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 Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 1  |  Issue : 1  |  Page : 45-53

Incidence, prevalence and risk factors for delirium in elderly admitted to a coronary care unit


1 Department of Psychiatry, Postgraduate Institute of Medical Education & Research, Chandigarh, India
2 Department of Cardiology, Postgraduate Institute of Medical Education & Research, Chandigarh, India

Date of Web Publication29-Sep-2014

Correspondence Address:
Sandeep Grover
Department of Psychiatry, Postgraduate Institute of Medical Education & Research, Chandigarh - 160 012, Punjab and Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2348-9995.141930

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  Abstract 

Aim: This study attempted to assess the incidence, prevalence, risk factors and outcome of delirium in elderly (≥60 years) patients admitted to a coronary care unit.
Materials and Methods: Confusion Assessment Method for Intensive Care Unit (CAM-ICU) was used to screen the patients for delirium and those found to have delirium on CAM-ICU were subjected to a detailed evaluation by a psychiatrist to confirm the diagnosis of delirium. Additionally risk factors were assessed by using a checklist and outcome was determined.
Results: One hundred and fifty two patients were evaluated for delirium. Of these, 37 (24.34%) patients had delirium at the first assessment (i.e. within 24 hours of admission in CCU) and were classified as 'prevalence cases' of delirium. Fifteen cases (13.04%) developed delirium after 24 hours of CCU stay and were considered as 'incidence cases' of delirium. Among the various risk factors studied, factors which were identified as predictors of delirium in binary logistic regression analysis were hypokalemia, Sequential Organ Failure Assessment (SOFA) score, use of warfarin, frusemide, ranitidine, benzodiazepine, opioids, steroids, more than 4/5 medications, presence of sepsis, cardiogenic shock, having undergone coronary artery bypass grafting, left ventricular ejection fraction <30, higher age, presence of uncontrolled diabetes mellitus and presence of congestive cardiac failure. Of the 52 patients who developed delirium, 10 (19.2%) died during their hospital stay, this was significantly higher than the mortality rate (1%) seen in the non-delirium group.
Conclusions: In coronary care units, delirium is a common entity in elderly and is predicted by the presence of modifiable risk factors. Delirium is also associated with increased mortality.

Keywords: Delirium, Elderly, Cardiac Illness


How to cite this article:
Grover S, Lahariya S, Bagga S, Sharma A. Incidence, prevalence and risk factors for delirium in elderly admitted to a coronary care unit . J Geriatr Ment Health 2014;1:45-53

How to cite this URL:
Grover S, Lahariya S, Bagga S, Sharma A. Incidence, prevalence and risk factors for delirium in elderly admitted to a coronary care unit . J Geriatr Ment Health [serial online] 2014 [cited 2019 Aug 25];1:45-53. Available from: http://www.jgmh.org/text.asp?2014/1/1/45/141930


  Introduction Top


Delirium is a mental disorder characterized by disturbances in consciousness, orientation, memory, thought, perception, and behavior. Despite its clinical importance, delirium in general and more so in intensive care unit (ICU) settings, is often not suspected, screened and looked for, so remains under-detected and misdiagnosed. [1] Delirium in ICU set up is understudied and neglected probably because it is "expected" to happen in patients with severe illness, and medical resources are preferentially dedicated to managing the more immediate "life threatening" problems. Clinicians generally give less importance to acute brain syndrome as a predictor of poorer overall outcome than acute dysfunction of other organ systems and regard it transitory with no long term adverse effect. [2] Due to the above factors epidemiology, phenomenology, clinical subtypes, efficacy of various treatments, course and outcome of delirium in various ICU set-ups has not been adequately investigated.

