Temporal disorganization of circadian rhythmicity and sleep-wake regulation in mechanically ventilated patients receiving continuous intravenous sedation

Sleep and Circadian Rhythm in Critical Illness

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

Melatonin in Critical Care

Melatonin is involved in regulation of a variety of physiologic functions, including circadian rhythm, reproduction, mood, and immune function. Exogenous melatonin has demonstrated many clinical effects. Numerous clinical studies have documented improved sleep quality following administration of exogenous melatonin. Recent studies also demonstrate the analgesic, anxiolytic, antiinflammatory, and antioxidative effects of melatonin. This article reviews the principal properties of melatonin and how these could find clinical applications in care of the critically ill patients.

Melatonin and cortisol exhibit different circadian rhythm profiles during septic shock depending on timing of onset: a prospective observational study

Background

Septic shock has been found to disrupt circadian rhythms. Moreover, timing of onset has been associated with different circadian profiles in experimental studies.

Results

In this prospective study, we enrolled 26 patients divided into two groups: Group A (N = 15) included subjects who had septic shock at the time of ICU admission and Group B (N = 11) included patients who developed septic shock during ICU admission. 6-Sulfatoxymelatonin (aMT6s) and cortisol levels were measured in urine samples every 4 h over a 24-h period. Two sets of samples were taken from Group A (entry/septic shock and exit) and three sets from Group B (entry, septic shock and exit). Mean, amplitude that is the difference between peak and mean values, as well as peak time, were estimated for both aMT6s and cortisol. In Group A, amplitude of aMT6s upon entry (septic shock) was reduced in relation to exit (437.2 ± 309.2 vs. 674.1 ± 657.6 ng/4 h, p < 0.05). Peak time occurred earlier (10:00 p.m. vs. 07:00 a.m, p < 0.05) and correlated with higher APACHE II score and longer ICU stay. In Group B, aMT6s mean values were significantly increased during septic shock (2492.2 ± 1709.1 ng/4 h) compared to both entry (895.4 ± 715.5 ng/4 h) and exit (1308.6 ± 1214.4 ng/4 h, p < 0.05 for all comparisons). Amplitude of aMT6s was also elevated during septic shock (794.8 ± 431.8 ng/4 h) in relation to entry (293.1 ± 275.9 ng/4 h, p < 0.05). Regarding cortisol rhythm in Group A, during septic shock amplitude was increased compared to exit (13.3 ± 31 ng/4 h vs. 8.7 ± 21.2 ng/4 h p < 0.05) and correlated with reduced hospital length of stay. In Group B, cortisol mean values and amplitude during septic shock (10 ± 5.3 and 3 ± 1.8 ng/4 h, respectively) were significantly reduced compared to both entry (30 ± 57.9 and 12.3 ± 27.3 ng/4 h) and exit (14.4 ± 20.7 and 6.6 ± 8.7 ng/4 h, p < 0.05 for all comparisons) and correlated with higher SOFA score and longer ICU and hospital stay.

Conclusions

Septic shock induced inverse changes of aMT6s and cortisol circadian rhythm profiles both within and between different groups of patients, depending on timing of onset. Reduced rhythmicity was correlated with severity of disease and longer ICU stay.

Non-circadian signals in the intensive care unit: Point prevalence morning, noon and night

BACKGROUND

Intensive care unit (ICU) sleep disturbance is severe and potentially related to abnormal light and sound exposure.

OBJECTIVES

To assess the prevalence of measures of light and sound disturbance in ICU patient rooms, and whether these could be modified by a sleep-promotion intervention.

METHODS

This observational study with a before and after design for a quality improvement initiative surveyed environmental factors in ICU rooms at 01:00 08:00, and 12:00. Surveys assessed light usage, television usage, window shade position, and room door/curtain position. Factors were compared before and after an ICU sleep-promotion intervention.

RESULTS

990 (pre-intervention) and 819 (post-intervention) occupied rooms were surveyed. Pre-intervention, the prevalence of night-time factors included: bright lights on (21%), television on (46%), and room door open (94%). Post-intervention, more rooms had all lights off at night (41% v 50%, p = 0.04), and fewer rooms had open door curtains (57% v 42%, p = 0.001) and window shades (78% v 62%, p = 0.002).

CONCLUSIONS

Disruptive environmental factors are common in the ICU. Some factors improve with sleep-promotion interventions.

Sleep Disturbance after Hospitalization and Critical Illness: A Systematic Review

RATIONALE

Sleep disturbance during intensive care unit (ICU) admission is common and severe. Sleep disturbance has been observed in survivors of critical illness even after transfer out of the ICU. Not only is sleep important to overall health and well being, but patients after critical illness are also in a physiologically vulnerable state. Understanding how sleep disturbance impacts recovery from critical illness after hospital discharge is therefore clinically meaningful.

OBJECTIVES

This Systematic Review aimed to summarize studies that identify the prevalence of and risk factors for sleep disturbance after hospital discharge for critical illness survivors.

DATA SOURCES

PubMed (January 4, 2017), MEDLINE (January 4, 2017), and EMBASE (February 1, 2017).

DATA EXTRACTION

Databases were searched for studies of critically ill adult patients after hospital discharge, with sleep disturbance measured as a primary outcome by standardized questionnaire or objective measurement tools. From each relevant study, we extracted prevalence and severity of sleep disturbance at each time point, objective sleep parameters (such as total sleep time, sleep efficiency, and arousal index), and risk factors for sleep disturbance.

