title: External carotid artery flow maintains near infrared spectroscopy-determined frontal lobe oxygenation during ephedrine administration.
abstract: BACKGROUND
  Phenylephrine and ephedrine affect frontal lobe oxygenation ([Formula: see text]) differently when assessed by spatially resolved near infrared spectroscopy. We evaluated the effect of phenylephrine and ephedrine on extra- vs intra-cerebral blood flow and on [Formula: see text].
  
  
  METHODS
  In 10 healthy males (age 20-54 yr), phenylephrine or ephedrine was infused for an ∼20 mm Hg increase in mean arterial pressure. Cerebral oxygenation (SavO₂) was calculated from the arterial and jugular bulb oxygen saturations. Blood flow in the internal carotid artery (ICAf) and blood flow in the external carotid artery (ECAf) were assessed by duplex ultrasonography. Invos-5100c (SinvosO₂) and Foresight (SforeO₂) determined [Formula: see text] while forehead skin oxygenation (SskinO₂) was assessed.
  
  
  RESULTS
  Phenylephrine reduced SforeO₂ by 6.9% (95% confidence interval: 4.8-9.0%; P<0.0001), SinvosO₂ by 10.5 (8.2-12.9%; P<0.0001), and ECAf (6-28%; P=0.0001), but increased ICAf (5-21%; P=0.003) albeit with no consequence for SskinO₂ or SavO₂. In contrast, SforeO₂ was maintained with administration of ephedrine while SinvosO₂ and SavO₂ decreased [by 3.1 (0.7-4.5%; P=0.017) and 2.1 (0.5-3.3%; P=0.012)] as arterial carbon dioxide pressure decreased (P=0.003). ICAf was stable and ECAf increased by 11 (4-18%; P=0.005) with administration of ephedrine while SskinO₂ did not change.
  
  
  CONCLUSIONS
  The effect of phenylephrine on ScO₂ is governed by a decrease in external carotid blood flow since it increases cerebral blood flow as determined by flow in the internal carotid artery. In contrast, ScO₂ is largely maintained with administration of ephedrine because blood flow to extracerebral tissue increases.
authors: Department of Anaesthesiology, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark hs770@hotmail.com.
authors: H
authors: H
authors: Sørensen
authors: Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
authors: P
authors: P
authors: Rasmussen
authors: Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan.
authors: K
authors: K
authors: Sato
authors: Department of Anaesthesiology, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: S
authors: S
authors: Persson
authors: Department of Anaesthesiology, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: N D
authors: ND
authors: Olesen
authors: Department of Anaesthesiology, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: H B
authors: HB
authors: Nielsen
authors: Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark Department of Neuroanaesthesia, The Neuroscience Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: N V
authors: NV
authors: Olsen
authors: Department of Biomedical Engineering, Toyo University, Tokyo, Japan.
authors: S
authors: S
authors: Ogoh
authors: Department of Anaesthesiology, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: N H
authors: NH
authors: Secher
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology; D000328:Adult; D002342:Carotid Artery, External / Q000187:drug effects* / Q000378:metabolism*; D004809:Ephedrine / Q000494:pharmacology*; D005625:Frontal Lobe / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D012016:Reference Values; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D055815:Young Adult
chemical_list: D018663:Adrenergic Agents; D004809:Ephedrine; D010100:Oxygen
keywords: cerebral blood flow; cerebral oxygenation; ephedrine; phenylephrine; skin blood flow