The CAM-ICU, More Flexible Than You Think

Remember that old joke your grandpa used to play on you? He’d say, “Well, you better keep your eyes peeled tomorrow.” And you’d ask, “Why?”. And grandpa would cackle and reply, “So you can see!” It’s a reminder to be aware and open to what’s happening around you.

Well, pursuant to remaining open and aware, I just got a message from Dr. Wes Ely about a new Czech research study in post-stroke patients about the Confusion Assessment Method-Intensive Care Unit (CAM-ICU), using a Czech version of the instrument.  If you don’t remember Dr. Ely, you’ve been dead. Seriously, see the post about delirium detection in the Leaders in Psychosomatic Medicine section, short link http://wp.me/p1glcu-1nA. I’ve posted before about the strengths and limitations of the CAM-ICU in delirium detection, and one recently published study seemed to cast doubt on its sensitivity in non-ICU patients, although there are many studies validating the CAM-ICU as the best instrument to use in ICU patients [1,2], and see  short link http://wp.me/p1glcu-jN.

Anyway, Dr. Ely is a co-author. Wes says the study is about validating the CAM-ICU in delirious post-stroke patients and only 7 of them were intubated [3].The point about verbal vs non-verbal hearkens back to the speculation about whether or not the CAM-ICU, in part, was less sensitive in non-ICU patients because patients were not ventilated (hence, non-verbal). Some quotes from the recent post (http://wp.me/p1glcu-1nA):

referring to the CAM-ICU: This brief delirium assessment instrument is going to lose some sensitivity… in populations that are less ill with perhaps less overt inattention. That is to say, in the ICU patient with very dense delirium, it is very easy to detect and also specifically detected with the CAM-ICU. But it absolutely will be missed in those in whom a more robust delirium examination should be / must be done to bring out the inattention. Thus, in wards and even… in non-ventilated ICU patients, it is great if someone will use a tool like minicog, SPMSQ, digit span or months backwards.

That caveat about “non-ventilated ICU patients” refers to the question of whether the CAM-ICU might lose sensitivity in more verbal patients, necessitating the use of another tool, such as the original CAM. I think the point of Wes’s remark about the “Bednarik Study” findings in non-intubated patients (I use this author’s name because Wes used it) might be that the CAM-ICU seemed to have adequate sensitivity and specificity in this post-stroke population, most of whom were non-intubated and therefore verbal (although see the caveat about aphasia below). This would seem to counter the findings of lowered sensitivity in the Neufeld study. Hey, different studies about the same phenomena often reach different conclusions.

Another quote from Wes from the same post:

Sharon and I did include non-ventilated ICU patients in our first ever CAM-ICU validation paper (Ely et al, CCM 2001;29:1379). We had 38 total patients in that study, and 18 of them were non-vent. We reported very high sensitivity and specificity for the overall population. While we did report the subpopulation of ventilated patients, which was likewise very high, we did not mention the actual sensitivity of nonventilated patients because the Reviewers asked us about the “more difficult to evaluate” patients. Then they meant those to whom you could not talk, while today we’re talking about those to whom you CAN talk….funny how times change. While I don’t have those numbers at my fingertips now, the overall sensitivity from three raters were 95, 96, and 100. When you consider that the subgroup reported of ventilated was 92, 100, and 100, it is obvious that the sensitivities in the non-vent were still very high in that one study….

Again, the same point seems to be stressed. If ventilated vs non-ventilated is equivalent to non-verbal vs verbal, then the Bednarik Study may say that the CAM-ICU might be  sensitive enough in the verbal post-stroke patients, although this was still a critical care population. Although the Bednarik Study doesn’t negate the findings of the Neufeld Study, it invites critical thinking and maintaining an open mind.

Post-stroke delirium incidence ranges widely from 10% to 48%. Long story short, in this population the CAM-ICU sensitivity was 76% and the specificity was 98%. The study conclusion was that the CAM-ICU was a valid tool for detecting delirium in post-stroke patients. This is the first study  to validate the CAM-ICU  in stroke patients.

Another caveat worth mentioning is about patients with aphasia, the disturbance of language expression and comprehension that can occur in stroke when it affects the brain centers that control language. There were three cases of false positive CAM-ICU assessments and this was attributed to severe aphasia., which made evaluation of attention and thinking challenging. In this situation, the authors recommend re-evaluation of positive CAM-ICU assessments in this population using “more comprehensive consult/liaison neuropsychiatric evaluations in patients with severe disturbance of comprehension with a focus on fluctuation of mental status and behavior.”

The other important feature of this study is that nurses were not the ones administering the CAM-ICU, which is usually the case in other ICUs. In this study, CAM-ICU assessments were done by “a junior physician compared with delirium diagnosis by delirium experts using the Diagnostic and Statistical manual of Mental Disorders, Fourth Edition criteria…”

Three guesses who the “delirium experts” were; first three don’t count. They were likely consultation-liaison psychiatrists, and along with using the DSM-IV diagnostic criteria for delirium, this further embeds the view in medicine that psychiatrists are the leaders in detection of delirium. I have always preferred to think of this as a team effort, and in my opinion, it’s debatable whether psychiatrists should always be considered the leaders in delirium detection, management, and prevention–because delirium by the most rational and practical definition is a medical emergency.

Keep your eyes peeled.

Neufeld, K. J., M. J. Hayat, et al. (2011). “Evaluation of Two Intensive Care Delirium Screening Tools for Non-Critically Ill Hospitalized Patients.” Psychosomatics 52(2): 133-140.

