Consciousness monitoring in ventilated patients: bispectral EEG monitors arousal not delirium

A Real-Time Neurophysiologic Stress Test for the Aging Brain: Novel Perioperative and ICU Applications of EEG in Older Surgical Patients

As of 2022, individuals age 65 and older represent approximately 10% of the global population [1], and older adults make up more than one third of anesthesia and surgical cases in developed countries [2, 3]. With approximately > 234 million major surgical procedures performed annually worldwide [4], this suggests that > 70 million surgeries are performed on older adults across the globe each year. The most common postoperative complications seen in these older surgical patients are perioperative neurocognitive disorders including postoperative delirium, which are associated with an increased risk for mortality [5], greater economic burden [6, 7], and greater risk for developing long-term cognitive decline [8] such as Alzheimer's disease and/or related dementias (ADRD). Thus, anesthesia, surgery, and postoperative hospitalization have been viewed as a biological "stress test" for the aging brain, in which postoperative delirium indicates a failed stress test and consequent risk for later cognitive decline (see Fig. 3). Further, it has been hypothesized that interventions that prevent postoperative delirium might reduce the risk of long-term cognitive decline. Recent advances suggest that rather than waiting for the development of postoperative delirium to indicate whether a patient "passed" or "failed" this stress test, the status of the brain can be monitored in real-time via electroencephalography (EEG) in the perioperative period. Beyond the traditional intraoperative use of EEG monitoring for anesthetic titration, perioperative EEG may be a viable tool for identifying waveforms indicative of reduced brain integrity and potential risk for postoperative delirium and long-term cognitive decline. In principle, research incorporating routine perioperative EEG monitoring may provide insight into neuronal patterns of dysfunction associated with risk of postoperative delirium, long-term cognitive decline, or even specific types of aging-related neurodegenerative disease pathology. This research would accelerate our understanding of which waveforms or neuronal patterns necessitate diagnostic workup and intervention in the perioperative period, which could potentially reduce postoperative delirium and/or dementia risk. Thus, here we present recommendations for the use of perioperative EEG as a "predictor" of delirium and perioperative cognitive decline in older surgical patients.

An Interdisciplinary Reappraisal of Delirium and Proposed Subtypes

An interdisciplinary plenary session entitled "Rethinking and Rehashing Delirium" was held during the 2021 Annual Meeting of the Academy of Consultation-Liaison Psychiatry to facilitate dialog on the prevalent approach to delirium. Panel members included a psychiatrist, neurointensivist, and critical care specialist, and attendee comments were solicited with the goal of developing a statement. Discussion was focused on a reappraisal of delirium and, in particular, its disparate terminology and history in relation to acute encephalopathy. The authors endorse a recent joint position statement that describes acute encephalopathy as a rapidly evolving (<4 weeks) pathobiological brain process that presents as subsyndromal delirium, delirium, or coma and suggest the following points of refinement: (1) to suggest that "delirium disorder" describe the diagnostic construct including its syndrome, precipitant(s), and unique pathophysiology; (2) to restrict the term "delirium" to describing the clinical syndrome encountered at the bedside; (3) to clarify that the disfavored term "altered mental status" may occasionally be an appropriate preliminary designation where the diagnosis cannot yet be specified further; and (4) to provide rationale for rejecting the terms acute brain injury, failure, or dysfunction. The final common pathway of delirium appears to involve higher-level brain network dysfunction, but there are many insults that can disrupt functional connectivity. We propose that future delirium classification systems should seek to characterize the unique pathophysiological disturbances ("endotypes") that underlie delirium and delirium's individual neuropsychiatric symptoms. We provide provisional means of classification in hopes that novel subtypes might lead to specific intervention to improve patient experience and outcomes. This paper concludes by considering future directions for the field. Key areas of opportunity include interdisciplinary initiatives to harmonize efforts across specialties and settings, enhance underrepresented groups in research, integration of delirium and encephalopathy in coding, development of relevant quality and safety measures, and exploration of opportunities for translational science.

Validation of the patient State Index for monitoring sedation state in critically ill patients: a prospective observational study

PURPOSE

The Patient State Index (PSI) is a newly introduced electroencephalogram-based tool for objective and continuous monitoring of sedation levels of patients under general anesthesia. This study investigated the potential correlation between the PSI and the Richmond Agitation‒Sedation Scale (RASS) score in intensive care unit (ICU) patients and established the utility of the PSI in assessing sedation levels.

METHODS

In this prospective observational study, PSI values were continuously monitored via SedLine® (Masimo, Irvine, CA, USA); the RASS score was recorded every 2 h for patients on mechanical ventilation. Physicians and nurses were blinded to the PSI values. Overall, 382 PSI and RASS score sets were recorded for 50 patients.

RESULTS

The PSI score correlated positively with RASS scores, and Spearman's rank correlation coefficient between the PSI and RASS was 0.79 (95% confidence interval [CI]: 0.75‒0.83). The PSI showed statistically significant difference among the RASS scores (Kruskal‒Wallis chi-square test: 242, df = 6, P < 2.2-e16). The PSI threshold for distinguishing light (RASS score ≥ - 2) sedation from deep sedation (RASS score ≤ - 3) was 54 (95% CI: 50-65; area under the curve, 0.92 [95% CI: 0.89‒0.95]; sensitivity, 0.91 [95% CI: 0.86‒0.95]; specificity, 0.81 [95% CI: 0.77-0.86]).

CONCLUSIONS

The PSI correlated positively with RASS scores, which represented a widely used tool for assessing sedation levels, and the values were significantly different among RASS scores. Additionally, the PSI had a high sensitivity and specificity for distinguishing light from deep sedation. The PSI could be useful for assessing sedation levels in ICU patients. University Hospital Medical Information Network (UMIN000035199, December 10, 2018).

Systematic review and meta‐analysis of the correlation between bispectral index ( BIS ) and clinical sedation scales: Toward defining the role of BIS in critically ill patients

INTRODUCTION

The bispectral index (BIS) is an attractive approach for monitoring level of consciousness in critically ill patients, particularly during paralysis, when commonly used sedation scales cannot be used.

OBJECTIVES

As a first step toward establishing the utility of BIS during paralysis, this review examines the strength of correlation between BIS and clinical sedation scales in a broad population of non-paralyzed, critically ill adults.

METHODS

We included studies evaluating the strength of correlation between concurrent assessments of BIS and Richmond Agitation Sedation Scale (RASS), Ramsay Sedation Scale (RSS), or Sedation Agitation Scale (SAS) in critically ill adult patients. Studies involving assessment of depth sedation periperative or procedural time periods, and those reporting BIS and sedation scale assessments conducted >5 min apart or while neuromuscular blocking agents (NMBA) were administered, were excluded. Data were abstracted on sedation scale, correlation coefficients, setting, patient characteristics, and BIS assessment characteristics that could impact the quality of the studies.

RESULTS

Twenty-four studies which enrolled 1235 patients met inclusion criteria. The correlation between BIS and RASS, RSS, and SAS overall was 0.68 (95% confidence interval, 0.61-0.74, Ƭ²  = 0.06 I²  = 71.26%). Subgroup analysis by sedation scale indicated that the correlation between BIS and RASS, RSS, and SAS were 0.66 (95% confidence interval 0.58-0.73, Ƭ²  = 0.01 I²  = 30.20%), 0.76 (95% confidence interval 0.69-0.82, Ƭ²  = 0.04 I²  = 67.15%), and 0.53 (95% confidence interval 0.42-0.63, Ƭ²  = 0.01 I²  = 26.59%), respectively. Factors associated with significant heterogeneity included comparator clinical sedation scale, neurologic injury, and the type of intensive care unit (ICU) population.

