Delirium is defined as a change in mental status characterized by confusion, disorientation, impaired reality testing, changes in level of consciousness, and changes in the sleep and wake cycle that usually is reversible.2 Delirium is common postoperatively in the elderly patient with a hip fracture, a reported incidence ranging from 9.5–61%.4,5,7,10,13,14,23,26,35,36 A fracture on admission is considered to be an independent risk factor toward the development of delirium.32
Although delirium is thought to be a transient, usually reversible episode, it has been associated with adverse outcomes in elderly individuals such as increased length of hospitalization, greater rates of institutional placement, and greater dependence in activities of daily living.12–14,16,20,22,25,29 The relationship between delirium and short and long-term mortality is controversial, with some studies21,29 showing increased mortality in elderly patients, whereas other studies12,13,16,20 showed that there is no relationship between delirium and mortality once other variables are accounted for.
The current study was designed to assess factors that contribute to the development of postoperative delirium postoperatively in elderly patients with a hip fracture, and subsequently to determine how the onset of delirium affects prognosis in this population.
MATERIALS AND METHODS
Information for this study came from a prospectively collected database. Patients included in this database fulfilled the following criteria: age 65 years or older, ambulatory before fracture, cognitively intact, living in their own home or apartment, and sustained a femoral neck or intertrochanteric fracture of nonpathologic origin. Patients with a history of dementia who were able to adequately answer a simple questionnaire were included in the database.
All patients were identified at the time of hospital admission and were prospectively entered into the database. Information on prefracture function, ambulatory ability, living situation, and cause and place of fracture were obtained at the time of hospital admission by interview with a patient or family member. Data regarding medical comorbidities, type of fracture, type of surgery, discharge status, and postoperative complications were recorded during hospitalization and at discharge through chart abstraction. Patient participation in this research database was voluntary; procedures for this study were reviewed and approved by the institutional review board of the hospital.
All patients were treated operatively and followed a similar postoperative protocol consisting of early mobilization on postoperative Day 1, with weightbearing as tolerated ambulation. All patients were contacted by one or two trained interviewers to obtain followup at 3, 6, and 12 months. If a patient was unavailable for interview, a family member or caregiver was interviewed.
Patients enrolled in this study were assessed by an experienced geriatrician (AK) for an episode of delirium throughout their hospital stay. Delirium was identified through a review of hospital chart notes and patient interview using Diagnostic and Statistical Manual of Mental Disorders criteria.2 Medical chart notes containing information on several aspects of behavior: inattention, disorganized thinking, disorientation, memory impairment, altered level of consciousness, perceptual disturbances, psychomotor agitation, and altered sleep and wake cycle were identified and used to help diagnose delirium. Dementia was defined by using the Diagnostic and Statistical Manual criteria, as a clinical state characterized by loss of function in multiple cognitive domains severe enough to cause impairment in social and occupational functioning.2
Outcomes examined included the development of a postoperative complication, in-hospital mortality, length of hospital stay, discharge status (home or skilled nursing facility), 1-year mortality, place of residence, return to prefracture basic and instrumental activities of daily living, and ambulatory level at the 1-year followup. The effect of postoperative delirium on each of these outcomes was evaluated.
Possible covariates examined included: patient age (65–84 years old or ≥ 85 years old), gender, associated comorbidities (0–2 or 3+), operative risk according to The American Society for Anesthesiologists rating scale (Classes I and II or Classes III and IV),28 fracture type (femoral neck or intertrochanteric), prefracture ambulatory ability, prefracture independence in basic and instrumental activities of daily living, and type of anesthesia (general versus spinal or epidural). The incidence of postoperative delirium was examined for each of these possible covariates.
Basic activities of daily living adapted from Katz et al17 included feeding, dressing, toileting, and bathing. Instrumental activities of daily living adapted from Lawton and Brody19 included food shopping, food preparation, doing housework, doing laundry, banking and finances, and use of public transportation. Each of these basic and instrumental activities of daily living was rated on a scale of 0–4, with 0 being completely dependent and 4 being completely independent in that activity.18 A composite score was calculated separately for basic activities of daily living and instrumental activities of daily living indicating the number of activities in which each patient was dependent. The patient’s ambulatory status was given a score between 1 (independent ambulator) and 6 (household ambulator with walker/crutches) for the prefracture status and 1 (independent ambulator) and 7 (restricted to wheelchair or bedridden) for postfracture status.15 Recovery of ambulatory level and independence in activities of daily living were scored as either a return to prefracture status, or as an increase in functional dependency.
General health status was characterized by the number of preexisting medical comorbidities, which included diabetes mellitus, congestive heart failure, cardiac arrhythmias, ischemic heart disease, previous cerebrovascular accident, renal disease, cancer, hypertension, chronic obstructive pulmonary disease, and the need for chronic anticoagulation. For this analysis, patients were categorized as either having 0, one or two, or more than two comorbidities.
Postoperative medical complications included allergic reaction, deep wound infection, urinary tract infection, decubitus ulcer, thrombophlebitis, pulmonary embolus, pneumonia, cardiac arrhythmia, and myocardial infarction. Patients either were categorized as having 0, or one or more postoperative complication as was used in a previous study.1
Preliminary analyses were done using contingency table methods (chi square). To simultaneously evaluate the effect of potential confounding variables, multiple regression analyses were done with a probability value less than .05 considered significant.
Between July 1, 1987 and June 30, 1998, 1159 patients were admitted to the hospital with a diagnosis of hip fracture. Of those, 166 (14.3%) were too demented, 49 (4.2%) were younger than 65 years, and 23 (1%) were excluded for other reasons. Nine hundred twenty-one patients met the selection criteria and were enrolled in the database. Characteristics of the 921 patients are summarized in Table 1. Forty-seven patients (5.1%) were diagnosed with delirium in the postoperative period. Patients who had postoperative delirium were more likely to have a history of dementia, have had surgery under general anesthesia, and be male (Table 2). Patient age, prefracture ambulatory status, prefracture living status, prefracture dependence in basic and instrumental activities of daily living, medical comorbidities, and fracture type did not differ between the two groups of patients. Two hundred fifty-five patients received blood transfusion (27.7%). Patients with delirium were three times as likely to have received blood transfusion compared with patients who did not have delirium develop (p < .001; odds ratio, 3.2; 95% confidence interval, 1.7–5.7). Hospital length of stay averaged 23 days (range, 1–166 days) for all patients which included the time spent in rehabilitation. The average length of hospital stay in the acute phase was 16.8 days (range, 1–73 days). This figure decreased throughout the study from 26.1 days in 1987 to 9.5 days in 1998. One hundred forty (15.2%) patients had a postoperative complication develop, and 26 (2.8%) patients died during hospitalization. Forty-six (5.0%) patients were discharged to a skilled nursing facility. Although patients who had delirium develop in the postoperative period were more likely to have had a longer mean total hospital length of stay than patients who did not have delirium develop (37 days versus 22 days; p < 0.001), there was no difference in length of acute hospital stay between the two groups. There were no differences between patients who did and did not have postoperative delirium develop regarding in-hospital mortality, postoperative complications, or rate of discharge to a skilled nursing facility.
At the 1-year followup, 99 (10.8%) patients had died, and 70 patients (7.6%) were residing in a skilled nursing facility. Patients who had delirium develop were more likely to have died within 1 year (odds ratio, 2.4; 95% confidence interval, 1.1–4.9; p = 0.02). There was no significant difference between patients who did and did not have postoperative delirium develop regarding residence in a skilled nursing home facility at the 1-year followup.
Of all patients still surviving by the 1-year followup, 184 patients (19.9%) either refused to be interviewed or were lost to followup. Functional outcome data were available for 638 patients (77.6%). Overall, 288 (45.0%) patients regained their prefracture ambulatory ability, 442 (69.0%) regained their prefracture level of independence in basic activities of daily living, and 286 (44.6%) regained their prefracture level in instrumental activities of daily living. Patients who had postoperative delirium develop were less likely to recover their prefracture level of ambulation (odds ratio, 2.7; 95% confidence interval, 1.1–1.6; p = .03), and were less likely to recover their independence in basic activities in daily living (odds ratio, 3.5; confidence interval, 1.6–7.6; p < 0.001) There was no difference between patients who did and did not have postoperative delirium develop regarding recovery of prefracture level of independence in instrumental activities of daily living (Table 3).
The incidence of postoperative delirium in the current patients (5.1%) is lower than the reported incidence (range, 9.5%-61.3%) postoperatively in patients with a hip fracture.4–7,13,14,26,35,36 The wide range in the literature may be attributable to different inclusion criteria used (such as Diagnostic and Statistical Manual, Confusion Assessment Method, and Mini-Mental Status Examination) to diagnose delirium, and the variability in the presentation of delirium. Another possible explanation for the low incidence of delirium in the current patients may be secondary to the strict inclusion criteria, which selected healthier individuals. In addition, delirium was assessed only at one point after surgery. Alternatively, the low incidence detected along with the low incidence in one article (9.5%)6 may suggest that the incidence of delirium postoperatively in patients with a hip fracture may not be as high as previously considered. The lower incidence of delirium in the current patients also may be attributable to improved care and attention these patients received compared with patients reported in previous studies.
In the current study, significant predictors for having postoperative delirium develop after hip fracture were a history of dementia, male gender, and the use of general anesthesia. The strongest predictor, dementia, also was found to be a strong predictor by others.13,36 Other authors have postulated that delirium and dementia may be similar processes in the continuum of a brain insult31 and patients with dementia may have a lower delirium threshold14 which would explain the close association between delirium and dementia.
A higher incidence of delirium was found in male patients. There is no consensus in the literature whether gender plays a role in the development of delirium in elderly patients who are hospitalized. Some studies14,32 showed an increased incidence of delirium in male patients, whereas other studies did not find this relationship.10,23,29
Higher rates of postoperative delirium were found in the current patients who received general anesthesia than in patients who received spinal anesthesia. General anesthesia may lead to cerebral hypoxia; cerebral hypoxia has been reported to play a role in postoperative confusion.3,8 It was not determined whether the current patients who received general anesthesia had higher rates of hypoxia, therefore this explanation is provisional. The association between type of anesthesia and incidence of delirium is controversial, with several studies showing no relationship between incidence of postoperative delirium and type of anesthesia.3,13,27
Patients who received blood transfusions were more likely to have delirium develop. It is unlikely however, that blood transfusion was a factor in the development of delirium. These patients could have had delirium develop because of dehydration or other important factors. No association was found between the onset of delirium and patient age, prefracture functional status, prefracture living status, prefracture ambulatory status, previous history of cerebrovascular accident, type of fracture, number of medical comorbidities, and American Society of Anesthesiologists rating of operative risk. Increased age, prefracture functional dependency, history of previous cerebrovascular accident, and comorbid illnesses all have been associated with development of delirium in the hospitalized elderly.13,23,32,35 A difference in the current findings versus findings in the literature may be attributable to the healthier patient population. The current findings suggest that prefracture cognitive status is more important than prefracture functional status as a predictor for having delirium develop.
The longer length of hospital stay in patients who had delirium develop may be attributable to the additional care these patients required, and the interference of delirium with rehabilitation. This increase in length of hospital stay is similar to that in other reports involving elderly patients who are hospitalized with a hip fracture.4,11,14,20–22,25,27,29
There was no observed increase in the rate of in-hospital mortality in patients who had postoperative delirium develop. These findings are similar to those in the literature.9,10,13,23 There also was no observed increase in the rate of postoperative complications in patients who had postoperative delirium develop. Another study23 found no increase in postoperative complications in elderly patients with a hip fracture who had postoperative delirium develop.
There was no increase in the incidence of skilled nursing facility placement at discharge or at the 1-year followup in patients who had postoperative delirium. Other studies10,12–14,20,22,23,29 showed a higher incidence of nursing home or long-term care placement or both in elderly patients who had delirium develop in the postoperative period. The lack of this finding in the current study may be attributable to the healthier cohort of patients versus other studies that tended to include sicker patients and also included many patients who were receiving long-term care before hospitalization.
The current study showed an increased 1-year mortality in patients who had postoperative delirium develop. The increase in 1-year mortality coupled with the lack of increased in-hospital mortality may indicate that the deleterious effects of postoperative delirium may not be attributable to the episode, but rather the effect that postoperative delirium has on rehabilitation, or that delirium may signify the incipient stages of a progressive decline in health.9,11,25 Other studies have found increased long-term mortality in elderly patients who are hospitalized with hip fracture and who had postoperative delirium develop.21,24,25,29,30,33,34 Those authors reported that the increase in mortality in elderly patients who are hospitalized who had delirium develop may be secondary to the underlying conditions that led to the development of delirium. We found that patients who had postoperative delirium develop were less likely to recover their prefracture level of ambulatory status and level of independence in basic activities of daily living. Postoperative delirium may lead to a functional decline by interfering with rehabilitation or alternatively, delirium may mark the onset of a progressive process of functional decline intrinsic to the episode of delirium. Long-term declines in activities of daily living functioning and ambulatory status are similar to findings in the literature regarding patients with hip fracture9,10,13,23 in elderly patients who are hospitalized.11,16,25
The main strength of the current study was that the data were collected prospectively from a large sample of patients, which avoids some of the inaccuracies of chart review found in retrospective studies. Phone followup is somewhat less reliable than direct patient observation, but studies in this patient group37,38 have supported its accuracy as it allows more efficient followup.
From this study, several conclusions can be drawn. In patients with hip fractures, the incidence of postoperative delirium is relatively uncommon. The presence of postoperative delirium is associated with preexisting dementia and male gender but not prior functional status. The use of general anesthesia may be associated with a higher incidence of postoperative delirium. Finally, patients who have delirium develop have a longer hospital length of stay, an increase in 1-year mortality, and are less likely to return to their prefracture functional status by the 1-year followup.
Because delirium by definition has identifiable causes and is reversible, greater efforts should be made in the care of these patients.14 Of the factors predicting delirium, male gender and history of dementia is out of the control of the surgeon. Nevertheless, according to the findings of this study, general anesthesia has been associated with an increased risk of development of delirium. Therefore, strong consideration should be given regarding the use of general anesthesia in patients with other risk factors for delirium. Anesthesiologists should inform patients and family member of this increased risk. Nursing and anesthesiologic interventions have been shown to reduce incidence of delirium in patients with hip fractures.14,36 Perhaps, a combination of the two interventions might be of even greater value to patients with a hip fracture.14 This intervention may help improve treatment and prognosis in elderly patients with a hip fracture.
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