SYNTHESIS

A total of 22 studies were identified, with assessment tools including subjective questionnaires, polysomnography, and actigraphy. Subjective questionnaire studies reveal a 50-66.7% (within 1 mo), 34-64.3% (>1-3 mo), 22-57% (>3-6 mo), and 10-61% (>6 mo) prevalence of abnormal sleep after hospital discharge after critical illness. Of the studies assessing multiple time points, four of five questionnaire studies and five of five polysomnography studies show improved aspects of sleep over time. Risk factors for poor sleep varied, but prehospital factors (chronic comorbidity, pre-existing sleep abnormality) and in-hospital factors (severity of acute illness, in-hospital sleep disturbance, pain medication use, and ICU acute stress symptoms) may play a role. Sleep disturbance was frequently associated with postdischarge psychological comorbidities and impaired quality of life.

CONCLUSIONS

Sleep disturbance is common in critically ill patients up to 12 months after hospital discharge. Both subjective and objective studies, however, suggest that sleep disturbance improves over time. More research is needed to understand and optimize sleep in recovery from critical illness.

Association of intensive care unit delirium with sleep disturbance and functional disability after critical illness: an observational cohort study

Background

In medical intensive care unit (MICU) patients, the predictors of post-discharge sleep disturbance and functional disability are poorly understood. ICU delirium is a risk factor with a plausible link to sleep disturbance and disability. This study evaluated the prevalence of self-reported post-ICU sleep disturbance and increased functional disability, and their association with MICU delirium and other ICU factors.

Methods

This was an observational cohort study of MICU patients enrolled in a biorepository and assessed upon MICU admission by demographics, comorbidities, and baseline characteristics. Delirium was assessed daily using the Confusion Assessment Method for the ICU. Telephone follow-up interview instruments occurred after hospital discharge and included the Pittsburgh Sleep Quality Index (PSQI), and basic and instrumental activities of daily living (BADLs, IADLs) for disability. We define sleep disturbance as a PSQI score > 5 and increased disability as an increase in composite BADL/IADL score at follow-up relative to baseline. Multivariable regression modeled the associations of delirium and other MICU factors on follow-up PSQI scores and change in disability scores.

Results

PSQI and BADL/IADL instruments were completed by 112 and 122 participants, respectively, at mean 147 days after hospital discharge. Of those surveyed, 63% had sleep disturbance by PSQI criteria, and 37% had increased disability by BADL/IADL scores compared to their pre-MICU baseline. Total days of MICU delirium (p = 0.013), younger age (p = 0.013), and preexisting depression (p = 0.025) were significantly associated with higher PSQI scores at follow-up. Lower baseline disability (p < 0.001), older age (p = 0.048), and less time to follow-up (p = 0.024) were significantly associated with worsening post-ICU disability, while the occurrence of MICU delirium showed a trend toward association (p = 0.077).

Conclusions

After adjusting for important covariates, total days of MICU delirium were significantly associated with increased post-discharge sleep disturbance. Delirium incidence showed a trend toward association with increased functional disability in the year following discharge.

Looking for light in the din: An examination of the circadian-disrupting properties of a medical intensive care unit

OBJECTIVE

Critically ill patients exhibit profound disturbances of circadian rhythmicity, most commonly in the form of a phase delay. We investigated the specific zeitgeber properties of a medical intensive care unit to develop a model that explained these abnormalities.

RESEARCH METHODOLOGY

Prospective, observational study conducted during 2013-2014. Twenty-four-hour ambient light (lux, 672 hours) and sound pressure levels (dBA, 504 hours) were measured in patient rooms. Patients and families were surveyed regarding their perceptions of the environment.

SETTING

University-based adult medical intensive care unit.

MAIN OUTCOME MEASURES

The timing and intensity of the ambient light-dark cycle and sound environment and the relationship of these measurements to patient/family perceptions.

RESULTS

Twenty-four-hour light-dark cycles were extremely weak and phase delayed relative to the solar cycle. Morning light averaged 12.1 (4.8, 37.2) lux, when only 24.9% ± 10.9% of available light was utilised; yet patients and families did not identify low daytime light levels as problematic. Median noise levels were invariably excessive (nighttime 47.9 [45.0, 51.3] dBA) with minimal variation, consistent with the absence of a defined rest period.

CONCLUSION

The intensive care unit functions as a near-constant routine protocol disconnected from solar time. Behavioural interventions to promote entrainment should be supported by objective measurements of light and sound.

Circadian leptin concentration changes in critically ill heart failure patients

Physiologically, leptin concentration is controlled by circadian rhythm. However, in critically ill patients, circadian rhythm is disrupted. Thus we hypothesized that circadian leptin concentration changes are not preserved in critically ill patients. Ten consecutive critically ill heart failure patients with the clinical indication for mechanical ventilation and sedation were included into our study. Plasma leptin concentration was measured every 4 h during the first day (0-24 h) and during the third day (48-72 h) after admission. During the first day, there were significant leptin concentration changes (ANOVA, p<0.05), characterized by an increase in concentration by 44 % (16-58 %); p=0.02 around noon (10 am-2 pm) and then a decrease in concentration by 7 % (1-27 %); p=0.04 in the morning (2 am-6 am). In contrast, there was no significant change in leptin concentration during the third day after admission (ANOVA, p=0.79). Based on our preliminary results, we concluded that in critically ill heart failure patients, the circadian rhythm of plasma leptin concentration seems to be preserved during the first but not during the third day after admission.

Melatonin and the Prevention and Management of Delirium: A Scoping Study

Background

The therapeutic benefit of melatonin in the prevention and treatment of delirium is uncertain.

Objective

To perform a scoping study to describe the existing literature regarding the use of melatonin and ramelteon in the prevention and treatment of delirium.

Methods

We performed a scoping study using the Arksey and O’Malley framework to explore our objective. Two independent panels searched MEDLINE, OVID, EMBASE, PubMed, Google Scholar, and Cochrane Library for relevant articles up to November 2017 describing the use of melatonin and ramelteon in the prevention or management of delirium. We extracted relevant summary data from the studies and attempted to draw conclusion regarding benefit.

Results

We summarized evidence from 20 relevant articles. There were a total of nine articles: five randomized controlled trials (RCTs), two retrospective medical record reviews, one non-randomized observational study, and one case report describing the role of either melatonin or ramelteon in preventing delirium. There were a total of 11 studies studying the role of either melatonin or ramelteon in the management of established delirium. None of these were RCT and were predominantly case series and case reports. Four of the five trials studying the effect of melatonin analogs in preventing delirium reported a beneficial effect but study heterogeneity limited any broad recommendations. Similarly, the lack of any well-designed trials limits any recommendations regarding the effect of melatonin analogs in treating delirium.

Conclusion

Large, well-designed clinical trials are required to explore the potential beneficial effects of melatonin and ramelteon on delirium prevention and management.

Melatonin Secretion Pattern in Critically Ill Patients: A Pilot Descriptive Study

Critically ill patients have abnormal circadian and sleep homeostasis. This may be associated with higher morbidity and mortality. The aims of this pilot study were (1) to describe melatonin secretion in conscious critically ill mechanically ventilated patients and (2) to describe whether melatonin secretion and sleep patterns differed in these patients with and without remifentanil infusion. Eight patients were included. Blood-melatonin was taken every 4th hour, and polysomnography was carried out continually during a 48-hour period. American Academy of Sleep Medicine criteria were used for sleep scoring if sleep patterns were identified; otherwise, Watson's classification was applied. As remifentanil was periodically administered during the study, its effect on melatonin and sleep was assessed. Melatonin secretion in these patients followed a phase-delayed diurnal curve. We did not observe any effect of remifentanil on melatonin secretion. We found that the risk of atypical sleep compared to normal sleep was significantly lower (p < 0.001) under remifentanil infusion. Rapid Eye Movement (REM) sleep was only observed during the nonsedation period. We found preserved diurnal pattern of melatonin secretion in these patients. Remifentanil did not affect melatonin secretion but was associated with lower risk of atypical sleep pattern. REM sleep was only registered during the period of nonsedation.

Significance of circadian rhythms in severely brain-injured patients: A clue to consciousness?

Objective:

To investigate the relationship between the presence of a circadian body temperature rhythm and behaviorally assessed consciousness levels in patients with disorders of consciousness (DOC; i.e., vegetative state/unresponsive wakefulness syndrome or minimally conscious state).

Methods:

In a cross-sectional study, we investigated the presence of circadian temperature rhythms across 6 to 7 days using external skin temperature sensors in 18 patients with DOC. Beyond this, we examined the relationship between behaviorally assessed consciousness levels and circadian rhythmicity.

Results:

Analyses with Lomb-Scargle periodograms revealed significant circadian rhythmicity in all patients (range 23.5–26.3 hours). We found that especially scores on the arousal subscale of the Coma Recovery Scale–Revised were closely linked to the integrity of circadian variations in body temperature. Finally, we piloted whether bright light stimulation could boost circadian rhythmicity and found positive evidence in 2 out of 8 patients.

Conclusion:

The study provides evidence for an association between circadian body temperature rhythms and arousal as a necessary precondition for consciousness. Our findings also make a case for circadian rhythms as a target for treatment as well as the application of diagnostic and therapeutic means at times when cognitive performance is expected to peak.

Nursing Interactions With Intensive Care Unit Patients Affected by Sleep Deprivation: An Observational Study

BACKGROUND

Patients in intensive care units (ICUs) often experience sleep deprivation due to different factors. Its consequences are damaging both physiologically and psychologically. This study focuses particularly on nursing interactions as the main factor involved in sleep deprivation issues.

OBJECTIVES

The aims of this study were to examine the frequency, pattern, and types of nocturnal care interactions with patients in the respiratory and cardiology ICUs; analyze the relationship between these interactions and patients' variables (age, sex, recovery diagnosis, and acuity of care); and analyze the differences in patterns of nocturnal care interactions among the units.

METHODS

This is an observational retrospective study that analyzes the frequency, pattern, and types of nocturnal care interactions with patients between 7 PM and 6 AM recording data in the activity data sheets.

RESULTS

Data consisted of 93 data assessment sheets. The mean number of care interactions per night was 18.65 (SD, 3.71). In both ICUs, interactions were most frequent at 7 PM, 10 PM, and 6 AM. Only 8 uninterrupted sleep periods occurred. Frequency of interactions correlated significantly with patients' acuity scores and the number of nurse interventions in both ICUs.

CONCLUSIONS

Patients in ICUs have fragmented sleep patterns. This study underlines the need to develop new management approaches to promote and maintain sleep.

Abnormal environmental light exposure in the intensive care environment

PURPOSE

We sought to characterize ambient light exposure in the intensive care unit (ICU) environment to identify patterns of light exposure relevant to circadian regulation.

METHODS

A light monitor was affixed to subjects' bed at eye level in a modern intensive care unit and continuously recorded illuminescence for at least 24h per subject. Blood was sampled hourly and measured for plasma melatonin. Subjects underwent hourly vital sign and bedside neurologic assessments. Care protocols and the ICU environment were not modified for the study.

RESULTS

A total of 67,324 30-second epochs of light data were collected from 17 subjects. Light intensity peaked in the late morning, median 64.1 (interquartile range 19.7-138.7) lux. The 75th percentile of light intensity exceeded 100lx only between 9AM and noon, and never exceeded 150lx. There was no correlation between melatonin amplitude and daytime, nighttime or total light exposure (Spearman's correlation coefficients all <0.2 and p>0.5).

CONCLUSIONS

Patients' environmental light exposure in the intensive care unit is consistently low and follows a diurnal pattern. No effect of nighttime light exposure was observed on melatonin secretion. Inadequate daytime light exposure in the ICU may contribute to abnormal circadian rhythms.

The effect of cycled lighting in the intensive care unit on sleep, activity and physiological parameters: A pilot study

Patients in intensive care suffer from severe illnesses or injuries and from symptoms related to care and treatments. Environmental factors, such as lighting at night, can disturb patients' circadian rhythms. The aim was to investigate whether patients displayed circadian rhythms and whether a cycled lighting intervention would impact it. In this pilot study (N=60), a cycled lighting intervention in a two-bed patient room was conducted. An ordinary hospital room functioned as the control. Patient activity, heart rate, mean arterial pressure and body temperature were recorded. All data were collected during the patients' final 24h in the intensive care unit. There was a significant difference between day and night patient activity within but not between conditions. Heart rates differed between day and night significantly for patients in the ordinary room but not in the intervention room or between conditions. Body temperature was lowest at night for all patients with no significant difference between conditions. Patients in both conditions had a natural circadian rhythm; and the cycled lighting intervention showed no significant impact. As the sample size was small, a larger repeated measures study should be conducted to determine if other types of lighting or environmental factors can impact patients' well-being.

The significance of circadian rhythms and dysrhythmias in critical illness

Many physiological and cellular processes cycle with time, with the period between one peak and the next being roughly equal to 24 h. These circadian rhythms underlie 'permissive homeostasis', whereby anticipation of periods of increased energy demand or stress may enhance the function of individual cells, organ systems or whole organisms. Many physiological variables related to survival during critical illness have a circadian rhythm, including the sleep/wake cycle, haemodynamic and respiratory indices, immunity and coagulation, but their clinical significance remains underappreciated. Critically ill patients suffer from circadian dysrhythmia, manifesting overtly as sleep disturbance and delirium, but with widespread covert effects on cellular and organ function. Environmental and pharmacological strategies that ameliorate or prevent circadian dysrhythmia have demonstrated clinical benefit. Harnessing these important biological phenomena to match metabolic supply to demand and bolster cell defenses at the apposite time may be a future therapeutic strategy in the intensive care unit.

Sleep quality and circadian rhythm disruption in the intensive care unit: a review

Sleep and circadian rhythm are reported to be severely abnormal in critically ill patients. Disturbed sleep can lead to the development of delirium and, as a result, can be associated with prolonged stay in the intensive care unit (ICU) and increased mortality. The standard criterion method of sleep assessment, polysomnography (PSG), is complicated in critically ill patients due to the practical challenges and interpretation difficulties. Several PSG sleep studies in the ICU reported the absence of normal sleep characteristics in many critically ill patients, making the standard method of sleep scoring insufficient in this patient group. Watson et al proposed a modified classification for sleep scoring in critically ill patients. This classification has not yet been validated. Sleep disturbance in the ICU is a multifactorial problem. The ICU environment, mechanical ventilation, medication, as well as the critical illness itself have been reported as important sleep disturbing factors. Secretion of sleep hormone, melatonin, expressing circadian rhythmicity was found abolished or phase delayed in critically ill patients. Various interventions have been tested in several studies aiming to improve sleep quality and circadian rhythm in the ICU. The results of these studies were inconclusive due to using the sleep assessment methods other than PSG or the absence of a reliable sleep scoring tool for the analysis of the PSG findings in this patient population. Development of a valid sleep scoring classification is essential for further sleep research in critically ill patients.

Melatonin in Critically Ill Children

Melatonin, while best known for its chronobiologic functions, has multiple effects that may be relevant in critical illness. It has been used for circadian rhythm maintenance, analgesia, and sedation, and has antihypertensive, anti-inflammatory, antioxidant, antiapoptotic, and antiexcitatory effects. This review examines melatonin physiology in health, the current state of knowledge regarding endogenous melatonin production in pediatric critical illness, and the potential uses of exogenous melatonin in this population, including relevant information from basic sciences and other fields of medicine. Pineal melatonin production and secretion appears to be altered in critical illness, though understanding in pediatric critical illness is in early stages, with only 102 children reported in the current literature. Exogenous melatonin may be used for circadian rhythm disturbances and, within the critically ill population, holds promise for diseases involving oxidant stress. There are no studies of exogenous melatonin administration to critically ill children beyond the neonatal period.

Low-dose Dexmedetomidine Improves Sleep Quality Pattern in Elderly Patients after Noncardiac Surgery in the Intensive Care Unit

Background

Patients admitted to the intensive care unit (ICU) after surgery often develop sleep disturbances. The authors tested the hypothesis that low-dose dexmedetomidine infusion could improve sleep architecture in nonmechanically ventilated elderly patients in the ICU after surgery.

Methods

This was a pilot, randomized controlled trial. Seventy-six patients age 65 yr or older who were admitted to the ICU after noncardiac surgery and did not require mechanical ventilation were randomized to receive dexmedetomidine (continuous infusion at a rate of 0.1 μg kg−1 h−1; n = 38) or placebo (n = 38) for 15 h, i.e., from 5:00 pm on the day of surgery until 8:00 am on the first day after surgery. Polysomnogram was monitored during the period of study-drug infusion. The primary endpoint was the percentage of stage 2 non–rapid eye movement (stage N2) sleep.

Results

Complete polysomnogram recordings were obtained in 61 patients (30 in the placebo group and 31 in the dexmedetomidine group). Dexmedetomidine infusion increased the percentage of stage N2 sleep from median 15.8% (interquartile range, 1.3 to 62.8) with placebo to 43.5% (16.6 to 80.2) with dexmedetomidine (difference, 14.7%; 95% CI, 0.0 to 31.9; P = 0.048); it also prolonged the total sleep time, decreased the percentage of stage N1 sleep, increased the sleep efficiency, and improved the subjective sleep quality. Dexmedetomidine increased the incidence of hypotension without significant intervention.

Conclusions

In nonmechanically ventilated elderly patients who were admitted to the ICU after noncardiac surgery, the prophylactic low-dose dexmedetomidine infusion may improve overall sleep quality.

