title: Neurosurgical procedures in the semisitting position: evaluation of the risk of paradoxical venous air embolism in patients with a patent foramen ovale.
abstract: OBJECTIVE
  To analyze the actual risk for patients with a patent foramen ovale (PFO) to experience a clinically relevant venous air embolism (VAE) during surgery performed in the semisitting position.
  
  
  METHODS
  All procedures were performed between January 2008 and December 2009, under general anesthesia and in the semisitting position. Transesophageal echocardiography (TEE) and capnometry were used intraoperatively to monitor for air bubbles in the venous system.
  
  
  RESULTS
  Of 200 consecutive patients who all were operated on in the semisitting position, 52 patients (26%) had a diagnosis of PFO. Rates of VAE in patients were graded as follows: grade 0 (no air bubbles visible, no air embolism), 23 patients (44.2%); grade I (air bubbles on TEE), 22 patients (42.3%); grade II (air bubbles on TEE with decrease of end-tidal carbon dioxide [ETCO2] ≤ 3 mm Hg), 2 patients (3.8%); grade III, air bubbles on TEE with decrease of ETCO2 >3 mm Hg, 4 patients (7.7%); grade IV, air bubbles on TEE with decrease of ETCO2 >3 mm Hg and decrease of mean arterial pressure ≥ 20% or increase of heart rate ≥ 40% (or both), 1 patient (1.9%); and grade V, VAE causing arrhythmia with hemodynamic instability requiring cardiopulmonary resuscitation, 0 patients (0%). There were no deaths in this series, and no new or unexplained, mild or severe neurologic deficits were caused by a VAE.
  
  
  CONCLUSIONS
  Under standardized anesthesia and neurosurgical protocols, patients with a PFO can be operated on safely in the semisitting position.
authors.affiliation: Department of Neurosurgery, University of Tübingen Medical Center, Tübingen, Germany. Electronic address: guenther.feigl@web.de.
authors.forename: Guenther C
authors.initials: GC
authors.lastname: Feigl
authors.affiliation: Department of Anesthesiology, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Decker
authors.affiliation: Department of Neurosurgery, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Wurms
authors.affiliation: Department of Neurosurgery, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Krischek
authors.affiliation: Department of Neurosurgery, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Ritz
authors.affiliation: Department of Anesthesiology, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Unertl
authors.affiliation: Department of Neurosurgery, University of Tübingen Medical Center, Tübingen, Germany.
authors.forename: Marcos
authors.initials: M
authors.lastname: Tatagiba
mesh_terms: D000328:Adult; D000368:Aged; D000758:Anesthesia; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000503:physiopathology; D062186:Arterial Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D017548:Echocardiography, Transesophageal; D004618:Embolism, Air / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D054092:Foramen Ovale, Patent / Q000150:complications*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D020766:Intracranial Embolism / Q000453:epidemiology* / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D019635:Neurosurgical Procedures / Q000379:methods*; D056888:Patient Positioning / Q000379:methods*; D018579:Patient Selection; D011446:Prospective Studies; D012306:Risk; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Craniotomy; Patent foramen ovale; Semisitting position; Venous air embolism