Delirium onset related to autonomic nervous system disorder caused by aging, illness and/or the environment (noise, blue-ray)

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Length of hospital stay and mortality rates are significantly higher in delirium patients than in non-delirium patients. A high incidence of postoperative delirium onset has been reported among abdominal aortic aneurysm patients. Patients admitted to the intensive care unit (ICU) also sometimes experience a condition of delirium. The patients are exposed to an stressful environment; they are isolated from their families, and their sleep is disrupted by continuous noise and lighting. Our investigation revealed that noise in the ICU was markedly higher than in the general wards and there were no circadian variations. In the present study, postabdominal aortic aneurysm laparotomy ICU-patients were randomly divided into two groups: a group using earplugs; and a control group without earplugs. Stress caused by the ICU environment (noise) during ICU stay was assessed by non-invasive measurement of heart rate and autonomic nervous system activity (ANS) and their circadian variations. Delirium and/or agitation decreased to 27% in the ICU patients fitted with earplugs from 50% in one without earplugs. Where delirium and/or agitation were observed in ICU patients whose circadian rhythms disappeared or reversed in their ANS and HR, the circadian rhythm in the HR recovered from irregularity in post-ICU ward care, while the ANS did not recover even5 days later. The results indicate that nighttime use of earplugs in the ICU patients reduces onset of delirium and/or agitation, implying that noise from the ICU backgroundnoise plays a part in delirium onset.