CONCLUSIONS

BIS demonstrated moderate to strong correlation with clinical sedation scales in adult ICU patients, providing preliminary evidence for the validity of BIS as a measure of sedation intensity when clinical scales cannot be used. Future studies should determine whether BIS monitoring is safe and effective in improving outcomes in patients receiving NMBA treatment.

Electroencephalogram-Based Evaluation of Impaired Sedation in Patients with Moderate to Severe COVID-19 ARDS

The sedation management of patients with severe COVID-19 is challenging. Processed electroencephalography (pEEG) has already been used for sedation management before COVID-19 in critical care, but its applicability in COVID-19 has not yet been investigated. We performed this prospective observational study to evaluate whether the patient sedation index (PSI) obtained via pEEG may adequately reflect sedation in ventilated COVID-19 patients. Statistical analysis was performed by linear regression analysis with mixed effects. We included data from 49 consecutive patients. None of the patients received neuromuscular blocking agents by the time of the measurement. The mean value of the PSI was 20 (±23). The suppression rate was determined to be 14% (±24%). A deep sedation equivalent to the Richmond Agitation and Sedation Scale of −3 to −4 (correlation expected PSI 25−50) in bedside examination was noted in 79.4% of the recordings. Linear regression analysis revealed a significant correlation between the sedative dosages of propofol, midazolam, clonidine, and sufentanil (p < 0.01) and the sedation index. Our results showed a distinct discrepancy between the RASS and the determined PSI. However, it remains unclear to what extent any discrepancy is due to the electrophysiological effects of neuroinflammation in terms of pEEG alteration, to the misinterpretation of spinal or vegetative reflexes during bedside evaluation, or to other causes.

Incidence and Risk Factors of Delirium in the Intensive Care Unit: A Prospective Cohort

Purpose

The purpose of this study was to determine the incidence, risk factors, and impact of delirium on outcomes in ICU patients. In addition, the scoring systems were measured consecutively to characterize how these scores changed with time in patients with and without delirium. Material and Methods. A prospective cohort study enrolling 400 consecutive patients admitted to the ICU between 2018 and 2019 due to trauma or surgery. Patients were followed up for the development of delirium over ICU days using the Confusion Assessment Method (CAM) for the ICU and Intensive Care Delirium Screening Checklist (ICDSC). Cox model logistic regression analysis was used to explore delirium risk factors.

Results

Delirium occurred in 108 (27%) patients during their ICU stay, and the median onset of delirium was 4 (IQR 3–4) days after admission. According to multivariate cox regression, the expected hazard for delirium was 1.523 times higher in patients who used mechanical ventilator as compared to those who did not (HR: 1.523, 95% CI: 1.197-2.388, P < 0.001).

Conclusion

Our findings suggest that an important opportunity for improving the care of critically ill patients may be the determination of modifiable risk factors for delirium in the ICU. In addition, the scoring systems (APACHE IV, SOFA, and RASS) are useful for the prediction of delirium in critically ill patients.

Investigating how electroencephalogram measures associate with delirium: A systematic review

Delirium is a common neurocognitive disorder in hospital settings, characterised by fluctuating impairments in attention and arousal following an acute precipitant. Electroencephalography (EEG) is a useful method to understand delirium pathophysiology. We performed a systematic review to investigate associations between delirium and EEG measures recorded prior, during, and after delirium. A total of 1,655 articles were identified using PsycINFO, Embase and MEDLINE, 31 of which satisfied inclusion criteria. Methodological quality assessment was undertaken, resulting in a mean quality score of 4 out of a maximum of 5. Qualitative synthesis revealed EEG slowing and reduced functional connectivity discriminated between those with and without delirium (i.e. EEG during delirium); the opposite pattern was apparent in children, with cortical hyperexcitability. EEG appears to have utility in differentiating those with and without delirium, but delirium vulnerability and the long-term effects on brain function require further investigation. Findings provide empirical support for the theory that delirium is a disorder of reduced functional brain integration.

Comparative Accuracy and Efficiency of Four Delirium Screening Protocols

BACKGROUND/OBJECTIVES

Systematic screening can improve detection of delirium, but lack of time is often cited as why such screening is not performed. We investigated the time required to implement four screening protocols that use the Ultra-Brief two-item screener for delirium (UB-2) and the 3-Minute Diagnostic Interview for Confusion Assessment Method (CAM)-defined Delirium (3D-CAM), with and without a skip pattern that can further shorten the assessment. Our objective was to compare the sensitivity, specificity, and time required to complete four protocols: (1) full 3D-CAM on all patients, (2) 3D-CAM with skip on all patients, (3) UB-2, followed by the full 3D-CAM in "positives," and (4) UB-2, followed by the 3D-CAM with skip in "positives."

DESIGN

Comparative efficiency simulation study using secondary data.

SETTING

Two studies (3D-CAM and Researching Efficient Approaches to Delirium Identification (READI)) conducted at a large academic medical center (3D-CAM and READI) and a small community hospital (READI only).

PARTICIPANTS

General medicine inpatients, aged 70 years and older (3D-CAM, n = 201; READI, n = 330).

MEASUREMENTS

We used 3D-CAM data to simulate the items administered under each protocol and READI data to calculate median administration time per item. We calculated sensitivity, specificity, and total administration time for each of the four protocols.

RESULTS

The 3D-CAM and READI samples had similar characteristics, and all four protocols had similar simulated sensitivity and specificity. Mean administration times were 3 minutes 13 seconds for 3D-CAM, 2 minutes 19 seconds for 3D-CAM with skip, 1 minute 52 seconds for UB-2 + 3D-CAM in positives, and 1 minute 14 seconds for UB-2 + 3D-CAM with skip in positives, which was 1 minute 59 seconds faster than the 3D-CAM (P < .001).

CONCLUSION

The UB-CAM, consisting of the UB-2, followed in positives by the 3D-CAM with skip pattern, is a time-efficient delirium screening protocol that holds promise for increasing systematic screening for delirium in hospitalized older adults.

Bispectral Index Monitoring With Density Spectral Array for Delirium Detection

BACKGROUND

Delirium in hospitalized patients often goes undetected. Cerebral state monitors, which measure limited-channel electroencephalography, have shown potential for improving delirium detection.

OBJECTIVE

The aim of this study was to compare an FDA-approved cerebral state monitor, bispectral index monitoring with density spectral array (DSA), for delirium identification with clinical screening methods.

METHODS

Hospitalized patients receiving psychiatric consultation were assessed for delirium using the 3-minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) and underwent bispectral index monitor + DSA monitoring. Visual inspection of frequency band power of the DSA was performed by 2 trained independent raters. Average hue values were calculated for each frequency band using image analysis software as the device did not allow for extraction of raw electroencephalography data. Delirious versus nondelirious group averages, sensitivity, specificity, and area under the curve were calculated for significant DSA variables and the 3D-CAM.

RESULTS

In an initial cohort of 43 patients, visual ratings of the DSA were not associated with delirium (P > 0.1). In a larger cohort of 123 subjects, multiple band hue ratios were associated with delirium, although none survived correction for multiple comparisons. In a subgroup of 74 non-neurological patients, low theta/low delta ratio was significantly associated with delirium (P = 0.001) (sensitivity/specificity/area under the curve: 83%/70%/0.757; 3D-CAM: 67%/77%/0.717; paired-sample area under the curve difference: -0.040, P = 0.68). In 21 patients with dementia, low theta power demonstrated significantly greater sensitivity/specificity/area under the curve of 83%/78%/0.824, whereas 3D-CAM achieved 50%/78%/0.639 (P = 0.04).

CONCLUSION

Bispectral index monitor + DSA was similar to 3D-CAM for detecting delirium in hospitalized patients with and without neurological disorders, and was significantly more accurate in patients with dementia. More studies are needed to validate the use of cerebral state monitors for quantitative delirium detection.

Association Between Level of Arousal and 30-Day Survival in Acutely Ill Older Adults

OBJECTIVE

To investigate the association between impaired arousal on admission and 30-day mortality in acutely ill older adults.

DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

Patients age +65 years admitted to the geriatric ward of a tertiary university hospital from 2010 to 2018 in Sao Paulo, Brazil.

METHODS

Participants were evaluated on admission according to a standardized comprehensive geriatric assessment model. Delirium was detected using the short version of the Confusion Assessment Method (Short-CAM). We used 2 alternative criteria to define impaired arousal: lethargy, stupor, or coma according to the Short-CAM; and a Glasgow Coma Scale (GCS) score of ≤13. Our primary outcome was time-to-death in 30 days, and we used Cox proportional hazards models to explore the association between impaired arousal and decreased survival.

RESULTS

We included 1554 admissions with a mean age of 81 years and of whom 61% were women. Overall, prevalent delirium was observed in 28% of the cases. We found that in 33% of admissions, patients were lethargic, stuporous, or comatose, and that in 23%, they had GCS scores of ≤13. General 30-day mortality was 19% but reached 32% in patients with GCS scores of ≤13. Impaired arousal was independently associated with lower survival in 30 days, both when defined using Short-CAM criteria [lethargy + stupor + coma: hazard ratio (HR) 2.33, 95% confidence interval (CI) 1.66‒3.27] and GCS scores (GCS 12‒13: HR 1.62, 95% CI 1.13‒2.33; GCS ≤ 11: HR 2.53, 95% CI 1.68‒3.80). In interaction analyses, we confirmed our results in patients who had impaired arousal but were neither delirious (lethargy + stupor + coma: HR 2.16, 95% CI 1.44‒3.24; GCS ≤ 11: HR 3.07; 95% CI 1.50‒6.29) nor demented (lethargy + stupor + coma: HR 1.95, 95% CI 1.15‒3.28).

CONCLUSIONS AND IMPLICATIONS

Level of arousal on admission was an independent predictor of 30-day survival in acutely ill older adults, regardless of delirium or baseline dementia. Clinicians should be aware that even if unsure of whether a patient has delirium, arousal assessment can provide crucial clinical and prognostic insight.

Diagnosing acute brain dysfunction due to sepsis

Developments in the management of critically ill patients suffering organ dysfunctions have demonstrated that brain is the prominent organ to be effected during critical illness. Acute brain dysfunction due to pathologic neuroinflammatory processes associated with sepsis is commonly seen and related to morbidity and mortality in the ICU treatment. Studies reported that survivors of sepsis may suffer long-term cognitive dysfunction that affects quality of life. However, there are no specific approaches to diagnose acute brain dysfunction in the early phase to target protective measures. In recent years, imaging methods and biomarkers are the most important issues of studies. This review will address the current diagnostic approaches to acute brain dysfunction related to sepsis.

Behavior of a dual closed-loop controller of propofol and remifentanil guided by the bispectral index for postoperative sedation of adult cardiac surgery patients: a preliminary open study

A dual-loop controller permits the automated titration of propofol and remifentanil during anesthesia; it has never been used in intensive care after cardiac surgery. The goal of this preliminary study was to determine the efficacy of this controller to provide postoperative sedation in 19 adult cardiac surgery patients with a Bispectral Index target of 50. Results are presented as numbers (percentages) or medians [25th-75th percentiles]. The sedation period lasted 139 min [89-205] during which the Richmond Agitation Sedation Scale was at - 5 and the Behavioral Pain Scale score at three points for all patients and observation times but one (82 out of 83 assessments). Sedation time in the range 40-60 for the Bispectral Index was 87% [57-95]; one patient had a period of electrical silence defined as Suppression Ratio at least > 10% for more than 60 s. The time between the end of infusions and tracheal extubation was 84 min [63-129]. The Richmond Agitation Sedation Scale was 0 [0-0], 0 [- 1 to 0], and 0 [0-0] respectively during the 3 h following extubation while the verbal numerical pain scores were 6 [4.5-7], 5 [4-6], and 2 [0-5]. Mean arterial pressure decreased during sedation requiring therapeutic interventions, mainly vascular filling in 15 (79%) patients. Automated sedation device was discontinued in two patients for hemodynamic instability. No patient had awareness of the postoperative sedation period. Dual closed-loop can provide postoperative sedation after cardiac surgery but the choice of the depth of sedation should take into account the risk of hypotension.

[Electroencephalography in delirium superimposed on dementia]

Recognizing delirium superimposed on pre-existing cognitive impairment or dementia, 'delirium superimposed on dementia' (DSD), is challenging because signs of delirium might be interpreted as symptoms of pre-existing cognitive dysfunction.In this paper, we review the literature on the role of electrencephalography (EEG) in the differential diagnosis of delirium, dementia and DSD.Conventional EEG, applying twenty to thirty electrodes, taking thirty minutes registration, is not feasible in psychogeriatric patients. Recent studies suggest that it is possible to reliably detect delirium using only a limited number of EEG electrodes for a short period of time.With this, use of EEG in the detection of delirium in patients with cognitive impairment or clinically manifest dementia could be possible.

Role of the Bispectral Index in Sedation Monitoring in the ICU

Objective:

To review and critique evidence for the use of the bispectral index (BIS) in intensive care unit (ICU) patients.

Data Sources:

A computer search of English-language articles in MEDLINE (1966–July 2005), International Pharmaceutical Abstracts (1971–July 2005), and Scientific Citation Index Expanded (1980–July 2005) was conducted. A manual search of abstracts was also performed using the key search terms BIS, sedation, and critical care.

Study Selection and Data Extraction:

Case series, letters, editorials, and clinical studies that evaluated BIS in ICU patients were considered for inclusion.

Data Synthesis:

Nineteen studies comparing the BIS with sedation scales were evaluated, revealing that the BIS trends lower with increasing sedation. The BIS appeared to correlate better when sedation scores were grouped rather than individual values. However, correlations between BIS and subjective scales were low in most studies (r2 0.21–0.93). Additionally, there was poor correlation between drug dosage and the BIS. Randomized, controlled trials demonstrating improved outcomes with BIS monitoring have not been reported.

Conclusions:

Interpreting literature on the usefulness of the BIS in the ICU is difficult for reasons that include heterogeneous populations, different methods of collecting BIS data, and use of different versions of BIS software and hardware. Outcomes data are lacking. The 2002 Society of Critical Care Medicine Sedation Guidelines recommendation that more data are needed before the BIS should be used routinely in the ICU remains unchanged. We recommend that further studies be conducted to determine the optimal method of obtaining BIS data and evaluate the impact of the BIS on relevant patient outcomes.

Burst suppression on processed electroencephalography as a predictor of postcoma delirium in mechanically ventilated ICU patients

OBJECTIVES

Many patients, due to a combination of illness and sedatives, spend a considerable amount of time in a comatose state that can include time in burst suppression. We sought to determine if burst suppression measured by processed electroencephalography during coma in sedative-exposed patients is a predictor of post-coma delirium during critical illness.

DESIGN

Observational convenience sample cohort.

SETTING

Medical and surgical ICUs in a tertiary care medical center.

