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Original Articles: Adult Cardiac

The Long-Term Cognitive and Functional Outcomes of Postoperative Delirium After Cardiac Surgery

^a Department of Thoracic Surgery, Medisch Spectrum Twente, Enschede, the Netherlands
^b Department of Epidemiology, Medisch Spectrum Twente, Enschede, the Netherlands

Accepted for publication February 26, 2009.

^_* Address correspondence to Dr Koster, Haaksbergerstraat 55, Enschede, 7500 KA, the Netherlands (Email: s.koster{at}ziekenhuis-mst.nl).

	Abstract

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Background: Delirium or acute confusion is a temporary mental disorder, which occurs frequently among hospitalized elderly patients. Patients who undergo cardiac surgery have an increased risk of developing delirium. This is associated with many negative consequences such as prolonged hospital stay, nursing home placement, and reduced cognitive and functional recovery.

Methods: In this prospective follow-up study, a questionnaire was used 1 to 1.5 years after cardiac surgery in our earlier cohort of 112 patients who underwent elective cardiac surgery, of which 24 patients (21%) developed postoperative delirium as diagnosed by a single psychiatrist.

Results: Postoperative delirium after cardiac surgery may be associated with increased mortality (12.5% in patients with delirium versus 4.5% in patients without delirium; p = 0.16), more readmissions to the hospital (47.6% vs 32.6%; p = 0.19), dysfunction in memory (31.6% vs 22.6%; p = 0.39), and concentration problems (36.8% vs 20.2%; p = 0.13); and is associated with sleep disturbance (47.4% vs 23.8%; p = 0.03).

Conclusions: Postoperative delirium after cardiac surgery may be associated with increased mortality and readmissions to the hospital, as well as poorer cognitive and functional outcomes. Therefore, prevention and (or) early recognition of delirium must be improved. In addition, patients and caregivers (family and general practitioner) must be better informed about the long-term consequences of delirium and what they can do about it.

	Introduction

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Delirium is a common temporary mental disorder among hospitalized elderly patients [1]. In the literature the incidence and prevalence of delirium vary widely among different study populations. Patients who undergo cardiac surgery have an increased risk of developing delirium. In our observational cohort study the incidence of delirium after elective cardiac surgery was 21% [2]. As a result of demographic aging, the incidence of delirium is likely to increase in the foreseeable future. Generally, delirium has been related to a prolonged hospital stay, nursing home placement, and reduced cognitive and functional recovery [3–7]. Francis and Kapoor [8] found that delirium identifies older patients at risk for mortality, loss of independence, and cognitive decline 2 years after an episode of delirium in general medical wards [8]. Rockwood and colleagues [9] observed in older patients without prior cognitive or functional impairment, that the incidence of dementia was 5.6% per year over 3 years for those without delirium and 18.1% per year for those with delirium. In addition, mortality was also increased for those with delirium. Of the 38 patients with delirium, only 8 (21%) were alive at follow-up, compared with 94 (57%) of those without delirium [9].

In cardiac surgery little is known about mortality, morbidity, and cognitive and functional outcomes of postoperative delirium. This study will examine mortality after discharge, readmission rate, and the long-term cognitive and functional outcomes of delirium after cardiac surgery.

	Patients and Methods

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Design and Sample
Between November 2006 and June 2007 our earlier prospective cohort study included 112 consecutive patients, of 45 years and older, who underwent elective cardiac surgery at the Department of Thoracic Surgery. The Ethics Committee of Medisch Spectrum Twente was asked whether approval was needed. Because this was an observational study, without invasive procedures, approval was not necessary. Informed consent was obtained in accordance with the policy of the hospital.

Of these 112 patients, 24 (21%) developed postoperative delirium as diagnosed by a single psychiatrist. The diagnostic criteria used by the psychiatrist to diagnose delirium were based on the nursing documentation and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria [10]. The DSM-IV criteria were based on specific diagnostic criteria to differentiate delirium from other syndromes (like anxiety, depression, dementia, et al). Table 1 shows the DSM-IV criteria for the diagnosis of delirium.

