Methods
Literature search, eligibility criteria, and study selection
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Type of patients: Adult patients undergoing surgery with general anesthesia
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Type of studies: Peer-reviewed, published, full-text-available RCTs in the English language in which patients, perioperative staff, and outcome assessors were all blinded
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Type of intervention and control: intraoperative auditory stimuli (for example: music, positive suggestions, stories) compared with a control group not receiving intraoperative auditory stimuli or a different intraoperative auditory stimulus
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Main outcome measure: postoperative patient outcomes and recovery, assessed through postoperative pain
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Secondary outcome measures: postoperative patient outcomes and recovery assessed through postoperative nausea and vomiting (PONV), postoperative antiemetic requirements, postoperative opioid requirements, length of stay, patient satisfaction, explicit memory formation, implicit memory formation
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Additional outcomes assessed: perioperative factors of potential influence on perception and processing of intraoperative auditory stimuli during general anesthesia
Data extraction
Statistical analysis
Deviations from the registered PROSPERO study protocol
Results
Study characteristics
Study | Surgical procedure | Auditory intervention | Group 1 | N1 | Group 2 | N2 | Outcome parameters |
---|---|---|---|---|---|---|---|
Aceto et al. 200338 | Elective laparoscopic cholecystectomy | Repetitive story-keywords using familiar Christian religious stories | Sevoflurane and air (FiO2 40%) | 10 | Sevoflurane and 60%N2O in 40%O2 | 10 | Explicit memory (open-recall) Implicit memory (story-related free association) Mid-latency auditory evoked potential relationship with memory formation |
Isoflurane and air (FiO2 40%) | 10 | Isoflurane and 60%N2O in 40%O2 | 10 | ||||
Aceto et al. 201336 | Elective laparoscopic cholecystectomy | Repetitive story-keywords thrice lasting 9 min | Fairy story Pinocchio or Puss in Boots with four keywords | 54 | Over-ear, isolating headphones | 52 | Explicit memory (open-recall) Implicit memory (story-related free association) Stress response effect on memory formation |
Aceto et al. 201537 | Elective thyroidectomy | Repetitive story-keywords thrice lasting 27 min | BIS-guided sevoflurane anesthesia | 63 | HP-guided sevoflurane anesthesia | 64 | Explicit memory (open-recall) Implicit memory (story-related free association) BIS-guided vs HP-guided anesthesia |
Adams et al. 199835 | Elective open cardiopulmonary bypass surgery | Two 15-word-pair list 1-min tapes played continuously | Word list A | 13 | Word list B | 12 | Explicit memory (open-recall, recognition test) Implicit memory (word pair free association) |
Bejjani et al. 200928 | Elective cardiopulmonary bypass surgery | Two 20-word-pair list tapes played continuously | Word list A | 19 | Word list B | 19 | Explicit memory (open-recall, free recall) Implicit memory (word-stem completion test) |
Bennett et al. 198546 | Inguinal hernia, cholecystectomy, orthopedic surgery | Positive therapeutic and postoperative motor suggestions played continuously | Personalized tape interspersed with music | 11 | Operating room sounds through earphone stereo microphone | 22 | Explicit memory (open-recall) Implicit memory (postoperative non-verbal motor response) |
Block et al. 199182 | Elective gastroplasty, cholecystectomy or gynecological surgery | Positive therapeutic suggestions 6-min tape, continuously played expect for the first 59 patients | Positive therapeutic suggestions | 109 | Headphones with blank tape | 100 | Patient outcome (pain, opioids, PONV, antiemetics, length of stay) |
Boeke et al. 198883 | Elective open cholecystectomy | Positive therapeutic suggestions and seaside sounds 30-min tape played continuously | Positive therapeutic suggestions with seaside sounds | 24 | Nonsense suggestions interspersed with seaside sounds | 26 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV, length of stay, subjective well-being) |
