title: Caffeine reduces cerebral blood flow in patients recovering from an ischaemic stroke.
abstract: BACKGROUND
  Caffeine is present in a variety of beverages and food and is widely consumed. In a previous study of patients recovering from an acute ischaemic stroke using transcranial Doppler ultrasound we demonstrated a fall in middle cerebral artery blood velocity of 12% following ingestion of 250 mg caffeine. The aim of this study was to investigate if this velocity change reflected a change in cerebral blood flow.
  
  
  METHODS
  The study used a randomised, double blind, cross-over design. Nineteen patients recovering from an acute ischaemic stroke in the middle cerebral artery territory and 10 controls attended two sessions, having abstained from caffeine for 48 hours previously. At each session cerebral blood flow was measured four times using xenon clearance, twice before the oral administration of 250 mg caffeine or matched placebo, and twice after. Similarly, three middle cerebral artery blood velocity readings using transcranial Doppler were made prior to administration and four after.
  
  
  RESULTS
  The caffeine resulted in a significant fall in cerebral blood flow and middle cerebral artery blood velocity compared to placebo.
  
  
  CONCLUSIONS
  Since caffeine is present in the diet of most patients recovering from an acute ischaemic stroke this effect may have adverse clinical consequences.
authors.affiliation: Poole Hospital NHS Trust, Elderly Medicine, Poole, Dorset, UK. Suzanne.Ragab@poole.nhs.uk
authors.forename: Suzanne
authors.initials: S
authors.lastname: Ragab
authors.forename: Michael
authors.initials: M
authors.lastname: Lunt
authors.forename: Anthony
authors.initials: A
authors.lastname: Birch
authors.forename: Peter
authors.initials: P
authors.lastname: Thomas
authors.forename: Damian F
authors.initials: DF
authors.lastname: Jenkinson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000187:drug effects; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery; D011877:Radionuclide Imaging; D020521:Stroke / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial; D014980:Xenon Radioisotopes
chemical_list: D000697:Central Nervous System Stimulants; D014980:Xenon Radioisotopes; D002110:Caffeine