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

OBJECTIVE: Bispectral index (BIS) is being evaluated as a monitor of consciousness, yet it is unclear what components of consciousness (i.e., arousal vs. content of consciousness) the BIS measures. This study compared BIS levels to well-validated clinical measures of arousal and the presence or absence of delirium. DESIGN: A prospective, blinded, observational cohort study. PATIENTS: 124 mechanically ventilated, adult, medical ICU patients. MEASUREMENTS AND RESULTS: Using BIS 3.4 and BIS-XP 4.0 algorithms, BIS values were calculated immediately prior to clinical assessments. The clinical assessments included the Richmond Agitation-Sedation Scale (RASS) and presence or absence of delirium using the Confusion Assessment Method for the ICU. A total of 484 assessments were collected among 124 patients. BIS-XP values demonstrated greater correlation with RASS than BIS 3.4 ( R(2)=0.36 vs. 0.20), although considerable overlap of BIS-XP scores remained across RASS levels. Median BIS-XP values for delirious and nondelirious observations were 74 and 96, respectively, while BIS 3.4 values were 91 and 96, respectively. However, neither BIS 3.4 nor BIS-XP were significantly associated with delirium after controlling for RASS value. CONCLUSIONS: In comparison with clinical measures of arousal in mechanically ventilated patients, BIS-XP algorithm demonstrated stronger correlation with RASS levels than did BIS 3.4, yet marked overlap across different levels of arousal persist using both algorithms. After controlling for level of arousal, neither BIS-XP nor BIS 3.4 algorithms distinguished between the presence and absence of delirium.

Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit.

CONTEXT: In the intensive care unit (ICU), delirium is a common yet underdiagnosed form of organ dysfunction, and its contribution to patient outcomes is unclear. OBJECTIVE: To determine if delirium is an independent predictor of clinical outcomes, including 6-month mortality and length of stay among ICU patients receiving mechanical ventilation. DESIGN, SETTING, AND PARTICIPANTS: Prospective cohort study enrolling 275 consecutive mechanically ventilated patients admitted to adult medical and coronary ICUs of a US university-based medical center between February 2000 and May 2001. Patients were followed up for development of delirium over 2158 ICU days using the Confusion Assessment Method for the ICU and the Richmond Agitation-Sedation Scale. MAIN OUTCOME MEASURES: Primary outcomes included 6-month mortality, overall hospital length of stay, and length of stay in the post-ICU period. Secondary outcomes were ventilator-free days and cognitive impairment at hospital discharge. RESULTS: Of 275 patients, 51 (18.5%) had persistent coma and died in the hospital. Among the remaining 224 patients, 183 (81.7%) developed delirium at some point during the ICU stay. Baseline demographics including age, comorbidity scores, dementia scores, activities of daily living, severity of illness, and admission diagnoses were similar between those with and without delirium (P>.05 for all). Patients who developed delirium had higher 6-month mortality rates (34% vs 15%, P =.03) and spent 10 days longer in the hospital than those who never developed delirium (P<.001). After adjusting for covariates (including age, severity of illness, comorbid conditions, coma, and use of sedatives or analgesic medications), delirium was independently associated with higher 6-month mortality (adjusted hazard ratio [HR], 3.2; 95% confidence interval [CI], 1.4-7.7; P =.008), and longer hospital stay (adjusted HR, 2.0; 95% CI, 1.4-3.0; P<.001). Delirium in the ICU was also independently associated with a longer post-ICU stay (adjusted HR, 1.6; 95% CI, 1.2-2.3; P =.009), fewer median days alive and without mechanical ventilation (19 [interquartile range, 4-23] vs 24 [19-26]; adjusted P =.03), and a higher incidence of cognitive impairment at hospital discharge (adjusted HR, 9.1; 95% CI, 2.3-35.3; P =.002). CONCLUSION: Delirium was an independent predictor of higher 6-month mortality and longer hospital stay even after adjusting for relevant covariates including coma, sedatives, and analgesics in patients receiving mechanical ventilation.

Monitoring sedation status over time in ICU patients: reliability and validity of the Richmond Agitation-Sedation Scale (RASS).

