Background: The impact of osmotic therapies on brain oxygen has not been extensively studied in humans. We examined the effects on brain tissue oxygen tension (PbtO2) of mannitol and hypertonic saline (HTS) in patients with severe traumatic brain injury (TBI) and refractory intracranial hypertension.
Methods: Twelve consecutive patients with severe TBI who underwent intracranial pressure (ICP) and PbtO2 monitoring were studied. Patients were treated with mannitol (25%, 0.75 g/kg) for episodes of elevated ICP (> 20 mm Hg) or HTS (7.5%, 250 ml) if ICP was not controlled with mannitol. PbtO2, ICP, mean arterial pressure (MAP), cerebral perfusion pressure (CPP), central venous pressure (CVP) and cardiac output were monitored continuously.
Results: Forty-two episodes of intracranial hypertension, treated with mannitol (n=28 boluses) or HTS (n=14 boluses), were analysed. HTS treatment was associated with an increase of PbtO2 (from baseline 28.3 +/- 13.8 mm Hg to 34.9 +/- 18.2 mm Hg at 30 minutes, 37.0 +/- 17.6 mm Hg at 60 minutes and 41.4 +/- 17.7 mm Hg at 120 minutes, all p<0.01), while mannitol did not affect PbtO2 (baseline 30.4 +/- 11.4 vs. 28.7 +/- 13.5 vs. 28.4 +/- 10.6 vs. 27.5 +/- 9.9 mm Hg, all p>0.1). Compared to mannitol, HTS was associated with lower ICP, and higher CPP and cardiac output.
Conclusions: In patients with severe TBI and elevated ICP refractory to previous mannitol treatment, 7.5% hypertonic saline administered as second tier therapy is associated with a significant increase of brain oxygenation, and improved cerebral and systemic hemodynamics.