376 The Salt Versus Sugar Debate: Urinary Sodium Losses Following Hypertonic Saline Administration Curtails Its Superior Osmolar Effect in Comparison to Mannitol in Severe Traumatic Brain Injury.

INTRODUCTION: Osmotherapy forms an integral part in the management of patients with severe traumatic brain injury (TBI). An ideal choice between mannitol and hypertonic saline (HTS) remains to be conclusively proven. More importantly, attention has not been paid to the long-term osmolarity changes during the therapy. The current prospective randomized study aims at evaluating the effect of serum and urine osmolarity and sodium achieved with mannitol and HTS on intracranial pressure (ICP) and outcome.

METHODS: Thirty-eight patients of severe TBI, aged between 15 and 70 years and managed as per Brain Trauma Foundation (BTF) guidelines were allocated to receive equiosmolar doses of either 20% mannitol or 3% HTS for refractory intracranial hypertension. Demographic data, physiological variables, ICP, serum and urine osmolarity/sodium were collected over 5 days. Data were analyzed for relationship between serum and urine sodium over 5 days in patients receiving mannitol and HTS for severe TBI.

RESULTS: A total of 301 and 186 boluses of mannitol and HTS, respectively, were administered over 5 days. There was no difference between mannitol and HTS with respect to demography, type of brain injury and Glasgow Outcome Scale (GOS). Serum sodium and osmolarity changes were similar between the groups (P = .16 and 0.35, respectively). Urinary sodium excretion was significantly higher with HTS (P = .02). The mean fall in ICP following a dose of hyperosmolar agent was 8.9 ± 8.4 mm Hg in the mannitol group and 10.1 ± 8.7 mm Hg in the hypertonic saline group (P = 0.135).

CONCLUSION: During long-term administration of hyperosmolar agents in TBI, HTS is no more effective than mannitol in controlling ICP. A major reason for this lack of benefit is an increased urinary loss of sodium with HTS and consequent inability to achieve higher serum sodium and osmolarity levels. Therapy aimed at retaining sodium holds the key for superior osmolar effect and good outcome.