equilibration of urea with brain water and cerebrospinal fluid