BACKGROUND: Delirium is a common, yet frequently under-recognized medical/psychiatric complication for hospitalized patients, associated with substantial morbidity and mortality. While easy-to-use delirium screening tools exist for ventilated patients, their use in non-critically ill, hospitalized patients has not been validated. METHODS: This prospective 4-week comparison of daily delirium status, using screening tools (Confusion Assessment Method for the Intensive Care Unit [CAM-ICU] and Intensive Care Delirium Screening Checklist [ICDSC]) vs. a daily neuropsychiatric examination as a reference standard, was conducted in 139 inpatients in two medical oncology units at a large teaching hospital during July, 2009. RESULTS: Based on neuropsychiatric examination, 36 (26%) patients had at least 1 day of delirium during their hospital admission. For 21 (15%) patients, delirium was present at the initial assessment, while 15 (11%) developed delirium at a median (IQR) of three (2-7) subsequent assessments. Delirium was present on 20% of all patient-days. For the initial evaluation, the CAM-ICU had a sensitivity of 18% (95% confidence interval [CI], 5%-44%), and a sensitivity of 18% (9% -32%) when using all assessments, adjusting for repeated measures on each patient. The ICDSC had sensitivities of 47% (24%-72%) and 62% (49%-74%). The specificity of both instruments was very high (>/=98%). CONCLUSIONS: This study suggests that in non-critically ill hospitalized patients, the CAM-ICU and ICDSC intensive care delirium screening tools are not adequately sensitive for use in routine clinical practice. Further work is needed to develop more sensitive, efficient tools in this population.

Ely, E. W., R. Margolin, et al. (2001). “Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).” Crit Care Med 29(7): 1370-1379.

OBJECTIVE: To develop and validate an instrument for use in the intensive care unit to accurately diagnose delirium in critically ill patients who are often nonverbal because of mechanical ventilation. DESIGN: Prospective cohort study. SETTING: The adult medical and coronary intensive care units of a tertiary care, university-based medical center. PATIENTS: Thirty-eight patients admitted to the intensive care units. MEASUREMENTS AND MAIN RESULTS: We designed and tested a modified version of the Confusion Assessment Method for use in intensive care unit patients and called it the CAM-ICU. Daily ratings from intensive care unit admission to hospital discharge by two study nurses and an intensivist who used the CAM-ICU were compared against the reference standard, a delirium expert who used delirium criteria from the Diagnostic and Statistical Manual of Mental Disorders (fourth edition). A total of 293 daily, paired evaluations were completed, with reference standard diagnoses of delirium in 42% and coma in 27% of all observations. To include only interactive patient evaluations and avoid repeat-observer bias for patients studied on multiple days, we used only the first-alert or lethargic comparison evaluation in each patient. Thirty-three of 38 patients (87%) developed delirium during their intensive care unit stay, mean duration of 4.2 +/- 1.7 days. Excluding evaluations of comatose patients because of lack of characteristic delirium features, the two critical care study nurses and intensivist demonstrated high interrater reliability for their CAM-ICU ratings with kappa statistics of 0.84, 0.79, and 0.95, respectively (p <.001). The two nurses’ and intensivist’s sensitivities when using the CAM-ICU compared with the reference standard were 95%, 96%, and 100%, respectively, whereas their specificities were 93%, 93%, and 89%, respectively. CONCLUSIONS: The CAM-ICU demonstrated excellent reliability and validity when used by nurses and physicians to identify delirium in intensive care unit patients. The CAM-ICU may be a useful instrument for both clinical and research purposes to monitor delirium in this challenging patient population.

Mitasova, A., M. Kostalova, et al. (2011). “Poststroke delirium incidence and outcomes: Validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).” Crit Care Med.

OBJECTIVE:: To describe the epidemiology and time spectrum of delirium using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria and to validate a tool for delirium assessment in patients in the acute poststroke period. DESIGN:: A prospective observational cohort study. SETTING AND PATIENTS:: A consecutive series of 129 patients with stroke (with infarction or intracerebral hemorrhage, 57 women and 72 men; mean age, 72.5 yrs; age range, 35-93 yrs) admitted to the stroke unit of a university hospital were evaluated for delirium incidence. INTERVENTIONS:: None. MEASUREMENTS AND MAIN RESULTS:: Criterion validity and overall accuracy of the Czech version of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) were determined using serial daily delirium assessments with CAM-ICU by a junior physician compared with delirium diagnosis by delirium experts using the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria that began the first day after stroke onset and continued for at least 7 days. Cox regression models using time-dependent covariate analysis adjusting for age, gender, prestroke dementia, National Institutes of Stroke Health Care at admission, first-day Sequential Organ Failure Assessment, and asphasia were used to understand the relationships between delirium and clinical outcomes. An episode of delirium based on reference Diagnostic and Statistical Manual assessment was detected in 55 patients with stroke (42.6%). In 37 of these (67.3%), delirium began within the first day and in all of them within 5 days of stroke onset. A total of 1003 paired CAM-ICU/Diagnostic and Statistical Manual of Mental Disorders daily assessments were completed. Compared with the reference standard for diagnosing delirium, the CAM-ICU demonstrated a sensitivity of 76% (95% confidence interval [CI], 55% to 91%), a specificity of 98% (95% CI, 93% to 100%), an overall accuracy of 94% (95% CI, 88% to 97%), and high interrater reliability (kappa = 0.94; 95% CI, 0.83-1.0). Delirium was an independent predictor of increased length of hospital stay (hazard ratio, 1.63; 95% CI, 1.11-2.38; p = .013). CONCLUSIONS:: Poststroke delirium may frequently be detected provided that the testing algorithm is appropriate to the time profile of poststroke delirium. Early (first day after stroke onset) and serial screening for delirium is recommended. CAM-ICU is a valid instrument for the diagnosis of delirium and should be considered an aid in delirium screening and assessment in future epidemiologic and interventional studies in patients with stroke.

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