Effect of early and late intravenous norepinephrine infusion on cerebral perfusion, microcirculation, brain tissue oxygenation, and edema formation in brain injured rats - Kroppenstedt, SN; Thomale, UW; Griebenow, M; Sakowitz, OW; Schaser, KD; Mayr, PS; Unterberg AW Stover, JF (Crit Care Med, 2003)