Inappropriate sudden blood pressure (BP) reductions may adversely affect cerebral perfusion. This study explores the effect of nicardipine on regional brain tissue O(2) (PbtO(2)) during treatment of acute hypertensive emergencies. A prospective case-control study was performed in 30 patients with neurological conditions and clinically elevated BP. All patients had a parenchymal PbtO(2) and intracranial pressure bolt inserted following resuscitation. Using a critical care guide, PbtO(2) was optimized. Intravenous nicardipine (5-15 mg/hour) was titrated to systolic BP < 160 mm Hg, diastolic BP < 90 mm Hg, mean arterial BP (MABP) 90-110 mm Hg, and PbtO(2) > 20 mm Hg. Physiological parameters-intracranial pressure, PbtO(2), central venous pressure, systolic BP, diastolic BP, MABP, fraction of inspired O(2), and cerebral perfusion pressure (CPP)-were compared before infusion, at 4 hours, and at 8 hours using a t-test. Sixty episodes of hypertension were reported in 30 patients (traumatic brain injury in 13 patients; aneurysmal subarachnoid hemorrhage in 11; intracerebral and intraventricular hemorrhage in 3 and 1, respectively; arteriovenous malformation in 1; and hypoxic brain injury in 1). Nicardipine was effective in 87% of the patients (with intravenous beta blockers in 4 patients), with a 19.7% reduction in mean 4-hour MABP (115.3 +/- 13.1 mm Hg preinfusion vs 92.9 +/- 11.40 mm Hg after 4 hours of therapy, p < 0.001). No deleterious effect on mean PbtO(2) was recorded (26.74 +/- 15.42 mm Hg preinfusion vs 27.68 +/- 12.51 mm Hg after 4 hours of therapy, p = 0.883) despite significant reduction in CPP. Less dependence on normobaric hyperoxia was achieved at 8 hours (0.72 +/- 0.289 mm Hg preinfusion vs 0.626 +/- 0.286 mm Hg after 8 hours of therapy, p < 0.01). Subgroup analysis revealed that 12 patients had low pretreatment PbtO(2) (10.30 +/- 6.49 mm Hg), with higher CPP (p < 0.001) requiring hyperoxia (p = 0.02). In this group, intravenous nicardipine resulted in an 83% improvement in 4- and 8-hour PbtO(2) levels (18.1 +/- 11.33 and 19.59 +/- 23.68 mm Hg, respectively; p < 0.01) despite significant reductions in both mean MABP (120.6 +/- 16.65 vs 95.8 +/- 8.3 mm Hg, p < 0.001) and CPP (105.00 +/- 20.7 vs 81.2 +/- 15.4 mm Hg, p < 0.001). Intravenous nicardipine is effective for the treatment of hypertensive neurological emergencies and has no adverse effect on PbtO(2).