Data from the West suggests that 50 to 80% of ventilated patients develop delirium and 20 to 50% of patients with lower severity of physical illness develop delirium. [3] Over 40,000 ventilated patients in US are delirious every day and it is suggested that 10% remain delirious at hospital discharge. [3],[4],[5],[6],[7],[8],[9] Further the data suggests that the incidence and prevalence of delirium is higher in mechanically ventilated elderly subjects. [3],[8],[10],[11]

Delirium in critical care setting has been found to be associated with increased ICU as well as increased total hospital duration of stay, increased time on ventilator, higher treatment costs, re-hospitalizations, increased risk of death and possibly increased long term cognitive impairment [7],[8],[9],[12],[13],[14] Various studies have shown that duration of delirium in ICU is associated with longer length of stay in ICU and overall length of hospital stay even after adjusting for severity of illness, age, gender, race and benzodiazepine and narcotic administration. [7],[8],[9] Further, development of delirium in critical care unit has also being reported to lead to increased risk of death (rate of death −64% in patients experiencing delirium in comparison to 34% in patients who did not develop delirium) [3] and long term cognitive impairment, even after adjustment for age, gender, race, preexisting comorbidity and cognitive impairment. [13],[15] Delirium is associated with (RR 1.6) higher rates of re-hospitalization or new nursing home placements of patients after adjusting for age, dementia, comorbidities and illness severity. [4] Studies done in cardiac patients undergoing surgery have also shown that the time to discharge was 11 days longer in patients with delirium. [16]

Besides the longer stay, data also suggests that delirium in ICU is associated with higher treatment costs. [13]

Data suggests that the risk for various cardiovascular diseases is increasing, especially in India. [17] Further over the years there is rise in the proportion of elderly population. [18] Hence, there is a need to have more and more health care facilities to cater the patients presenting with various cardiovascular ailments. However, numbers of Coronary Care Unit (CCU) beds are limited. To optimally use the available resources, it is important to limit the duration of stay of patients in CCU. Hence it is important to study delirium in ICU, because if identified and treated adequately, it can lead to reduction in duration of the stay, decrease health care cost, reduction in burden and improve patient outcome in terms of morbidity and mortality.

In this background the present study aimed to evaluate the incidence and prevalence of delirium in elderly (age ≥60 years) patients ICU. Additionally risk factors for development of delirium and outcome of delirium was studied.


  Materials and methods Top


The study was approved by the Institute Ethics Committee. The study attempted to study the incidence, prevalence, risk factors, outcome, phenomenology, motor subtypes, psychiatric comorbidity in consecutive patients admitted to the Coronary Care Unit (CCU) of a tertiary care teaching hospital during the 2 month period. However, in this paper, we only present data with respect to incidence, prevalence, risk factor and outcome of patients older than 60 years of age. Data pertaining to the whole study sample which included all patients admitted to CCU was recently published. [19]

Patients were recruited after obtaining the written informed consent from either patient themselves, their relative or both. Study was conducted in a 22 bedded CCU of a tertiary care teaching hospital. Each patient meeting the selection criteria was assessed daily throughout their CCU stay till they are detected to have delirium. The study followed a prospective design. All consecutive patients admitted to CCU were screened for delirium subject to fulfillment of the selection criteria. Patients who are deaf or unable to speak or understand Hindi, English or Punjabi were excluded.

Instruments

Richmond Agitation and Sedation Scale (RASS): [20] It is an instrument to assess sedation and agitation of adult ICU patients. It is a 10-point scale with 4 levels of anxiety or agitation (+1 to +4), one level to denote a calm and alert state (0) and 5 levels to assess the level of sedation (−1 to −5). A score of −4 indicates that the patient is unresponsive to verbal stimulation and finally, culminating in unarousable states (−5). It has good inter-rater reliability and validity.

Confusion Assessment Method for Intensive Care Unit (CAM-ICU): [8] CAM-ICU was developed to screen patients admitted to ICUs, specifically for those patients who cannot verbalize (i.e. mechanically ventilated). It can be administered if the patient is arousable to voice without the need for any physical stimulation. Delirium is diagnosed if the patient is found to have

  1. An acute change in mental status or fluctuating changes in mental status,
  2. Inattention measured using either an auditory or visual test, and either
  3. Disorganized thinking, or
  4. An altered level of consciousness.


In the hands of trained health care professional, assessment on the CAM-ICU can be completed in only 1 to 2 minutes. It has been found have high sensitivity (93%) and high specificity (89%) for detecting delirium in comparison to full DSM-IV assessment.