CONTEXT: Goal-directed delivery of sedative and analgesic medications is recommended as standard care in intensive care units (ICUs) because of the impact these medications have on ventilator weaning and ICU length of stay, but few of the available sedation scales have been appropriately tested for reliability and validity. OBJECTIVE: To test the reliability and validity of the Richmond Agitation-Sedation Scale (RASS). DESIGN: Prospective cohort study. SETTING: Adult medical and coronary ICUs of a university-based medical center. PARTICIPANTS: Thirty-eight medical ICU patients enrolled for reliability testing (46% receiving mechanical ventilation) from July 21, 1999, to September 7, 1999, and an independent cohort of 275 patients receiving mechanical ventilation were enrolled for validity testing from February 1, 2000, to May 3, 2001. MAIN OUTCOME MEASURES: Interrater reliability of the RASS, Glasgow Coma Scale (GCS), and Ramsay Scale (RS); validity of the RASS correlated with reference standard ratings, assessments of content of consciousness, GCS scores, doses of sedatives and analgesics, and bispectral electroencephalography. RESULTS: In 290-paired observations by nurses, results of both the RASS and RS demonstrated excellent interrater reliability (weighted kappa, 0.91 and 0.94, respectively), which were both superior to the GCS (weighted kappa, 0.64; P<.001 for both comparisons). Criterion validity was tested in 411-paired observations in the first 96 patients of the validation cohort, in whom the RASS showed significant differences between levels of consciousness (P<.001 for all) and correctly identified fluctuations within patients over time (P<.001). In addition, 5 methods were used to test the construct validity of the RASS, including correlation with an attention screening examination (r = 0.78, P<.001), GCS scores (r = 0.91, P<.001), quantity of different psychoactive medication dosages 8 hours prior to assessment (eg, lorazepam: r = - 0.31, P<.001), successful extubation (P =.07), and bispectral electroencephalography (r = 0.63, P<.001). Face validity was demonstrated via a survey of 26 critical care nurses, which the results showed that 92% agreed or strongly agreed with the RASS scoring scheme, and 81% agreed or strongly agreed that the instrument provided a consensus for goal-directed delivery of medications. CONCLUSIONS: The RASS demonstrated excellent interrater reliability and criterion, construct, and face validity. This is the first sedation scale to be validated for its ability to detect changes in sedation status over consecutive days of ICU care, against constructs of level of consciousness and delirium, and correlated with the administered dose of sedative and analgesic medications.

Six-month neuropsychological outcome of medical intensive care unit patients.

OBJECTIVE: To examine neuropsychological function, depression, and quality of life 6 months after discharge in patients who received mechanical ventilation in the intensive care unit. DESIGN: Prospective cohort study. SETTING: Tertiary care, medical and coronary intensive care unit of a university-based medical center. STUDY POPULATION: A total of 275 consecutive, mechanically ventilated patients from a medical intensive care unit were prospectively followed. At 6 months, 157 were alive, of whom 41 (26%) returned for extensive follow-up testing. MEASUREMENT AND MAIN RESULTS: Neuropsychological testing and assessment of depression and quality of life were performed at 6-month follow-up. Seven of 41 patients were excluded from further analysis due to preexisting cognitive impairment determined via surrogate interviews using the Modified Blessed Dementia Rating Scale and a review of medical records. On the basis of strict criteria derived from normative data, we found that 11 of 34 patients (32%) were neuropsychologically impaired. Impairment was generally diffuse but occurred primarily in areas of psychomotor speed, visual and working memory, verbal fluency, and visuo-construction. The rate of neuropsychological deficits in the study population was markedly higher than population norms for mild dementia. Scores on the Geriatric Depression Scale-Short Form were significantly more abnormal in the neuropsychologically impaired group than in the nonimpaired group at hospital discharge (p =.04) and at 6-month follow-up (p =.02), and clinically significant depression was found in 27% of impaired subjects at hospital discharge and in 36% at 6-month follow-up. No differences were observed between groups in quality of life as measured with the Short Form Health Survey-12 at discharge or 6-month follow-up. CONCLUSIONS: Prolonged neuropsychological impairment is common among survivors of the medical intensive care unit and occurs with greater than anticipated frequency when compared with relevant normative data. Future investigations are warranted to elucidate the nature of the association between critical illness, neuropsychological impairment, depression, and decreased quality of life.

