August 7, 2012
Cognition, Post-Op Delirium, and Post-Op Outcomes
You’ve heard us harp on this topic before (see our August 17, 2010 Patient Safety Tip of the Week “”) – rather than wasting a lot of time and money doing extensive preoperative cardiac evaluations for non-cardiac surgery we get a lot more bang for the buck doing simple screening for three risks: obstructive sleep apnea (OSA), frailty, and cognition/delirium. An otherwise excellent recent review on the preoperative medical consultation (Rivera 2012) briefly discusses OSA but does not even mention screening for frailty or cognitive dysfunction at all.
Yet identification of each of these three risk factors increases the likelihood that the patient will have postoperative complications and poor outcomes. More importantly identification of these risks should lead to interventions designed to reduce the chances of those adverse postoperative outcomes. Screening tools for each are simple and inexpensive. For OSA the STOP-Bang questionnaire is very good at identifying patients likely to have OSA. For frailty there are several frailty indices or tools available but the timed up-and-go test is easy to do and reliable. And there are simple tools described below (such as the mini-Cog test) that can be done quickly in the office that help predict post-op delirium and post-op decline in cognitive function.
We had previously cited the work of Robinson and colleagues (see our November 2011 What’s New in the Patient Safety World column “Timed Up-and-Go Test and Surgical Outcomes” and our August 9, 2011 Patient Safety Tip of the Week “Frailty and the Surgical Patient”) in predicting postoperative complications based on frailty measures (Robinson 2009, Robinson 2011).
A new study by that group (Robinson 2012) of elderly patients scheduled to undergo elective surgery with expected post-op ICU stays (mostly males in the VA system) used the Mini-Cog score to assess cognitive function preoperatively and demonstrated that patients scoring 3 or less were more likely to have post-op delirium, longer hospital stays, increased likelihood of discharge to institutional care, and higher 6-month mortality. The risk of delirium was doubled (78% vs. 37%) and delirium lasted longer in those patients scoring 3 or below on the Mini-Cog. Average LOS was 15 days in those with low Mini-Cog scores compared to 9 days in those with higher scores. Six-month mortality rates were 13% vs. 5% and discharge institutionalization rates were 42% vs. 18% respectively for those scoring 3 or below vs. those above 3 on the Mini-Cog.
The Mini-Cog (Borson 2000) consists of giving the patient 3 unrelated words to recall, then having them draw a clock with hands at a specified time (the patient is asked what the 3 words are after they have finished drawing the clock). Scoring (SHM 2004) is 0 to 5 (1 poiint for each word recalled and 2 points for drawing a normal clock). The whole test usually only takes about 2-3 minutes. It is well validated in multiple populations.
The relationship of delirium to mortality is well known and the Robinson study suggests that delirium was an effect modifier rather than a confounder in the relationship of cognitive impairment with mortality.
Two very instructive articles on cognition and delirium in surgical patients were just published. Marcantonio (Marcantonio 2012) uses a clinical case to discuss multiple aspects of delirium, including pathophysiology, risk factors, precipitating factors, management, and preventive interventions. It is an interesting case where a patient developed a slightly delayed delirium (that coincided with onset of another post-op complication), then had a recurrence of delirium after a second surgery, yet underwent a third surgery without developing delirium. A highlighted point was that the patient had not yet fully recovered from the first delirium episode when the second surgery was needed but had fully returned to baseline before the third surgery. The article has a nice table showing the additive effects of predisposing factors (eg. advanced age, preexisting dementia, depression, functional disability) and precipitating factors (eg. surgery, anesthesia, sedative drugs, benzodiazepines, poorly controlled pain, prolonged ICU stays, other postop complications, etc.). He makes a good point that a patient with few predisposing factors needs more precipitating factors in order for delirium to develop, whereas a patient with several predisposing factors may only need a few precipitating factors. The article also provides a good discussion of the evidence base for treating or preventing delirium (including both what works and what does not work). Excellent article.
Mercantonio was also a coauthor of the second article (Saczynski 2012) that deals with the trajectories of cognitive dysfunction seen after postoperative delirium. In this study they followed 225 patients aged 60 or older who underwent CABG or heart valve surgery. 46% of the patients developed delirium. Those that did develop delirium had lower pre-op MMSE (mini-mental state exam) scores, had bigger drops in MMSE scores shortly after surgery, and had lower cognitive function at one year after surgery. A higher percentage of those with delirium had not returned to their pre-op cognitive level by 6 months but the difference was no longer significant at 12 months. Thus, the typical trajectory for those who develop postop delirium is an initial rapid decline in cognitive function followed by a prolonged period of impairment.
These articles stress the value of assessment of the patient’s cognitive status by simple means before the patient undergoes surgery. Knowledge of that status may help avoid the occurrence of post-op delirium and other complications and also help in planning the patient’s immediate and prolonged postoperative course and management. A few minutes up front can save a lot of time down the line!
Some of our prior columns on delirium assessment and management:
· October 21, 2008 “Preventing Delirium”
· October 14, 2009 “Managing Delirium”
· February 10, 2009 “Sedation in the ICU: The Dexmedetomidine Study”
· March 31, 2009 “Screening Patients for Risk of Delirium”
· June 23, 2009 “More on Delirium in the ICU”
· January 26, 2010 “Preventing Postoperative Delirium”
· August 31, 2010 “”
· September 2011 “Modified HELP Helps Outcomes in Elderly Undergoing Abdominal Surgery”)
· December 2010 “The ABCDE Bundle”
· February 28, 2012 “AACN Practice Alert on Delirium in Critical Care”
· April 3, 2012 “New Risk for Postoperative Delirium: Obstructive Sleep Apnea”
Rivera RA, Nguyen MT, Martinez-Osorio JI, et al. Preoperative medical consultation: maximizing its benefits. Am J Surg 2012; ahead of print July 9, 2012
Robinson TN, Eiseman B, Wallace JI, et al. Redefining Geriatric Preoperative Assessment Using Frailty, Disability and Co-Morbidity. Annals of Surgery 2009; 250(3): 449-455, September 2009
Robinson TN, Wallace JI, Wu DS, et al. Accumulated Frailty Characteristics Predict Postoperative Discharge Institutionalization in the Geriatric Patient. J Am Coll Surg 2011; 213(1): 37-42, July 2011
Robinson TN, Wu DS, Pointer LF, et al. Preoperative Cognitive Dysfunction Is Related to Adverse Postoperative Outcomes in the Elderly. J Am Coll Surg 2012; 215(1): 12-18
Marcantonio ER. Clinician's Corner. Postoperative DeliriumA 76-Year-Old Woman With Delirium Following Surgery. JAMA. 2012; 308(1): 73-81
Saczynski JS, Marcantonio ER, Quach L, et al. Cognitive Trajectories after Postoperative Delirium. N Engl J Med 2012; 367: 30-39
Borson S, Scanlan J, Brush M, Vitaliano P, Dokmak A. The mini-cog: a cognitive “vital signs” measure for dementia screening in multi-lingual elderly. Int J Geriatr Psychiatry 2000; 15(11): 1021–1027
SHM (Society for Hospital Medicine). The Mini-Cog Assessment Instrument for Dementia. 2004