There is no standard or validated questionnaire available to examine cognitive and functional outcomes; therefore, we designed one. The questionnaire was made, together with an epidemiologist and two delirium experts, to at least obtain face validity. Before we used the questionnaire for the study we did a pilot with the questionnaire to see whether the questionnaire was clear and understandable. After peer review and the pilot study, the questionnaire contained questions on readmission to the hospital, memory, concentration, confusion, sleep pattern, emotions, activities of daily living, mobility, and in case of a postoperative delirium the experience of the episode of confusion (see Appendix 1 for the questionnaire). We defined problems about memory, concentration, confusion, etc, to be present when the patient feels, thinks, or believes he has a problem in this area. The Medical Computer System (MCS) of the Hospital was used to ascertain the readmissions and whether patients had died.

Statistical Analysis
The univariate association between postoperative delirium and cognitive or functional outcomes was estimated. The independent 2-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 utilized. The following outcomes were analyzed as continuous variables: readmission rate to the hospital, memory, concentration, confusion, sleep pattern, emotions, activities of daily living, mobility, and in case of a postoperative delirium the experience of the episode of confusion. The ² test was used for the comparison of categoric variables between those with and without delirium.

	Results

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Study Population
One hundred and twelve patients were invited to participate in the study. All 103 nondeceased patients returned the questionnaire.

Long-term Outcomes of Delirium After Cardiac Surgery
Mortality
Seven patients (6.3%) died during the follow-up period: 3 (12.5%) among those who had experienced a postoperative delirium and 4 (4.5%) among those who had not experienced a delirium (p = 0.16). Four of the 7 patients (57.1%) died during the hospital period after cardiac surgery, of which 50% had developed a postoperative delirium (Table 2).

Experience of Delirium in the Hospital
Patients' experience of delirium during hospitalization varies widely. Seven patients (36.8%) remembered having been confused and described anxiety, fear, and helplessness. A third of them experienced disorientation, especially in place and time, while one quarter reported seeing or hearing things that did not exist. In 12 patients (63.2%) the psychiatrist had diagnosed postoperative delirium, but these patients did not remember the postoperative delirium. Four patients (4.9%) remembered having been confused, in whom the psychiatrist had not diagnosed delirium.

Cognitive and Functional Outcomes
After discharge from the hospital 25 patients (24.3%) had memory problems and 24 (23.3%) had concentration problems. The higher incidence of memory problems and concentration problems in those with delirium seems to be relevant, but is not significant. Eleven patients (10.7%) were confused after discharge with no difference between patients with or without delirium. Twenty-nine patients (28.2%) experienced sleep disturbance after discharge from the hospital; 51.9% reported "fall asleep" problems and 48.1% "sleep on" problems. In those who had experienced delirium, the incidence of sleep disturbance was significantly higher. Eleven patients (10.8%) experienced nightmares or bad dreams after discharge, of which two patients (28.6%) still experienced nightmares at the time of our study (Table 3).

Almost all patients (96.1%) were mobile before cardiac surgery. After discharge 18 patients (17.8%) were in some way less mobile in comparison with the period before cardiac surgery. Most commonly mentioned were the use of a walking-stick or a walker (36.8%). In the event of delirium, the number of patients who reported to be less mobile was not significantly higher. Thirty-six patients (35.3%) had emotional problems after discharge with no difference between patients with or without delirium.

	Comment

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A postoperative delirium after cardiac surgery seems to be associated with increased mortality and a higher readmission rate to the hospital, as well as long-term cognitive and functional effects. Cognitive and functional effects included the following: negative experience of delirium, memory and concentration problems, sleep disturbance, and dependency in activities of daily living.

