October 21, 2008
This is the second part of our series on delirium in the hospital setting. Many of you who read last week’s Patient Safety Tip of the Week “Managing Delirium” probably said to yourselves “Sounds like the best way to manage delirium is to prevent it in the first place…”. So did we! It’s interesting to see how we have evolved in our thinking in medicine over the years. We went back and looked at a chapter on neurological problems we had written in a geriatric textbook almost 20 years ago (Truax 1989). It was a short segment about diagnosing and treating delirium and acute confusional states in the geriatric population. Not much has actually changed about the diagnostic or therapeutic approach once delirium occurs but we didn’t even mention prevention! Obviously what has to change is our approach to identifying patients at risk for delirium before they develop it so that we can prevent it all together.
Much of what we know about delirium today comes from the work of Sharon Inouye and her colleagues at Yale and their Hospital Elder Life Program (HELP). Two comprehensive reviews of delirium in older people (Inouye 2006; Young and Inouye 2008) provide good statistical data about delirium as well as clinical and practical management recommendations. Both cite $2500 additional cost per patient and an annual total impact for Medicare of $6.9 billion resulting from delirium. Delirium affects 20% of all hospitalized patients over the age of 65 and care of such patients accounts for 49% of all hospital days. Some studies show even higher costs in certain settings. Milbrandt et al (Mildbrandt 2004) looked at the financial impact of delirium in ICU patients and found that it increased ICU costs by about $9000 and total hospital costs by about $14,500.
How much time and resources have you seen wasted in the “preoperative workup”? Inordinate amounts of resources are wasted getting laboratory and imaging studies that never impact upon a patient’s hospitalization. The same applies to the preoperative “medical clearance”. The evidence base for a shotgun approach to preoperative testing and clearance is thin at best. What makes more sense is a very targeted approach, basing any preoperative evaluation on known medical problems and risk factors and problems likely to occur during the surgery or other reason for hospitalization. But identifying risk factors for delirium should be a very productive endeavor, given the high human and financial costs that accompany delirium and the number of strategies that are available to prevent deilirum.
The strongest risk factor for delirium is pre-existing dementia. Also, of those patients suffering delirium during a hospitalization, a substantial number show cognitive decline in the subsequent year. So there is a complex but clearcut relationship between dementia and delirium. In addition, we’ve mentioned that most cases of delirium are multifactorial in etiology. In patients with pre-existing dementia, fewer other risk factors and/or triggers are necessary to cause delirium whereas several such factors usually must be present to cause delirium in patients lacking dementia. So it makes sense that identifying dementia would be a logical step in predicting a patient is at risk for delirium.
The simplest evaluation that can be done is the standard Mini-Mental Status Examination (MMSE) or one of the shorter derivative tests. Even though there are several more compehensive screening tools that have been used to predict delirium risk, almost all use the MMSE or similar tool as part of their protocol and the additional tools usually just add to the sensitivity and specificity of the MMSE.
A number of tools or instruments have been touted as being predictive of postoperative delirium. The DEAR (Delirium Elderly At-Risk) instrument uses 5 parameters (age > 80, hearing aid/poor vision, activities of daily living, the MMSE, and use of alcohol/benzodiazepines). Use of the DEAR tool preoperatively predicted delirium in 100 hip fracture patients (Freter 2005) with a sensitivity of 71% and specificity of 48%. Surprisingly, the MMSE alone (using a cutoff score of 23) actually had better sensitivity and specificity for postoperative delirium. The same group (Freter 2005b) used the DEAR instrument in 132 patients having elective arthroplasty of the hip or knee and found that having 2 or more risk factors increased the risk of postoperative delirium eight-fold.
Priner et al (Priner 2008) used the short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) in patients 60 and older who were admitted for elective hip and knee arthroplasty and found a score of >50 was predictive of postoperative delirium with an odds ratio of 12.7.
Kalisvaart et al (Kalisvaart 2006) used a medical risk factor model combining 4 risk factors for delirium (MMSE <24, APACHE II score > 16, visual acuity by Snellen chart worse than 20/70, and dehydration as assessed by a BUN/creatinine ratio >18) and were able to stratify elderly hip surgery patients into low-, intermediate-, and high-risk categories. The MMSE and APACHE II scores were independent predictors of postoperative delirium. They also noted that adding age and type of admission (emergency vs. elective) might further strengthen the predictive power of their model but the model needs validation with these risk factors added.
A systematic review (Dasgupta 2006) of preoperative risk assessment for delirium after noncardiac surgery found 25 articles that validated 2 scales, a clinical prediction rule, and a delirium classification system but concluded that further research is needed to better identify patients at risk for postoperative delirium.
And just this week at the American Society of Anesthesiologists annual meeting a new study from Duke by Mork et al was released identifying risk factors to flag patients at risk for postoperative delirium. That study of 100 patients found a 16% incidence of postoperative delirium in patients over 65 who underwent noncardiac surgery. They used 2 tools as potential screening tools to predict postoperative delirium – the Geriatric Depression Scale (short form) and the Trail Making Test. The results are promising.
We recommend that any patient over the age of 65 have a delirium risk assessment prior to admission. If the patient does not have a primary care physician or geriatrician who routinely does such screening, you should have a preoperative program staffed by a nurse or physician extender. That program should include a screening for delirium risk factors in addition to looking for risk factors for other conditions that may complicate a hospitalization. Doing the MMSE (or shorter versions) would be the minimum assessment we’d recommend until future studies validate more complex instruments but it is certainly logical to look for other delirium risk factors noted above as well.
The presence of delirium as patients emerge from anesthesia or in the recovery room is also a good predictor of postoperative delirium occurring later. Sharma et al (Sharma 2005) noted a prevalence of delirium in the recovery room of 45% and prevalence of later postoperative delirium of 36% of elderly hip fracture patients. All patients who later developed postoperative delirium had delirium in the recovery room as well so the sensitivity of recovery room delirium as a predictor of postoperative delirium was 100%.
Once you have identified a patient at risk of delirium, regular screening for delirium with a tool such as the CAM should be done as described in last week’s Tip of the Week.
So what preventive steps do you need to take when you identify a patient as being at risk for delirium and do they work? Inouye et al (Inouye 1999) had shown in a landmark study of 852 medical patients aged 70 and older that management of 6 risk factors was able to reduce the incidence of delirium from 15% to 9.9%. The number of days with delirium and the number of episodes of delirium was also reduced by the intervention. The intervention targeted cognitive impairment, sleep deprivation, immobility, visual impairment, hearing impairment, and dehydration. This was strong evidence that a multicomponent intervention could be of benefit in reducing delirium.
Last week we also mentioned several studies that have demonstrated that multifactorial interventions targeted at elderly inpatients at risk for delirium may shorten hospital length of stay, reduce duration of delirium, and reduce mortality (Lundstrom et al. 2005; Naughton et al 2005) and other hospital outcomes (Kratz 2008). Those strategies include patient orientation, early mobilization, nonpharmacologic sleep, appropriate pain management, good hydration, avoiding a variety of drugs (but especially benzodiazepines and other sedatives), and avoiding physical restraints and urinary catheters or other unnecessary intrusive devices.
Delirium is a common problem in elderly hospitalized patients, with potentially devastating consequences to the patient, their families, the hospital, and society. Delirium’s occurrence should be anticipated. Patients at risk should be identified as soon as possible, preferably even before admission so that appropriate preventive interventions and surveillance can be put in place.
Update: See also our February 10, 2009 Patient Safety Tip of the Week “Sedation in the ICU: The Dexmedetomidine Study” and our March 31, 2009 Patient Safety Tip of the Week “Screening Patients for Risk of Delirium” and our June 23, 2009 Patient Safety Tip of the Week “More on Delirium in the ICU” and our January 26, 2010 Patient Safety Tip of the Week “Preventing Postoperative Delirium”.
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