title: The hemodynamic response of the cerebral bridging veins to changes in ICP.
abstract: BACKGROUND
  To investigate the hemodynamic response of the cerebral bridging veins to increased intracranial pressure (ICP) during normo- and hyperventilation.
  
  
  METHODS
  Flow velocity (FV(m)), diameter (D), and pulsatility index (PI) were measured and calculated in the cerebral bridging veins using Color Doppler Ultrasound in seven pigs, and cerebral blood flow (CBF) was measured using (133)Xe clearance in nine pigs, both during normo- and hyperventilation. ICP was increased stepwise from baseline (about 10 mmHg) to 20 and 30 mmHg by infusion of mock CSF into the cisterna magna.
  
  
  RESULTS
  Moderate elevations of ICP caused venous relative stasis as evidenced by a decrease in FV(m) and increase in diameter and PI, but no change of volume flow in the veins. CBF was stable indicating autoregulation at ICP of 20 and 30 mmHg. Parallel observations were made during normo- and hyperventilation, but at two different levels of CBF.
  
  
  CONCLUSIONS
  The cerebral bridging veins dilation and blood flow velocity decrease indicate the venous relative stasis in response to the elevated ICP. This response is proposed to be caused by an ICP-dependent increase in resistance to the outflow from the cerebral bridging veins.
authors.affiliation: The Department of Neurosurgery, The China-Japan Friendship Hospital, East Yinghua Road, He Pingli, Chao Yang District, 100029, Beijing, People's Republic of China.
authors.forename: Yanbing
authors.initials: Y
authors.lastname: Yu
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Si
authors.forename: Guangyu
authors.initials: G
authors.lastname: Zhao
authors.forename: Shangchen
authors.initials: S
authors.lastname: Xu
authors.forename: Guangbin
authors.initials: G
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Ding
authors.forename: Liming
authors.initials: L
authors.lastname: Luan
authors.forename: Lebin
authors.initials: L
authors.lastname: Wu
authors.forename: Qi
authors.initials: Q
authors.lastname: Pang
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D002550:Cerebral Veins / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology; D006985:Hyperventilation / Q000503:physiopathology; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D011673:Pulsatile Flow / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D013552:Swine; D018615:Ultrasonography, Doppler, Color; D014664:Vasodilation / Q000502:physiology; D014689:Venous Insufficiency / Q000503:physiopathology