title: The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects.
abstract: OBJECTIVE
  Sympathetic regulation of the cerebral circulation remains controversial. Although intravenous phenylephrine (PE) infusion reduces the near-infrared spectroscopy (NIRS)-determined measure of frontal lobe oxygenation (S(c) O(2) ) and increases middle cerebral artery mean blood velocity (MCA V(mean) ), suggesting α-adrenergic-mediated cerebral vasoconstriction, this remains unconfirmed by evaluation of arterial and venous cerebral blood flow.
  
  
  METHODS
  We determined S(c) O(2) , MCA V(mean) , and right internal carotid artery (ICA) and internal jugular venous (IJV) blood flow (duplex ultrasound) during infusion of PE in eight supine young healthy men [26 (3) years, 177 (7) cm and 74 (8) kg; mean (SD)].
  
  
  RESULTS
  Compared with saline, during infusion of PE, mean arterial pressure increased 26 ± 3% (mean ± SE) and MCA V(mean) by 4·8 ± 1·9% (P<0·05), while S(c) O(2) decreased by 13·7 ± 3·7% (P<0·05) with no significant changes in the arterial oxygen or carbon dioxide tensions. ICA blood flow did not change significantly in response to PE administration (351 ± 12 versus 373 ± 21 ml min(-1) ; P = 0·236), while IJV blood flow increased (443 ± 57 versus 507 ± 58 ml min(-1) ; P = 0·023).
  
  
  CONCLUSIONS
  These findings confirm that PE induces a reduction in S(c) O(2) measured by NIRS and causes an increase in MCA V(mean) indicative of cerebral arterial vasoconstriction, although ICA was preserved and IJV increased. These results suggest that a decrease in S(c) O(2) during infusion of PE reflects an altered cerebral contribution of arterial versus venous blood to the NIRS signal, although we cannot rule out that an effect of PE on skin blood flow is important.
authors: Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan. ogoh@toyo.jp
authors: Shigehiko
authors: S
authors: Ogoh
authors: Kohei
authors: K
authors: Sato
authors: James P
authors: JP
authors: Fisher
authors: Thomas
authors: T
authors: Seifert
authors: Morten
authors: M
authors: Overgaard
authors: Niels H
authors: NH
authors: Secher
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists / Q000008:administration & dosage*; D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D003718:Denmark; D006801:Humans; D007262:Infusions, Intravenous; D007601:Jugular Veins / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology; D008297:Male; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects; D010656:Phenylephrine / Q000008:administration & dosage*; D012039:Regional Blood Flow / Q000187:drug effects; D019265:Spectroscopy, Near-Infrared; D018615:Ultrasonography, Doppler, Color; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D010100:Oxygen