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: 12 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, cerebral perfusion pressure (CPP), central venous pressure and cardiac output were monitored continuously.
Results: 42 episodes of intracranial hypertension, treated with mannitol (n = 28 boluses) or HTS (n = 14 boluses), were analysed. HTS treatment was associated with an increase in PbtO2 (from baseline 28.3 (13.8) mm Hg to 34.9 (18.2) mm Hg at 30 min, 37.0 (17.6) mm Hg at 60 min and 41.4 (17.7) mm Hg at 120 min; 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 with 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 in brain oxygenation, and improved cerebral and systemic haemodynamics.
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This work was performed at the Neurointensive Care Unit, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania, USA.
Funding: Supported by Research Grants from the SICPA Foundation, Switzerland (to MO and EC), the Swiss National Science Foundation, Grant PBLAB-119620 (EC), the Integra Foundation (PDL) and the Mary Elisabeth Groff Surgical and Medical Research Trust (PDL).
Competing interests: None.
Ethics approval: The study was approved by the Institutional Review Board, Hospital of the University of Pennsylvania, Philadelphia, USA.