DSM-IV-TR [21] Criteria for Delirium: DSM-IVTR criteria for delirium is considered to be standard criteria for making the diagnosis of delirium and many instruments which have been designed to screen or rate the severity of delirium are based on the criteria of DSM-IV criteria, which was similar to DSM-IVTR criteria.

Risk Factor Check List: A risk factor sheet was specifically designed for this study after the review of literature with respect to risk factors for delirium in cardiac patients. [22]

Charlson Comorbidity index [23] : The Charlson co-morbidity index is used to predict the 10-year mortality for a patient who may have a range of co-morbid conditions such as heart disease, Acquired immunodeficiency disease or cancer (a total of 22 conditions). Each physical condition is rated on the basis of associated risk of dying with that condition. Total score is used to predict mortality.

Acute Physiology and Chronic Health Evaluation II (APACHE-II) scores: [24] APACHE II is a measure of severity of disease for adult patients admitted to ICUs. Routine physiological parameters (such as blood pressure, body temperature, heart rate etc.) during the first 24 hours after admission, information about previous health status and some information obtained at admission (such as age) are taken into account to calculate the total score. Only one score is calculated based on the physiological parameters in an admission and no new score can be determined during the hospital stay. However, a new score can be assigned if the patient is readmitted.

Sequential Organ Failure Assessment (SOFA) Score: [25] SOFA, developed by European Society of Critical Care Medicine (ESCCM), is a scoring system to determine the extent of a person's organ function or rate of failure. It is used to assess organ dysfunction or failure over time and is useful in evaluation of morbidity. Six different parameters, one each for the respiratory, cardiovascular, hepatic, coagulation, renal and neurological systems are taken into account to calculate the total score. Each parameter is rated on 4 points (0 to 4) with a maximum score of 24. Sequential assessment of organ dysfunction during the first few days of ICU admission is considered to be a good indicator of prognosis. Independent of the initial score, an increase in SOFA score during the first 48 hours in the ICU predicts a mortality rate of at least 50%.

The patients and/or caregiver of all the patients admitted to CCU and available at the particular time of the day (between 5-9 PM) were approached for consent for inclusion in the study. All the patients or whose caregivers provided written informed consent (if the patient is not in a state to provide informed consent) were assessed. The information was collected from the patient, caregivers, treating physician and nurses to reach the final conclusion about the diagnosis. Assessments were carried out at a fixed time period (5-9 PM) of each day. Patients were assessed everyday till the time they were found to be positive for delirium during their CCU stay or discharged.

Every patient meeting the selection criteria was first evaluated on the Richmond Agitation and Sedation Scale (RASS) on the day of admission. Those patients, who were rated-3 through 4 (i.e. arousable on verbal stimulation) on RASS, were assessed for delirium by using CAM-ICU. If a patient was found to be positive on the CAM-ICU, she/he was further assessed on DSM-IVTR criteria to confirm the diagnosis of delirium by a psychiatrist.

APACHE-II scores were recorded on the day of admission. The risk factor checklist was completed based on the information recorded in the case notes and that provided by the caregivers, the treating team and the patient wherever possible on the day of admission and subsequently updated depending on the clinical status.

Any patient, who was rated as unresponsive at the first assessment, was reassessed on the next day and every subsequent day throughout the CCU stay, to ascertain his level of sedation and agitation using RASS. If at any stage she/he was found to be arousable, then she/he was assessed on CAM-ICU to ascertain delirium and if found positive for delirium, was assessed on DSM-IV TR criteria by a psychiatrist. The risk factor and etiology checklist was updated at the time of patient found positive for delirium.

Further all the patients were followed up throughout their hospital stay to record their clinical outcome (i.e., delirium resolved, delirium improved, delirium persisting as before, delirium worsened and death).

Statistical analysis

Data was analysed using the mean, standard deviation, frequency and percentages. Comparisons were done by using t-test, Mann Whitney U test, Chi-square test and Fisher Exact test. Binary logistic regression analysis was carried out to study the predictors of delirium and mortality.


  Results Top


Sociodemographic and clinical profile

During the study period 160 patients aged ≥60 years were admitted to CCU of which 152 (95%) could be screened for delirium and these patients formed the study sample. The mean age of study sample was 68.82 (SD-7.02; range 66-88) years. More than two third of the sample comprised of males (N = 102; 67.13%) and the mean number of years of education of the study sample was 8.01 (SD-5.96; range 0-21) years.