Seaside sounds | 27 | Earphones with operation room sound | 29 | ||||
Bonebakker et al. 199344 | Elective surgery | Category word pair tape 30 min, followed by bird sounds continuously | 30-word-pair presentation tape | 23 | 5-word-pair presentation tape | 18 | Explicit memory (open-recall) Implicit memory (category exemplar generation task) |
Headphones without words | 15 | ||||||
Bonke et al. 1986†66 | Elective cholecystectomy with or without choledochotomy | Positive therapeutic suggestions 3-min tape played continuously | Positive therapeutic suggestions | 31 | Continuous monotone noise | 30 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV, length of stay) |
Earphones with operation room sound | 30 | ||||||
Caseley-Rondi et al. 199425 | Total abdominal hysterectomy with or without salpingo-oophorectomy | Positive therapeutic suggestions with 24 Japanese melodies 60-min tape played continuously | Positive therapeutic suggestions | 38 | Headphones with blank tape | 36 | Explicit memory (open-recall, recognition test) Implicit memory (preference task) Patient outcome (opioids, PONV, length of stay) |
Dawson et al. 2001†59 | Total abdominal hysterectomy | Three positive suggestions tapes played continuously | Positive therapeutic suggestions | 103 | White noise | 35 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV, antiemetics, length of stay) |
De Roode et al. 199539 | Strabismus surgery | Ten facts or names 15-min tape, with natural seaside sounds continuously | Presented facts (ten previously learned, largely forgotten historical facts) | 43 | Target names (ten fictitious non-famous people) | 40 | Explicit memory (open-recall) Implicit memory (presented facts and target names) Midazolam effect on memory formation |
Deeprose et al. 200526 | Day care orthopedic surgery | Four 28-word list 14-min tapes played continuously | Propofol and N2O anesthesia with 1.5mg/kg fentanyl induction | 32 | Propofol and N2O anesthesia, no fentanyl | 30 | Explicit memory (open-recall, recognition test) Implicit memory (word-stem completion test) Fentanyl effect on memory formation |
Donker et al. 199640 | Arthroscopy day care surgery | Eight tapes with ten facts or names with filler sound continuously | Presented facts | 29 | Target names | 29 | Explicit memory (open-recall) Implicit memory (presented facts and target names) |
Eberhart et al. 1998†60 | Thyroidectomy | Positive therapeutic suggestion tape played continuously | Positive therapeutic suggestions | 36 | Headphones with blank tape | 35 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV, antiemetics, length of stay) |
Evans and Richardson 1988†50 | Total abdominal hysterectomy | Positive therapeutic suggestion 12-min tape repeated thrice | Positive therapeutic suggestions | 19 | Headphones with blank tape | 20 | Explicit memory (open-recall) Patient outcome (pain, PONV, length of stay) |
Ghoneim et al. 200021 | Elective general, gynecological, orthopedic, and plastic surgery | Repetitive story-keyword 30-min tape repeated four times | Opioid 7.5 µg·kg−1 fentanyl bolus | 100 | N2O-opioid infusion 1.5 µg·kg−1·min−1 alfentanil | 40 | Explicit memory (open-recall, recognition test) Implicit memory (story-related free association) Mid-latency auditory evoked potential relationship with memory formation |
Isoflurane 0.3% - fentanyl 1 µg·kg−1 | 16 | Isoflurane 0.7% - fentanyl 1 µg·kg−1 | 24 | ||||
Hughes et al. 199448 | Elective ear-nose-throat, urological, gynecological, orthopedic surgery | Behavioural suggestion tape on smoking cessation played continuously | Smoking cessation message | 50 | Control tape with counted numbers | 50 | Explicit memory (open-recall) Implicit memory (postoperative behavioural response) |
Ikedo et al. 200769 | Coronary artery bypass graft and/or open valve heart surgery | Prayer or hemisync played continuously | Generic prayer | 24 | Headphones with blank compact disc | 27 | Patient outcome (opioids, postoperative complications, length of stay) |
Hemisync | 27 | ||||||
Jansen et al. 199147 | Elective surgery lasting 45 to 240 min | Positive therapeutic suggestions and motor instructions 10 times during 15 min | Seaside sounds with motor suggestions | 38 | Seaside sounds | 42 | Explicit memory (open-recall) Implicit memory (postoperative motor response) |
