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Differential effects of in vitro norepinephrine on platelets isolated from severely traumatic brain injured patients
Critical Care volume 11, Article number: P361 (2007)
Norepinephrine used in clinical routine to increase cerebral perfusion following severe traumatic brain injury (TBI) may activate α2-adrenergic receptors on platelets, thereby possibly promoting formation of microthrombosis and inducing additional brain injury.
Arterial and jugular venous platelets isolated from norepinephrine-receiving TBI patients (n = 11) and healthy volunteers (n = 36) (cubital vein) were stimulated in vitro with increasing norepinephrine concentrations (10 nM to 100 μM); thrombin receptor activator peptide (TRAP) served as positive control. P-selectin expression was determined by flow cytometry (FACS).
Following TBI, the number of unstimulated P-selectin-positive platelets was significantly decreased in the second week by 60%. During the first week, the in vitro stimulatory effect was significantly reduced; in the second week, however, norepinephrine-mediated effects exceeded changes in controls and the first week without a difference between arterial and jugular venous platelets (Figure 1).
Clinically relevant norepinephrine concentrations are <25 nM. The present in vitro effects occurred at concentrations >500 nM. Thus, a clinically relevant impact appears doubtful.
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Stover, J., Tschuor, C., Asmis, L. et al. Differential effects of in vitro norepinephrine on platelets isolated from severely traumatic brain injured patients. Crit Care 11, P361 (2007). https://0-doi-org.brum.beds.ac.uk/10.1186/cc5521
- Healthy Volunteer
- Traumatic Brain Injury
- Cerebral Perfusion