The Effect of Low Doses of Mannitol on Serum Osmolality

Authors: V. Špatenková 1;  III. V. Beneš 1;  A. Kazda 2;  D. Králová 3;  P. Suchomel 1
Authors‘ workplace: Neurocentrum, Krajská nemocnice, Liberec 1;  Katedra klinické biochemie IPVZ, Praha 2;  Institut biostatistiky a analýz, Lékařská a Přírodovědecká fakulta MU, Brno 3
Published in: Cesk Slov Neurol N 2008; 71/104(1): 61-65
Category: Original Paper


Mannitol is still used for the reduction of intracranial pressure in various acute brain diseases, especially if they are associated with cerebral oedema. The aim of this study was to establish the effect of low but often prescribed doses of mannitol on measured serum osmolality. 

The prospective observational study was carried out on 60 patients admitted to the neurologic-neurosurgical intensive care unit (NNICU) over a period of three years, who fulfilled the inclusion criteria: 1. The patient’s clinical state (GCS 11-15) did not necessitate a higher dose of mannitol, 2. the patient received a minimum of 24 hours of 20% mannitol therapy prior to admittance to the NNICU, 3. normal renal parameters, 4. no diuretic agens, 5. hemodynamic stability and 6. normoglycaemia. Mannitol was given at 4 and 6 hour intervals with the mean individual dose of  0,17 ± 0,07 g/kg, and the mean daily dose of  0,76 ± 0,25 g/kg. Serum biochemical parameters were measured before mannitol infusion (T0), after infusion (T1) and before the next dose (T2 – 4 hours, T3 – 6 hours).

  The mean values of measured serum osmolality were around the upper reference level in all measurements (T0 = 295,5 ± 9,4 mmol/kg; T1 = 296,1 ± 8,3 mmol/kg; T2 = 294,0 ± 7,9 mmol/kg, T3 = 297,7 ± 8,0 mmol/kg), but was significantly higher only in T3 (p = 0,042). There were no significant changes either after administration of mannitol (T1, p = 0,311) or before further doses (T2, p = 0,721; T3, p = 0,710).

The values of measured serum osmolality did not significantly change during low doses of 20% mannitol therapy, but the values were around the upper reference level.

Cerebral oedema, intracranial hypertension, mannitol, osmotic agents, serum osmolality


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