Sleep in Critically III Chemically Paralyzed Patients Requiring Mechanical Ventilation: Causes
Patients were not quantitatively sleep deprived, but > 50% of sleep occurred during the daytime period, illustrating the disruption of nighttime sleep, alteration in normal circadian rhythm, and the importance of daytime sleep periods in preventing sleep depriva-tion. In contrast to the study of Gabor et al, in which REM sleep was determined to be normal, we found REM sleep to be severely reduced in the IS group and could not be comparatively analyzed with the other groups due to lack of detection in the patients receiving NMBAs, and only 50% of patients in the CS group had detectable REM. Decreased REM sleep observed in this study may have several causes, including use of vasopressor agents, narcotics, and increased difficulty in detecting REM in patient with neuromuscular blockade. further
In contrast to prior studies that reported increased stage 1 and stage 2 sleep and decreased SWS, we found increased stage 1 sleep only in the CS group, decreased stage 2 sleep only in the CS group, and increased SWS in all groups. Patients who received IS had the lowest TST but largest amount of stage 2 sleep (57.7%). Intermittent doses of benzodiazepines are known to increase spindle activity and may have contributed to the increased stage 2 sleep compared to the other groups. Environmental noise, talking, and patient-care activities have been shown to account for 30% of arousals or awakenings in ICU patients.
The IS group had the least amount of patient-care interventions but the largest amount of wake time, and may have been influenced by these factors more than the other two groups receiving CS. The CS/NMBA group had the largest number of arousals and awakenings, although no correlation was established with the number of patient-care interventions and may reflect the low power of the study. Delayed arousals, > 1 min from the event, were noted with invasive procedures. Not all patients in the CS/NMBA group received narcotics, and underlying pain may have contributed to higher spontaneous and procedure-related arousals. Although sedated, their EEG reflected wakefulness 22% of the time; how this impacted their clinical outcome is unknown.
Compared to a recent study by Parthasarathy and Tobin, we did not find a relationship between awakenings or arousals and ventilator mode.
Category: Respiratory Symptoms
Tags: ICU, mechanical ventilation, polysomnography, sleep