PATIENTS

Cohort of 124 mechanically ventilated ICU patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Depth of sedation was monitored twice daily using the Richmond Agitation-Sedation Scale and continuously monitored by processed electroencephalography. When noncomatose, patients were assessed for delirium twice daily using Confusion Assessment Method for the ICU. Multiple logistic regression and Cox proportional hazards regression were used to assess associations between time in burst suppression and both prevalence and time to resolution of delirium, respectively, adjusting for time in deep sedation and a principal component score consisting of Acute Physiology and Chronic Health Evaluation II score and cumulative doses of sedatives while comatose. Of the 124 patients enrolled and monitored, 55 patients either never had coma or never emerged from coma, yielding 69 patients for whom we performed these analyses; 42 of these 69 (61%) had post-coma delirium. Most patients had burst suppression during coma, although often short-lived (median [interquartile range] time in burst suppression, 6.4 [1-58] min). After adjusting for covariates, even this short time in burst suppression independently predicted a higher prevalence of post-coma delirium (odds ratio, 4.16; 95% CI, 1.27-13.62; p = 0.02) and a lower likelihood (delayed) resolution of delirium (hazard ratio, 0.78; 95% CI, 0.53-0.98; p = 0.04).

CONCLUSIONS

Time in burst suppression during coma, as measured by processed electroencephalography, was an independent predictor of prevalence and time to resolution of postcoma/post-deep sedation delirium. These findings of this single-center investigation support lighter sedation strategies.

Validation of the Confusion Assessment Method for the Intensive Care Unit in older emergency department patients

OBJECTIVES

In the emergency department (ED), health care providers miss delirium approximately 75% of the time, because they do not routinely screen for this syndrome. The Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) is a brief (<1 minute) delirium assessment that may be feasible for use in the ED. The study objective was to determine its validity and reliability in older ED patients.

METHODS

In this prospective observational cohort study, patients aged 65 years or older were enrolled at an academic, tertiary care ED from July 2009 to February 2012. An emergency physician (EP) and research assistants (RAs) performed the CAM-ICU. The reference standard for delirium was a comprehensive (~30 minutes) psychiatrist assessment using the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision criteria. All assessments were blinded to each other and were conducted within 3 hours. Sensitivities, specificities, and likelihood ratios were calculated for both the EP and the RAs using the psychiatrist's assessment as the reference standard. Kappa values between the EP and RAs were also calculated to measure reliability.

RESULTS

Of 406 patients enrolled, 50 (12.3%) had delirium. The median age was 73.5 years old (interquartile range [IQR] = 69 to 80 years), 202 (49.8%) were female, and 57 (14.0%) were nonwhite. The CAM-ICU's sensitivities were 72.0% (95% confidence interval [CI] = 58.3% to 82.5%) and 68.0% (95% CI = 54.2% to 79.2%) in the EP and RAs, respectively. The CAM-ICU's specificity was 98.6% (95% CI = 96.8% to 99.4%) for both raters. The negative likelihood ratios (LR-) were 0.28 (95% CI = 0.18 to 0.44) and 0.32 (95% CI = 0.22 to 0.49) in the EP and RAs, respectively. The positive likelihood ratios (LR+) were 51.3 (95% CI = 21.1 to 124.5) and 48.4 (95% CI = 19.9 to 118.0), respectively. The kappa between the EP and RAs was 0.92 (95% CI = 0.85 to 0.98), indicating excellent interobserver reliability.

CONCLUSIONS

In older ED patients, the CAM-ICU is highly specific, and a positive test is nearly diagnostic for delirium when used by both the EP and RAs. However, the CAM-ICU's sensitivity was modest, and a negative test decreased the likelihood of delirium by a small amount. The consequences of a false-negative CAM-ICU are unknown and deserve further study.

Sepsis-induced brain dysfunction

Systemic infection is often revealed by or associated with brain dysfunction, which is characterized by alteration of consciousness, ranging from delirium to coma, seizure or focal neurological signs. Its pathophysiology involves an ischemic process, secondary to impairment of cerebral perfusion and its determinants and a neuroinflammatory process that includes endothelial activation, alteration of the blood-brain barrier and passage of neurotoxic mediators. Microcirculatory dysfunction is common to these two processes. This brain dysfunction is associated with increased mortality, morbidity and long-term cognitive disability. Its diagnosis relies essentially on neurological examination that can lead to specific investigations, including electrophysiological testing or neuroimaging. In practice, cerebrospinal fluid analysis is indisputably required when meningitis is suspected. Hepatic, uremic or respiratory encephalopathy, metabolic disturbances, drug overdose, sedative or opioid withdrawal, alcohol withdrawal delirium or Wernicke's encephalopathy are the main differential diagnoses. Currently, treatment consists mainly of controlling sepsis. The effects of insulin therapy and steroids need to be assessed. Various drugs acting on sepsis-induced blood-brain barrier dysfunction, brain oxidative stress and inflammation have been tested in septic animals but not yet in patients.

Diagnosing delirium in older emergency department patients: validity and reliability of the delirium triage screen and the brief confusion assessment method

STUDY OBJECTIVE

Delirium is a common form of acute brain dysfunction with prognostic significance. Health care professionals caring for older emergency department (ED) patients miss delirium in approximately 75% of cases. This error results from a lack of available measures that can be performed rapidly enough to be incorporated into clinical practice. Therefore, we developed and evaluated a novel 2-step approach to delirium surveillance for the ED.

METHODS

This prospective observational study was conducted at an academic ED in patients aged 65 years or older. A research assistant and physician performed the Delirium Triage Screen (DTS), designed to be a highly sensitive rule-out test, and the Brief Confusion Assessment Method (bCAM), designed to be a highly specific rule-in test for delirium. The reference standard for delirium was a comprehensive psychiatrist assessment using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision criteria. All assessments were independently conducted within 3 hours of one another. Sensitivities, specificities, and likelihood ratios with their 95% confidence intervals (95% CIs) were calculated.

RESULTS

Of 406 enrolled patients, 50 (12.3%) had delirium diagnosed by the psychiatrist reference standard. The DTS was 98.0% sensitive (95% CI 89.5% to 99.5%), with an expected specificity of approximately 55% for both raters. The DTS's negative likelihood ratio was 0.04 (95% CI 0.01 to 0.25) for both raters. As the complement, the bCAM had a specificity of 95.8% (95% CI 93.2% to 97.4%) and 96.9% (95% CI 94.6% to 98.3%) and a sensitivity of 84.0% (95% CI 71.5% to 91.7%) and 78.0% (95% CI 64.8% to 87.2%) when performed by the physician and research assistant, respectively. The positive likelihood ratios for the bCAM were 19.9 (95% CI 12.0 to 33.2) and 25.2 (95% CI 13.9 to 46.0), respectively. If the research assistant DTS was followed by the physician bCAM, the sensitivity of this combination was 84.0% (95% CI 71.5% to 91.7%) and specificity was 95.8% (95% CI 93.2% to 97.4%). If the research assistant performed both the DTS and bCAM, this combination was 78.0% sensitive (95% CI 64.8% to 87.2%) and 97.2% specific (95% CI 94.9% to 98.5%). If the physician performed both the DTS and bCAM, this combination was 82.0% sensitive (95% CI 69.2% to 90.2%) and 95.8% specific (95% CI 93.2% to 97.4%).

CONCLUSION

In older ED patients, this 2-step approach (highly sensitive DTS followed by highly specific bCAM) may enable health care professionals, regardless of clinical background, to efficiently screen for delirium. Larger, multicenter trials are needed to confirm these findings and to determine the effect of these assessments on delirium recognition in the ED.

Use of bispectral index to monitor the depth of sedation in mechanically ventilated patients in the prehospital setting

BACKGROUND

Sedative drug administration is a challenging aspect of the management of mechanically ventilated patients in the out-of-hospital critical care medicine. We hypothesised that the bispectral index of the EEG (BIS) could be a helpful tool in evaluating the depth of sedation in this difficult environment. The main objective of the present study was to assess the agreement of BIS with the clinical scales in the out-of-hospital setting.

METHODS

This prospective study included mechanically ventilated patients. BIS values were blindly recorded continuously. A Ramsay score was performed every 5 min. The main judgement criterion was the correlation between BIS values and the Ramsay score.

