Reduced level of arousal and increased mortality in adult acute medical admissions: a systematic review and meta-analysis

Abstract

BackgroundReduced level of arousal is commonly observed in medical admissions and may predict in-hospital mortality. Delirium and reduced level of arousal are closely related. We systematically reviewed and conducted a meta-analysis of studies in adult acute medical patients of the relationship between reduced level of arousal on admission and in-hospital mortality.MethodsWe conducted a systematic review (PROSPERO: CRD42016022048), searching MEDLINE and EMBASE. We included studies of adult patients admitted with acute medical illness with level of arousal assessed on admission and mortality rates reported. We performed meta-analysis using a random effects model.ResultsFrom 23,941 studies we included 21 with 14 included in the meta-analysis. Mean age range was 33.4 - 83.8 years. Studies considered unselected general medical admissions (8 studies, n=13,039) or specific medical conditions (13 studies, n=38,882). Methods of evaluating level of arousal varied. The prevalence of reduced level of arousal was 3.1%-76.9% (median 13.5%). Mortality rates were 1.7%-58% (median 15.9%). Reduced level of arousal was associated with higher in-hospital mortality (pooled OR 5.71; 95% CI 4.21-7.74; low quality evidence: high risk of bias, clinical heterogeneity and possible publication bias).ConclusionsReduced level of arousal on hospital admission may be a strong predictor of in-hospital mortality. Most evidence was of low quality. Reduced level of arousal is highly specific to delirium, better formal detection of hypoactive delirium and implementation of care pathways may improve outcomes. Future studies to assess the impact of interventions on in-hospital mortality should use validated assessments of both level of arousal and delirium.Electronic supplementary materialThe online version of this article (10.1186/s12877-017-0661-7) contains supplementary material, which is available to authorized users.

Delirium

“…Whether specific components of the delirium syndrome are better at predicting poor outcomes than others remains unclear. For example, in a systematic review, acutely reduced arousal (above the level of coma), which is virtually diagnostic of delirium 198 , was associated with a sixfold increase in 30-day hospital mortality 302 . Another study found that the duration of hypoactive delirium but not that of hyperactive delirium was associated with worse long-term cognitive function among critically ill patients experiencing delirium 303 .…”

Delirium detection in older acute medical inpatients: a multicentre prospective comparative diagnostic test accuracy study of the 4AT and the confusion assessment method

“…The present study had limited exclusion criteria, allowing patients with a wide spectrum of level of severity to be approached, including patients with a severely reduced level of arousal. This is pertinent because reduced level of arousal is common in emergency admissions; in one study of clinically collected data from 35,585 consecutive, unselected acute medical admissions aged > 15, 7.6% of patients had reduced level of arousal above the level of coma, and in older populations, the prevalence is higher [71, 81–83]. Given the close relationship of reduced arousal with delirium [29, 32, 71, 83], it is important that studies of delirium assessment instruments include the full spectrum of patients with reduced arousal (excluding coma).…”

“…Additional relevant considerations are that the 4AT can be scored if no informant history is available at the time of assessment, and also if arousal is impaired such that cognitive testing is not possible, which occurs in a substantial proportion of delirium assessments [35, 38, 64]. Given that acutely altered arousal is a highly specific indicator of delirium [29, 30, 70, 71, 83, 90–92] and that it often indicates a poor prognosis [81], a rapid provisional diagnosis of delirium with appropriate investigation and treatment in the absence of an external informant history is reasonable. The 4AT is designed to be able to yield a positive score in patients too unwell to undergo an interview or cognitive testing [31, 32], and so no patients are classed as 'unable to assess'; this facilitates implementation and higher completion rates in clinical practice.…”

Assessment of Delirium Using the Confusion Assessment Method in Older Adult Inpatients in Malaysia

“…Despite the widespread use of the CAM as screening tool for delirium in hospital, the tools’ scoring mechanism does not allow categorization of patients who presents to acute hospitals with reduced consciousness (not comatose) that affect their ability to engage with cognitive testing or interview [26]. This group of “untestable” patients with drowsiness, stupor, obtundation, or agitation has multiple negative outcomes and mortality risk [27,28]. The European Delirium Association and American Delirium Society suggest that it is clinically safer to include these patients within the delirium group until proven otherwise [29].…”