Chapter 44
Sleep Disturbances in the Intensive Care Unit
Normal Sleep
The physiologic function of sleep remains unknown. However, evidence suggests that it may be needed for normal growth and repair of body tissues. It is suspected, but not proven, that sleep deprivation impairs healing and recovery. In most tissues, peak rates of protein synthesis and cell division coincide with sleep. Hormones that inhibit protein synthesis, such as cortisol and catecholamines, remain low during most of the night (when there is a normal circadian variation). Sleep is the normal stimulus for the release of the majority of growth hormone. In contrast, degradative metabolism is greater during wakefulness, and prolonged sleeplessness promotes a catabolic state. Sleep deprivation may impair all these physiologic functions. In fact, animal studies have shown that 2 to 3 weeks of total sleep deprivation in rats ultimately leads to death.
Factors That Contribute to Sleep Deprivation and Fragmentation in the ICU
Myriad factors interact to disrupt sleep in the ICU (Table 44.1). While many of these factors are non modifiable, others, such as ambient light, noise, timing of patient procedures, and certain medications, can be modified to decrease sleep disruption.
TABLE 44.1
Factors That Contribute to Sleep Disruption in Patients in the Intensive Care Unit (ICU)
| Patient Factors | Environmental Factors |
| Preexisting Primary Sleep Pathology Obstructive or central sleep apnea (Chapter 80) Obesity hypoventilation syndrome (Chapter 80) Restless legs syndrome and periodic limb movements Parasomnias Hypersomnia (e.g., narcolepsy) Patient Symptoms Pain Anxiety Agitation Fear Underlying Disease Process and Treatment Modalities Severity of illness Metabolic derangements associated with illness Treatment modalities —Medication effects —Dialysis, etc. Ventilation and mode of ventilation | Ambient Noise Equipment alarms Conversation Pagers Television Monitoring equipment Ventilator alarms Ambient Light Overhead lights Television Monitoring equipment Procedures and Patient Interactions during Night or When Patient Is Asleep Phlebotomy Bathing Vital signs Medication administration Diagnostic studies at bedside and outside of the ICU |
Ambient Noise
Noise is a pervasive feature of hospitals, especially ICUs. ICU noise levels in the range of 60 to 84 dB have been documented. As a reference, a typical busy office environment’s noise level would be approximately 60 to 70 dB. The alarm denoting the arrival of a pneumatic tube canister may generate 85 dB. Both baseline ambient noise levels and noise peaks are important. Noise peaks can cause arousals and disrupt sleep while loud background noise can act as a barrier to sleep initiation and maintenance. Studies have not yet determined if background noise or peak noise is more detrimental to restorative sleep. Studies that have correlated noise levels to polysomnographic recordings of sleep in the ICU have shown that noise accounts for approximately 17% of all arousals and 24% of awakenings. Although these data suggest that other factors contribute to sleep disruption in the ICU, noise reduction presents one opportunity to facilitate more consolidated sleep. Noise levels account for a greater degree of sleep disruption in healthy volunteers compared to ICU patients, suggesting that ICU patients may acclimatize to ICU noise with ongoing exposure. The use of patient earplugs is a low cost, practical intervention that is acceptable and comfortable for patients. ICU personnel need to be cognizant of the impact of noise on patients’ sleep and should make efforts to minimize nocturnal noise. The provision of single-patient rooms and attention to positioning of monitoring alarms outside of patient’s room are other effective strategies to reduce noise. Bedside devices that are noisy (such as nebulizers and infusion pumps) should not be placed at the head of the bed if feasible. Periodically, ICU noise levels should be monitored as part of a quality control initiative.
Procedures and Patient Interactions
Patient care activities have been shown to account for approximately 20% of patients’ arousals during sleep (measured by polysomnography). Patient interruptions can often be decreased by bundling multiple interventions simultaneously (e.g., routine vital signs, radiographic studies, and morning phlebotomy). Furthermore, these interventions should take place between 5 and 6:30 a.m. when possible, rather than between 3 and 5 a.m. Routine nursing care should be evaluated for necessity and timing. For instance, the non-urgent administration of oral medication can be deferred for 1 to 2 hours if it can avoid disruption of a sleep period. Similarly, assessment of vital signs may not be indicated as frequently in a stable ICU patient. Telemedicine and remote patient monitoring is a promising development that may also help to minimize disturbed sleep and patient interruptions. Box 44.1 lists practical nonpharmacologic recommendations intended to facilitate restorative sleep in the ICU.
BOX 44.1 Practical Measures to Improve Sleep Quality in Intensive Care Units
Place patients in rooms with windows to maximize natural light during daytime hours.
Use dimmer switches in rooms to allow a dark environment at night.
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