title: The relationship between hypotension, cerebral flow, and the surgical field during endoscopic sinus surgery.
abstract: OBJECTIVE
  Hypotensive anesthesia is often used in endoscopic sinus surgery (ESS) to improve surgical visibility; however, its safety and efficacy in this role are yet to be justified. This study aimed to evaluate the effect of hypotensive anesthesia on both real-time middle cerebral artery blood flow velocity (Vmca) and the severity of surgical bleeding in patients undergoing ESS.
  
  
  METHODS
  Prospective, observational cohort study.
  
  
  METHODS
  Thirty-two patients undergoing hypotensive anesthesia for ESS at a single tertiary institution during February 2011 to July 2012 were recruited for the study. Transcranial Doppler ultrasonography measured periodic Vmca, which were time-matched for hemodynamic and respiratory factors. One-minute video segments corresponding with each Vmca reading were randomized and distributed to two blinded observers for bleeding assessment.
  
  
  RESULTS
  Three hundred and fifty-six data time points were recorded for systolic, diastolic, and mean arterial blood pressure (MAP), pulse rate, respiratory rate, end-tidal carbon dioxide concentration, Vmca, and bleeding assessment score (BAS). A direct relationship exists between MAP and Vmca (r = 0.77, P < .0001) as well as MAP and BAS (r = 0.36, P < .0001). MAP levels above 60 mm Hg maintained at least 50% of baseline Vmca flow in almost 90% of all time points.
  
  
  CONCLUSIONS
  Hypotensive anesthesia is an effective method of controlling intraoperative bleeding during endoscopic sinus surgery; however the effect is clinically small in low MAP ranges. In otherwise healthy patients undergoing ESS with general anesthesia, reducing MAP to below 60 mm Hg may increase the risk of cerebral ischemia.
authors.affiliation: Department of Surgery-Otolaryngology Head and Neck Surgery, The University of Adelaide, Adelaide, Australia.
authors.forename: Thanh Ngoc
authors.initials: TN
authors.lastname: Ha
authors.forename: Robert Graham
authors.initials: RG
authors.lastname: van Renen
authors.forename: Guy L
authors.initials: GL
authors.lastname: Ludbrook
authors.forename: Rowan
authors.initials: R
authors.lastname: Valentine
authors.forename: Judy
authors.initials: J
authors.lastname: Ou
authors.forename: Peter-John
authors.initials: PJ
authors.lastname: Wormald
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004724:Endoscopy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007022:Hypotension / Q000503:physiopathology*; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010254:Paranasal Sinus Diseases / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D015203:Reproducibility of Results; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: Endoscopic sinus surgery; bleeding score; hypotensive anesthesia; intraoperative bleeding; middle cerebral artery blood flow velocity; transcranial Doppler ultrasonography