Environmental 24-hr Cycles Are Essential for Health

Circadian rhythms are deeply rooted in the biology of virtually all organisms. The pervasive use of artificial lighting in modern society disrupts circadian rhythms and can be detrimental to our health. To investigate the relationship between disrupting circadian rhythmicity and disease, we exposed mice to continuous light (LL) for 24 weeks and measured several major health parameters. Long-term neuronal recordings revealed that 24 weeks of LL reduced rhythmicity in the central circadian pacemaker of the suprachiasmatic nucleus (SCN) by 70%. Strikingly, LL exposure also reduced skeletal muscle function (forelimb grip strength, wire hanging duration, and grid hanging duration), caused trabecular bone deterioration, and induced a transient pro-inflammatory state. After the mice were returned to a standard light-dark cycle, the SCN neurons rapidly recovered their normal high-amplitude rhythm, and the aforementioned health parameters returned to normal. These findings strongly suggest that a disrupted circadian rhythm reversibly induces detrimental effects on multiple biological processes.

Sleep Neurobiology and Critical Care Illness

The intensive care unit (ICU) environment is not propitious for restoring sleep and many studies have reported that critically ill patients have severe sleep disruptions. However, sleep alterations in critically ill patients are specific and differ significantly from those in ambulatory patients. Polysomnographic patterns of normal sleep are frequently lacking in critically ill patients and the neurobiology of sleep is important to consider regarding alternative methods to quantify sleep in the ICU. This article discusses elements of sleep neurobiology affecting the specificity of sleep patterns and sleep alterations in patients admitted to the ICU.

Intra-day variability of cystatin C, creatinine and estimated GFR in intensive care patients

BACKGROUND

Markers of renal function are widely used in intensive care and sudden changes are important indicators of acute kidney injury. The problem is to distinguish between disease progression/improvement from the natural variation in the patient. The aim of the present study was thus to study the normal intraday variation in ICU patients.

METHODS

We studied the intra-day variation of creatinine, cystatin C and estimated GFR based on these two markers in 28 clinically stable ICU patients.

RESULTS

The median diurnal coefficient of variation sCV) for creatinine was 3.70% (1.92-9.25%) while the median CV for cystatin C was 3.66% (1.36-8.11%). The corresponding CVs for the estimated GFRs were 2.00% (0.89-9.82%) for eGFRcreatinine and 4.60% (1.65-10.24%) for eGFRcystc.

CONCLUSIONS

The eGFRcreatinine values in individual patients were clearly higher than the eGFRcystc values. The median CV for creatinine, cystatin C and the eGFR measurements were below 5% which means that 95% of the test results will vary by <10% between sampling times in stable ICU patients. Differences >10% between sampling times are thus likely to be an indication of changes in biomarker levels due to the disease/treatment.

Circadian Rhythm Disruption in the Critically Ill: An Opportunity for Improving Outcomes

OBJECTIVES

Circadian rhythms are severely disrupted among the critically ill. These circadian arrhythmias impair mentation, immunity, autonomic function, endocrine activity, hormonal signaling, and ultimately healing. In this review, we present a modern model of circadian disruption among the critically ill, discuss causes of these circadian arrhythmias, review observational and intervention studies of the effects of circadian-rhythm-restoring factors on medical outcomes, and identify needed key trials of circadian interventions in the critically ill.

DATA SOURCES

MEDLINE, EMBASE, PsychINFO, Google Scholar through December 2014.

STUDY SELECTION

Articles relevant to circadian rhythms, melatonin, and light in the critically ill were selected.

DATA EXTRACTION AND DATA SYNTHESIS

Articles were synthesized for this review of circadian arrhythmia and the use of circadian-rhythm-restoring interventions among the critically ill.

CONCLUSIONS

Circadian disruption often demonstrates serial degradation: initially, the amplitude attenuates along with delayed circadian phase. With increasing acuity of illness, circadian rhythmicity may be lost entirely. Causes of chronodisruption may be environmental or internal to the patient. In particular, inadequate daytime illumination and nocturnal light pollution disrupt healthy circadian periodicity. Internal causes of circadian arrhythmia include critical illness itself and subjective experience of distress and pain. Observational studies of windowed rooms and real-time ambient lighting have found that physiologic light-dark patterns may support recovery from critical illness. Studies of early morning bright light or evening melatonin agonists have found improved rates of delirium, enhanced sleep, and lower arrhythmia prevalence. The current evidence base emphasizes that lighting and melatoninergic interventions deserve to be tested in full-scale trials.

Sleep and Mechanical Ventilation in Critical Care

Sleep disturbances in critically ill mechanically ventilated patients are common. Although many factors may potentially contribute to sleep loss in critical care, issues around mechanical ventilation are among the more complex. Sleep deprivation has systemic effects that may prolong the need for mechanical ventilation and length of stay in critical care and result in worse outcomes. This article provides a brief review of the physiology of sleep, physiologic changes in breathing associated with sleep, and the impact of mechanical ventilation on sleep. A summary of the issues regarding research studies to date is also included. Recommendations for the critical care nurse are provided.

Positive and negative effects of mechanical ventilation on sleep in the ICU: a review with clinical recommendations

PURPOSE

Sleep is an essential physiologic process that helps to restore normal body homeostasis. Sleep disturbances have been shown to be associated with poor clinical outcomes, such as a greater risk of cardiovascular disease and increasing mortality. Critically ill patients, particularly those receiving mechanical ventilation, may be more susceptible to sleep disruption.

