title: Ocular perfusion pressure during pars plana vitrectomy: a pilot study.
abstract: OBJECTIVE
  Unexplained visual field loss after pars plana vitrectomy (PPV) has been reported in up to 14% of all uncomplicated cases with signs varying from visual field defect and disc pallor, to optic atrophy, loss of vision, and phthisis bulbi. Among the postulated pathogenic mechanism is ocular hypoperfusion due to insufficient blood pressure (NBP) and/or elevated IOP, or to their mismatch. The purpose of this study is to assess if, to what extent, and for how long the intraoperative simultaneous variation of IOP and NBP causes mean ocular perfusion pressure (MOPP) to drop below values considered safe, during PPV.
  
  
  METHODS
  An IOP sensor placed in the infusion cannula recorded 6 readings per second, while arm systolic and diastolic NBP were taken every 5 minutes throughout surgery and deemed stable in between readings. Supine MOPP was calculated as (115/130) mean arterial pressure--IOP. Surgical monitor video overlay displayed all data in real time and saved them for analysis.
  
  
  RESULTS
  Average IOP significantly increased during surgery, while NBP decreased, compared to baseline. As a result, intraoperative MOPP decreased an average 37.1% compared to baseline (range, 13.8%-58.6%; P < 0.05). Of 18 patients, 16 (88.8%) had a significant intraoperative MOPP decrease; 15/18 (83.3%) spent more than 20%, and 5/18 (27.7%) more than 50% of the entire surgery below 30 mm Hg MOPP. Surgical maneuvers, such as phacoemulsification, silicone oil removal, and fluid injection, were associated with significant MOPP decrease, while peeling and vitrectomy were not.
  
  
  CONCLUSIONS
  The MOPP may decrease significantly in course of PPV, acutely and for longer time. Surgical maneuvers, including silicone oil removal and combined phacoemulsification, pose a higher risk for MOPP reduction. Discretion should be exercised while administering deep sedation, since it may further lower MOPP through undue blood pressure reduction.
authors.affiliation: Eye Hospital of Rome, Rome, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Rossi
authors.affiliation: University of Cagliari, DICAAR, Cagliari, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Querzoli
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Giampiero
authors.initials: G
authors.lastname: Angelini
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Malvasi
authors.affiliation: Eye Hospital of Rome, Rome, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Iossa
authors.affiliation: Fondazione G.B. Bietti IRCCS, Rome, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Ripandelli
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology*; D005128:Eye Diseases / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology; D010477:Perfusion; D059035:Perioperative Period; D010865:Pilot Projects; D016683:Supine Position; D014821:Vitrectomy / Q000379:methods
keywords: intraocular pressure; mean arterial pressure; mean ocular perfusion pressure; pars plana vitrectomy