Efficacy of therapeutic suggestions under general anesthesia: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND: 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). METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12871-016-0292-0) contains supplementary material, which is available to authorized users.