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Original Articles: Adult Cardiac

Consequences of Delirium After Cardiac Operations

^a Department of Cardio Thoracic Surgery, Medisch Spectrum Twente, Enschede, The Netherlands
^d Department of Epidemiology, Medisch Spectrum Twente, Enschede, The Netherlands
^b Department of Healthcare, University of Professional Education Utrecht, Utrecht, The Netherlands
^c Nursing Science, University Medical Center Utrecht, Utrecht, The Netherlands
^e Department of Research Methodology, Measurement and Data Analysis, Faculty of Behavioral Sciences, University of Twente, Enschede, The Netherlands

Accepted for publication July 12, 2011.

^_* Address correspondence to Dr Koster, Department of Cardio Thoracic Surgery, Medisch Spectrum Twente, Haaksbergerstraat 55, 7500KA Enschede, The Netherlands (Email: s.koster{at}mst.nl).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Background: Delirium is a transient mental syndrome characterized by disturbances in consciousness, cognition, and perception. The risk that delirium will develop is increased in patients who undergo cardiac operations, especially the elderly. Generally, delirium during hospital admission is independently associated with many negative consequences, such as higher mortality, increased length of hospital stay, nursing home placement after admission, and cognitive and functional decline.

Methods: This prospective follow-up study used the Short Form 36-Item questionnaire, the Cognitive Failure Questionnaire, and a purpose-designed questionnaire to assess 300 patients who underwent elective cardiac operations at 6 months after the procedure. Postoperative delirium developed in 52 patients (17%). Mortality and readmission were also assessed.

Results: Delirium after cardiac procedures is associated with increased mortality (13.5% vs 2.0% in patients without), more hospital readmissions (45.7% vs 26.5%), and reduced quality of life. It is also associated with reduced cognitive functioning, including failures in attention, memory, perception, and motor function, and with functional dysfunction such as independency in activities of daily living and mobility.

Conclusions: Postoperative delirium after cardiac operations is associated with many important consequences. These findings provide justification for intervention studies to evaluate whether delirium prevention, early recognition, or treatment strategies might improve postoperative functional and cognitive function.

	Introduction

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CARDIOTHORACIC ANESTHESIOLOGY: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

Delirium, or acute confusion, is a transient mental syndrome characterized by disturbances in consciousness, cognition, and perception [1]. The risk of postoperative delirium is increased in patients who undergo cardiac operations, especially the elderly. The reported incidence of delirium in patients after cardiac operations was 3% [2] to 52% [3]. In our observational cohort study, the incidence of delirium after elective cardiac operations was 21% [4]. Developments in operative and anesthetic techniques have enabled older patients to undergo cardiac operations [5], which, together with the aging of the population, will lead to an increase in the incidence of delirium in the near future.

Delirium has been related to higher mortality, increased hospital length of stay and nursing home placement after admission, reduced quality of life, and cognitive and functional decline in older general medical patients as well as in surgical patients [6–10]. In cardiac surgery specifically, however, little is known about the consequences of postoperative delirium.

Gottesman and colleagues [11] recently found that delirium after cardiac operations is a strong independent predictor of death for up to 10 years postoperatively. In our earlier cohort study of 112 elective cardiac surgical patients, postoperative delirium seemed to be associated with increased death and hospital readmissions, as well as poorer cognitive and functional outcomes [12]. We were not able to draw firm conclusions because of the low number of patients; therefore, we repeated the study in a larger cohort of patients and added new outcomes. The present study examined the consequences of delirium after cardiac operations, including the mortality rate after discharge, readmission rate, cognitive and functional outcomes, and quality of life.

	Patients and Methods

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The Ethics Committee of Medisch Spectrum Twente ruled that approval was not required because this was an observational study, without invasive procedures. Informed consent was obtained from participating patients in accordance with hospital policy.

Design and Sample
Between October 2008 and January 2010, our study included 300 consecutive patients, aged 45 years and older, who underwent elective cardiac operations at the Department of Thoracic Surgery (Table 1).

The purpose-designed questionnaire to assess cognitive and functional outcomes contained questions on hospital readmission, memory, concentration, confusion, sleep patterns, emotions, activities of daily living (ADL), mobility, and in patients with postoperative delirium, the experience of the episode of confusion. We determined problems with memory, concentration, and confusion were present when the patient felt, thought, or believed he or she had a problem in this area.

The multipurpose SF-36 measures eight domains of health: physical functioning, role limitations due to physical health, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and mental health. It yields scale scores for each of these eight health domains.

The CFQ is a measure of self-reported deficits in the completion of simple everyday tasks that a person should normally be capable of completing without error and includes failures in attention, memory, perception, and motor function. The patient can answer the questions with "never," "rarely," "sometimes," "frequent," and "most of the time"; the range of the scores is 0 to 100.

The hospital's Medical Computer System was used to ascertain mortality and readmission rates.

Statistical Analysis
The univariate association between postoperative delirium and death, readmission, quality of life, and cognitive or functional outcomes was estimated. The independent two-tailed t test was used to compare the means of variables in case of continuous normally distributed data. When data were not distributed normally, the Wilcoxon rank sum test was used. The ² test was used for the comparison of categoric variables between patients with and without delirium, and relative risks (RR) are presented. A correction for age was done using logistic regression analysis, with the odds ratio (OR), or linear regression analysis, as appropriate.

	Results

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Study Population
The study included 300 patients, and postoperative delirium developed in 52 (17%), as diagnosed with the DOS scale. The mean duration of delirium was 1 to 3 days in most patients, sometimes 4 to 7 days, and in 2 patients, 11 and 14 days. The duration of delirium in some patients could not be estimated because they were transferred to another hospital for further postoperative recovery. Almost all patients were treated with a low dose of haloperidol (1 to 3 mg/d), and some patients received a higher dose (5 to 15 mg/d). Haloperidol did not have any effect In 2 patients and the psychiatrist prescribed Quetiapine (300 once daily, or 100 to 150 mg/d). Of the 288 surviving patients, 264 returned the questionnaire, for a 91.7%. response rate.

Long-Term Outcomes of Delirium After Cardiac Operation
Details of long-term outcomes in patients, including survival, readmission, cognitive and functional outcomes, morality, subjective cognitive function, and quality of life, in patients with postoperative delirium are summarized in Tables 3, 4, 5, and 6.

Readmission
Hospital readmission was required in 82 patients (29.7%): 21 (45.7%) in the delirium group and 61 (26.5%) in the nondelirium group (RR, 1.72; p = 0.010). We did not have information about readmission for 24 patients, of whom delirium developed in 6. Therefore, only 47 patients with delirium are listed in Table 3. Hospital readmission was required in 12 patients who died. The most commonly mentioned reason for readmission was a cardiac problem (52.2%). Correction for age led to an OR of 2.16 (p = 0.028).

Cognitive and functional outcomes
According to the questionnaires, the patients with and without postoperative delirium did not differ significantly in memory, concentration, confusion, sleep disturbance, or emotions (Table 4). When results were corrected for age, the incidence of dependency in ADL in the event of delirium was not significantly higher. The results of the other cognitive and functional outcomes remained largely unchanged after correction for age.

After hospital discharge, 85 patients (32.2%) had memory problems and 32% still had memory problems after 6 months. Of the 79 patients (30.0%) who had concentration problems at discharge, 26.6% had these problems at 3 to 6 months after discharge or still had concentration problems at the time they completed the questionnaire. After hospital discharge, 36 patients (13.7%) were disorientated and 13.9% of them still exhibited these problems at 6 months, 102 (38.8%) experienced sleep disturbances, and 112 (42.4%) had emotional problems. There was a significant difference in the duration of the emotional problems in patients with and without delirium. In those with postoperative delirium, 58.8% still had emotional problems at 6 months compared with 23.2% of the patients without postoperative delirium (p = 0.03).

There were statistically significant differences between patients with and without postoperative delirium for experiencing nightmares or bad dreams, ADL, and dependency in mobility. Nightmares or bad dreams were reported by 36 patients (13.6%) after discharge, of which 16 (44.4%) still experienced nightmares at 6 months. Before they underwent the cardiac operation, 94% of patients were independent in ADL. After hospital discharge, 81 patients (30.7%) were in some way dependent in ADL. The most commonly mentioned dependency was taking a shower (67.5%); but 40.3% of patients were independent within 1 month after hospital discharge. In the event of delirium, the incidence of dependency in ADL was significantly higher (p = 0.008). When corrected for age, dependency in ADL was no longer significantly higher (p = 0.084).

Before the cardiac operation, 95% of patients were mobile. After discharge, 58 patients (22.0%) were in some way less mobile compared with the period before the cardiac operation. Most commonly mentioned was the use of a cane or a walker (57.6%). In the event of delirium, the number of patients who were less mobile was significantly higher (p< 0.001), and the duration of the "less mobile period" was also significantly longer in the event of delirium. When corrected for age, the number of patients with mobility problems was still significantly higher in patients with postoperative delirium (p = 0.014).

Subjective cognitive function
The mean (standard deviation) total score on the CFQ was 31.8 (14.6) in patients with postoperative delirium and 25.3 (12.2) in those without postoperative delirium, for a difference of 6.5 (95% confidence interval [CI], 2.2 to 10.8; p = 0.003; Table 5). When corrected for age, the difference was 5.7 (95% CI, 1.3 to 10.2; p = 0.012). In 9 questions, there was a significant difference between patients with and without postoperative delirium in the domains of memory, concentration, acting, and observation.

Quality of life
Only two domains of the SF-36 were normally distributed: vitality and general health perceptions (Table 6). Patients with postoperative delirium had significantly lower scores in seven of the eight domains of the SF-36: physical functioning, role limitations due to physical health, bodily pain, general health perceptions, vitality, social functioning, and role limitations due to mental health. Only in role limitations due to emotional problems was there no significant difference. No correction for age was done because only in the domain of physical functioning was there a very weak correlation between age and physical functioning (Spearman = –0.33). All other correlations were smaller than 0.2 and not significant.

	Comment

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Delirium occurring after cardiac operations is associated with increased mortality and a higher hospital readmission rate, lower quality of life, cognitive failure as measured with the CFQ, functional dysfunction such as dependency in ADL, and reduced mobility. Because we assumed age could be a confounder, we corrected the outcomes for age, and found that in the event of delirium, only the incidence of dependency in ADL was no longer significantly higher. In the other outcomes, the correction for age did not influence the results. A very weak correlation was found between age and the domain physical functioning of the SF-36, but because physical functioning was not distributed normally, it was not possible to do a correction for age.

These findings correspond well with the literature that shows that in general, delirium is related to nursing home placement and reduced cognitive and functional recovery [6–10]. In our earlier study, we concluded that delirium after a cardiac operation seems to be associated with increased death and readmissions to the hospital, as well as poorer cognitive and functional outcomes. Because of the low number of patients, it was not possible to draw far-reaching conclusions; we only saw a consistent negative tendency in patients with delirium. The follow-up in our current study was at 6 months compared with after 1 year in the earlier study.

No significant difference was noted in the level of emotional problems between patients with or without postoperative delirium as measured with the SF-36 and the purpose-designed questionnaire. Emotional problems might be more a result of the cardiac operation or may preexist in patients with cardiac diseases and may not be dependent on having postoperative delirium. Emotional problems, such as anxiety and depression, are common in patients with coronary heart disease. Recently, Spezzaferri and colleagues [16] observed a high prevalence of depression and a state anxiety at 8 to 12 days after coronary artery bypass grafting. The authors of another recent study found that cardiac surgical patients who undergo long procedures commonly have postoperative anxiety and tension [17].

In cardiac operations, little is known about the cognitive and functional outcomes after postoperative delirium. It may exert a negative influence on health-related quality of life during the first 6 months after coronary artery bypass grafting [18]. Rudolph and colleagues [19] found that functional decline occurred in 36.3% at 1 month and in 14.6% at 12 months. In our earlier study, patients with postoperative delirium showed a consistent negative tendency concerning cognitive and functional outcomes [12], but we could not draw firm conclusions.

We used two instruments to examine the cognitive function: our own purpose-designed questionnaire and the CFQ. Concentration was addressed by 1 question in the questionnaire and by 5 questions in the CFQ. In the questionnaire, there was no significant difference in concentration between patients with and without delirium, whereas in 3 of the 6 CFQ questions there was a significant relationship between concentration and postoperative delirium. The results of our questionnaire concerning the cognitive function and CFQ are difficult to compare because the CFQ is a more specific and comprehensive list. Because the questionnaire is not a validated instrument to measure the cognitive function and the CFQ is a validated instrument, the outcome of the questionnaire concerning the cognitive function can be questioned.

In contrast to findings of other studies, we did not find a difference in patients with and without delirium in confusion at 6 months after cardiac operations. Although we have no data to support this, we hypothesize that the presurgical cognitive status in our patients was relatively good compared with other studies.

A number of critical considerations pertaining to our study can be made. The diagnosis of delirium was determined by the DOS scale rather than by a psychiatrist. A psychiatrist was consulted only when the treatment of delirium was not successful or the delirium was very severe. In all these patients, the psychiatrist diagnosed delirium. With a DOS score of less than 3, we assumed that there was no delirium. It is very unlikely that delirium was present in patients with a DOS score of less than 3 because of the similarity between the DOS scale items and the diagnostic criteria for delirium. Also, an earlier study showed the validity of the DOS scale was very accurate, with a sensitivity of 100% and a specificity of 96.6% [20]. Therefore, using the DOS scale has probably not influenced the results of the study.

Another limitation is that we did not see the patient face-to-face at the 6-month follow-up, but we used a questionnaire. An interview might have rendered more specific information. In addition, although we sent the questionnaire to the patients, we cannot be sure that the patients completed questionnaires themselves. Spouses or significant others could have completed the questionnaire or influenced the answers. When patients completed the questionnaire by themselves, there was a possibility of a confounding effect of depression on self-reported cognitive symptoms.

In conclusion, our findings provide justification for intervention studies to evaluate whether delirium prevention, early recognition, or treatment strategies might improve postoperative functional and cognitive function and thereby the quality of life. To prevent postoperative delirium, it is important to identify the risk factors for delirium in patients when they present themselves to the hospital and observe any changes in these risk factors during the admission [21].

The initial management of delirium, according to the National Institute for Health and Clinical Excellence guideline, is to identify and manage the possible underlying cause(s) of delirium. Next, it is important to ensure effective communication and reorientation, consider involving family, friends, and other caregivers to help with this, and provide a suitable care environment [21]. Finally, it may be possible to design interventions to stimulate cognitive and functional functioning after delirium in cardiac surgical patients.

	Acknowledgments

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We thank all included patients, nurses, doctors, and medical secretarial staff for their help and cooperation with this study.

	References

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ab G. Hensens Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Koster, S. Articles by van der Palen, J. Search for Related Content PubMed PubMed Citation Articles by Koster, S. Articles by van der Palen, J. Related Collections Cardiac - other