METHODS AND RESULTS

Mechanical ventilation is an important factor influencing sleep in critically ill patients as it may have positive or negative effects, depending on patient population, mode, and specific settings. Other causes of sleep disruption include the acute illness itself, the daily routine care, and the effects of medications. Improving sleep in patients admitted to an intensive care unit has the potential to improve both short- and long-term clinical outcomes. In this article we review the specific aspects of sleep in critically ill mechanically ventilated patients, including abnormal sleep patterns and loss of circadian rhythm, as well as the effects of mechanical ventilation and intravenous sedatives on sleep quality and quantity.

CONCLUSIONS

We provide recommendations for clinicians regarding optimal ventilatory settings and discuss fields for future research.

Sleep neurobiology and critical care illness

The intensive care unit (ICU) environment is not propitious for restoring sleep and many studies have reported that critically ill patients have severe sleep disruptions. However, sleep alterations in critically ill patients are specific and differ significantly from those in ambulatory patients. Polysomnographic patterns of normal sleep are frequently lacking in critically ill patients and the neurobiology of sleep is important to consider regarding alternative methods to quantify sleep in the ICU. This article discusses elements of sleep neurobiology affecting the specificity of sleep patterns and sleep alterations in patients admitted to the ICU.

Circadian dysrhythmias in the intensive care unit

Circadian rhythms underlie nearly all physiologic functions and organ systems. Circadian abnormalities have attendant implications for critical illness survival. The intensive care unit (ICU) environment, with its lack of diurnal variation in sound, light, and social cues, may precipitate circadian dysrhythmias. Additional features of critical care, including mechanical ventilation and sedation, likely perpetuate circadian misalignment. Critical illness itself, from sepsis to severe brain injury, can compromise circadian health. Use of daylight, time-restricted feedings, and administration of melatonin can possibly restore circadian rhythm. However, further study is necessary to assess the effectiveness of these interventions and their impact on ICU outcomes.

Temporal Characteristics of the Sleep EEG Power Spectrum in Critically Ill Children

STUDY OBJECTIVES

Although empirical evidence is limited, critical illness in children is associated with disruption of the normal sleep-wake rhythm. The objective of the current study was to examine the temporal characteristics of the sleep electroencephalogram (EEG) in a sample of children with critical illness.

METHODS

Limited montage EEG recordings were collected for at least 24 hours from 8 critically ill children on mechanical ventilation for respiratory failure in a pediatric intensive care unit (PICU) of a tertiary-care hospital. Each PICU patient was age- and gender-matched to a healthy subject from the community. Power spectral analysis with the fast Fourier transform (FFT) was used to characterize EEG spectral power and categorized into 4 frequency bands: δ (0.8 to 4.0 Hz), θ (4.1 to 8.0 Hz), α (8.1 to 13.0 Hz), and β1/β2 (13.1 to 20.0 Hz).

RESULTS

PICU patients did not manifest the ultradian variability in EEG power spectra including the typical increase in δ-power during the first third of the night that was observed in healthy children. Differences noted included significantly lower mean nighttime δ and θ power in the PICU patients compared to healthy children (p < 0.001). Moreover, in the PICU patients, mean δ and θ power were higher during daytime hours than nighttime hours (p < 0.001).

CONCLUSIONS

The results presented herein challenge the assumption that children experience restorative sleep during critical illness, highlighting the need for interventional studies to determine whether sleep promotion improves outcomes in critically ill children undergoing active neurocognitive development.

Lighting, sleep and circadian rhythm: An intervention study in the intensive care unit

Patients in an intensive care unit (ICU) may risk disruption of their circadian rhythm. In an intervention research project a cycled lighting system was set up in an ICU room to support patients' circadian rhythm. Part I aimed to compare experiences of the lighting environment in two rooms with different lighting environments by lighting experiences questionnaire. The results indicated differences in advantage for the patients in the intervention room (n=48), in perception of daytime brightness (p=0.004). In nighttime, greater lighting variation (p=0.005) was found in the ordinary room (n=52). Part II aimed to describe experiences of lighting in the room equipped with the cycled lighting environment. Patients (n=19) were interviewed and the results were presented in categories: "A dynamic lighting environment", "Impact of lighting on patients' sleep", "The impact of lighting/lights on circadian rhythm" and "The lighting calms". Most had experiences from sleep disorders and half had nightmares/sights and circadian rhythm disruption. Nearly all were pleased with the cycled lighting environment, which together with daylight supported their circadian rhythm. In night's actual lighting levels helped patients and staff to connect which engendered feelings of calm.

Hypopituitarism in Traumatic Brain Injury-A Critical Note

While hypopituitarism after traumatic brain injury (TBI) was previously considered rare, it is now thought to be a major cause of treatable morbidity among TBI survivors. Consequently, recommendations for assessment of pituitary function and replacement in TBI were recently introduced. Given the high incidence of TBI with more than 100 pr. 100,000 inhabitants, TBI would be by far the most common cause of hypopituitarism if the recently reported prevalence rates hold true. The disproportion between this proposed incidence and the occasional cases of post-TBI hypopituitarism in clinical practice justifies reflection as to whether hypopituitarism has been unrecognized in TBI patients or whether diagnostic testing designed for high risk populations such as patients with obvious pituitary pathology has overestimated the true risk and thereby the disease burden of hypopituitarism in TBI. The findings on mainly isolated deficiencies in TBI patients, and particularly isolated growth hormone (GH) deficiency, raise the question of the potential impact of methodological confounding, determined by variable test-retest reproducibility, appropriateness of cut-off values, importance of BMI stratified cut-offs, assay heterogeneity, pre-test probability of hypopituitarism and lack of proper individual laboratory controls as reference population. In this review, current recommendations are discussed in light of recent available evidence.

