a b s t r a c t

Delirium is a widespread and serious but under-recognized problem. Increasing evidence argues that emergency health care providers need to assess the mental status of the patient as the “sixth vital sign”. A simple, sensitive, time-efficient, and cost-effective tool is needed to identify delirium in patients in the emergency department (ED); however, a stand-alone measurement has not yet been established despite previous studies partly because the differential diagnosis of dementia and delirium superimposed on dementia (DSD) is too difficult to achieve using a single indicator. To fill up the gap, multiple aspects of a case should be assessed including inattention and arousal. For instance, we proposed the 100 countdown test as an effective means of detecting inattention. Further dedicated studies are warranted to shed light on the pathophysiology and better management of demen- tia, delirium and/or “altered mental status”. We reviewed herein the clinical questions and controversies concerning delirium in an ED setting.

(C) 2017

Introduction

Delirium is a widespread and serious but under-recognized prob- lem. Approximately 8-10% of older patients visiting the emergency de- partment (ED) present with delirium, which is overlooked by emergency health care providers in 75% of the cases [1]. Delirium basi- cally represents a decompensation of cerebral function in response to pathophysiological stressors [2]. The patient with delirium typically has adverse outcomes including mortality [3] and cognitive decline [4]. A previous study recommended that mental status be included as the “sixth vital sign” [5] along with the respiratory rate (respiratory sys- tem), pulse rate, blood pressure (cardiac system), temperature (im- mune system), and pain (neurological system).

Herein we reviewed the clinical questions and controversies

concerning delirium in an ED setting based on previous systematic re- views [6,7]. This article includes: 1) a summary of previous studies of delirium in the ED; 2) delirium superimposed on dementia (DSD); 3) inattention as a component of consciousness; and 4) future prospects

? The authors received no support, grant, or funding for this project.

* Corresponding author at: Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

E-mail address: [email protected] (H. Tamune).

for better understanding of dementia, delirium and “altered mental status”.

Summary of previous studies of delirium in the ED

Table 1 shows a list of previous studies of delirium in the ED setting, which validated and reported the diagnostic value of various screening tests used in the ED. The tests were found to have good sensitivity and specificity; however, Han et al. showed that ED health care providers were often busy and reluctant to adopt a delirium assessment tool into their routine clinical practice, even if such a procedure required b 2 min [1,8]. These studies underscore the need for much more simple, sensitive, time-efficient and cost-effective tool for identifying delirium in the ED setting such as those currently used for other diseases [9,10]. In this volume, Grossmann et al. [11] discussed whether the modi- fied Richmond Agitation-Sedation Scale (mRASS), which requires only about 30 s implement, was effective in identifying delirium in consecu- tive patients in the ED with this symptom. The sensitivity, specificity, and the positive and negative predictive values were shown to be 0.70, 0.93, 0.44, and 0.98, respectively (see [11] for details including the 95% confidence interval). Grossmann et al. also performed a relevant subclass analysis, allocating subjects to either a group with or without dementia [11]. The aforementioned parameters in patients with de- mentia were 0.55, 0.83, 0.55 and 0.83, respectively, leading the authors

http://dx.doi.org/10.1016/j.ajem.2017.05.026

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Table 1

Selective reports of delirium screening tests used in the emergency department. This Table was modified from Mariz et al. [7].

to conclude that the mRASS was not sensitive enough to identify delir- ium in the ED setting especially in patients with dementia [11]. Howev- er, the same parameters were 0.89, 0.94, 0.38 and 1.00, respectively, in patients without dementia [11],a finding which seems sufficient to in- tegrate mRASS into routine ED practice for patients with no previous history of dementia.

Delirium superimposed on dementia

One of crucial clinical questions is the differential diagnosis of de- mentia and DSD [12,13]. The Diagnostic and Statistical Manual of Mental disorders, fifth edition (DSM-5) lists the five diagnostic criteria for delir- ium [14] as follows:

Disturbance in attention and awareness

Acute onset and fluctuation in severity during the course of a day

An additional disturbance in cognition (e.g. memory deficit, dis- orientation, language, visuospatial ability, or perception.)

The disturbances in Criteria A and C are not better explained by a pre-existing, established or evolving neuro-cognitive disorder and do not occur in the context of a severely reduced level of arousal such as coma.

Evidence that the disturbance is a direct physiological conse- quence of another medical condition or substance effects.

These criteria suggest that delirium cannot be correctly identified based on any one of these aspects alone, and that multiple aspects should be assessed using a systematic battery of tests (even in basic sci- ence, a battery of behavioral tests has been used to study post-operative delirium in mice [15]).

Inattention as a component of consciousness

Consciousness includes a function of awareness (content), arousal/ wakefulness (level), and attention (tentatively considered as content) [2,16]. The European Delirium Association and American Delirium Soci- ety criticized the definition of delirium in the DSM-5 [2], proposing in- stead that attention and arousal are hierarchically related and that the level of arousal must be sufficient before attention can be reasonably assessed [2]. The DSM-5 defines awareness as reduced orientation to the environment; however, this definition might be too vague and the DSM-5 has not suggested how awareness might be assessed. Because the assessment of awareness is complicated and requires time, arousal and attention may be more suitable as assessment targets on a screen- ing test. Previous studies concluded that inattention as well as arousal should be assessed to detect delirium [2,7,13]. We assumed that mRASS allowed assessment of arousal, but which of the attention sub- types - sustained attention, selective attention, switching attention, di- vided attention, or working memory [13] - should be assessed, and which test should be used for assessment, remain unclear.

Several assessment techniques are currently in use. The “months of the year backwards” (MOYB) is a widely used assessment technique.

The Brief Confusion Assessment Method (bCAM) utilizes an abbreviated version of MOYB (December to July). Both these methods are useful in an English-language context, but the names of the months and the dif- ficulty of reciting them backwards differ according to language. For ex- ample, in Japanese or Chinese, the names of months are number-based, presumably making the task easier. Thus, the evidence using English- language context cannot apply the real-world setting in such countlies. We have therefore proposed the “100 countdown” method as a simple, sensitive, time-efficient, and cost-effective means of detecting inatten- tion [17]. An examiner simply asks a patient to count backwards from 100 to 70 in a manner similar to that used in Wechsler’s mental control, in which the patient is asked to count backwards from 20 to 1, although the 100 countdown method has much higher sensitivity. Comparative studies based on the concurrent use of the various tests for detecting in- attention will help to identify which subType of ATtention should be test- ed to identify delirium.

Future prospects for better understanding of dementia, delirium and “altered mental status”

Quick Sequential Organ Failure Assessment comprises only the respiratory rate (>=22/min), systolic blood pressure (<= 100 mm Hg), and "altered mental status" [18] and actually has better prognostic value outside the ICU [19]. Given this fact, we may be justified in reconsidering what “altered mental status” means in clinical terms [20]. Even if mental status were to be accepted as the sixth vital sign, it remains to be solved whether the Glasgow Coma Scale is the best way to detect “altered mental status”. Hence further studies dedicated to shedding light on the pathophysiology and better management of de- mentia, delirium, and/or “altered mental status” are warranted.

In this paper, we reviewed some of the clinical questions and contro- versies surrounding delirium in the ED setting. A screening test for delir- ium needs to have reasonably high sensitivity, but a stand-alone measurement for this purpose has yet to be established. In the interim, multiple aspects of a patient’s symptomatology including inattention and arousal should be assessed. Together with other researchers who have examined this issue, we believe that a screening method for inat- tention and parameters for assessing dementia and delirium in the ED setting are desirable.

Acknowledgement

We thank Mr. James Robert Valera for English proofreading of this manuscript.

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