Most of the subjects (N = 138; 90.8%) were admitted for management of acute cardiac illnesses. Only a minority of patients (N = 14; 9.2%) were admitted for a planned cardiac procedure/surgery. Most (N = 138; 90.8%) of the patients had coronary artery disease with or without chronic physical illness, i.e., diabetes mellitus.

The mean of APACHE II score of the whole sample was 10.92 (SD = 4.24; range-1-25) and the Charlton Comorbidity Index was 1.48 (SD = 0.87; range-1-4) and Sequential Organ failure Assessment (SOFA) score was 1.52 (SD = 2.2; range 0-8).

Most of the patients (N = 136; 89.5%) were receiving 3 or more number of medications and 76.3% of the total sample was receiving more than 5 medications. The mean number of medications received by the patients was 6.65 (SD = 2.24; Range: 1-11). However, when the nutritional supplements were taken into account the mean number of medications rose to 7.61 (SD = 2.46; Range: 2-13).

Incidence and prevalence of delirium

All the eligible patients were assessed on Richmond Agitation Sedation Scale (RASS). If a patient was not detected to have delirium on a particular day or was not assessable (rated as −4 or −5), he was again evaluated on RASS on the subsequent day and if found assessable (rated −3 through 4), further evaluations were carried out. Those patients who were rated -3 through 4 on RASS were evaluated on CAM-ICU to screen for delirium. Out of 152 patients, 54 (35.52%) patients screened positive for delirium on CAM-ICU. All the patients who screened positive for delirium on CAM-ICU were evaluated further on DSM-IVTR criteria for delirium and the diagnosis was confirmed in the 52 (32.9%) patients.

Out of 152 patients, 37 (24.34%) patients had delirium at the first assessment (i.e. within 24 hours of admission in CCU) and were classified as 'prevalence cases' of delirium. Of the 115 patients who were non delirious at first assessment, 15 (13.04%) developed delirium after 24 hours of CCU stay and were considered as 'incidence cases' of delirium. The prevalence cases accounted for 71.1% of all delirium cases and incident cases accounted for 28.9% of cases.

Risk factors for development of delirium

Patients were evaluated for risk factors for delirium by using a risk factor checklist specifically designed for this study, where each factor was rated as 'present' or 'absent' depending on its presence or absence at the time of development of delirium. As shown in [Table 1], patients who developed delirium were significantly older and less educated.
Table 1: Risk factors for development of delirium

Click here to view


As is evident from [Table 1], those who developed delirium had significantly higher frequency of history of stroke in the past and more frequently had history of diabetes mellitus. Those who developed delirium more frequently had coronary artery disease with comorbid chronic physical illness. Those with delirium also had significantly higher APACHE-II score, SOFA score and Charlson comorbidity index score.

Those who had delirium also had significantly higher frequency of congestive cardiac failure, cardiogenic shock, had undergone angioplasty and/or coronary artery bypass grafting during the CCU stay or just prior to the same and had left ventricular ejection fraction less than 30%. With regard to psychiatric risk factors, those with delirium more frequently had history of cognitive deficits.

With regard to medications those who developed delirium were more frequently receiving/taking benzodiazepines, opioids, warfarin, frusemide, non-steroidal anti-inflammatory drugs, antibiotics, ranitidine, and ionotropes and were more frequently receiving 4-5 medications.

With regards to other clinical and laboratory findings, those with delirium more frequently had evidence of acute infection, hyponatremia, hypokalemia, raised urea levels and raised creatinine levels. Among the other risk factors, those with delirium more frequently had hyperthermia, acid-base imbalance and changes in the hematocrit value.

Outcome of delirium

All the study participants were followed up till they were discharged from the hospital or their death. Of the patients who developed delirium, one-fifth (N = 10; 19.2%) died during their CCU/hospital stay, this was in contrast to 1 patients (1%) in the non-delirium group and the difference was statistically significant (Chi-square test value-14.33; P < 0.001 *** ).