Sleep in the intensive care unit

Sleep is an important physiologic process, and lack of sleep is associated with a host of adverse outcomes. Basic and clinical research has documented the important role circadian rhythm plays in biologic function. Critical illness is a time of extreme vulnerability for patients, and the important role sleep may play in recovery for intensive care unit (ICU) patients is just beginning to be explored. This concise clinical review focuses on the current state of research examining sleep in critical illness. We discuss sleep and circadian rhythm abnormalities that occur in ICU patients and the challenges to measuring alterations in circadian rhythm in critical illness and review methods to measure sleep in the ICU, including polysomnography, actigraphy, and questionnaires. We discuss data on the impact of potentially modifiable disruptors to patient sleep, such as noise, light, and patient care activities, and report on potential methods to improve sleep in the setting of critical illness. Finally, we review the latest literature on sleep disturbances that persist or develop after critical illness.

Examining the evidence to guide practice: challenging practice habits

Nurses are the largest segment of the nation's health care workforce, which makes nurses vital to the translation of evidence-based practice as a practice norm. Critical care nurses are in a position to critically appraise and apply best evidence in daily practice to improve patients' outcomes. It is important for critical care nurses to continually evaluate their current practice to ensure that they are applying the current best evidence rather than practicing on the basis of tradition. This article is based on a presentation at the 2013 National Teaching Institute of the American Association of Critical-Care Nurses. Four practice interventions that are within the realm of nursing are critiqued on the basis of current best evidence: (1) turning critically ill patients, (2) sleep promotion in the intensive care unit, (3) feeding tube management in infants and children, and (4) prevention of venothromboembolism…again. The related beliefs, current evidence, and implications for practice associated with each topic are described.

Health care worker attitudes and identified barriers to patient sleep in the medical intensive care unit

OBJECTIVE

To identify barriers to sleep for intensive care unit (ICU) patients.

DESIGN

A qualitative study using semi-structured interviews.

SUBJECTS

Nurses and physicians who had experience working the night shift.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Multiple environmental barriers to sleep in the ICU were identified when participants were directly asked about factors affecting sleep. Responses highlighted healthcare system-based barriers related to hospital/ICU policy and workflow. Implicit barriers to sleep were found when participants responded to open-ended questions. These included attitudinal barriers such as the uncertainty about the significance of sleep, the tension between providing protocol-driven ICU care and allowing uninterrupted patient sleep, and lack of consensus regarding interventions to promote sleep.

CONCLUSIONS

This qualitative study suggests that health care worker attitudes, methods of sleep promotion, hospital institutional policies and workflow may contribute to sleep disruption in the ICU. These barriers provide additional targets for intervention in studies designed to improve sleep in the ICU.

Delirium and sleep disturbances in the intensive care unit: can we do better?

PURPOSE OF REVIEW

Delirium in the ICU affects as many as 60-80% of mechanically ventilated patients and a smaller but substantial percentage of other critically ill patients. Poor sleep quality has been consistently observed in critically ill patients. These problems are associated with worse ICU outcomes and, in many cases, delirium and poor sleep quality may be related. This review will summarize the recent literature relevant to both the problems and provide a potential pathway toward improvement.

RECENT FINDINGS

Many cases of delirium and the poor sleep experienced by ICU patients may be iatrogenic. How critical care practitioners prescribe sedatives and analgesics and, perhaps more broadly, how all medications are administered to critically ill patients, may be at the root of some of these problems. Reducing the administration of some commonly used ICU medications, especially some sedatives and anticholinergic medications, and keeping patients more awake and actively engaged in their care during the day may lead to better outcomes.

SUMMARY

It is our responsibility to apply the best available, evidence-based medicine to our practice. Adherence to new guidelines for the treatment of pain, agitation, and delirium may be the best pathway toward reducing delirium, improving sleep quality, and improving related outcomes.

Dexmedetomidine-induced sedation does not mimic the neurobehavioral phenotypes of sleep in Sprague Dawley rat

STUDY OBJECTIVES

Dexmedetomidine is used clinically to induce states of sedation that have been described as homologous to nonrapid eye movement (NREM) sleep. A better understanding of the similarities and differences between NREM sleep and dexmedetomidine-induced sedation is essential for efforts to clarify the relationship between these two states. This study tested the hypothesis that dexmedetomidine-induced sedation is homologous to sleep.

DESIGN

This study used between-groups and within-groups designs.

SETTING

University of Michigan.

PARTICIPANTS

Adult male Sprague Dawley rats (n = 40).

INTERVENTIONS

Independent variables were administration of dexmedetomidine and saline or Ringer's solution (control). Dependent variables included time spent in states of wakefulness, sleep, and sedation, electroencephalographic (EEG) power, adenosine levels in the substantia innominata (SI), and activation of pCREB and c-Fos in sleep related forebrain regions.

MEASUREMENTS AND RESULTS

Dexmedetomidine significantly decreased time spent in wakefulness (-49%), increased duration of sedation (1995%), increased EEG delta power (546%), and eliminated the rapid eye movement (REM) phase of sleep for 16 h. Sedation was followed by a rebound increase in NREM and REM sleep. Systemically administered dexmedetomidine significantly decreased (-39%) SI adenosine levels. Dialysis delivery of dexmedetomidine into SI did not decrease adenosine level. Systemic delivery of dexmedetomidine did not alter c-Fos or pCREB expression in the horizontal diagonal band, or ventrolateral, median, and medial preoptic areas of the hypothalamus.

CONCLUSIONS

Dexmedetomidine significantly altered normal sleep phenotypes, and the dexmedetomidine-induced state did not compensate for sleep need. Thus, in the Sprague Dawley rat, dexmedetomidine-induced sedation is characterized by behavioral, electrographic, and immunohistochemical phenotypes that are distinctly different from similar measures obtained during sleep.

Sleep continuity: a new metric to quantify disrupted hypnograms in non-sedated intensive care unit patients

INTRODUCTION

Sleep in intensive care unit (ICU) patients is severely altered. In a large proportion of critically ill patients, conventional sleep electroencephalogram (EEG) patterns are replaced by atypical sleep. On the other hand, some non-sedated patients can display usual sleep EEG patterns. In the latter, sleep is highly fragmented and disrupted and conventional rules may not be optimal. We sought to determine whether sleep continuity could be a useful metric to quantify the amount of sleep with recuperative function in critically ill patients with usual sleep EEG features.

