The topic of sleep disturbance in the ICU has been of some considerable interest, considering how many articles pop up when you look up "sleep disturbance in the ICU". Much of the information I used to generate the discussion section for Question 25 from the first paper of 2008 has been derived from this excellent article from the The Open Critical Care Medicine Journal. The LITFL page on sleep in the ICU also offers an excellent brief overview, perfect for pre-exam cramming.
- Sleep is a normal active physiological state which serves a poorly understood but apparently vital function.
- Sedation does not seem to have the same restorative function.
- The sleep of ICU patients is fragmented, light, non-circadian, and decreased in quantity.
- In ICU, sleep quality is poor because of noise, light pollution, constant care-related awakenings, pain, and the lack of REm sleep resulting from the use of sedatives.
- Monitoring sleep in ICU is complicated by the presence of non-standard EEG activity
- Non-pharmacological measures to reduce sleep disruption include limiting noise, dimming light at night, and using relaxation techniques (eg, white noise or calming music, biofeedback, massage)
- Pharmacological measures may involve the use of melatonin, short acting sedatives (eg. zolpidem) and reducing reliance on classical sedative agents (benzodiazepines and propofol)
Kamdar et al (2012) have many negative things to say about sleep in the ICU population
The following factors have been found to act as negative influences on sleep:
The following consequences have been ascribed to sleep deprivation, though in truth there really is no way of testing that. Several good resources exist for this, for example Kamdar et al, 2012 and Jolanta Orzeł-Gryglewska's "Consequences of sleep deprivation", 2010. The experts offer the following list of problems:
LITFL recommend daily sleep diaries, visual analog scales (VAS), questionnaires, and symptom or quality of life questionnaires with sleep items (subject to recall bias and other problems), direct observation of arousals and motor activity, actigraphy (using movement detectors), BIS and Bispectral index and multichannel polysomnography (gold standard). An excellent recent article by Delaney et al (2015) offers a detailed overview of the issues involved.
Polysomnography, even though viewed as the gold standard for normal patients, has many barriers to its application in the ICU, particularly in context of the ECG-befuddling effects of exotic sedatives and encephalopathy. To give an extreme example, a patient who has had a hemispherectomy and then went on to develop HSV encephalitis will offer a highly unusual pattern of EEG activity, which will be difficult to interpret within the framework of standard EEG definitions for sleep stages. Drouot et al (2012) found that about 28% of all polysomnography studies collected in the ICU could not be classified using conventional scoring rules.
Bispectral (BIS) monitoring is barely even validated for use in anaesthetised normal subjects, and its application to sleeping ICU patients is even more dodgy. It suffers from all the deficits of polysomnography in the ICU setting, and is confounded by all the same problems, but it does not offer much opportunity for specialist waveform interpretation, as it reduces the majestic electrochemical complexity of the human consciousness into a single numerical variable. Patel et al (2001) made an attempt to assess sleep in the ICU using BIS, working from the knowledge that BIS at least correlates with EEG during normal sleep. They used a value of over 85 to define "awake", 60-85 as "light sleep" (presumably, N1) and under 60 as "slow wave sleep". REM was detected using a combination of BIS waveform analysis and EMG recordings. The study was frustrated by the fact that the patients did not demonstrate any recognisable sleep stage patterns (eg. there were no rapid eye movements during the stages that were supposed to be REM sleep), and the authors could not arrive at anything solid about the use of BIS for sleep monitoring, concluding only that "traditional classifications of EEG sleep staging are deficient when used to describe sleep in intensive care unit patients". The major advantage of BIS is the fact that it does frequently correlate with the clinically observed state of arousal, and requires little intelligence to interpret.
Actigraphy is performed by the use of a wristwatch-like accelerometer, which tells you when the patient is moving. The obvious limitation of this is the lack of correlation between movement and arousal among ICU patients. The classical extreme example of this is the patient who is paralysed with muscle relaxants. Beecroft et al (2008) compared it to polysomnography in a group of twelve intubated ICU patients, and concluded that it was "inaccurate and unreliable", as it consistently overestimated sleep time and sleep efficiency.
Subjective behavioural assessment is basically asking of the bedside nurse whether he or she thinks the patient is asleep or awake. It sure is a cheap method, but also almost useless. For instance, Bourne et al (2007) found that ICU staff consistently mistook sedation for sleep (why wouldn't they, as it looks the same) and overestimated the duration and efficiency of sleep. The limitations are basically the same as those of actigraphy, as the bedside staff really only have movement to go off when determining whether the patient is awake. Not only are they collecting inaccurate data, they also frequently fail to record it (unlike the always-reliable actigraphy robot).
Hybrid systems are being developed. A recent article (Namba et al, 2015) added validity to the use of a wristwatch-like ambulatory sleep monitor (the Watch PAT 200 by Itamar), normally meant for outpatient sleep apnoea studies. That thing measures peripheral arterial tone as a means of estimating autonomic nervous system activity. The utility of these devices in ICU remains to be established; presently it seems like an expensive toy (imagine how many central lines you could buy instead).
The best reference for this seems to be the 2015 article by Kamdar et al, which details the implementation of a "multifaceted quality improvement intervention" to improve sleep quality among ICU patients at the Johns Hopkins Hospital Medical ICU. The following list of interventions is largely modelled on their program (see their Table 2); it sounds like a nice program, even though they did not assess the sleep quality in any objective way.