Predictors of delirium

Predictors of delirium were studied by using binary logistic regression analysis. For this presence or absence of delirium was entered as a dependent variable and all the risk factors which differed significantly between those who developed delirium and those who did not develop delirium were entered as independent variables. Highest predictive values were noted for hypokalemia (OR-68.3) and SOFA (OR-67.1) score. Other risk factors were use of warfarin (OR -20.43), frusemide (OR-12.27), ranitidine (OR -14.2), more than 4 medications (OR-13.5), presence of sepsis (9.58), presence of cardiogenic shock (OR-5.79), having undergone coronary artery bypass grafting (OR-16.03), left ventricular ejection fraction <30 (OR-5.4) and use of benzodiazepine (OR-6.31), opioids (OR-6.31) and receiving more than 5 medications (OR-8.04). Other variables with odds ratio of more than one were presence of uncontrolled diabetes mellitus (OR-1.53), presence of congestive cardiac failure (OR-3.94) and currently receiving/taking steroids (OR-4.06).


  Discussion Top


Cardiovascular diseases (CVD) are ranked as the most common contributor of morbidity and mortality worldwide. Data suggests that in last 3-4 decades there has been an emergence of CVD epidemic in the South-east Asian countries. In low resource countries like that of India, the rising burden of CVDs imposes severe economic consequences that range from impoverishment of families to high health system costs and the weakening of country economies. Developing countries like India are less equipped with facilities for catering the large need of critically ill subjects, hence it is expected that available resources are utilized optimally and all the needy subjects are able to receive the ICU facilities at the time of need. For doing the same it is required that, whenever sick patients are admitted to ICU, their stay in ICU is maintained to the minimum.

In recent times it is well known understood that presence of delirium increase the ICU stay and due to this the ICU facilities are consumed by these patients for long duration and resultantly many other needy patients suffer too. Hence, it is thought that proper timely identification of delirium can lead to treatment of these subjects and reduction in ICU stay [12] and appropriate use of existing infrastructure and manpower. The first step in this direction is to understand the incidence, prevalence, risk factors and outcome of delirium in developing countries. Understanding the incidence, prevalence, risk factors and outcome can sensitize the clinicians attending these subjects and lead to early and proper identification, adequate treatment and reduction in overall ICU stay. The current study was an attempt in same direction.

The methodology followed in the current study tried to overcome some of the limitations of existing literature in the form of obtaining longitudinal assessment, careful screening on RASS and CAM-ICU, confirmation of diagnosis of delirium based on DSM IVTR diagnostic criteria by a psychiatrist, studying the risk factors for development of delirium and outcome of patients admitted to CCU.

Incidence and prevalence of delirium

During the study period out of 152 assessable patients, 52 (34.21%) patients had delirium during their CCU stay. Out of 152 patients, 37 (24.34%) patients had delirium at the first assessment (i.e. within 24 hours of admission in CCU) and were classified as 'prevalence cases' of delirium. Of the 115 patients who were non delirious at first assessment, 15 (13.04%) developed delirium after 24 hours of CCU stay and were considered as 'incidence cases' of delirium. The prevalence cases accounted for 71.1% of all delirium cases and incident cases accounted for 28.9% of cases. When one compares this finding with the whole study group, [19] it is evident that the incidence and prevalence of delirium in elderly is higher than that seen in other age groups. Studies from the developed countries which have evaluated the prevalence of delirium in patients with ICU have reported a range of 20-80% with prevalence figures varying between 20-50% in patients with physical illnesses of lower severity and 50-80% in severely ill mechanically ventilated patients during ICU stay. [3] Studies which have evaluated the incidence of delirium in ICU patients have reported a figure of 17.3%. [22] When one specifically looks at the incidence and prevalence of delirium in cardiac patients, studies have in general focused on cardiac patients undergoing surgery. [22],[26],[27] These studies have reported an incidence rate varying from 3 to 72%. [28],[29],[30],[31] Some of these studies have followed prospective design and have included a sample size of 53 to 260 patients, whereas the studies which have followed the retrospective design have reviewed the data of 288 to 16184 patients. [28],[29] In general the studies which have followed retrospective design have reported lower incidence rates for delirium. [28] A study which evaluated consecutive 212 patients with acute myocardial infarction admitted in coronary care unit reported an incidence rate of delirium to be 5.7%. [32] The present study mostly included those patients who come to the hospital with a cardiac emergency and are admitted to coronary care unit. These patients are usually stabilized initially and depending on the need many undergo cardiac interventions after immediate stabilization. Almost all of the patients with coronary artery disease underwent angiography (89.64%) and about two-third (64.72%) of the total study sample underwent angioplasty and 4.2% underwent coronary artery bypass grafting. Due to this clinical profile, it would be difficult to compare the incidence and prevalence of delirium as seen in this study with many studies from the west, as these studies have specifically not focused on a treatment setting, but have either focused on patients with myocardial infarction only or those undergoing surgery. However, when we compare the finding of prevalence of delirium seen in this study, it is in the reported range of 20-80% and the incidence is in the reported range for those undergoing cardiac surgery [21],[33] or those present with myocardial infarction. [32] From the above it can be concluded that findings incidence and prevalence of delirium as seen in the present study is in the range of the available literature and suggest that delirium is equally prevalent in CCU in developing countries.