RESULTS

72 patients were included, mostly presenting with toxic coma (36%) or neurological coma (21%). The median (IQR) BIS value was 85 (84-86) when the Ramsay score was 3, 80 (76-84) when the Ramsay score was 4, 61 (55-80) when the Ramsay score was 5 and 45 (38-60) when the Ramsay score was 6. According to Receiver operating characteristic (ROC) curves, BIS was categorised into three classes (BIS<54 corresponding to Ramsay score 6, 54≤BIS<72 for Ramsay score 5 and BIS≥73 for Ramsay score ≤4). Based on these categories, the proportion of appropriate BIS values was 67% (217/323). The concordance correlation coefficient for repeated measurements was 0.54 (0.43-0.64). The agreement between BIS and the Ramsay score is moderate.

CONCLUSIONS

Prehospital measured BIS values appear poorly correlated with clinical assessment of the depth of sedation. For this reason, the use of BIS to guide prehospital sedation cannot be recommended.

Biomarkers and clinical tools in critically ill children: are we heading toward tailored drug therapy?

In pediatric critical care, validated biomarkers are essential for guiding drug therapy. The aim of this article is to present examples of current biomarker developments in its full breadth, including biochemical substances, physiological measurements and clinical scoring tools, with a focus on the field of circulatory, renal and neurophysiologic failure. Within each field we consecutively discuss the rationale for the selected biomarkers, studies in critically ill children, biomarker validation stage and biomarker use or potential use in drug studies and clinical drug dosing. This article demonstrates that there is paucity of properly validated biomarkers. Nevertheless, recent developments in, for instance, the field of sepsis, point us toward a future wherein, for critically ill children, drug therapy may be personalized using proteomic profiling instead of a small number of biomarkers, in order to establish a personal and dynamic disease profile.

Sleep deprivation in critical illness: its role in physical and psychological recovery

Critically ill patients frequently experience poor sleep, characterized by frequent disruptions, loss of circadian rhythms, and a paucity of time spent in restorative sleep stages. Factors that are associated with sleep disruption in the intensive care unit (ICU) include patient-ventilator dysynchrony, medications, patient care interactions, and environmental noise and light. As the field of critical care increasingly focuses on patients' physical and psychological outcomes following critical illness, understanding the potential contribution of ICU-related sleep disruption on patient recovery is an important area of investigation. This review article summarizes the literature regarding sleep architecture and measurement in the critically ill, causes of ICU sleep fragmentation, and potential implications of ICU-related sleep disruption on patients' recovery from critical illness. With this background information, strategies to optimize sleep in the ICU are also discussed.

Bispectral index to monitor propofol sedation in trauma patients

BACKGROUND

This study tested the hypothesis that the bispectral index (BIS) is reliable relative to clinical judgment for estimating sedation level during daily propofol spontaneous awakening trials (SATs) in trauma patients.

METHODS

This was a prospective observational trial with waiver of consent conducted in the intensive care unit of Level I trauma center in 94 mechanically ventilated trauma patients sedated with propofol alone or in combination with midazolam. BIS, Richmond Agitation Sedation Scale (RASS), electromyography, and heart rate variability, as a test of autonomic function, were measured for 45 minutes during daily SATs. Data were evaluated with analysis of variance, linear regression, and nonparametric tests.

RESULTS

The BIS wave form coincided almost exactly with propofol on/off. Steady-state BIS correlated with RASS (p < 0.0001) and with propofol dose (p < 0.0001), but the strengths of association were relatively low (all r(2) < 0.5). BIS wave form was not altered by age, heart rate, or heart rate variability and was similar with propofol alone or propofol plus midazolam, but the presence of brain injury or the use of paralytics shifted the curve downward (both p < 0.001). The overall test characteristics for BIS versus RASS without neuromuscular blockade were sensitivity: 90% versus 77% (p = 0.034); specificity: 90% versus 75% (p = 0.021); positive predictive value: 90% versus 76% (p = 0.021), and negative predictive value: 90% versus 76% (p = 0.021).

CONCLUSIONS

In the first trial in trauma patients and largest trial in any surgical population, the (1) BIS was reliable and has advantages over RASS of being continuous and objective, at least during a propofol SAT; (2) BIS interpretation remains somewhat subjective in patients receiving paralytic agents or with traumatic brain injury.

Responsiveness of the frontal EMG for monitoring the sedation state of critically ill patients

BACKGROUND

Excessive sedation is associated with adverse patient outcomes during critical illness, and a validated monitoring technology could improve care. We developed a novel method, the responsiveness index (RI) of the frontal EMG. We compared RI data with Ramsay clinical sedation assessments in general and cardiac intensive care unit (ICU) patients.

METHODS

We developed the algorithm by iterative analysis of detailed observational data in 30 medical-surgical ICU patients and described its performance in this cohort and 15 patients recovering from scheduled cardiac surgery. Continuous EMG data were collected via frontal electrodes and RI data compared with modified Ramsay sedation state assessments recorded regularly by a blinded trained observer. RI performance was compared with Entropy™ across Ramsay categories to assess validity.

RESULTS

RI correlated well with the Ramsay category, especially for the cardiac surgery cohort (general ICU patients ρ=0.55; cardiac surgery patients ρ=0.85, both P<0.0001). Discrimination across all Ramsay categories was reasonable in the general ICU patient cohort [P(K)=0.74 (sem 0.02)] and excellent in the cardiac surgery cohort [P(K)=0.92 (0.02)]. Discrimination between 'lighter' vs 'deeper' (Ramsay 1-3 vs 4-6) was good for general ICU patients [P(K)=0.80 (0.02)] and excellent for cardiac surgery patients [P(K)=0.96 (0.02)]. Performance was significantly better than Entropy™. Examination of individual cases suggested good face validity.

CONCLUSIONS

RI of the frontal EMG has promise as a continuous sedation state monitor in critically ill patients. Further investigation to determine its utility in ICU decision-making is warranted.

Sepsis-associated encephalopathy and its differential diagnosis

Sepsis-associated encephalopathy (SAE) is defined as a diffuse cerebral dysfunction resulting from the systemic inflammatory response to an infection without direct infestation of the CNS. Although the pathophysiology of SAE is as yet unknown, some mechanisms have been suggested that involve BBB disruption as a consequence of proinflammatory mediators’ effects on endothelial cells. This leads to an increased passage of neurotoxic and proinflammatory mediators into the brain parenchyma, as well as an impairment of the movements of oxygen and metabolites through the BBB. Both neurons and glial cells are affected, resulting in neural functioning and neurotransmission impairment. The clinical translation of this process is an alteration of consciousness and awareness. SAE is a frequent condition in septic patients. Despite being considered reversible, SAE appears to be associated with long-term cognitive impairment. Detection and diagnosis can be challenging; it requires daily neurological assessment with the assistance of clinical scores. Use of biomarkers and neurophysiological testing is discussed. The aim of this article is to provide practical tools for detection of SAE, as well as an updated overview of its pathophysiology and therapeutic perspectives.

Validity and reliability of an intuitive conscious sedation scoring tool: the nursing instrument for the communication of sedation

OBJECTIVE

To develop a symmetrical 7-level scale (+3, "dangerously agitated" to -3, "deeply sedated") that is both intuitive and easy to use, the Nursing Instrument for the Communication of Sedation (NICS).

DESIGN

Prospective cohort study.

SETTING

University medical center.

PATIENTS

Mixed surgical, medical intensive care unit (ICU) population.

INTERVENTIONS

Patient assessment.

