Clinical Question: What preoperative factors can be used to predict delirium after vascular surgery?

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Purpose: To determine the most common risk factors of post-operative delirium after vascular surgery.

Evidence:
Databases: PubMed, CINHAL
Search Terms: prediction, delirium, cardiac, heart, vascular, surgery, post-operative, post-op
Boolean Terms: AND, OR
Inclusion Criteria: related to pre-operative risk factors (as opposed to intra- or post-operative)
Exclusion Criteria: focused primarily on a different procedure other than vascular (ex: orthopedic)

Importance:
According to the American Delirium Society1:
  • More than 7 million hospitalized American suffer from delirium each year
  • More than 60% of patients with delirium are not recognized by the health care system
  • Compared to hospitalized patients with no delirium (after adjusting for age, gender, race, and comorbidity), delirious patients have...
    • Higher mortality rates at one month (14% vs. 5%), at six months (22% vs. 11%), and 23 months (38% vs. 28%)
    • Longer hospital lengths of stay (21 vs. 9 days)
    • A higher probability of receiving care in long-term care setting at discharge (47% vs. 18%), 6 months (43% vs. 8%), and at 15 months (33% vs. 11%)
    • A higher probability of developing dementia at 48 months (63% vs. 8%)

According to a study done in 2008:
:
  • Patients with delirium, on average, had daily health care related costs that were 2.5 times greater than patients without delirium
  • Total costs attributable to delirium ranged from $16,303 to $16,421 per patient, which estimates the national cost per year of delirium to be between $38 billion and $152 billion 2

Background:
  • Delirium: "A disturbance of consciousness with reduced ability to focus, sustain, or shift attention; a change in cognition; or the development of a perceptual disturbance that occurs over a short period of time and tends to fluctuate over the course of the day" 3
    • Vascular surgeries have a high degree of operative stress, with post-operative delirium (POD) incidence as high as 36%
    • Hyperactive: Occurs when a patient is restless, irritable, combative, or agitated (<1% of cases)
    • Hypoactive: Presents with lethargy, decreased alertness/motor activity, and unawareness (71% of cases)
    • Mixed: Characteristics of both hyperactive and hypoactive (29% of cases) 4

Why is it important to diagnose delirium?

Post-op delirium is associated with the following consequences:
  • Prolonged hospital stay
  • Reduced cognitive and functional recovery
  • Increased postoperative complications
  • Increased mortality
  • Increased readmission to hospital
  • Poor cognitive and functional outcomes 3



external image Dog-w-Glasses.jpgKhan Academy on Delirium: https://www.youtube.com/watch?v=dhlkyIiD_RA

Prediction of Delirium After Cardiac Surgery and the Use of a Risk Checklist 3

  • Participants: 300 participants 45 years and older to create and confirm
  • Independent Variable: 28 risk factors
  • Dependent Variable: Presence of delirium
    • Delirium Observation Screening (DOS) Scale: Measure used by the nursing staff pre- and post-operatively to diagnose POD
      • Sensitivity 100%, Specificity 96.6% after cardiac surgery
  • Outcome Measures: Short Mini Mental State Exam (SMMSE), hospital anxiety and depression scale (HADS), Four-Dimensional Symptom Questionnaire (4DSQ), Geriatric Depression Scale (GDS), Internal and External Locus of Control-18 (IE18)
  • Results:
    • Part of the intent of this study was to validate a CPR for vascular post-operative delirium that the authors had studied and developed in 2008 that consisted of only two risk factors. In the process they discovered seven predictors that were independently associated with POD.
    • The post-operative delirium incidence,17.3% (52 patients) in the sample was used to create the CPR. To validate the CPR they used a predicted probability of 20% for post-op delirium.
    • Risk Factors: Euroscore, older age (>70), cognitive impairment, number of co-morbidities, type of surgery, history of delirium and alcohol use
    • Sensitivity 80.8%, Specificity 82.2%, and an area under the curve 0.89
    • Other literature has suggested that preoperative anxiety can be a strong predictor of POD. This study found no significance in regards to anxiety, which they attribute to the fact that anxiety is a common reason for participation refusal.