These findings correspond well with the literature, which shows that delirium is related to nursing home placement and reduced cognitive and functional recovery [3–7]. Also, other negative effects of delirium have been described. Patients with postoperative delirium were more prone to have postoperative respiratory insufficiency, had a higher prevalence of sternum instability, were more likely to require surgical revision of the sternal wound, and had a significantly longer intensive care stay and longer postoperative hospitalization [4]. Another study [9] found that the incidence of dementia was 5.6% per year over 3 years for those without delirium and 18.1% per year for those with delirium. In a longitudinal study by Francis and Kapoor [8] of patients admitted to general medical wards it was found that after 2 years only one-third of individuals who had experienced delirium still lived independently in the community. The two-year mortality was significantly higher in the case of delirium (39% vs 23%). They concluded that delirium identifies older patients at risk for mortality and loss of independence. Rockwood and colleagues [9] followed 38 older patients with delirium and demonstrated that delirium is an important marker of the risk for death, even in those without prior cognitive and functional impairment. The median follow-up of this cohort was 32.5 months. Only eight patients (21%) with delirium in hospital were alive at follow-up, compared with 94 patients (57%) of those without delirium. The median survival time was significantly shorter for those with delirium (510 days vs 1,122 days). In comparison with these mortality percentages, our mortality of 6.3% in patients with delirium is relatively low. A number of reasons for this are the shorter follow-up period, the younger age of the patients, and the reason for admission to the hospital (elective versus nonelective) in our study. The study of Rockwood and colleagues also included patients with dementia, which is a marker of the risk for death.

There was no significant relation between emotional problems, confusion, and dependency in mobility in relation with a postoperative delirium. Emotional problems, confusion, and dependency in mobility are apparently a result of cardiac surgery, no matter if the patients developed a postoperative delirium or not. A number of patients indicated that the emotional difficulties they experienced were considered by them as a normal reaction after cardiac surgery.

Emotional problems are common in patients with coronary heart disease. Many studies showed the relation between depressive symptoms and coronary heart disease. For example, Whooley and colleagues [11] found a significant relation between depressive symptoms and patients with coronary heart disease. Also, Detroyer and colleagues [12] found a high prevalence of preoperative anxiety and depressive symptoms in older patients with cardiac surgery. According to Wang and colleagues [13], depressive disorders occurred in 42.7% of the patients preoperatively and in 23.1% of the patients 6 months after the cardiac surgery. Murphy and colleagues [14] concluded that although initial anxiety and depression resolved or lessened for most patients, some patients experienced persistent or worsening depression after coronary artery bypass grafting.

In cardiac surgery little is known about the cognitive and functional outcomes of postoperative delirium. Only health-related quality of life has been evaluated 6 to 12 months after cardiac surgery [15]. A postoperative delirium may exert negative influence on health-related quality of life during the first 6 months after coronary artery bypass grafting [15]. It is likely that the observed negative cognitive and functional outcomes exert a negative influence on health-related quality of life.

A number of critical considerations pertaining to our study can be made. First we did not see the patient face to face, but we used a questionnaire. The use of an interview might have rendered more specific information. Another point is that although we sent the questionnaire to the patients, we cannot be sure whether the questionnaire was completed by the patients themselves. It is possible that spouses or significant others completed the questionnaire or influenced the answers of the patient. When patients completed the questionnaire by themselves, there is a possibility of a confounding effect of depression on self-reported cognitive symptoms.

Second, because quite some time had passed after the cardiac surgery, patients could perhaps not remember the whole period since the surgery. This might be the reason why some patients with a confirmed delirium did not remember delirium, or remembered delirium when none was diagnosed.

Finally, due to the low number of patients it is not possible to draw far-reaching conclusions. Only the incidence of sleep disturbance was significantly higher in those who had experienced delirium. For the other outcomes like mortality, readmission, memory and concentration problems, and dependency in activities of daily living we only see a consistent negative tendency in patients with delirium. Therefore, we only can say a postoperative delirium after cardiac surgery seems to be associated with increased mortality and a higher readmission rate to the hospital, as well as long-term cognitive and functional effects. Repeating the study with a higher number of patients is recommended.

