title: Venous air embolism in sitting and supine patients undergoing vestibular schwannoma resection.
abstract: OBJECTIVE
  This study retrospectively compares the incidence of venous air embolism (VAE) detection and morbidity in the sitting and supine positions. All patients underwent vestibular schwannoma resection via the retrosigmoid approach by a single surgical team.
  
  
  METHODS
  A total of 432 consecutive operations were reviewed, 222 of which were performed with the patients in the sitting position and 210 of which were performed with the patients in the supine position. Charts were reviewed for evidence of intraoperative VAE, intraoperative hypotension secondary to VAE, postoperative morbidity related to VAE, and other variables to compare the groups.
  
  
  RESULTS
  This study demonstrated a 28% incidence of VAE detection when patients were in the sitting position compared to a 5% incidence of VAE detection when patients were in the supine position (P < 0.0001). Intraoperative hypotension secondary to VAE was noted in 1.8% of the sitting patients and 1.4% of the supine patients (P=0.72, no significant difference). Postoperative morbidity caused by VAE was noted in one sitting patient (0.5%) (pulmonary edema) and in no supine patients (P=0.48, no significant difference). Blood loss was slightly greater in the supine group, and operative times were similar in both groups, despite that the average tumor size of patients operated on in the sitting position was 2.8 cm versus 2.2 cm in the supine group (P < 0.0001).
  
  
  CONCLUSIONS
  Our results indicate that although there is a higher incidence of VAE detection in sitting patients, the morbidity is not statistically greater. We conclude that because morbidity from VAE is similar in either position, patient positioning should be based on surgical team preference.
authors.affiliation: Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Duke
authors.forename: J J
authors.initials: JJ
authors.lastname: Lynch
authors.forename: S G
authors.initials: SG
authors.lastname: Harner
authors.forename: R J
authors.initials: RJ
authors.lastname: Faust
authors.forename: M J
authors.initials: MJ
authors.lastname: Ebersold
mesh_terms: D002550:Cerebral Veins; D004428:Ear Neoplasms / Q000601:surgery*; D004618:Embolism, Air / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007431:Intraoperative Complications; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000601:surgery*; D011187:Posture; D012189:Retrospective Studies; D016683:Supine Position; D015837:Vestibular Diseases / Q000601:surgery*