Delirium is a common acute confusion state among critical patients in intensive care units (ICUs). The symptoms are serious disturbance in mental abilities which may cause inattention, confused thinking, agitated mood, and fluctuated consciousness. Delirium also lead to higher mortality, longer hospital stay, higher cost of healthcare and poor recovery. However, the mechanism of delirium still not fully understand. Imbalanced neurotransmitters may be one of the possible explain for such situation. It is related to increased level of dopamine and acetylcholine deficiency. In addition, the relation between low level of melatonin and postoperative delirium was also reported. Glucocorticoid which represent the stress response is also related to postoperative delirium. Both changes of neurotransmitters and hormone levels would affect sleep-awake cycle. It is observed that patients who is delirium show a relative higher EEG theta power and a reduced alpha power than non-delirious patients. Several modifiable risk factors, such as noise, light, physical restrain, pain, anxiety, and sedatives, may contribute to poor sleep quality or sleep disruption and further delirium occurrence. Effectiveness interventions are extremely important when patients are inevitably exposed to such risk factors.

Pharmacological interventions are rapid and effective way for delirium management. However, the concern about side effect and increased mortality among high risk patients are needed. According to 2018 Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU, non-pharmacological intervention was suggested for delirium management firstly. Non-pharmacological interventions, such as using earplug or eye mask at night, music therapy or early mobilization, should be safe, less side effect and widely applicable for first-line healthcare providers. In addition, multicomponent interventions should be more effective than single component intervention. However, the evidence of direct comparison is limited.

Music intervention is a non-invasive, low-cost and non-pharmacological intervention. Several clinical trials were proved that music therapy could reduce the pain and anxiety among postoperative and old age population for better clinical progress. Listening to soft music can enhance brain alpha wave, and there is a negative correlation between alpha wave of EEG and sympathetic excitation. The preference of music also influences power of alpha wave. Recent studies report that implying music intervention on postoperative patients could lead to fewer acute confusion status, however, the incidence and potential exposed risk factors of delirium between medical and surgical populations were different. The effect of music intervention on medical critical patients and the related mechanism still need further investigation. In addition, whether the multicomponent intervention could obtain greater effect than single component intervention still not ascertained. Furthermore, the evidences of music intervention in decreasing the duration of mechanical ventilation, length of ICU stay, sedation time and mortality were still lacking. The mechanism between music intervention and delirium occurrence also need to further investigate.