Prevention and (or) early recognition of delirium must be improved. Early recognition of delirium symptoms enables the underlying cause to be diagnosed and treated and can prevent negative outcomes [7]. Systematic interventions regarding medical, nurse-led, environmental, and educational items are effective in preventing delirium [16]. The approach to delirium has shifted from ad hoc treatment to systematic screening and prevention. Management may be improved with primary prevention, early detection, and prompt management [17]. In patients who develop postoperative delirium, interventions are needed to improve delirium treatment; providing adequate information to patients, their family, and their general practitioner, including the fact that these problems are very common. Possibly, interventions can be designed to stimulate cognitive functioning after delirium in cardiac surgery patients.

	Appendix

 
Questionnaire Follow-Up Study Delirium

Questionnaire follow-up study delirium 1 Was there a re-admission to the hospital after the discharge from the hospital after your cardiac surgery? Yes No 2 If yes, what was the reason for the re-admission to the hospital?   cardiac problems   infection   psychiatric reason   other reason, namely: 3 Did you have, more than in the time before you underwent the cardiac surgery, memory problems after discharge from the hospital? Yes No 4 If yes, for how long did you have memory problems?   1 month   2 months   3 - 6 months   more than 6 months   still memomy problems at the moment 5 Did you have, more than in the time before you underwent the cardiac surgery, concentration problems after discharge from the hospital? Yes No 6 If yes, for how long did you have concentrations problems?   1 month   2 months   3 - 6 months   more than 6 months   still concentration problems at the moment 7 Have you been confused after discharge from the hospital? Yes No 8 If yes, for how long have you been confused?   1 month   2 months   3 - 6 months   more than 6 months   still confused at the moment 9 Did you have sleep problems after discharge from the hospital? Yes No 10 If yes, what kind of sleep problems did you have?   "fall asleep" problems   "sleep on" problems 11 For how long did these sleep problems persist?   1 month   2 months   3 - 6 months   more than 6 months   still sleep problems at the moment 12 Did you have bad dreams or nightmares after discharge from the hospital? Yes No 13 If yes, for how long have did you have these bad dreams or nightmares?   1 month   2 months   3 - 6 months   more than 6 months   still have bad dreams or nightmares at the moment 14 Did you have emotional problems (suddenly and/or often emotional like crying) after discharge from the hospital? Yes No 15 If yes, for how long did these emotional problems exist?   1 month   2 months   3 - 6 months   more than 6 months   still emotional at the moment 16 Were you independent in activities of daily living before the cardiac surgery (like bathing, dressing, going to the toilet)? Yes No 17 If not, what kind of help did you need?   bathing and/or taking a shower   dressing   going to the toilet   preparing meals   other activity in daily living, namely: 18 Were you independent in activities of daily living after the cardiac surgery (bathing, dressing, going to the toilet)? Yes No 19 If not, what kind of help did you need?   bathing and/or taking a shower   dressing   going to the toilet   preparing meals   other activity in daily living, namely: 20 For how long did you need help for activities in daily living?   1 month   2 months   3 - 6 months   more than 6 months   still need help at the moment 21 Were you mobile before the cardiac surgery (able to move yourself, eventual with help of a walking-stick, walker or wheelchair)? Yes No 22 Were you less mobile after discharge from the hospital? Yes No 23 If yes, what was the reason why you were less mobile?   I use a walker/walking-stick that I did not use before the cardiac surgery   I can only move myself in a wheel chair that I did not use before the cardiac surgery   I need help to move myself, for example to move from the bed to the chair, and I did not need this kind of help before the cardiac surgery   other reason, namely: 24 For how long did you need this help to be mobile?   1 month   2 months   3 - 6 months   more than 6 months   still need help at the moment 25 Have you been confused during your stay in the hospital because of the cardiac surgery? Yes No 26 If yes, what do you remember of this confusion period?   I saw and heard things that did not exist (for example animals or people)   I did not know where I was   I was anxious and very frightened   I was very suspicious and did not trust anybody   other things, namely:

	Acknowledgments

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The authors wish to 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 Related Article