title: Feasibility of blinding in a randomized controlled trial comparing preoperative autologous blood donation and acute normovolemic hemodilution in adult cardiac surgery.
abstract: BACKGROUND
  Acute normovolemic hemodilution and preoperative autologous donation have been shown to be effective techniques for decreasing the exposure of patients to allogeneic blood during cardiac surgery. They have not, however, been compared to each other, because of perceived difficulties in blinding in such a clinical study. The feasibility of blinding was tested in a pilot trial.
  
  
  METHODS
  Ten patients were randomly assigned to undergo preoperative autologous blood donation or acute normovolemic hemodilution during cardiac surgery. Patients were blinded during this process by shielding of the arm and by insertion of an intravenous line in each patient. Every attempt was made to blind the clinical staff during and after surgery. The effectiveness of this blinding was determined by using a questionnaire.
  
  
  RESULTS
  In the 10 cases, six patients, four surgeons, and one anesthetist answered, "I do not know," with respect to whether preoperative autologous blood donation had occurred. The remaining people interviewed believed the blinding was unsuccessful. However, correct answers were given by 75 percent of the patients (95% CI, 19-99%), 83 percent of the surgeons (95% CI, 36-99.6%), and 66 percent of the anesthetists (95% CI, 29.9-92.5%). The frequency of correct answers did not differ significantly from the 50 percent expected by chance, but the CIs are wide.
  
  
  CONCLUSIONS
  Blinding of patients and all members of the surgical team during both the preoperative donation process and acute normovolemic hemodilution in the operating theater was successful most of the time, as the frequency of correct answers did not differ significantly from the 50 percent expected by chance. However, more accurate estimates of the success of blinding require a study with a larger sample. It is possible that, with a larger series, the physician's ability to determine patient assignment would be significantly better than that by chance alone.
authors.affiliation: Departments of Surgery, Anaesthesia, and Medicine, University of Ottawa, Ottawa, Ontario, Canada. frubens@ottawaheart.ca
authors.forename: F D
authors.initials: FD
authors.lastname: Rubens
authors.forename: J Y
authors.initials: JY
authors.lastname: Dupuis
authors.forename: J
authors.initials: J
authors.lastname: Robblee
authors.forename: G
authors.initials: G
authors.lastname: Rock
authors.forename: G L
authors.initials: GL
authors.lastname: Bryson
authors.forename: P S
authors.initials: PS
authors.lastname: Wells
mesh_terms: D000328:Adult; D001804:Blood Transfusion, Autologous; D006348:Cardiac Surgical Procedures / Q000379:methods*; D004311:Double-Blind Method; D006438:Hemodilution; D006801:Humans; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies