The unfavorable nature of preoperative delirium in elderly hip fractured patients

Article Outline

• Abstract
• 1. Introduction
• 2. Patients and methods
  • 2.1. Design and setting
  • 2.2. Patients
  • 2.3. Assessment of cognition, delirium and function
  • 2.4. Other data
  • 2.5. Statistical analysis
• 3. Results
  • 3.1. General characteristics
  • 3.2. Preoperative versus postoperative delirium
• 4. Discussion
• References
• Copyright

Abstract 

The onset of delirium is frequent in elderly patients who sustain hip fractures. The purpose of this study was to characterize different patterns of preoperative and postoperative delirium, to study factors associated with preoperative delirium and to evaluate the possible different outcome of these patients. This retrospective study comprised 281 elderly patients with hip fractures undergoing surgical fixation. Data collection included age, sex, length of stay, type of fracture, cognitive status by mini mental state examination (MMSE), assessment of possible delirium by the confusion assessment method (CAM) and functional outcome assessed by functional independence measure (FIM). A database search was conducted to identify whether delirium onset occurred prior to or following surgery. About 31% of the total sample developed delirium. Delirious patients tended to be more disabled (P=0.03) and cognitively impaired (P=0.018), compared with non-delirious patients. Most delirious cases (53%) had their onset in the preoperative period. Patients with preoperative delirium were older (P=0.03), had a lower prefracture mobility (P<0.01), impaired cognition (P=0.04) and showed an adverse functional outcome in terms of FIM score. Regression analysis showed that prefracture dementia, prefracture mobility and low MMSE scores were strongly associated with higher probability of having preoperative delirium, with no additional effect of other variables. It is concluded that preoperative delirium should be viewed as a separate entity with unfavorable nature and adverse outcome. Careful preventive measures and better treating strategies should be employed to avoid this clinical condition.

Keywords:  Delirium, Dementia, Hip fracture, Elderly

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1. Introduction 

Delirium is an acute confusional state involving a disturbance of consciousness. This serious complication is common in many aged hip fracture patients (Gustafson et al., 1988). It is associated with lower functional outcome (Murray et al., 1993, O'Keeffe and Lavan, 1997, Marcantonio et al., 2000), increased length of stay (Pompei et al., 1994) and higher rates of institutionalization and mortality (Magaziner et al., 1989, Inouye et al., 1998). These problems prompted the development of many costly and complex strategies, aimed at reducing its incidence by taking preventive measures.

Many factors associated with or precipitating delirium are mentioned in the literature. However, delirium is traditionally considered as perioperative, and there is only a single recently published study considering the critical issue of time onset of delirium. The distinction between preoperative and postoperative delirium should assist in a better recognition of factors involved in delirium onset and, thereby, focusing on the proper intervention.

We undertook this retrospective study to determine the prevalence of preoperative and postoperative delirium, in elderly hip fracture patients, and to look for the factors which are independently associated with delirium onset, after controlling for some potential variables.

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2. Patients and methods 

2.1. Design and setting 

This study was designed as a retrospective cohort study, aimed at evaluating the relations between some clinically important factors and time onset of delirium, in patients undergoing surgical intervention for hip fractures. It was conducted in a geriatric-orthopedic ward, which is a 30-bed unit utilizing an interdisciplinary team approach. The nature and characteristics of this orthogeriatric facility has already been described in details (Adunsky et al., 2002). Briefly, this is geriatrics-based ward, admitting elderly with hip fractures from the emergency room. The ward integrates a multidisciplinary staff and takes care of patients’ surgical, medical and rehabilitation needs in a single setting, from admission to discharge.

2.2. Patients 

We have included consecutive elderly hip fractured patients with trochanteric or subcapital fractures, referred directly from the emergency ward with primary inclusion criteria of a fractured hip. Patients admitted for elective hip surgery due to osteoarthritis etc. were excluded, as well as patients admitted for rehabilitation after being operated upon elsewhere and then transferred to our ward. The presence of other acute disabilities (e.g. other fractures) or other acute medical problems (concurrent febrile disease, stroke, etc.) did not exclude the patients, nor did their cognitive level.

2.3. Assessment of cognition, delirium and function 

2.4. Other data 

Data were abstracted from chart reviews of the patients and included age, gender, interval from admission to surgery, type of fractures and surgical procedures, as well as American Society of Anesthesiology (ASA) score (Keats, 1978). Pre-fracture functional status was recorded in all cases. Pre-fracture mental status was assessed by interviewing caregivers or family members. The ward adopts a strict policy regarding documentation of delirium and, thus, time onset of delirium was extracted from medical files.

2.5. Statistical analysis 

Differences in the distribution of baseline characteristics between delirious and non-delirious, as well as among patients with preoperative and postoperative delirium were assessed using Pearson χ² for categorical variables, and two-sample t-tests for the continuous variables. Multivariate analysis using a linear regression model was employed to assess the association of statistically important variables with onset of delirium, whether preoperative or postoperative, adjusted for the effect of other clinical variables. Statistical significance was set at the 0.05 level. Data were analyzed by the bmdp software (BMDP Statistical Software, 1990. University of California Press, LA, CA).

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3. Results 

3.1. General characteristics 

The analyses included the first 302 consecutive hip fracture patients, aged 60 years or older, who had been admitted to the ward during a 2 year period and had been treated by surgery. Data regarding the presence or absence of delirium, and the precise time onset of delirium were available for 281 patients (93%) who were included in the final analysis. The general characteristics of these patients are shown in Table 1. Mean MMSE score was 22.4±5.9. Since cognitive impairment is defined according to the standard cutoff score equal to or below 24 points, 126 out of 281 patients (45%) exhibited cognitive deficits. About 31% of the studied sample (87 patients) were diagnosed as suffering from delirium. Overall, there was a high rate of patients with independent (i.e. whether with or without walking aids) prefracture mobility (92%). This probably reflects the tendency to avoid surgery of patients with a low prefracture mobility or those who were bedridden or wheelchair-bound patients, unless surgery for other reasons (such as pain control) was considered.

Table 1. General characteristics of patients

Table 2 presents the characteristics of the two groups (delirious vs. non-delirious patients). There was no significant difference between the two groups in terms of age, gender, fracture type or surgical procedure, admission to surgery interval, total length of stay, ASA, or duration of surgery. However, the two groups differed with regards to prefracture mobility with statistically significant more dependent patients belonging to the delirious group (χ²=3.8, df 1, P=0.030). These patients also performed worse on the MMSE (P=0.018).

Table 2. Clinical characteristics of delirious and non-delirious patients

*, P=0.03 (by Pearson χ²); **, P=0.018 (by t-test).

3.2. Preoperative versus postoperative delirium 

Table 3 shows the comparison of clinical data of patients with preoperative and postoperative delirium. There were more cases of preoperative than postoperative delirium. Patients who presented delirious preoperatively were older (=0.03), had a lower prefracture mobility (P=0.01) and were more cognitively impaired (P=0.04). We did not find any male preponderance as suggested by others. The two groups differed also with respect to outcome in terms of FIM score, at the time of hospital discharge (Table 4). Though the aim of the study was not to study the efficiency of rehabilitation process and functional outcome, it is imperative in the sense that it shows the relatively favorable outcome of patients with postoperative delirium, as compared with preoperative delirium.

Table 3. Groups’ characteristics related to delirium onset

Table 4. Functional outcome (by FIM score) at time of hospital discharge

To further identify variables associated with probability of developing preoperative delirium, a logistic regression analysis was used (Table 5). Results showed that prefracture dementia, prefracture mobility and low MMSE scores were strongly associated with probability of having preoperative delirium, with no additional effect of age, sex, length of stay or fracture type. These three predictors of the preoperative delirium accounted for 31.1% of the variance.

Table 5. Logistic regression analysis-adjusted odds ratio (OR) and 95% confidence interval (CI) for selective variables potentially predicting preoperative delirium

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4. Discussion 

Preoperative delirium is insufficiently recognized. It is a common belief that delirium ‘typically presents early in the postoperative period’, but this seems to mislead. The present study specifically examines the important issue of preoperative versus postoperative delirium in elderly hip fractured patients, in a relatively large sample of patients, using strict criteria for assessing cognition, delirium and function. The results are important with regards to practical management, showing the adverse nature and poor outcome of patients with preoperative delirium.

The overall cumulative incidence of delirium in the present series (31%) was somewhat lower than in other studies and may result from the nature of the orthogeriatric unit which is highly aware of the need to prevent delirium, by implementing strategies aimed at reducing its incidence. Postoperative delirium involved less than half of the total number of delirious patients. This is in accordance with data of a recent Swedish study (Edlund et al., 2001) that showed nearly 70% of cases to be delirious preoperatively. The high prevalence of preoperative delirium in these two studies may be explained by the fact that a great deal of attention was paid to diagnosing even non-severe cases of delirium, which may have been dismissed in other studies.

Post operative delirium is believed to be avoided by better control of intraoperative hypotension, hydration and prevention of complications such as deep vein thrombosis, pulmonary emboli, urinary retention, infections, etc.

However, the fact that the majority of delirious patients have developed preoperative delirium, calls for attention to other factors. Some of these factors, such as age, prefracture cognition and function, are usually nonmodifiable. This calls for more attention to preoperative modifiable factors. One good example is the possibility to reduce the incidence of preoperative delirium by a better selection of opioid analgesics that is so common in elderly patients presenting to the emergency room with acute pain of a hip fracture. Similarly, cautious use of other medications that are frequently associated with delirium such as anticholinergics, benzodiazepines, neuroleptics, antiparkisonian drugs etc., is warranted. Other options should include better control of infections, feeding and hydration, control of anemia, prevention of urinary retention and shorter admission to surgery intervals.

Delirium has been independently associated with poor functional recovery after hip fracture in both short and long terms. (Francis and Kapoor, 1992, Murray et al., 1993, O'Keeffe and Lavan, 1997, Dolan et al., 2000). A recent study (Marcantonio et al., 2000) showed that delirium was independently associated with poor functional outcome 1 month after fracture even after adjusting for prefracture frailty. Our data further extend this observation with regards to patients with preoperative delirium, showing adverse functional outcome as compared with patients suffering postoperative delirium. Since geriatric consultation has been proved effective in reducing delirium incidence and severity when begun perioperatively (Marcantonio et al., 2001), we suggest that a greater deal of effort to prevent delirium should be made as early as possible, perhaps starting at the level of emergency ward.

Limitations of this study are its retrospective descriptive nature and the use of medical chart data, the relatively small sample size, and the fact that it was limited to a specific medical center. Secondly, the difficulties associated with differentiation between delirium and pre-existing dementia or even pre-fracture delirium, which prevents us from making any definite claims regarding source of the acute confusional state. Nevertheless, it is representative in the sense that it may have a some impact on the actual daily management in the medical wards treating old people with hip fractures.

In conclusion, this study further emphasizes the unfavorable nature and adverse functional outcome of patients with preoperative delirium, and calls for adoption of better preventive and treating strategies.

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