Jayaraman et al. 200662 | Laparoscopic cholecystectomy | Positive therapeutic suggestions and calming music played continuously | Music | 24 | Routine operating room sounds | 34 | Explicit memory (open-recall) Patient outcome (pain, PONV, subjective well-being) |
Music with positive therapeutic suggestions | 27 | ||||||
Jelicic et al. 199241 | Strabismus surgery | Ten facts or names 15 min tape, with filler seaside sounds continuously | Presented facts | 21 | Target names | 22 | Explicit memory (open-recall) Implicit memory (presented facts and target names) |
Jelicic et al. 199342 | Body surface surgery (majority breast surgery) | Ten facts or names 15 min tape, with filler seaside sounds continuously | Presented facts | 20 | Target names | 21 | Explicit memory (open-recall) Implicit memory (presented facts and target names) |
Kahloul et al. 2017†51 | Elective liver cyst, abdominal cancer biliary, proctologic surgery | Tunisian, Eastern, instrumental, or Western music played continuously | Music | 70 | Headphones with no music | 70 | Explicit memory (unspecified test) Patient outcome (pain, patient satisfaction, Riker recovery scale) |
Kerssens et al. 200145 | Elective general, orthopedic, urological outpatient surgery | Four common exemplars repeated 15 min followed by filler bird singing sounds continuously | Category exemplar list | 41 | Filler bird singing | 41 | Explicit memory (open-recall, recognition test) Implicit memory (category exemplar generation task) |
Kerssens et al. 200922 | Elective hip or knee replacement surgery | Three 15-word lists with one played continuously | BIS-guided sevoflurane anesthesia | 62 | HP-guided sevoflurane anesthesia | 47 | Explicit memory (open-recall, recognition test) Preoperative fentanyl and BIS-guiding effect on recall |
Kliempt et al. 199984 | General, non-cancer surgery | Classical music or hemisync played continuously | Adagio Karajan | 25 | Headphones with blank tape | 16 | Patient outcome (intraoperative fentanyl requirement) |
Hemisync | 25 | ||||||
Lebovits et al. 199963 | Elective day care hernia repair | Positive therapeutic suggestions or 7 min hospital story tape played continuously | Positive therapeutic suggestions | 34 | Hospital history story | 36 | Explicit memory (open-recall) Patient outcome (pain, PONV) |
Lequeux et al. 201429 | Unspecified ASA I–II surgery patients | Two 20-word lists with one played continuously | High-opioid remifentanil | 39 | No auditory stimuli control group for baseline | 40 | Explicit memory (open-recall, free recall, recognition test) Implicit memory (word-stem completion test) Noxious stimuli and opioid effect on memory |
Low-opioid remifentanil | 39 | ||||||
Lewis et al. 200485 | Laparoscopic bariatric or lumbar disk surgery | Hemisync played continuously | Hemisync | 30 | Headphones with blank tape | 30 | Patient outcome (intraoperative fentanyl requirement) |
Liu et al. 1992†52 | Total abdominal hysterectomy | Positive therapeutic suggestions 10 min tape or hospital story played continuously | Positive therapeutic suggestions | 24 | Hospital history story | 25 | Explicit memory (open-recall) Patient outcome (pain, analgesic requirement, PONV, length of stay) |
Headphones with blank tape | 24 | ||||||
Maroof et al. 199764 | Elective abdominal hysterectomy | Positive therapeutic suggestions 15 min tape played continuously | Positive therapeutic suggestions | 25 | Headphones with blank tape | 25 | Explicit memory (open-recall) Patient outcome (PONV, antiemetics) |
McLintock et al. 1990†53 | Elective open abdominal hysterectomy | Positive therapeutic suggestions 15 min tape played continuously | Positive therapeutic suggestions | 25 | Headphones with blank tape | 25 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV) |
Melzack et al. 199632 | Elective cholecystectomy or hysterectomy | Positive therapeutic suggestions and motor instructions 4 min tape | Positive therapeutic and postoperative motor response suggestions | 10 | Story-keywords on sensory perception and pain | 10 | Explicit memory (recognition test) Implicit memory (postoperative behavioural response) Patient outcome (pain, length of stay) |
Migneault et al. 2004†61 | Abdominal hysterectomy with (hystero)salpingo-oophorectomy | Classical, jazz, new-age, or popular piano music compact disc | Music | 15 | Headphones without music | 15 | Explicit memory (open-recall) Patient outcome (opioids, intraoperative fentanyl requirement) |
