Acute hospital care is fast becoming acute geriatric care: people aged 65 years or older are only 13% of the population but account for 44% of days of care in nonfederal hospitals and 38% of discharges.1 In general, the elderly have longer hospital stays, incur greater costs, and have a higher risk of adverse outcomes than do their younger counterparts.2
Among the most common surgical procedures for patients older than 65 are percutaneous coronary intervention with stenting, coronary artery bypass graft surgery, and open reduction internal fixation for hip fracture; the latter is the most common operation in patients aged 85 years or older.3
Elderly patients frequently pose many challenges perioperatively that are not often seen in younger patients. Dementia, frailty, impaired ability to care for oneself, and malnourishment may be present at baseline and are likely to worsen postoperatively. The elderly are at increased risk of acute delirium and cognitive impairment postoperatively, which often complicates recovery and discharge placement.
This article uses a case study to review perioperative problems commonly encountered in elderly surgical patients, particularly those undergoing hip surgery. As the case is presented, I will review strategies to assess risks and prevent and mitigate postoperative cognitive dysfunction and other barriers to recovery.
CASE: AN 82-YEAR-OLD WOMAN WITH HIP FRACTURE
An 82-year-old woman is admitted to undergo open reduction internal fixation for hip fracture. She has a history of osteoarthritis, systolic hypertension, and visual impairment (20/70). Her medications include a beta-blocker, a thiazide diuretic, analgesics as needed, and a multivitamin. She was independent in all activities of daily living before the fracture. She is a social drinker and does not smoke. She has no known cardiovascular, lung, or renal disease.
Her laboratory test results are as follows:
- Blood urea nitrogen (BUN), 24 mg/dL
- Creatinine, 1.0 mg/dL
- Hemoglobin, 12.8 g/dL
- Albumin, 3.8 gm/dL
- Normal levels of thyroid-stimulating hormone and vitamin B12.
Thus, her lab results are normal except for the BUN:creatinine ratio being a bit high, at 24:1 (normal is 10:1, with ratios greater than 18:1 being associated with an increased risk of delirium4).
ASSESSING COGNITIVE RISK: POSTOPERATIVE COGNITIVE DYSFUNCTION VS DELIRIUM
Question: Which of these statements about this patient is most correct?
A. She is at high risk (> 40%) of postoperative cognitive dysfunction
B. Her risk of postoperative delirium is 5% to 10%
C. Postoperative delirium cannot be prevented
D. Preoperative haloperidol (1.5 mg/day for 3 days) will reduce the risk of delirium by 25%
The best answer is A. Postoperative cognitive dysfunction is different from delirium, though it is part of a spectrum of cognitive impairment that may occur after surgery and even persist for a prolonged period. The patient’s risk of postoperative delirium is actually a bit higher than 10% (see “Estimating the risk of delirium” below). Some evidence shows that postoperative delirium can be prevented, at least in hip fracture patients. Kalisvaart et al found that preoperative treatment with low-dose haloperidol reduced the duration and severity of delirium in elderly patients following hip surgery but did not reduce its incidence.5
Cognitive dysfunction often follows surgery
Postoperative cognitive dysfunction has long been recognized and was first described in patients after cardiac surgery, especially following coronary artery bypass graft procedures. In the last several years, we have recognized that it also occurs in patients who undergo noncardiac surgery. Postoperative cognitive dysfunction, which may persist for weeks to months, may not be obvious but can be detected by standard neuropsychological testing.6
Postoperative cognitive dysfunction is different from the “emergence delirium” that may immediately follow surgery and that is often associated with the wearing off of anesthesia. It is also distinct from “incident delirium,” which sometimes occurs over the first few postoperative days (discussed below).
Postoperative dysfunction is especially persistent in the elderly
A recent study found cognitive dysfunction to be common at hospital discharge after major noncardiac surgery in adults of all ages: rates at discharge were 36.6% in patients aged 18 to 39 years, 30.4% in those aged 40 to 59, and 41.4% in those 60 or older.7 Notably, however, the oldest group was most likely to have persistent symptoms. Three months after surgery, 12.7% of patients aged 60 or older continued to have postoperative cognitive dysfunction, which was more than double the rates in the young and middle-aged patient groups (5.7% and 5.6%, respectively).7
Although the cause of postoperative cognitive dysfunction is not well understood, predisposing factors in addition to advanced age include metabolic problems, lower educational level, and previous cerebral vascular accident.7 When elective surgery is considered by elderly patients, the decision should take into account their risk of postoperative cognitive dysfunction and the impact it may have on their quality of life.
PREDICTING AND PREVENTING DELIRIUM
Delirium is easily recognized
Delirium is a common complication of surgery. Unlike postoperative cognitive dysfunction, delirium is easy to detect clinically. It is a disorder of attention and cognition and classically presents as an acute change in mental status accompanied by the following8:
- Fluctuation in awareness
- Memory impairment
- Inattention (inability to stay on task, distractibility)
- Disorganized or illogical thinking
- Altered level of consciousness—ie, hyperalertness (agitation, pulling out intravenous lines, etc) or hypoalertness (“quiet delirium”).
Estimating the risk of delirium
Marcantonio and colleagues developed a model to predict the likelihood that delirium will develop in patients undergoing elective surgery.9 The model assigns points to various risk factors as follows:
- Age ≥ 70 years (1 point)
- History of alcohol abuse (1 point)
- Baseline cognitive impairment (1 point)
- Severe physical impairment (reduced ability to walk or perform daily activities) (1 point)
- Abnormal preoperative blood levels of electrolytes or glucose (1 point)
- Noncardiac thoracic surgery (1 point)
- Abdominal aortic aneurysm surgery (2 points).
The study to validate this model found that a score of 0 points is associated with only a 2% risk of developing postoperative delirium. A score of 3 or more points is associated with a 50% risk of postoperative delirium. A score of 1 or 2 points (as for the patient in our case study) is associated with an 11% risk, according to this Marcantonio model.9
Additionally, well-designed cohort studies of medical patients10 have identified four major independent predictors of incident delirium:
- Severe illness (eg, high fever, complicated infections)
- Baseline dementia
- Dehydration (high BUN:creatinine ratio)
- Sensory impairments (particularly visual).
Kalisvaart et al conducted a prospective cohort study to determine whether these risk factors in medical patients are applicable to elderly patients undergoing hip surgery.11 They found that the incidence of delirium was low (4%) in hip surgery patients with none of these factors, increased to 11% in patients with one or two of these factors, and increased to 37% in patients with three or four factors. These findings suggest that hip surgery patients (like our case patient) may be at greater risk of postoperative delirium than is reflected in the Marcantonio model discussed above,9 which was validated in a study of patients undergoing elective (not emergent) surgery.