title: Blood flow velocity in the middle cerebral artery during transnasal endoscopic skull base surgery performed in controlled hypotension.
abstract: OBJECTIVE
  To assess blood flow velocity in the middle cerebral artery (MCA) during transnasal endoscopic procedures performed with decreased hemodynamic parameters.
  
  
  METHODS
  In 40 patients who underwent endoscopic skull base surgery in controlled hypotension (studied group) and in 13 patients operated without reduction of hemodynamic parameters (control group), blood flow velocity in MCA was assessed with transcranial color Doppler sonography.
  
  
  RESULTS
  Blood flow velocity in MCA remained within the range of age-specific reference values in all patients before operation. It decreased significantly in both groups after induction of anesthesia and then dropped even further in studied group of patients when hemodynamic parameters were reduced; the systolic velocity fell below the normal reference values in 25% of patients, the mean velocity in 50% and the diastolic velocity in 57% of patients. The diastolic velocity was much more heavily influenced by diminished hemodynamic parameters than systolic velocity in the studied group as opposed to the control group where reduction of blood flow velocity pertained equally systolic and diastolic velocity.
  
  
  CONCLUSIONS
  During transnasal endoscopic procedures performed in moderate hypotension, in addition to significant drop of blood flow velocity to values well below the normal reference range, a divergent reduction of systolic and diastolic velocity was detected. Since divergent systolic and diastolic velocity may indicate an early phase of cerebral autoregulation compromise, and the decrease of mean blood flow velocity in MCA corresponds with a decrease of cerebral blood flow, further investigations in this field seem warranted.
authors: Department of Otolaryngology, Medical University of Bialystok, Poland. Electronic address: sieska@interia.pl.
authors: Andrzej
authors: A
authors: Sieskiewicz
authors: Department of Neurosurgery, Medical University of Bialystok, Poland.
authors: Tomasz
authors: T
authors: Lyson
authors: Department of Anaestesiology, Medical University of Bialystok, Poland.
authors: Andrzej
authors: A
authors: Drozdowski
authors: Department of Otolaryngology, Medical University of Bialystok, Poland.
authors: Bartosz
authors: B
authors: Piszczatowski
authors: Department of Neurosurgery, Medical University of Bialystok, Poland.
authors: Robert
authors: R
authors: Rutkowski
authors: Department of Neurosurgery, Medical University of Bialystok, Poland.
authors: Grzegorz
authors: G
authors: Turek
authors: Department of Cardiosurgery, Medical University of Bialystok, Poland.
authors: Anna
authors: A
authors: Lewczuk
authors: Department of Otolaryngology, Medical University of Bialystok, Poland.
authors: Marek
authors: M
authors: Rogowski
authors: Department of Neurosurgery, Medical University of Bialystok, Poland.
authors: Zenon
authors: Z
authors: Mariak
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D016894:Endarterectomy, Carotid; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007023:Hypotension, Controlled / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000503:physiopathology*; D018709:Statistics, Nonparametric; D013997:Time Factors; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: Cerebral blood flow; Endoscopic surgery; Hypotension; Middle cerebral artery; Transcranial Doppler sonography