Millar and Watkinson 198330 | Upper-abdominal, gynecological surgery | Four ten-word lists 14- min tape | Word list | 27 | Headphone with static radio noise | 26 | Explicit memory (open-recall, free recall, recognition test) |
Myles et al. 199649 | Elective or semi-elective surgery | Behavioural 3-min suggestion tape on smoking cessation played continuously | Positive suggestion for smoking cessation | 185 | Headphones with blank tape | 178 | Explicit memory (open-recall) Implicit memory (postoperative behavioural response) |
Nilsson et al. 2001†54 | Elective open abdominal hysterectomy | Positive therapeutic suggestions with or without music played continuously | Relaxing and calming music | 30 | Headphones with OR noise | 28 | Explicit memory (open-recall) Patient outcome (pain, opioids, PONV, length of stay, subjective well-being) |
Positive therapeutic suggestions with music | 31 | ||||||
Nilsson et al. 2003†55 | Day care inguinal hernia repair or varicose vein surgery | Slow, flowing, new age 43-min music tape played continuously | Instrumental music | 51 | Headphones with blank CD | 49 | Explicit memory (open-recall) Patient outcome (pain, opioids, patient satisfaction) |
Nilsson et al. 2005†56 | Open inguinal Lichtenstein hernia repair | Slow, flowing, new age 43-min music tape played continuously | Instrumental music | 25 | Headphones with blank CD | 25 | Patient outcome (pain, opioids) |
Oddby-Muhrbeck et al. 1995†67 | Elective breast surgery | Positive therapeutic suggestions with soft music 32-min tape played continuously | Positive therapeutic suggestions with music | 35 | Headphones with blank tape containing low background sound | 35 | Explicit memory (open-recall) Patient outcome (pain, analgesic requirement, PONV, antiemetics, length of stay) |
Parker et al. 199431 | Minor or moderate surgery | Four 20-min, 10-word lists with music played continuously | Word list | 24 | Headphones with blank tape | 24 | Explicit memory (free recall, recognition test) |
Kalyani et al. 201586 | Elective laparoscopic cholecystectomy | Classical instrumental music played continuously | Music | 30 | Headphones without music | 30 | Explicit memory (open-recall) Patient outcome (intraoperative opioid and sedative requirement) |
Renna et al. 200027 | Gynecological minor surgery | Positive suggestions and 8-word list played once before surgical stimuli start | Sevoflurane 1.2% | 15 | Sevoflurane 2.0% | 16 | Explicit memory (open-recall, recognition test) Implicit memory (postoperative behavioural response) |
Sevoflurane 1.5% | 16 | ||||||
Reza et al. 2007†57 | Elective Cesarean section | Soft instrumental Spanish guitar music played continuously | Music | 50 | White noise | 50 | Patient outcome (pain, opioids, PONV, antiemetics) |
Russel and Wang 200133 | Gynecological major surgery | Motor instructions with vegetable or fruit word list played continuously | Fruit word list | 20 | Vegetable word list | 20 | Explicit memory (open-recall) Implicit memory (word pair free association, category exemplar generation task) |
Simcock et al. 2008†23 | Primary total knee arthroplasty | Music played continuously | Music | 15 | White noise | 15 | Explicit memory (open-recall) Patient outcome (pain, patient satisfaction) |
Szmuk et al. 2008†58 | Laparoscopic hernia repair or cholecystectomy | Classical, pop, rock or Israeli music played continuously | Music | 15 | Headphones without music | 20 | Patient outcome (pain, analgesic requirement) |
Tsuchiya et al. 200386 | Elective laparoscopic cholecystectomy | Sounds of a ripple, small stream, soft wind and twitter played continuously | Natural environmental sounds | 29 | Undistinguishable dummy headphones and OR noise | 30 | Explicit memory (open-recall) Patient outcome (intraoperative hemodynamic parameters) |
Westmoreland et al. 199334 | Elective surgery | Two 20-word-pair 50-min tapes, 2 four-exemplar categories and 10 homophones | Premedication midazolam 2 mg intravenous | 24 | No premedication midazolam 2 mg, but 2 ml saline intravenous | 24 | Implicit memory (category exemplar generation task, word pair free association, homophone spelling) Midazolam effect on memory formation |
