Previous investigators have reported that patients who listen to music while undergoing surgical procedures under regional anesthesia require significantly less sedatives (1,2). It remains unclear, however, whether this decrease in sedative requirements results from the music intervention or from elimination of operating room (OR) noises. Indeed, studies that assess noise levels in the OR indicate that although overall sound levels are not excessive, intermittent loud noises up to 108 dB are present (3,4). Thus, the primary aim of this study was to identify the mechanism by which music decreases intraoperative sedative requirements in patients undergoing surgical procedures under regional anesthesia, that is, to determine whether this decrease in sedative requirements results from music or from the elimination of OR noise. A secondary aim of the study was to examine the relationship between the response to intraoperative music and the participants’ culture.
Subjects undergoing urological procedures using spinal anesthesia, who were 18–60 yr old, and ASA physical status I–III, were enrolled in this multi-site study, conducted at Yale New Haven Hospital (n = 36) and the American University of Beirut Medical Center (n = 54). Subjects who were taking any psychiatric medications or who had a history of affective disorders were excluded from the study, which was approved by the human investigation committees of both institutions.
An investigator called the subjects the night before surgery, obtained initial consent, and asked each subject to bring a favorite CD to the hospital. The patients were also told that they may or may not have the opportunity to listen to the CD. Substitution was provided for patients without access to a CD. On the morning of surgery, demographic data were obtained, baseline sedation was assessed using the observational Observer’s Assessment of Alertness/Sedation Scale (OAA/S) (5), and baseline anxiety was assessed via self-report with the State-Trait Anxiety inventory (STAI) (6). A validated, reliable, Arabic version of the STAI was used for Lebanese subjects (Psychological Assessment Resources, Inc, Odessa, FL).
The research team consisted of a nonblinded member who randomized participants and administered the intervention and a blinded member who assessed outcomes only. The principal investigator led the investigation in both countries and the same protocol was applied in both sites. Patients were randomized into three groups. Ambient OR noise was controlled for via occlusive headphones in each group as follows:
- Patient-selected music, delivered by a CD player (Discman ESP; Sony Corporation, Tokyo, Japan).
- White noise, delivered by a SoundSpa Acoustic Relaxation Machine (Homedics).
- OR noise, delivered by a mini amplifier-speaker via occlusive headphones. This Radio Shack® mini amplifier has a mini-microphone for voice acquisition.
After randomization and before surgery, the nonblinded researcher placed the CD player in an opaque box specially constructed to assure the blindness of the outcome assessor and connected the occlusive headphones. After administration of a spinal anesthetic and confirmation of an adequate dermatomal level of anesthesia, subjects received an IV dose of 1 μg/kg fentanyl citrate and 0.5 mg/kg propofol over 5 min. A sedation pump (Bard Ambulatory PCA, North Reading, MA) set to deliver 30 mg of propofol as often as every 5 min was connected to all patients.
Next, the nonblinded researcher placed the occlusive headphones and the assigned intervention was delivered. Vital signs (arterial blood pressure [BP], heart rate [HR], Spo2), propofol consumption, and OAA/S score were documented every 5 min by the blinded researcher. An external power switch was connected to the opaque box and power was temporarily turned off before each OAA/S was determined to assure blindness of the outcomes assessor. Duration of postanesthesia care unit (PACU) length of stay was also recorded.
The primary end-point of this study was propofol requirements in the various study groups. Sample size was computed a priori for the three groups using analysis of variance estimates.1 A previous investigation by our laboratory indicated that intraoperative propofol requirements for patients undergoing urological procedures under spinal anesthesia is approximately 1.6 ± 0.4 mg/min (1). Assuming a moderate/large effect size of 0.45 and a two-tailed α of 0.05, 30 participants in each of the 3 groups would yield power of about 0.90, sufficient to identify group differences. One-way analysis of variance with Scheffé post hoc analysis was used for continuous analyses and χ2 for categorical analysis. Comparisons were considered significant if P < 0.05.
All groups were similar with regard to all baseline variables (Table 1). The music group required significantly less propofol as compared with the two other study groups (19.4 ± 37 mg versus 59 ± 82 mg versus 51 ± 52 mg; P = 0.026). Because of a wide variation noted in surgery duration and patient weight, we normalized propofol requirements for these variables. Analysis showed that propofol requirements by the music group remained significantly less as compared with the two other groups (0.004 ± 0.002 mg · kg−1 · min−1 versus 0.014 ± 0.004 mg · kg−1 · min−1 versus 0.012 ± 0.002 mg · kg−1 · min−1; P = 0.026). We also found that significantly more patients in the music group did not use any propofol intraoperatively as compared with patients who received white noise or OR noise (72% versus 28% versus 36%; P = 0.01). Using analysis of covariance with baseline anxiety as a covariable and propofol as the outcome, we found no interaction between anxiety and the response to the intervention (P = not significant). That is, response to music was not dependent on baseline anxiety levels.
