title: Lack of effect of CO2 on cerebral arterial diameter in man.
abstract: OBJECTIVE
  To establish the quantitative effects on the diameter of cerebral arteries following controlled changes in arterial carbon dioxide tension (PaCO2).
  
  
  METHODS
  Nonrandomized interventional study.
  
  
  METHODS
  Angiography suite of a tertiary referral hospital.
  
  
  METHODS
  12 anesthetized patients suffering from a cerebral arteriovenous malformation undergoing endovascular treatment.
  
  
  METHODS
  Induced hypocapnia by hyperventilation and induced graded hypercapnia by the administration of carbon dioxide to the anesthetized patient's breathing circuit.
  
  
  RESULTS
  A digital angiography computer was used to make computerized measurements and calculations of the diameter of deep and small cortical arteries outside the vascular territory of cerebral arteriovenous malformations following controlled and standardized changes in PaCO2. Cardiovascular parameters were simultaneously measured and cardiac output (CO) calculated. No statistically significant changes in the diameter of cerebral arteries down to a size of 0.57 mm, which was the smallest artery studied, could be observed following changes in PaCO2 in the range between 28 +/- 4 mmHg and 74 +/- 4 mmHg. However, there was a 64% change in cardiac index following the above change in PaCO2.
  
  
  CONCLUSIONS
  Deep cortical cerebral arteries down to a diameter of 0.57 mm seem to act merely as conductance vessels. The observed dramatic increase in CO following an increase in PaCO2 may offer an explanation for the changes in cerebral blood flow and cerebral flow velocity recorded by others and usually attributed to cerebral vasodilatation, which we were unable to demonstrate in this study.
authors.affiliation: Department of Anesthesia, Armed Forces Hospital, Riyadh, Saudi Arabia.
authors.forename: H G
authors.initials: HG
authors.lastname: Djurberg
authors.forename: R F
authors.initials: RF
authors.lastname: Seed
authors.forename: D A
authors.initials: DA
authors.lastname: Evans
authors.forename: F A
authors.initials: FA
authors.lastname: Brohi
authors.forename: D L
authors.initials: DL
authors.lastname: Pyper
authors.forename: G T
authors.initials: GT
authors.lastname: Tjan
authors.forename: K R
authors.initials: KR
authors.lastname: al Moutaery
mesh_terms: D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000097:blood*; D002302:Cardiac Output / Q000502:physiology; D002533:Cerebral Angiography; D002536:Cerebral Arteries / Q000473:pathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D002648:Child; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000097:blood; D016857:Hypocapnia / Q000097:blood; D007091:Image Processing, Computer-Assisted; D002538:Intracranial Arteriovenous Malformations / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011856:Radiographic Image Enhancement; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen