The present study results showed no significant difference between the two groups of patients undergoing eye surgery in terms of age and gender. Hence, randomization process was carried out well, and age and gender variables could not affect the difference between the two groups in treatment outcomes as confounding factors.
According to the most important results, state anxiety level after surgery was lower in BBM group than that in conventional group. No difference was observed between the two groups undergoing eye surgery in state anxiety and pain after surgery. State and trait anxiety levels decreased after surgery compared to before in both BBM and conventional groups. Moreover, pain level reduced after surgery compared to before in BBM group, but no difference was observed between pain levels before and after surgery in conventional group. Therefore, using BBM can be said to be as effective as opioids in anesthesia in reducing state and trait anxiety and pain levels. Some studies have recently recommended the use of BBM for reducing anxiety and pain in patients undergoing various surgeries (
11,
18,
20,
21). In agreement with the present study results, Wiwatwongwana et al. (
18) realized that using BBM and easy music compared to no music group led to reduced anxiety after intervention (based on SATI scale) in patients undergoing cataract surgery. However, no difference was found between BBM and plain music groups in terms of anxiety level. In agreement with the present study results, Chuter et al. (
21) found that anxiety (based on VAS scale) reduced further in patients receiving BBM compared to plain music after elective surgeries (
22). In agreement with the present study results, Padmanabhan et al. (
11) found that using BBM and plain music compared to no music group led to reduced anxiety after intervention (based on SATI scale) by 26.3%, 11.1%, and 3.4% respectively in patients undergoing elective surgery. Hence, BBM has a significant potential for reducing acute preoperative anxiety. Weiland et al. (
23) compared different types of music and listening methods in emergency patients with anxiety, and found that BBM reduced anxiety most (based on SATI) in these patients. The mechanism of action of BBM in reducing anxiety of patients undergoing eye surgery can be attributed to the sedative and anxiolytic effects of beta-endorphin and serotonin neurotransmitters and inhibition of dopamine’s anxiety effects. The results obtained by Jemmer showed that at beta and gamma frequencies, stimulation of brain waves leads to increased dopamine, and at alpha and theta leads to increased serotonin in the brain (
24). The results obtained by Wahbeh et al. showed that adjusting brain waves at theta frequency leads to depletion of dopamine neurotransmitter in the brain (
25). The results of a study by Peniston and Kulkosky showed that alpha/theta protocol leads to increased beta-endorphin in the brain, and the mechanism of this effect is revealed by the fact that beta-endorphin and serotonin neurotransmitters have a key role in sedation and control of anxiety, and that dopamine is known as the key factor in most anxiety disorders. Hence, mitigating anxiety by adjusting brain waves can be considered to be due to changes in the level of neurotransmitters (
26). The results of a study conducted by Kienast et al. showed that dopamine release under stress leads to storage of this neurotransmitter in the amygdala and increased dopamine reserves in the amygdala is a factor for the person’s anxious mood. Thus, reduced dopamine level due to adjustment of brain waves can lead to reduced dopamine reserves in the amygdala, resulting in reduced trait anxiety in the person (
27). Comparison of hemodynamic changes in the present study revealed that postoperative diastolic blood pressure was lower in BBM compared to conventional group. However, no difference was observed between the two groups in postoperative systolic blood pressure, heart rate, and SPO
2. But, systolic and diastolic blood pressure, and heart rate in BBM group reduced after surgery compared to before. Moreover, systolic blood pressure and heart rate in conventional group decreased after surgery compared to before. But, no difference was found in systolic blood pressure between before and after surgery in conventional group, and no significant difference was observed between before and after surgery SPO
2 level in both BBM and conventional groups. Therefore, using BBM appears to be as effective as opioids and sedatives in controlling hemodynamic changes in patients undergoing eye surgery. In agreement with the present study results, Wiwatwongwana et al. (
18) found that using BBM and plain music compared to no music group leads to reduced systolic blood pressure in patients undergoing cataract surgery. However, only heart rate reduced in BBM group compared to no music group. No difference was found in systolic blood pressure before and after surgery in all three groups. The present study results showed no difference between BBM and conventional groups in satisfaction levels of patients and surgeons.
Being a clinical trial was among strong points of the present study. However, it had some limitations. First, we could not compare our results with other studies because there were only few similar studies. Thus, it is recommended that similar studies be conducted in future. Second, our sample size was small, which may have resulted in finding no significant differences between the two groups. Thus, it is recommended that future studies be designed with larger sample sizes. Finally, given the present and previous studies results, using BBM appears to be effective in reducing state and trait anxiety and pain, controlling hemodynamic changes, and increasing satisfaction of patients undergoing eye surgery, and can be an appropriate alternative to opioids and sedatives in anesthesia of patients undergoing eye surgery.