Risk Factors

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Equation to determine probability of acquiring delirium
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  • Limitations:
    • The study used the DOS for patients in the ICU, and the DOS is not the best tool to diagnose delirium in this setting. They used the DOS for consistency but suggested the CAM-ICU or NEECHAM confusion scale-ICU be used for this population. Also, they did not include preoperative medication in the study due to inconsistency in previous studies.
    • The authors recommended other factors such as carefully monitoring the patient's environment, promoting sleep and music therapy that have been shown to be preventative of post-operative delirium.

Age

  • Incidence and Precipitating Factors of Delirium after Coronary Artery Bypass Grafting 5
    • A prospective study involving 1,327 patients
    • Found that advanced age (over 65 years) was one of the strongest independent predictors for developing postoperative delirium with an odds ratio (OR) of 3.82 (95% CI=1.44-10.12)
  • Predicting Delirium After Vascular Surgery: A Model Based on Pre- and Intraoperative Data 6
    • A prospective study with 153 patients, 60 of whom developed post-operative delirium
    • Found that advanced age (over 64 years) was one of the significant predictors for developing postoperative delirium with an OR of 3.03 (p=0.018)
  • Prevalence and risk factors for post-operative delirium in a cardiovascular ICU 7
    • A retrospective study with 288 patients who had open heart surgery.
    • A checklist of 52 patient-related risk factors for delirium was used to collect preoperative, intra-operative and postoperative data.
    • Prevalence of postoperative delirium was 41.7%
    • Advanced age was listed as one of the factors that would predict postoperative delirium.
  • Standardised Frailty Indicator as Predictor for Postoperative Delirium after Vascular Surgery: A Prospective Cohort Study 8
    • A prospective study with 142 vascular surgery patients.
    • Although age alone appeared to have no significant relation to POD, high age (over 65 years) did account for over 75% of all complications.

Cognitive Impairment

  • Predicting Delirium After Vascular Surgery A Model Based on Pre- and Intraoperative Data 6
    • The same study that found age to be a significant predictor
    • An MMSE score of under 25 was listed as one of the predictors for developing post-operative delirium with an OR of 28 (p=0.001).
  • Cognitive and functional status predictors of delirium and delirium severity after coronary artery bypass graft surgery: an interim analysis of the Neuropsychiatric Outcomes After Heart Surgery study 9
    • An observational cohort study that included 102 patients who have undergone cardiac catheterization and have been referred for elective CABG.
    • Conclusion: Mild cognitive impairment-clinical dementia rating (MCI-CDR), MMSE, and functional status serve as predictors for post-operative delirium among study participants. Cognitive and functional impairment independently predict post-operative delirium and delirium severity.
      • MCI-CDR had an OR of 5.6 (95% CI=1.46-21.14)
      • MMSE had an OR of 0.6 (95% CI=0.42-0.92)
        • higher score means the patient is less likely to get POD
  • Predicting postoperative delirium after vascular surgical procedures 10
    • A prospective study with 566 patients
    • 22 patients (4.8%) developed POD
    • The CPR developed in this study predicted POD with 86% specificity and 92% sensitivity
    • Cognitive impairment (measured with the Groningen Frailty Index) was found to be an independent predictor with an OR of 16.4 (95% CI=4.7-57.0)
  • Preoperative and operative predictors of delirium after cardiac surgery in elderly patients 11
    • A prospective study with 201 patients all over 70 years who underwent cardiac surgery
    • 63 patients (31%) developed POD.
    • Pre-operative MMSE scores were found to be an independent predictor with an OR of 2.32 (95% CI=1.20-4.46)
      • lower scores were likely to develop POD

Co-Morbidities

  • Derivation and Validation of a Preoperative Prediction Rule for Delirium After Cardiac Surgery 12
    • Prospective study of cardiac surgery patients > or = 60 years
    • Their derivation cohort was 122 patients and their validation cohort was 109 patients
    • Prior history of a stroke or transient ischemic attack (TIA) was associated with POD with a risk ratio (RR) of 1.6 (95% CI=1.2-2.3)
  • Predicting postoperative delirium after vascular surgical procedures 10
    • Included increasing co-morbidities as a risk factor for POD
    • Found hypertention [OR = 7.6 (95% CI=1.9-30.5)] and current smoking [OR = 10.5 (95% CI=2.8-40.2)] to be independent risk factors
  • Prevalence and Risk Factors for Post-Operative Delirium in a Cardiovascular Intensive Care Unit 7
    • Diabetes mellitus, history of stroke, and history of renal disease were some factors listed as preoperative predictors of developing POD
  • Standardised Frailty Indicator as Predictor for Postoperative Delirium after Vascular Surgery: A Prospective Cohort Study 8
    • The number of comorbidities a patient has can be a predictive factor for developing POD after a vascular surgery
    • It wasn't found to be an independent risk factor, but it was significant with p=0.006
  • Incidence and Precipitating Factors of Delirium after Coronary Artery Bypass Grafting 5
    • Peripheral vascular disease had an OR of 2.80 (95% CI=1.11-7.04)