Williams et al. 199465 | Major gynecological surgery | Positive therapeutic suggestions 15 min tape played continuously | Positive therapeutic suggestions | 22 | Headphones with blank tape | 29 | Explicit memory (open-recall)Patient outcome (analgesic requirement, PONV, antiemetics) |
Zhang 2005†68 | Elective total abdominal hysterectomy | Participant-selected music played continuously | Music | 55 | Headphones without music | 55 | Explicit memory (open-recall) Patient outcome (patient satisfaction) |
Baseline study characteristics | Overall | Explicit memory | Implicit memory | Patient outcome | |
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Number of studies (patients) | 53 (4,200) | 45 (3,528) | 23 (1,864) | 29 (2,249) | |
Auditory intervention | Positive therapeutic suggestions | 22 | 21 | 8 | 16 |
Words, facts, or names list | 17 | 15 | 13 | 0 | |
Music | 12 | 8 | 0 | 12 | |
Stories | 7 | 7 | 5 | 4 | |
Other | 3 | 1 | 0 | 2 | |
ASA Physical Status | I | 4 | 3 | 2 | 2 |
I–II | 27 | 24 | 13 | 15 | |
I–III | 7 | 5 | 2 | 4 | |
Not specified | 15 | 13 | 6 | 8 | |
Surgical severity classification | Minor | 7 | 6 | 5 | 2 |
Moderate | 11 | 8 | 3 | 8 | |
Major | 19 | 18 | 5 | 15 | |
Multiple severity classes | 7 | 6 | 4 | 0 | |
Not specified | 9 | 7 | 6 | 4 | |
Surgery duration | 0–60 minutes | 9 | 6 | 4 | 4 |
60–120 minutes | 18 | 17 | 5 | 14 | |
> 120 minutes | 8 | 5 | 2 | 5 | |
Not specified | 18 | 17 | 12 | 6 | |
Auditory intervention duration | Continuously throughout surgery | 38 | 31 | 12 | 27 |
Prespecified tape duration | 13 | 12 | 10 | 1 | |
Not specified | 2 | 2 | 1 | 1 | |
General anesthesia regimen | Premedication (opioid/benzodiazepines) | 31 (9/17) | 28 (7/17) | 13 (2/7) | 16 (6/10) |
Balanced anesthesia | 40 | 33 | 16 | 23 | |
Total intravenous propofol anesthesia | 10 | 10 | 6 | 4 | |
Inhalational induction and maintenance | 2 | 2 | 1 | 1 | |
Unspecified intraoperative anesthesia | 1 | 0 | 0 | 1 | |
Patient controlled analgesia or spinal/epidural | 9 | 9 | 2 | 7 | |
Bispectral index monitor | 14 | 12 | 7 | 6 |
Explicit memory formation
Study | Intervention | ANA | Explicit recall | Implicit memory formation | Time | Comments |
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Aceto et al. 2003††38 | Repetitive Christian story-keyword sequence | Balanced | Open-recall test (0%) | Story-related free association test (1/40, 2.5%) | 24 h | MLAER Pa latency increase related to implicit memory formation |
Aceto et al. 2013††36 | Repetitive fairy story-keyword sequence | Balanced | Open-recall test (0%) | Story-related free association test (3/54, 5.5%) | End, 24 h | Auditory stimulation associated with lower prolactin concentrations |
Aceto et al. 2015††37 | Repetitive fairy story-keyword sequence | Balanced | Open-recall test (0%) | Story-related free association test (8/127, 6.3%) | End, 24 h | BIS or HP-guided anesthesia no difference in implicit memory formation, cut-off value mean age-adjusted MAC of 0.9 for implicit memory formation |
Adams et al. 1998††35 | Repetitive word list | Balanced | Open-recall test (0%) Recognition test (NS) | Word pair free association test (evidence of preserved implicit memory) | POD 3–6 | 23 of 25 patients showed higher rate of correct word pair associations of intraoperatively presented word list |
Bejjani et al. 200928 | Repetitive word list | TIVA | Open-recall test (0%) Free recall test (0%) | Word-stem completion test (no evidence of implicit memory formation) | POD 1 | Correct answer rate between word list that was played and was not played not different |
Bennett et al. 1985††46 | Positive suggestions with postoperative motor suggestions and music | Balanced | Open-recall test (0%) | Postoperative non-verbal motor response (significant higher motor response in suggestions group) | After POD 2 | Although twice more patient allocated to control, postoperative motor response still higher in suggestions group |
Boeke et al. 198883 | Positive therapeutic and nonsense suggestions, seaside sounds | Balanced | Open-recall test (0%) | Not assessed | POD 6 or 7 | No explicit memory formation |
Bonebakker et al. 199344 | Unfamiliar word categories with bird sound filler | Balanced | Open-recall test (0%) | Category exemplar generation task (no evidence of implicit memory formation) | 115 min (mean) | Unfamiliar target words exemplars of common categories were tested, with a high number of possible exemplars |