MEASUREMENTS AND MAIN RESULTS

Criterion, construct, face validity, and interrater reliability of NICS over time and comparison of ease of use and nursing preference between NICS and four common intensive care unit sedation scales. A total of 395 observations were performed in 104 patients (20 intubated [INT], 84 non intubated) by 59 intensive care unit providers. Criterion validity was tested comparing NICS WITH the 8-point level of arousal scale, demonstrating excellent correlation (rs = .96 overall, .95 non intubated, 0.85 intubated, all p < .001). Construct validity was confirmed by comparing NICS with the Richmond Agitation-Sedation Scale, demonstrating excellent correlation (rs = .98, p < .001). Face validity was determined in a blinded survey of 53 intensive care unit nurses evaluating NICS and four other sedation scales. NICS was highly rated as easy to score, intuitive, and a clinically relevant measure of sedation, and agitation and was preferred overall (74% NICS, 17% Richmond Agitation-Sedation Scale, 11% Other, p < .001 NICS vs. Richmond Agitation-Sedation Scale). Interrater reliability was assessed, using the five scales at three timed intervals, during which 37% of patients received sedative medication. The mean NICS score consistently correlated with each of the other scales over time with an rs of >.9. Using the intraclass correlation coefficient as a measure of Interrater reliability, NICS scored as high, or higher than Richmond Agitation-Sedation Scale, Riker Sedation-Agitation Scale, Motor Activity Assessment Scale, or Ramsay over the three time periods.

CONCLUSION

NICS is a valid and reliable sedation scale for use in a mixed population of intensive care unit patients. NICS ranked highest in nursing preference and ease of communication and may thus permit more effective and interactive management of sedation.

Early postoperative delirium after open-heart cardiac surgery is associated with decreased bispectral EEG and increased cortisol and interleukin-6

PURPOSE

It is difficult to substantiate the clinical diagnosis of postoperative delirium with objective parameters in intensive care units (ICU). The purpose of this study was to analyze (1) whether the bilateral bispectral (BIS) index, (2) cortisol as a stress marker, and (3) interleukin-6 as a marker of inflammation were different in delirious patients as compared to nondelirious ones after cardiac surgery.

METHODS

On the first postoperative day, delirium was analyzed in 114 patients by using the confusion assessment method for ICU (CAM-ICU). Bilateral BIS data were determined; immediately thereafter plasma samples were drawn to analyze patients' blood characteristics. The current ICU medication, hemodynamic characteristics, SOFA and APACHE II scores, and artificial ventilation were noted.

RESULTS

Delirium was detected at 19.1 ± 4.8 h after the end of surgery in 32 of 114 patients (28%). Delirious patients were significantly older than nondelirious ones and were artificially ventilated 4.7-fold more often during the testing. In delirious patients, plasma cortisol and interleukin-6 levels were higher (p = 0.01). The mean BIS index was significantly lower in delirious patients (72.6 (69.6-89.1); median [interquartile range (IQR), 25th-75th percentiles] than in nondelirious patients, 84.8 (76.8-89.9). BIS EEG raw data analysis detected significant lower relative alpha and higher theta power. A significant correlation was found between plasma cortisol levels and BIS index.

CONCLUSIONS

Early postoperative delirium after cardiac surgery was characterized by increased stress levels and inflammatory reaction. BIS index measurements showed lower cortical activity in delirious patients with a low sensitivity (27%) and high specificity (96%).

Toward an integrated research agenda for critical illness in aging

Aging brings an increased predisposition to critical illness. Patients older than 65 years of age account for approximately half of all intensive care unit (ICU) admissions in the United States, a proportion that is expected to increase considerably with the aging of the population. Emerging research suggests that elderly survivors of intensive care suffer significant long-term sequelae, including accelerated age-related functional decline. Existing evidence-based interventions are frequently underused and their efficacy untested in older subjects. Improving ICU outcomes in the elderly will require not only better methods for translating sound science into improved ICU practice but also an enhanced understanding of the underlying molecular, physiological, and pathophysiological interactions of critical illness with the aging process itself. Yet, significant barriers to research for critical illness in aging exist. We review the state of knowledge and identify gaps in knowledge, research opportunities, and barriers to research, with the goal of promoting an integrated research agenda for critical illness in aging.

Sepsis-associated encephalopathy and its differential diagnosis

Sepsis is often complicated by an acute and reversible deterioration of mental status, which is associated with increased mortality and is consistent with delirium but can also be revealed by a focal neurologic sign. Sepsis-associated encephalopathy is accompanied by abnormalities of electroencephalogram and somatosensory-evoked potentials, increased in biomarkers of brain injury (i.e., neuron-specific enolase, S-100 beta-protein) and, frequently, by neuroradiological abnormalities, notably leukoencephalopathy. Its mechanism is highly complex, resulting from both inflammatory and noninflammatory processes that affect all brain cells and induce blood-brain barrier breakdown, dysfunction of intracellular metabolism, brain cell death, and brain injuries. Its diagnosis relies essentially on neurologic examination that can lead one to perform specific neurologic tests. Electroencephalography is required in the presence of seizure; neuroimaging in the presence of seizure, focal neurologic signs or suspicion of cerebral infection; and both when encephalopathy remains unexplained. In practice, cerebrospinal fluid analysis should be performed if there is any doubt of meningitis. Hepatic, uremic, or respiratory encephalopathy, metabolic disturbances, drug overdose, withdrawal of sedatives or opioids, alcohol withdrawal delirium, and Wernicke's encephalopathy are the main differential diagnoses of sepsis-associated encephalopathy. Patient management is based mainly on controlling infection, organ system failure, and metabolic homeostasis, at the same time avoiding neurotoxic drugs.

Diagnostic considerations regarding pediatric delirium: a review and a proposal for an algorithm for pediatric intensive care units

CONTEXT

If delirium is not diagnosed, it is unlikely that any effort will be made to reverse it. Given evidence for under-diagnosis, tools that aid recognition are required.

OBJECTIVE

Relating three presentations of pediatric delirium (PD) to standard criteria and developing a diagnostic algorithm.

RESULTS

Delirium-inducing factors, disturbance of consciousness and inattention are common in PICU patients: a pre-delirious state is present in most. An algorithm is introduced, containing (1) evaluation of the sedation-agitation level, (2) psychometric assessment of behavior and (3) opinion of the caregivers.

DISCUSSION

It may be argued that the behavioral focus of the algorithm would benefit from the inclusion of neurocognitive measures.

LIMITATIONS

No sufficiently validated diagnostic instrument covering the entire algorithm is available yet.

CONCLUSION

This is the first proposal for a PD diagnostic algorithm. Given the high prevalence of predelirious states at the PICU, daily evaluation is mandatory. Future algorithmic refinement is urgently required.

Presence of electroencephalogram burst suppression in sedated, critically ill patients is associated with increased mortality

OBJECTIVES

This study investigates the possibility of a relationship between oversedation and mortality in mechanically ventilated patients. The presence of burst suppression, a pattern of severely decreased brain wave activity on the electroencephalogram, may be unintentionally induced by heavy doses of sedatives. Burst suppression has never been studied as a potential risk factor for death in patients without a known neurologic disorder or injury.

DESIGN

Post hoc analysis of a prospectively observational cohort study.

SETTING

Medical intensive care units of a tertiary care, university-based medical center.

PATIENTS

A total of 125 mechanically ventilated, adult, critically ill patients.