Next, we compared Yale New Haven Hospital data (n = 36) to American University of Beirut Medical Center data (n = 54). We found that, regardless of group assignment, patients at American University of Beirut Medical Center used less propofol as compared with patients at Yale New Haven Hospital (0.005 ± 0.001 mg · kg−1 · min−1 versus 0.017 ± 0.003; P = 0.001). Patients in the music group required less propofol at both centers (Table 2).
The range of OAA scores was 1–4 during the surgical procedure and there were no group differences (P = not significant). No patient in this study experienced a critical respiratory event (defined as Spo2<90%) and all values of HR and BP were within normal limits. Finally, PACU times did not differ among groups (98 ± 45 min versus 110 ± 56 min versus 119 ± 64 min; P = not significant).
We found that, controlling for ambient OR noise, intraoperative music decreases propofol requirements of both Lebanese and American patients who undergo urological surgery under spinal anesthesia. This finding is consistent with previous studies that have documented the sedative-sparing effects of intraoperative music for patients undergoing surgery under regional techniques (1,2).
Although two previous investigations report that intraoperative music decreases sedative requirements in patients undergoing regional anesthesia (1,2), it was unclear if this decrease was attributable to the music or to the elimination of ambient OR noise. Dropping a surgical instrument into a bowl in the OR can produce noise levels of up to 80 dB (very loud to uncomfortably loud). Moreover, because sound is measured on a logarithmic scale, sudden noise as little as 30 dB above background noise may cause an immediate startle response with sympathetic activation (8). Thus, although decreases in sensory input during surgery may result in decreased sedative requirements, the results of the current study indicate that there is no such effect and that merely blocking the sensory overload of the OR with the use of white noise does not decrease sedative requirements. However, although previous studies show that ORs are noisy (3,4), in this study there was no measurement of ambient OR noise nor was there a patient assessment of the OR noise and environment. This is a clear limitation of the current study.
Previously, Cruise et al. (7) randomized patients to hear relaxing suggestions, white noise, OR noise, or relaxing music via headphones. The investigators found no differences in anxiety levels among groups at any time. Differences were noted in systolic BP but not in other vital signs. However, patients were more satisfied with their experience if they heard relaxing music rather than relaxing suggestions, white noise, or OR noise.
Of particular interest is our finding that Lebanese patients required less propofol than did American patients. An article examining anesthetic requirements of two different ethnic groups found that African blacks recovered more slowly from propofol than did Caucasians (9). The relationship between recovery time and overall propofol requirements remains unclear, and further investigation into this issue is warranted.
In conclusion, we have found that intraoperative music decreases sedative requirements in patients who undergo surgery under spinal anesthesia while controlling for OR ambient noise.
1. Koch M, Kain Z, Ayoub C, Rosenbaum S. The sedative and analgesic sparing effect of music. Anesthesiology 1998;89:300–6.
2. Lepage C, Drolet P, Girard M, et al. Music decreases sedative requirements during spinal anesthesia. Anesth Analg 2001;93:912–6.
3. Hodge B, Thompson JF. Noise pollution in the operating theatre. Lancet 1990;335:891–4.
4. Shapiro RA, Berland T. Noise in the operating room. N Engl J Med 1972;287:1236–8.
5. Chernick D, Gillings D, Laine H, et al. Validity and reliability of the Observer’s Assessment of Alertness/Sedation Scale: study with intravenous midazolam. J Clin Psychopharmacol 1990;10:244–51.
6. Spielberger C, Gorsuch R, Lushene R. State-Trait anxiety inventory manual, 1st ed. Palo Alto, CA: Consulting Psychologist Press, 1970.
7. Cruise CJ, Chung F, Yogendran S, Little D. Music increases satisfaction in elderly outpatients undergoing cataract surgery. Can J Anaesth 1997;44:43–8.
8. Falk SA, Woods NF. Hospital noise: levels and potential health hazards. N Engl J Med 1973;289:774–81.
9. Ortolani O, Conti A, Sall-Ka B, et al. The recovery of Senegalese African blacks from intravenous anesthesia with propofol and remifentanil is slower than that of Caucasians. Anesth Analg 2001;93:1222–6.