Bonke et al. 198666 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | POD 6 or 7 | No explicit memory formation |
Caseley-Rondi et al. 1994†25 | Personalized positive suggestions with music | Balanced | Open-recall test (0%) Recognition test (above chance recognition) | Preference task (no evidence of implicit memory formation) | 24 h, POD 3 | Above chance accuracy on patient’s guesses who correctly assessed that suggestions were played |
Dawson et ak, 200159 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | POD 5 | No explicit memory formation |
De Roode et al. 199539 | Presented facts and target names with seaside sounds | Balanced | Open-recall test (0%) | Presented facts and target names (no evidence of implicit memory formation) | End | No implicit memory in contrast to earlier study with same anesthesia regimen but no midazolam premedication |
Deeprose et al. 2005† ††26 | Repetitive word list | Balanced | Open-recall test (0%)Recognition test (above chance recognition) | Word-stem completion test (implicit memory formation present both in fentanyl and no fentanyl group) | 1.5 h | Slightly higher mean implicit memory formation score for no fentanyl group, but not statistically significant |
Donker et al. 199640 | Presented facts and target names | TIVA | Open-recall test (0%) | Presented facts and target names (no evidence of implicit memory formation) | 30-60 min | Overall higher mean score in more familiar target name list than in unfamiliar list |
Eberhart 199860 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Evans and Richardson 198850 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | POD 5 | No explicit memory formation, all but one in the intervention group correctly guessed the suggestion tape played |
Ghoneim et al. 2000† ††21 | Repetitive story-keyword sequence | Balanced | Open-recall test (6/179; 3.4%) Recognition test (NS) | Story-related free association test (implicit memory formation present in opioid bolus-70% N2O group) | POD 1 or POD 3-4 | Significant explicit and implicit memory formation in opioid bolus-70% N2O MLAER Nb amplitude increase related to explicit, while Na, Pa, and Nb latency decrease related to implicit recall |
Hughes et al. 1994††48 | Behavioural change message | Balanced | Open-recall test (0%) | Postoperative behavioural response (significantly changed) | 4 weeks | Significant more stopped or reduced smoking in intervention group |
Jansen et al. 199147 | Postoperative motor suggestion | Balanced | Open-recall test (0%) | Postoperative motor response (no difference between groups) | POD 1 or 2 | Relatively low number overall of motor response |
Jayaraman et al. 200662 | Music and positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | End | No explicit memory formation |
Jelicic et al. 1992††41 | Presented facts; target names with natural seaside filler sounds | Balanced | Open-recall test (0%) | Presented facts and target names (evidence present of implicit memory formation) | End | Implicit memory present in contrast to later 1993 study, during which enflurane was added as maintenance anesthetic |
Jelicic et al. 199342 | Presented facts; target names with natural seaside filler sounds | Balanced | Open-recall test (0%) | Presented facts and target names (no evidence of implicit memory formation) | POD 1 | No implicit memory in spontaneously breathing patients, in contrast to N2O-opioid anesthesia in 1992 study |
Kahloul et al. 201751 | Tunisian, Eastern, Western or instrumental music | Balanced | Not specified | Not assessed | 24 hr | No significant difference in awareness between intervention and control group |
Kerssens et al. 200145 | Familiar word category exemplars with filler birds singing sound | TIVA | Open-recall test (0%) Recognition test (NS) | Category exemplar generation task (no evidence of implicit memory formation) | 113 min (mean) | Indication that words presented at BIS levels of 45 are not processed to the extent of memory formation |
Kerssens et al. 2009†22 | 15-word list | Balanced | Open-recall test (3/109; 2.3%) Recognition test (above chance recognition in BIS-guided group) | Not assessed | 6 h | BIS-guided group higher mean BIS and above chance recognition, no higher recognition rate in HP-guided group. Preoperative fentanyl reduces change of memory formation. |