MEASUREMENTS AND MAIN RESULTS

A validated arousal scale (Richmond Agitation-Sedation Scale) was used to measure sedation level, and the bispectral index monitor was used to capture electroencephalogram data. Burst suppression occurred in 49 of 125 patients (39%). For analysis, the patients were divided into those with burst suppression (49 of 125, 39%) and those without burst suppression (76 of 125, 61%). All baseline variables were similar between the two groups, with the overall cohort demonstrating a high severity of illness (Acute Physiology and Chronic Health Evaluation II scores of 27.4 +/- 8.2) and 98% receiving sedation. Of those with burst suppression, 29 of 49 (59%) died within 6 months compared with 25 of 76 (33%) who did not demonstrate burst suppression. Using time-dependent Cox regression to adjust for clinically important covariates (age, Charlson comorbidity score, baseline dementia, Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment, coma, and delirium), patients who experienced burst suppression were found to have a statistically significant higher 6-month mortality [Hazard's ratio = 2.04, 95% confidence interval, 1.12-3.70, p = 0.02].

CONCLUSION

The presence of burst suppression, which was unexpectedly high in this medical intensive care unit population, was an independent predictor of increased risk of death at 6 months. This association should be studied prospectively on a larger scale in mechanically ventilated, critically ill patients.

Prevalence and risk factors for development of delirium in surgical and trauma intensive care unit patients

BACKGROUND

Although known to be an independent predictor of poor outcomes in medical intensive care unit (ICU) patients, limited data exist regarding the prevalence of and risk factors for delirium among surgical (SICU) and trauma ICU (TICU) patients. The purpose of this study was to analyze the prevalence of and risk factors for delirium in surgical and trauma ICU patients.

METHODS

SICU and TICU patients requiring mechanical ventilation (MV) >24 hours were prospectively evaluated for delirium using the Richmond Agitation Sedation Scale (RASS) and the Confusion Assessment Method for the ICU (CAM-ICU). Those with baseline dementia, intracranial injury, or ischemic/hemorrhagic strokes that would confound the evaluation of delirium were excluded. Markov models were used to analyze predictors for daily transition to delirium.

RESULTS

One hundred patients (46 SICU and 54 TICU) were enrolled. Prevalence of delirium was 73% in the SICU and 67% in the TICU. Multivariable analyses identified midazolam [OR 2.75 (CI 1.43-5.26, p = 0.002)] exposure as the strongest independent risk factor for transitioning to delirium. Opiate exposure showed an inconsistent message such that fentanyl was a risk factor for delirium in the SICU (p = 0.007) but not in the TICU (p = 0.936), whereas morphine exposure was associated with a lower risk of delirium (SICU, p = 0.069; TICU p = 0.024).

CONCLUSION

Approximately 7 of 10 SICU and TICU patients experience delirium. In keeping with other recent data on benzodiazepines, exposure to midazolam is an independent and potentially modifiable risk factor for the transitioning to delirium.

[Sedation and analgesia assessment tools in ICU patients]

Sedative and analgesic treatment administered to critically ill patients need to be regularly assessed to ensure that predefinite goals are well achieved as the risk of complications of oversedation is minimized. In most of the cases, which are lightly sedation patients, the goal to reach is a calm, cooperative and painless patient, adapted to the ventilator. Recently, eight new bedside scoring systems to monitor sedation have been developed and mainly tested for reliability and validity. The choice of a sedation scale measuring level of consciousness, could be made between the Ramsay sedation scale, the Richmond Agitation Sedation scale (RASS) and the Adaptation to The Intensive Care Environment scale-ATICE. The Behavioral Pain Scale (BPS) is a behavioral pain scale. Two of them have been tested with strong evidence of their clinimetric properties: ATICE, RASS. The nurses'preference for a convenient tool could be defined by the level of reliability, the level of clarity, the variety of sedation and agitation states represented user friendliness and speed. In fine, the choice between a simple scale easy to use and a well-defined and complex scale has to be discussed and determined in each unit. Actually, randomized controlled studies are needed to assess the potential superiority of one scale compared with others scales, including evaluation of the reliability and the compliance to the scale. The usefulness of the BIS in ICU for patients lightly sedated is limited, mainly because of EMG artefact, when subjective scales are more appropriated in this situation. On the other hand, subjective scales are insensitive to detect oversedation in patients requiring deep sedation. The contribution of the BIS in deeply sedation patients, patients under neuromuscular blockade or barbiturates has to be proved. Pharmacoeconomics studies are lacking.

Relative Reliability of the Auditory Evoked Potential and Bispectral Index for Monitoring Sedation Level in Surgical Intensive Care Patients

Sedation is an important adjunct therapy for patients in the intensive care unit. The objective of the present study was to observe correlation between an established subjective measure, the Ramsay Sedation Scale, and two objective tools for monitoring critically ill patients: the Bispectral Index (BIS) and auditory evoked potential. Ninety patients undergoing major surgery scheduled for postoperative mechanical ventilation and continuous sedation with propofol and fentanyl were selected. Electrodes for determining BIS and auditory evoked potential were placed on the foreheads of all patients according to manufacturer's specifications at least six hours after patients’ arrival at the intensive care unit. Ramsay Sedation Scale, BIS, signal quality index, composite A-line autoregressive index (AAI) and electromyographic activities were recorded every five minutes for 30 minutes. BIS and AAI showed good correlation amongst readings (rs=0.697, P <0.07). Both were significantly influenced by electromyographic activities (BIS, rs=0.735, P <0.07; AAI, rs=0.856, P <0.07). Comparison of BIS and AAI revealed an acceptable correlation between electroencephalogram variables and the Ramsay Sedation Scale (BIS, τ=-0.689; AAI, τ=-0.621; P <0.07). In conclusion, the auditory evoked potential and BIS monitors revealed an acceptable correlation with the Ramsay Sedation Scale. However, the BIS and auditory evoked potential monitors do not perform adequately as a substitute in the assessment of sedated intensive care unit patients. These monitors could be used as part of an integrated approach for the evaluation of those patients especially when the subjective scales do not work well in the setting of neuromuscular blockade or may not be sufficiently sensitive to evaluate very deep sedation.

Evaluating and monitoring analgesia and sedation in the intensive care unit

Management of analgesia and sedation in the intensive care unit requires evaluation and monitoring of key parameters in order to detect and quantify pain and agitation, and to quantify sedation. The routine use of subjective scales for pain, agitation, and sedation promotes more effective management, including patient-focused titration of medications to specific end-points. The need for frequent measurement reflects the dynamic nature of pain, agitation, and sedation, which change constantly in critically ill patients. Further, close monitoring promotes repeated evaluation of response to therapy, thus helping to avoid over-sedation and to eliminate pain and agitation. Pain assessment tools include self-report (often using a numeric pain scale) for communicative patients and pain scales that incorporate observed behaviors and physiologic measures for noncommunicative patients. Some of these tools have undergone validity testing but more work is needed. Sedation-agitation scales can be used to identify and quantify agitation, and to grade the depth of sedation. Some scales incorporate a step-wise assessment of response to increasingly noxious stimuli and a brief assessment of cognition to define levels of consciousness; these tools can often be quickly performed and easily recalled. Many of the sedation-agitation scales have been extensively tested for inter-rater reliability and validated against a variety of parameters. Objective measurement of indicators of consciousness and brain function, such as with processed electroencephalography signals, holds considerable promise, but has not achieved widespread implementation. Further clarification of the roles of these tools, particularly within the context of patient safety, is needed, as is further technology development to eliminate artifacts and investigation to demonstrate added value.

The encephalopathy in sepsis

Brain dysfunction is a severe complication of sepsis with an incidence ranging from 9% to 71% that is associated with increased morbidity and mortality. Its diagnosis relies mainly on neurologic examination with clinical manifestations ranging from confusion to coma. An electroencephalogram, somatosensory evoked potentials, and measurement of plasma S-100b protein and neuron-specific enolase can be useful for the detection of brain dysfunction. Brain MRI can identify brain lesions such as cerebral infarction, posterior reversible encephalopathy syndrome, and leukoencephalopathy. The mechanism of sepsis-associated encephalopathy involves inflammatory and non-inflammatory processes that affect endothelial cells, glial cells, and neurons and induce blood-brain barrier breakdown, derangements of intracellular metabolism, and cell death. Specific treatments for sepsis-associated encephalopathy need to be developed. Currently, treatment is mainly the management of sepsis.

