title: Transcranial Doppler ultrasonography as a screening technique for detection of a patent foramen ovale before surgery in the sitting position.
abstract: BACKGROUND
  Venous air embolism has been reported to occur in 23-45% of patients undergoing neurosurgical procedures in the sitting position. If venous air embolism occurs, a patent foramen ovale (PFO) is a risk factor for paradoxical air embolism and its sequelae. Preoperative screening for a PFO is therefore recommended by some investigators. The reference standard for identifying a PFO is contrast-enhanced transesophageal echocardiography (c-TEE). Contrast-enhanced transcranial Doppler ultrasonography (c-TCD) and contrast-enhanced transthoracic echocardiography (c-TTE) are noninvasive alternative methods, but so far there are no studies as to their diagnostic validity in neurosurgical patients.
  
  
  METHODS
  The sensitivity and specificity of c-TCD and c-TTE in detecting a PFO were determined in a prospective study using c-TEE as the reference standard. Preoperative c-TCD, c-TTE, and c-TEE studies were performed during the Valsalva maneuver after intravenous echo-contrast medium (D-Galactose, Echovist-300, Schering AG, Berlin, Germany) was administered in 92 consecutive candidates (47 men and 45 women; mean age, 51 yr; range, 25-72 yr) before neurosurgical procedures in the sitting position.
  
  
  RESULTS
  A PFO was detected in 24 of the 92 patients (26.0%) using c-TEE. c-TCD correctly identified 22 patients, whereas c-TTE only correctly identified 10. This corresponds to a sensitivity of 0.92 for c-TCD and 0.42 for c-TTE. The negative predictive value was 0.97 for c-TCD compared with 0.83 for c-TTE. The prevalence of a PFO in patients with a posterior fossa lesion was 27%, and in the group with cervical disc herniation was 24% as detected by c-TEE. The incidence of intraoperative venous air embolism was 35% in cases of cervical foraminotomy and 75% in posterior fossa surgery as detected by c-TEE.
  
  
  CONCLUSIONS
  c-TCD is a highly sensitive and highly specific method for detecting a PFO. Because c-TCD is noninvasive, it may be more suitable than c-TEE for routine preoperative screening for a PFO. C-TTE is not reliable in detecting a PFO.
authors.affiliation: Departments of Neurosurgery, Anesthesiology and Critical Care Medicine, and Cardiology and Pulmonology, Benjamin Franklin Medical Center, Freie Universität Berlin, Berlin, Germany. stendel@medizin.fuberlin.de
authors.forename: R
authors.initials: R
authors.lastname: Stendel
authors.forename: H J
authors.initials: HJ
authors.lastname: Gramm
authors.forename: K
authors.initials: K
authors.lastname: Schröder
authors.forename: C
authors.initials: C
authors.lastname: Lober
authors.forename: M
authors.initials: M
authors.lastname: Brock
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media / Q000627:therapeutic use; D017548:Echocardiography, Transesophageal / Q000379:methods; D004618:Embolism, Air / Q000209:etiology; D019320:Embolism, Paradoxical / Q000209:etiology; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D011187:Posture / Q000502:physiology; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
chemical_list: D003287:Contrast Media