METHODS

We retrospectively reanalyzed polysomnographies recorded in non-sedated critically ill patients requiring non-invasive ventilation (NIV) for acute hypercapnic respiratory failure. Using conventional rules, we built two-state hypnograms (sleep and wake) and identified all sleep episodes. The percentage of time spent in sleep bouts (<10 minutes), short naps (>10 and <30 minutes) and long naps (>30 minutes) was used to describe sleep continuity. In a first study, we compared these measures regarding good (NIV success) or poor outcome (NIV failure). In a second study performed on a different patient group, we compared these measurements during NIV and during spontaneous breathing.

RESULTS

While fragmentation indices were similar in the two groups, the percentage of total sleep time spent in short naps was higher and the percentage of sleep time spent in sleep bouts was lower in patients with successful NIV. The percentage of total sleep time spent in long naps was higher and the percentage of sleep time spent in sleep bouts was lower during NIV than during spontaneous breathing; the level of reproducibility of sleep continuity measures between scorers was high.

CONCLUSIONS

Sleep continuity measurements could constitute a clinically relevant and reproducible assessment of sleep disruption in non-sedated ICU patients with usual sleep EEG.

The impact of poor sleep on cognition and activities of daily living after traumatic brain injury: a review

BACKGROUND/AIM

Patients frequently report sleep disruptions or insomnia during their hospital stay, particularly after a traumatic brain injury (TBI). The consequences of these sleep disturbances on everyday activities are not well documented and are therefore not considered in the evaluation of independence in activities of daily living (ADLs). The goal of this narrative review is to explore the consequences of poor sleep quality on cognition and ADLs in the acute and subacute stages of a moderate and severe TBI, when patients are in acute care or inpatient rehabilitation.

METHODS

We will present an overview of normal sleep and its role in cognitive functioning, and then present the findings of studies that have investigated sleep characteristics in hospital settings and the consequences of sleep disturbances on ADLs.

RESULTS

During hospitalisation, TBI patients present severe sleep disturbances such as insomnia and sleep fragmentation, which are probably influenced by both the medical condition and the hospital or rehabilitation environment. Sleep disruption is associated with several cognitive deficits, including attention, memory and executive function impairments. Poor quality and/or insufficient quantity of sleep in acute TBI probably affect general functioning and ADLs calling for these cognitive functions.

CONCLUSIONS AND SIGNIFICANCE

The cognitive impairments present following TBI are probably exacerbated by poor sleep quality and sleep deprivation during hospitalisation, which in turn impact ADLs among this population. Health-care personnel should further consider sleep disturbances among people with TBI and a sleep protocol should be established.

Circadian rhythms in anesthesia and critical care medicine: potential importance of circadian disruptions

The rotation of the earth and associated alternating cycles of light and dark--the basis of our circadian rhythms--are fundamental to human biology and culture. However, it was not until 1971 that researchers first began to describe the molecular mechanisms for the circadian system. During the past few years, groundbreaking research has revealed a multitude of circadian genes affecting a variety of clinical diseases, including diabetes, obesity, sepsis, cardiac ischemia, and sudden cardiac death. Anesthesiologists, in the operating room and intensive care units, manage these diseases on a daily basis as they significantly affect patient outcomes. Intriguingly, sedatives, anesthetics, and the intensive care unit environment have all been shown to disrupt the circadian system in patients. In the current review, we will discuss how newly acquired knowledge of circadian rhythms could lead to changes in clinical practice and new therapeutic concepts.

Effects of Dexmedetomidine on Sleep Quality in Critically Ill Patients

Background:

Dexmedetomidine, a potent α-2-adrenergic agonist, is widely used as sedative in critically ill patients. This pilot study was designed to assess the effect of dexmedetomidine administration on sleep quality in critically ill patients.

Methods:

Polysomnography was performed on hemodynamically stable critically ill patients for 57 consecutive hours, divided into three night-time (9:00 pm to 6:00 am) and two daytime (6:00 am to 9:00 pm) periods. On the second night, dexmedetomidine was given by a continuous infusion targeting a sedation level −1 to −2 on the Richmond Agitation Sedation Scale. Other sedatives were not permitted.

Results:

Thirteen patients were studied. Dexmedetomidine was given in a dose of 0.6 μg kg−1 h−1 (0.4 to 0.7) (median [interquartile range]). Compared to first and third nights (without dexmedetomidine), sleep efficiency was significantly higher during the second night (first: 9.7% [1.6 to 45.1], second: 64.8% [51.4 to 79.9], third: 6.9% [0.0 to 17.1], P &lt; 0.002). Without dexmedetomidine, night-time sleep fragmentation index (7.6 events per hour [4.8 to 14.2]) and stage 1 of sleep (48.0% [30.1 to 66.4]) were significantly higher (P = 0.023 and P = 0.006, respectively), and stage 2 (47.0% [27.5 to 61.2]) showed values lower (P = 0.006) than the corresponding values (2.7 events per hour [1.6 to 4.9], 13.1% [6.2 to 23.6], 80.2% [68.9 to 92.8]) observed with dexmedetomidine. Without sedation, sleep was equally distributed between day and night, a pattern that was modified significantly (P = 0.032) by night-time dexmedetomidine infusion, with more than three quarters of sleep occurring during the night (79% [66 to 87]).

Conclusion:

In highly selected critically ill patients, dexmedetomidine infusion during the night to achieve light sedation improves sleep by increasing sleep efficiency and stage 2 and modifies the 24-h sleep pattern by shifting sleep mainly to the night.