Clinical review: Sleep measurement in critical care patients: research and clinical implications

Sleep disturbances are common in critically ill patients and have been characterised by numerous studies using polysomnography. Issues regarding patient populations, monitoring duration and timing (nocturnal versus continuous), as well as practical problems encountered in critical care studies using polysomnography are considered with regard to future interventional studies on sleep. Polysomnography is the gold standard in objectively measuring the quality and quantity of sleep. However, it is difficult to undertake, particularly in patients recovering from critical illness in an acute-care area. Therefore, other objective (actigraphy and bispectral index) and subjective (nurse or patient assessment) methods have been used in other critical care studies. Each of these techniques has its own particular advantages and disadvantages. We use data from an interventional study to compare agreement between four of these alternative techniques in the measurement of nocturnal sleep quantity. Recommendations for further developments in sleep monitoring techniques for research and clinical application are made. Also, methodological problems in studies validating various sleep measurement techniques are explored.

Current Controlled Trials ISRCTN47578325.

Perspectives on sedation assessment in critical care

Multiple studies have been undertaken to show that neurofunction monitors can correlate to objective sedation assessments. Showing a correlation between these 2 patient assessments tools may not be the correct approach for validation of neurofunction monitors. Two different methods of assessing 2 different modes of the patient's response to sedation should not be expected to precisely correlate unless the desire is to replace one method with the other. We provide a brief summary of several sedation scales, physiologic measures and neurofunction monitoring tools, and correlations literature for bispectral index monitoring, and the Ramsay Scale and the Sedation Agitation Scale. Neurofunction monitors provide near continuous information about a different domain of the sedation response than intermittent observational assessments. Further research should focus on contributions from this technology to the improvement of patient outcomes when neurofunction monitoring is used as a complement, not a replacement, for observational methods of sedation assessment.

Hyperactive delirium and blood glucose control in critically ill patients

Delirium is a common complication of critically ill patients and is often associated with metabolic disorders. One of the most frequent metabolic disorders in intensive care unit (ICU) patients is hyperglycaemia. The aim of this retrospective study of 196 adult ICU patients was to determine if there is an association between hyperactive delirium and blood glucose levels in ICU patients. Hyperactive delirium was diagnosed using the delirium detection score. Blood glucose levels were monitored by blood gas analysis every 4 h. Hyperactive delirium was detected in 55 (28%) patients. Delirious patients showed significantly higher blood glucose levels than non-delirious patients Higher overall complication rates, length of ventilation, ICU stay and mortality rates were seen in the delirium group. In a multivariate analysis, glucose level, alcohol abuse, APACHE II score, complication by hospital-acquired pneumonia and a diagnosis of polytrauma on-admission all significantly influenced the appearance of delirium.

The importance of diagnosing and managing ICU delirium

ICU delirium represents a form of brain dysfunction that in many cohorts has been diagnosed in 60 to 85% of patients receiving mechanical ventilation. This organ dysfunction is grossly underrecognized because a majority of patients have hypoactive or "quiet" delirium characterized by "negative" symptoms (eg, inattention and a flat affect) not alarming the treating team. Hyperactive delirium, formerly called ICU psychosis, stands out because of symptoms such as agitation that may cause harm to self or staff, but is actually rare relative to hypoactive delirium and associated with a better prognosis. Delirium is often incorrectly thought to be transient and of little consequence. After adjusting for numerous covariates, delirium is a strong, independent predictor of prolonged length of stay, reintubation, higher mortality, and cost of care. Expanded work on patient safety and recommendations by professional societies have established the importance of delirium monitoring and recommended it as standard practice in ICUs all over the world. This evidence-based review for physicians, nurses, respiratory therapists, and pharmacists will outline why it is imperative that patients be routinely monitored for delirium. This review will discuss modifiable risk factors for delirium, such as metabolic disturbances or potent sedative and analgesic medications. Attention to mitigating risk factors, along with recommended pharmacologic approaches such as antipsychotic medications, may provide resolution of delirium in some patients, while others will persist with refractory brain dysfunction and long-term cognitive impairment following critical illness.

An assessment of the validity of spectral entropy as a measure of sedation statein mechanically ventilated critically ill patients

OBJECTIVE

To assess whether the Entropy Module (GE Healthcare, Helsinki, Finland), a device to measure hypnosis in anesthesia, is a valid measure of sedation state in critically ill patients by comparing clinically assessed sedation state with Spectral Entropy

DESIGN

Prospective observational study.

SETTING

Teaching hospital general ICU.

PATIENTS AND PARTICIPANTS

30 intubated, mechanically ventilated patients without primary neurological diagnoses or drug overdose receiving continuous sedation.

INTERVENTIONS

Monitoring of EEG and fEMG activity via forehead electrodes for up to 72h and assessments of conscious level using a modified Ramsay Sedation Scale.

MEASUREMENTS AND RESULTS

475 trained observer assessments were made and compared with concurrent Entropy numbers. Median State (SE) and Response (RE) Entropy values decreased as Ramsay score increased, but wide variation occurred, especially in Ramsay 4-6 categories. Discrimination between different sedation scores [mean (SEM) P(K) value: RE 0.713 (0.019); SE 0.710 (0.019)] and between lighter (Ramsay 1-3) vs.deeper (Ramsay 4-6) sedation ranges was inadequate [P(K): RE 0.750 (0.025); SE 0.748 (0.025)]. fEMG power decreased with increasing Ramsay score but was often significant even at Ramsay 4-6 states. Frequent "on-off" effects occurred for both RE and SE, which were associated with fEMG activity. Values switched from low to high values even in deeply sedated patients. High Entropy values during deeper sedation were strongly associated with simultaneous high relative fEMG powers.

CONCLUSIONS

Entropy of the frontal EEG does not discriminate sedation state adequately for clinical use in ICU patients. Facial EMG is a major confounder in clinical sedation ranges.

Bispectral index as a predictor of sedation depth during isoflurane or midazolam sedation in ICU patients

Bispectral index (BIS) is used for monitoring anaesthetic depth with inhaled anaesthetic agents in the operating room but has not been evaluated as a monitor of sedation depth in the intensive care unit (ICU) setting with these agents. If BIS could predict sedation depth in ICU patients, patient disturbances could be reduced and oversedation avoided. Twenty ventilator-dependent ICU patients aged 27 to 80 years were randomised to sedation with isoflurane via the AnaConDa or intravenous midazolam. BIS (A-2000 XP, version 3.12), electromyogram activity (EMG) and Signal Quality Index were measured continuously. Hourly clinical evaluation of sedation depth according to Bloomsbury Sedation Score (Bloomsbury) was performed. The median BIS value during a 10-minute interval prior to the clinical evaluation at the bedside was compared with Bloomsbury. Nurses performing the clinical sedation scoring were blinded to the BIS values. End-tidal isoflurane concentration was measured and compared with Bloomsbury. Correlation was poor between BIS and Bloomsbury in both groups (Spearman's rho 0.012 in the isoflurane group and -0.057 in the midazolam group). Strong correlation was found between BIS and EMG (Spearman's rho 0.74). Significant correlation was found between end-tidal isoflurane concentration and Bloomsbury (Spearman's rho 0.47). In conclusion, BIS XP does not reliably predict sedation depth as measured by clinical evaluation in non-paralysed ICU patients sedated with isoflurane or midazolam. EMG contributes significantly to BIS values in isoflurane or midazolam sedated, non-paralysed ICU patients. End-tidal isoflurane concentration appeared to be a better indicator of clinical sedation depth than BIS.