title: Neurosurgical operations with the patient in sitting position: analysis of risk factors using transcranial Doppler sonography.
abstract: BACKGROUND
  One major risk factor of the sitting position for neurosurgery is air embolism, especially in patients with persistent foramen ovale (PFO). The first aim of this prospective study was to evaluate a bedside method for detecting PFO using transcranial Doppler sonography (TCD) with contrast medium. A second aim was to address intraoperative monitoring, patient positioning and the occurrence and clinical relevance of air embolism.
  
  
  METHODS
  Ninety patients with a mean age of 56.5 yr (range 14-81 yr) undergoing surgery in sitting position were investigated by TCD with contrast agent to detect functional PFO, that is PFO that can be provoked with a Valsalva manoeuvre. In patients in whom TCD was not possible, transcranial duplex sonography, duplex sonography of the carotid artery at the neck or transoesophageal ECG was performed.
  
  
  RESULTS
  In 26 patients PFO was detected. Thirteen of them presented a persistent PFO with high-intensity transient signal in both middle cerebral arteries without Valsalva manoeuvre. The intraoperative positioning in these patients was adapted to the risk for a paradoxical air embolism, although, after surgical recommendations, three patients with a persistent PFO underwent surgery in sitting position. Intraoperative air embolisms were seen in 8 of 80 patients in sitting or semi-sitting position with air aspirable through the central venous catheter.
  
  
  CONCLUSIONS
  To address the risk of a paradoxical air embolism, especially in patients undergoing surgery in sitting position, preoperative detection of PFO is advisable. If surgery is performed in seated PFO patients, additional monitoring and special care are warranted.
authors.affiliation: Department of Neurosurgery, Intensive Care Medicine and Pain Therapy, Ruhr-University Bochum, Knappschaftskrankenhaus Bochum, In der Schornau 23-25, 44892 Bochum, Germany. martin.engelhardt@ruhr-uni-bochum.de
authors.forename: M
authors.initials: M
authors.lastname: Engelhardt
authors.forename: W
authors.initials: W
authors.lastname: Folkers
authors.forename: C
authors.initials: C
authors.lastname: Brenke
authors.forename: M
authors.initials: M
authors.lastname: Scholz
authors.forename: A
authors.initials: A
authors.lastname: Harders
authors.forename: H
authors.initials: H
authors.lastname: Fidorra
authors.forename: K
authors.initials: K
authors.lastname: Schmieder
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000601:surgery*; D017548:Echocardiography, Transesophageal; D019320:Embolism, Paradoxical / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D007431:Intraoperative Complications / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D019095:Point-of-Care Systems; D011187:Posture; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies; D012307:Risk Factors; D017585:Ultrasonography, Doppler, Transcranial