Object: Intracranial hypertension, defined as intracranial pressure (ICP) >/= 20 mm Hg, is a complication typically associated with head injury. Its impact on cerebral metabolism, ICP therapy, and outcome has rarely been studied in patients with aneurysmal subarachnoid hemorrhage (aSAH); such an assessment is the authors' goal in the present study.
Methods: Cerebral metabolism was prospectively studied in 182 patients with aSAH. The database was retrospectively analyzed with respect to ICP. Patients were classified into 2 groups based on ICP. There were 164 with low ICP (<20 mm Hg) and 18 with high ICP (>or=20 mm Hg, measured>6 hours/day). Cerebral microdialysis parameters of energy metabolism, glycerol, and glutamate levels were analyzed hourly from the brain parenchyma of interest for 7 days. The 12-month outcome in these patients was evaluated.
Results: In the high ICP group, extended ICP therapy including decompressive craniectomy was necessary in 7 patients (39%). Cerebral glycerol levels and the lactate/pyruvate ratio were pathologically increased on Days 1-7 after aSAH (p<0.001). The excitotoxic neurotransmitter glutamate and glycerol, a marker of membrane degradation, further increased on Days 5-7, probably reflecting the development of secondary brain damage. An ICP>or=20 mm Hg was shown to have a significant influence on the 12-month Glasgow Outcome Scale (GOS) score (p=0.001) and was a strong predictor of mortality (OR=24.6; p<0.001). Glutamate (p=0.012), the lactate/pyruvate ratio as a marker of anaerobic metabolism (p=0.028), age (p<0.001), and Fisher grade (p=0.001) also influenced the GOS score at 12 months.
Conclusions: The authors confirmed the relevance of intracranial hypertension as a severe complication in patients with aSAH. Because high ICP is associated with a severely deranged cerebral metabolism and poor outcome, future studies focusing on metabolism-guided, optimized ICP therapy could help minimize secondary brain damage and improve prognosis in patients with aSAH.