Lebovits et al. 199963 | Positive therapeutic suggestions, story | TIVA | Open-recall test (0%) | Not assessed | End, 6 hr, 24 hr | No explicit memory formation |
Lequeux et al. 201429 | 2- word list | TIVA | Open-recall test (0%) Free-recall test (NS) Recognition test (NS) | Word-stem completion test (no evidence of implicit memory formation) | 2-3 hr | No implicit memory formation during BIS-guided propofol-remifentanil anesthesia with low remifentanil doses |
Liu et al. 199252 | Positive therapeutic suggestions, story | Balanced | Open-recall test (0%) | Not assessed | POD 1 | No explicit memory formation |
Maroof et al. 199764 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
McLintock et al. 199053 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Melzack et al. 199632 | Personalized positive therapeutic and motor suggestions vs repetitive story keyword | Balanced | Free recall (NS) | Postoperative behavioural response (no difference between groups, no trend in keywords chosen postoperatively) | POD 1-4 | Also did not observe a significant beneficial effect on postoperative pain levels and hospital length of stay |
Migneault et al. 200461 | Classical, jazz, new-age, or popular piano music | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Millar and Watkinson 198330 | 10-word list | Balanced | Open-recall test (0%) Free-recall test (NS) Recognition test (higher recognition rate, but NS) | Not assessed | 24 hr | Although higher word recognition rate indicating explicit recall, no significant difference in hand movements for isolated forearm technique |
Myles et al. 199649 | Behavioural change message | Balanced | Open-recall test (0%) | VAS motivation to stop smoking Postoperative behavioural response (no difference between groups) | End (explicit); 2 and 6 months | Only 29 patients (8%) had stopped smoking at 6 months, which is similar to spontaneous smoking cessation rates |
Nilsson et al. 200154 | Music with either sea wave sounds or positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Nilsson et al. 200355 | Instrumental new-age synthesizer music | Balanced | Open-recall test (0%) | Not assessed | PACU release | No explicit memory formation |
Oddby-Muhrbeck et al. 199567 | Positive therapeutic suggestions interspersed with soft music | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Parker et al. 199431 | 10-word list | Balanced | Free-recall test (0%) Recognition test (NS) | Not assessed | POD 1 | Almost all patients attributed the recognition test as guesswork |
Kalyani et al. 201586 | Classical instrumental music | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Renna et al. 2000†27 | Positive suggestions and 8-word list played once before surgical stimuli | IMM | Open-recall test (0%) Recognition test (higher recognition rate, only present in 1.2% group) | Postoperative behavioural response (no difference in subjective assessment postoperatively) | 2–3 hr | Recognition test was classified as an implicit memory formation assessment instead of an explicit recall test |
Russel and Wang 200133 | Personalized motor command followed by either fruit or vegetable category word list | TIVA | Open-recall test (0%) | Category exemplar generation task and word pair free association test (no evidence of implicit memory formation) | Within 2 hr | Only one word pair was correctly chosen repeatedly during the word pair association test, but not significantly different in both groups |
Simcock et al. 200823 | Choice of 3 music compact discs | TIVA | Open-recall test (60%) | Not assessed | 24 hr | 60% patients reported correctly that they were exposed to music |
Tsuchiya et al. 200387 | Natural environmental sounds (ripple, stream, wind, and twitter) | TIVA | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Westmoreland et al. 199334 | 10 homophones, 10 word pairs, and 2 categories | Balanced | Not tested | Category exemplar generation task, word pair free association test, homophone spelling (no implicit memory formation) | 2 h and 48 hr | No implicit memory formation, therefore unclear whether premedication midazolam influences memory formation |
Williams et al. 199465 | Positive therapeutic suggestions | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |
Zhang et al. 200568 | Participant-selected music | Balanced | Open-recall test (0%) | Not assessed | 24 hr | No explicit memory formation |