Current opinions regarding the importance, diagnosis, and management of delirium in the intensive care unit: a survey of 912 healthcare professionals.

OBJECTIVE: Recently published clinical practice guidelines of the Society of Critical Care Medicine recommend monitoring for the presence of delirium in all mechanically ventilated patients because of the potential for adverse outcomes associated with this comorbidity, yet little is known about healthcare professionals' opinions regarding intensive care unit delirium or how they manage this organ dysfunction. The aim of this survey was to assess the medical community's beliefs and practices regarding delirium in the intensive care unit. DESIGN: Survey administration was conducted both without a delirium definition (phase 1) and then with a definition of delirium (phase 2). SETTING: Critical care meetings and continuing medical education/board review courses from October 2001 to July 2002. PARTICIPANTS: A convenience sample of physicians (n = 753), nurses (n = 113), pharmacists (n = 13), physician assistants (n = 12), respiratory care practitioners (n = 8), and others (n = 13). INTERVENTIONS: Survey. MEASUREMENTS AND MAIN RESULTS: Participants completed 912 of the surveys. The majority (68%) of respondents thought that >25% of adult mechanically ventilated patients experience delirium. Delirium was considered a significant or very serious problem in the intensive care unit by 92% of healthcare professionals, yet underdiagnosis was acknowledged by 78%. Only 40% reported routinely screening for delirium, and only 16% indicated using a specific tool for delirium assessment. Delirium was considered important in the outcome of elderly and young patients by 89% and 60% of the respondents, respectively (p <.0001). The most serious complications these professionals associated with delirium were prolonged mechanical ventilation, self-injury, and respiratory difficulties. Delirium was treated with haloperidol by 66% of the respondents, with lorazepam by 12%, and with atypical antipsychotics by <5%. More than 55% administered haloperidol and lorazepam at daily doses of < or =10 mg, but some used >50 mg/day of either medication. CONCLUSIONS: Most healthcare professionals consider delirium in the intensive care unit a common and serious problem, although few actually monitor for this condition and most admit that it is underdiagnosed. Data from this survey point to a disconnect between the perceived significance of delirium in the intensive care unit and current practices of monitoring and treatment.

Costs associated with delirium in mechanically ventilated patients.

OBJECTIVE: To determine the costs associated with delirium in mechanically ventilated medical intensive care unit patients. DESIGN: Prospective cohort study. SETTING: A tertiary care academic hospital. PATIENTS: Patients were 275 consecutive mechanically ventilated medical intensive care unit patients. INTERVENTIONS: We prospectively examined patients for delirium using the Confusion Assessment Method for the Intensive Care Unit. MEASUREMENTS AND MAIN RESULTS: Delirium was categorized as "ever vs. never" and by a cumulative delirium severity index. Costs were determined from individual ledger-level patient charges using cost-center-specific cost-to-charge ratios and were reported in year 2001 U.S. dollars. Fifty-one of 275 patients (18.5%) had persistent coma and died in the hospital and were excluded from further analysis. Of the remaining 224 patients, delirium developed in 183 (81.7%) and lasted a median of 2.1 (interquartile range, 1-3) days. Baseline demographics were similar between those with and without delirium. Intensive care unit costs (median, interquartile range) were significantly higher for those with at least one episode of delirium ($22,346, $15,083-$35,521) vs. those with no delirium ($13,332, $8,837-$21,471, p <.001). Total hospital costs were also higher in those who developed delirium ($41,836, $22,782-$68,134 vs. $27,106, $13,875-$37,419, p =.002). Higher severity and duration of delirium were associated with incrementally greater costs (all p <.001). After adjustment for age, comorbidity, severity of illness, degree of organ dysfunction, nosocomial infection, hospital mortality, and other potential confounders, delirium was associated with 39% higher intensive care unit (95% confidence interval, 12-72%) and 31% higher hospital (95% confidence interval, 1-70%) costs. CONCLUSIONS: Delirium is a common clinical event in mechanically ventilated medical intensive care unit patients and is associated with significantly higher intensive care unit and hospital costs. Future efforts to prevent or treat intensive care unit delirium have the potential to improve patient outcomes and reduce costs of care.