Evaluation of mannitol as an osmotherapeutic agent in traumatic brain injuries by measuring serum osmolality

ABSTRACTBACKGROUNDThe effectiveness of mannitol as an osmotherapeutic agent has never been subjected to a controlled clinical trial against placebo. Excessive use of mannitol in brain trauma patients can result in hyperosmolar states, hypernatremia and renal failure. This prospective study was conducted to evaluate the institutional protocol of using mannitol and assess its effects on serum osmolality.METHODThirty patients with brain injury were included in the study. All the patients were given 100 mL of 20% mannitol three times a day as bolus infusion over 20–30 minutes. Serum osmolality was measured at 12 hourly intervals using Fiske osmometer. Mannitol administration was stopped whenever serum osmolality reached ≥ 320 mOsmol/Kg H2O. The total dose and duration of mannitol used to reach target osmolality of ≥ 320 mOsmol/Kg H2O was recorded.RESULTSOn 33% of all occasions, the patients had a serum osmolality which was in excess of the desired values (i.e. ≥ 320 mOsmol/Kg H2O). This indicates that the standard protocol of administering 20% mannitol 100 mL three times a day for more than 48 hours is perhaps excessive.CONCLUSIONThe mannitol therapy should be guided by 12 hourly measurement of serum osmolality. Mannitol should be used for 48 hours only if facilities for measuring serum osmolality are not available.