title: Efficacy of therapeutic suggestions under general anesthesia: a systematic review and meta-analysis of randomized controlled trials.
abstract: General anesthesia does not block central nervous processing of auditive information. Therefore, positive suggestions even given during surgery might have the potential to encourage well-being and recovery of patients. Aim of this review was to summarize the evidence on the efficacy of therapeutic suggestions under general anesthesia in adults undergoing surgery compared to an attention control (i.e. white noise).
  
  
  
  We included randomized controlled trials that investigated therapeutic suggestions presented during general anesthesia to adult patients undergoing surgery or medical procedures. Outcomes on pain intensity, mental distress, recovery, use of medication, measured postoperatively within hospitalization were considered. Electronic searches were carried out in the following databases (last search February 23, 2015): MEDLINE, CENTRAL, Web of Science, PsycINFO, ProQuest Dissertations and Theses.
  
  
  
  Thirty-two eligible randomized controlled trials were included, comprising a total of 2102 patients. All studies used taped suggestions. Random effects meta-analyses revealed no effects on pain intensity (Hedges' g = 0.04, CI 95% [-0.04; 0.12], number needed to treat [NNT] = 44.3) and mental distress (g = 0.03, CI 95% [-0.11; 0.16], NNT = 68.2). In contrast, we found small but significant positive effects on use of medication (g = 0.19, CI 95% [0.09; 0.29], NNT = 9.2) and on recovery (g = 0.14, CI 95% [0.03; 0.25], NNT = 13.0). All effects were homogeneous and robust.
  
  
  
  Even though effects were small, our results provide indications that intraoperative suggestions can have the potential to reduce the need for medication and enhance recovery. Further high quality trials are needed to strengthen the promising evidence on the efficacy of therapeutic suggestions under general anesthesia for patients undergoing surgery.
authors.affiliation: Institute of Psychosocial Medicine and Psychotherapy, Jena University Hospital, Friedrich-Schiller University, Stoystr. 3, 07743, Jena, Germany. jenny.rosendahl@med.uni-jena.de.
authors.forename: Jenny
authors.identifier: 0000-0001-7535-7571
authors.initials: J
authors.lastname: Rosendahl
authors.affiliation: Department of Medical Psychology and Medical Sociology, University Hospital Leipzig, Philipp-Rosenthal-Str. 55, 04103, Leipzig, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Koranyi
authors.affiliation: Institute of Psychosocial Medicine and Psychotherapy, Jena University Hospital, Friedrich-Schiller University, Stoystr. 3, 07743, Jena, Germany.
authors.forename: Davina
authors.initials: D
authors.lastname: Jacob
authors.affiliation: Department of Anaesthesiology, University Hospital Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Zech
authors.affiliation: Department of Anaesthesiology, University Hospital Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
authors.forename: Ernil
authors.initials: E
authors.lastname: Hansen
mesh_terms: D000328:Adult; D000768:Anesthesia, General / Q000379:methods*; D006801:Humans; D010149:Postoperative Pain / Q000523:psychology*; D016032:Randomized Controlled Trials as Topic; D013315:Stress, Psychological / Q000523:psychology; D013404:Suggestion
keywords: Anesthesia, general; Efficacy, treatment; Meta-analysis; Therapeutic suggestions