A previous study which evaluated 151 patients admitted to Respiratory Intensive Care Unit at our institute reported an incidence rate of delirium 24.4% and prevalence rate of delirium 53.6% respectively. Findings of incidence and prevalence of delirium in the present study are lower than this study. These differences possibly could be due to severity of illness which is reflected by the fact that the mean APACHE-II score of patients who developed in previous study was about 20 in contrast in the present study the mean APACHE-II score of patients who developed delirium was 14.8. Similarly the mean APACHE-II score of non-delirium patients in the patient was also lower in the present study compared to that reported by Sharma et al. [34]

Risk factors for delirium

Many studies have evaluated the risk factors for delirium in patients undergoing cardiac surgery.

When one closely looks at the findings of the present study and compares it with literature from other countries [16],[22],[31],[32] , which is mostly from the Western countries, it emerges that there are certain factors which are common to development of delirium, irrespective of the country and these factors includes older age, higher number of medications, higher severity of physical illness and presence of comorbidity. However, certain other factors like type of metabolic disturbance, sepsis etc vary from study to study and possibly influence the incidence and prevalence of delirium. Considering the fact that there are certain risk factors for delirium which can be modified, the clinician dealing with CCU patients must be made aware of these risk factors to cut down on the possibly avoidable risk factor and overall incidence and prevalence of delirium. Further if these cannot be avoided than the clinician should be vigilant for emergence of delirium and manage it appropriately.

Outcome of subjects with delirium

In the present study about one-fourth (27%) of patients with delirium died during their CCU/hospital stay, this was in contrast to 1 patients (1%) in the non-delirium group and the difference between the two groups was statistically significant. This finding supports the existing vast literature which suggests that delirium leads to higher mortality irrespective of the study setting. [33],[34],[35],[36],[37] When one compares the odds ratio of predictions of delirium seen in elderly in present paper, with the whole study sample, it is evident that certain risk factors like use of medications like benzodiazepines, opioids, frusemide and ranitidine are more commonly associated with delirium in elderly. Accordingly number of medications used in elderly patients admitted to CCU must be minimized.

Findings of the present study must be interpreted in the light of the limitations of our study. The present study was restricted to a single unit (CCU) of cardiology department. In the present study, long term outcome in the form of cognitive deficits as a result of delirium and mortality were not assessed. Different factors associated with cardiac interventions (duration of intervention, blood loss, complications etc.) were not evaluated as the predictors of delirium.

To conclude this prospective study with daily assessment was able to identify cases of delirium in patients with cardiac illnesses admitted to CCU. This study shows that about one-third of elderly patients admitted to CCU develop delirium. Further this study shows that there are many predictors of delirium, some of which can be easily modified. This study also shows that delirium is associated with high mortality. Hence, it is important that clinicians working in the CCU set-up must be made aware of the incidence and prevalence of delirium must be alerted to modify the reversible predictors of delirium to reduce the mortality of these patients.



 
  References Top

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1 Predictors for postoperative delirium after vascular surgery
Hosam Roshdy,Youmna Sabri
Egyptian Journal of Psychiatry. 2016; 37(1): 1
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