http://bja.oxfordjournals.org/content/102/6/800
Abstract
Background Vasopressor
agents are commonly used to increase mean arterial pressure (MAP) in
order to secure a pressure gradient to perfuse
vital organs. The influence of norepinephrine on
cerebral oxygenation is not clear. The aim of this study was to evaluate
the impact of the infusion of norepinephrine on
cerebral oxygenation in healthy subjects.
Methods Three doses of norepinephrine (0.05, 0.1, and 0.15 µg kg−1 min−1 for 20 min each) were infused in nine healthy subjects [six males; 26 (6) yr, mean (sd)]. MAP, cerebral oxygenation characterized by frontal lobe oxygenation (Sco2) and internal jugular venous oxygen saturation (Sjvo2), middle cerebral artery mean flow velocity (MCA Vmean), cardiac output (CO), and arterial partial pressure for carbon dioxide
(Paco2) were evaluated.
Results MAP increased from 88 (79–101) [median (range)] to 115 (98–128) mm Hg with increasing doses of norepinephrine (P < 0.05), reflecting an increase in total peripheral resistance [20.3 (12.2–25.8) to 25.2 (16.4–28.5) mm Hg min litre−1; P < 0.05] since CO remained at baseline values. Sco2 and Sjvo2 decreased with increasing doses of norepinephrine, reaching statistical significance with norepinephrine infused at 0.1 µg
kg−1 min−1 [Sco2: 78 (75–94) to 69 (61–83)%; P < 0.05; Sjvo2: 67 (8) to 64 (7)%; P < 0.01]. MCA Vmean was reduced with each dose of norepinephrine [56.9 (11.2) to 55.0 (11.7) cm s−1; P < 0.05] and Paco2 lowered from 5.4 (0.4) to 5.1 (0.4) kPa (P < 0.001).
Conclusions This study suggests that infusion of norepinephrine at 0.1 µg kg−1 min−1 or higher may negatively affect cerebral oxygenation.
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