Delirium: Screening, Prevention and Diagnosis - A Systematic Review of the Evidence
Delirium is a common syndrome in hospitalized or institutionalized adults, and frequently causes patients, families, and healthcare providers considerable distress. Delirium is associated with increased morbidity, longer hospital stays, higher healthcare costs, and increased risk of institutionalization and death. In surgical settings, older adults and those with multiple medical conditions are at increased risk for post-operative delirium. Predisposing factors for delirium include: poor nutrition, dehydration, alcohol or drug abuse, medication use (e.g., sleep medications, narcotic pain relievers, sedative hypnotics, antidepressants, and muscle relaxants), sleep deprivation, infection, pain, and stress. Typically, prevention strategies target one or more of these factors. Strategies to detect delirium earlier and among those with milder symptoms — and to prevent the development of delirium in those at risk — have been advocated. Identifying and implementing effective strategies could improve clinical outcomes and lower costs.
Investigators at the Minneapolis VA Evidence-based Synthesis Program, part of the Minneapolis VA Health Care System, conducted a review of the literature from 1950 through November 2010 to evaluate the effectiveness of screening for delirium, the effectiveness and harms of strategies to prevent delirium, and the comparative diagnostic accuracy of tools used to detect delirium. After reviewing 375 articles, 79 were eligible to answer the following key questions.
What is the effectiveness of screening for delirium in adult inpatients?
- Investigators identified no randomized controlled trials of screening for delirium in hospitalized patients. There is no direct evidence that screening for delirium is beneficial or harmful.
- Universal screening may identify more patients, as well as those with less severe symptoms. This may permit greater and earlier use of potentially effective interventions. However, screening may pose harms, such as false-positive and false-negative results, subsequent treatment of non-delirious patients, or misdiagnosis and failure to treat those with delirium.
- Opportunity costs of delirium screening include the time to administer screening tests and follow-up required for positive results.
Do these results vary by medical unit, age, gender or comorbid conditions?
- No studies assessed the effectiveness of screening for delirium according to medical unit or patient age, gender, or comorbid conditions. Therefore, evidence is insufficient about the benefits and harms of delirium screening among all hospitalized patients or subgroups of patients as defined by age, gender, comorbidities, or admission to intensive care units.
Does screening for delirium improve clinical outcomes?
- No evidence was found that screening or subsequent pharmacologic or non-pharmacologic delirium treatments improve clinical outcomes in patients with screen-detected delirium.
What are the effectiveness and harms of delirium prevention strategies in acute elderly inpatients?
- There is low-quality evidence regarding the effectiveness of strategies to prevent delirium. Studies using pharmacologic interventions were few in number, small in size, and examined different categories of preventive medications, often in unique patient populations and settings. The evidence for the effectiveness of atypical antipsychotics was mixed.
- A variety of multi-component strategies (e.g., geriatric consultation, individual care planning, pain management) have been examined and were generally successful in preventing delirium, but the wide variation in the interventions and the lack of assessment of individual intervention components made it difficult to determine which components may be effective.
- The outcomes reported by individual studies were not consistent and usually incomplete.
Do these results vary by medical unit, age, gender or comorbid conditions?
- None of the included studies provided outcomes according to medical unit, age, or comorbid conditions; therefore, investigators were unable to ascertain whether effectiveness or harms varied by these factors.
What is the comparative diagnostic accuracy of the tools used to detect delirium, including among elderly medical and surgical inpatients, as well as elderly ICU inpatients?
- Compared to other tools for delirium detection, the Confusion Assessment Method (CAM) appears to have satisfactory accuracy and ease of administration for detecting or ruling out delirium in medical and surgical inpatients, many of whom were evaluated in geriatric units. However, the CAM was originally developed for use in conjunction with a formal cognitive assessment.
- The accuracy of bedside diagnostic instruments administered by individuals without training — or as stand-alone tools for delirium screening — is unknown.
- Fewer studies have evaluated the diagnostic accuracy of tools to detect delirium for elderly ICU inpatients. The CAM-ICU (CAM adapted for use in the ICU), appears to have high specificity but sensitivity varies, indicating that some patients with delirium will not be identified using the CAM-ICU alone. Other tools have been evaluated in only one or two studies.
- Not all of these studies were restricted to elderly patients, and most excluded patients with neurological disease or cognitive dysfunction.
Suggestions for Future Research
An important area for future research would be to conduct a large multi-center, randomized trial to evaluate the clinical effectiveness, feasibility, and harms of screening for delirium in a broad spectrum of patients admitted to hospitals. More research is needed to verify the findings that pharmacologic and non-pharmacologic strategies can prevent delirium, particularly in larger and more diverse populations. Future studies should report results stratified by age, medical unit, and comorbid conditions. Additionally, more research is needed to identify which components of the multi-component non-pharmacologic strategies may be most successful in delirium prevention. Finally, continued evaluation of diagnostic tools (especially bedside tools in stand-alone settings administered by clinical personnel) is warranted, particularly across a wide range of populations and settings.
A Cyber Seminar session on this ESP Report was held on October 13, 2011. The archived session may be accessed 24/7.
This report is a product of the HSR&D Evidence-based Synthesis Program (ESP), which was established to provide timely and accurate synthesis of targeted healthcare topics of particular importance to VA managers and policymakers -- and to disseminate these reports throughout VA.
Greer N, Rossom R, Anderson P, et al. Delirium: Screening, Prevention, and Diagnosis - A Systematic Review of the Evidence. VA-ESP Project #09-009;2011.
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