Type of Surgery

  • CABG (coronary artery bypass graft)
  • CABG and valve replacement
    • Valve replacement associated with a higher risk of POD than CABG alone 13
  • TAVR (Transcatheter aortic valve replacement) 13
    • Non-transfemoral catheterization was strongly associated with POD
    • Other predictors included current smoker, CAD, A-fib, and age
  • Vascular surgeries have a much higher risk of POD than other surgeries with less operative stress
    • Cataract surgery has around a 4% risk of POD (low operative stress)
    • Vascular surgeries have as high as 36% (high operative stress)4

Euroscore

  • EuroSCORE Calculator

  • European System for Cardiac Operative Risk Evaluation
  • EuroSCORE includes many of the risk factors for POD in a logistic calculation of predicted operative mortality for cardiac surgery
  • Incidence and precipitating factors of delirium after coronary artery bypass grafting 5
    • Euroscore of > or = 5 was an independent predictor of POD with an OR of 2.46 (95% CI=1.16-5.12)

Alcohol Use

  • Derivation and Validation of a Preoperative Prediction Rule for Delirium After Cardiac Surgery 12
    • alcohol use was actually associated with a decrease in delirium risk
    • So Koster et al. might have found a relationship, but alcohol use shouldn't be referenced as the only factor in predicting whether or not a patient will get delirium post-operatively

Other Risk Factors Associated with Postoperative Delirium

  • Albumin levels
    • Derivation and Validation of a Preoperative Prediction Rule for Delirium After Cardiac Surgery 12
      • Abnormal albumin levels (less than or equal to 3.5 or greater than or equal to 4.5 g/dL) assigned as independent predictive factor for POD [RR=1.4 (95% CI=1.0-2.0)]
      • Albumin level associated with operative mortality and plays role in intravascular volume status and drug binding.
  • Diagnosis of dementia was in the exclusion criteria for a number of studies, due to the complexity of diagnosing a patient who has dementia with delirium.
  • Current Smoker
  • History of Delirium
  • Poor Nutrition
  • Psychological involvement (Depression, Anxiety, etc.)
  • Elevated CRP (C-reactive protein) levels
  • Renal Impairment
  • Acute Infection
    • Found to be a significant independent predictor of POD after open heart surgery

Conclusion and Clinical Recommendation


  • Van Meenan et al. in a systematic review on risk prediction models found older age, preoperative cognitive function, and preoperative alcohol use as the most common risk factors 14
  • From our research, the most common risk factors are:
    • Age > 65 years old
    • Preoperative cognitive status
    • Past Medical History
      • Including amputation, stroke, dementia, etc.
    • Co-Morbidities
      • DM, HTN, heart disease, etc.
  • These factors seem to be the most common in current literature for determining a patient’s risk for postoperative delirium.

Clinical Application to Physical Therapy


  • Preoperative Outpatient
    • recognize risk factors and discuss with the doctor
    • sensitively discuss certain risk factors that can be altered
  • Postoperative Inpatient
    • Acute care PT
    • recognize risk factors and be prepared (on alert) for the status your patient might be in when you do your initial examination

Video

Delirium Video

References


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  1. Delirium is a “Dangerous Diagnosis”. American Delirium Society Web site. https://www.americandeliriumsociety.org/ Published 2015. Accessed April 14, 2016.
  2. Leslie DL, Marcantonio ER, Zhang Y, et al. One-Year Health Care Costs Associated with Delirium in the Elderly. Archives of Internal Medicine. 2008; 168(1): 27-32. doi: 10.1001/archinternmed.2007.4.
  3. Koster S, Hensens AG, Schuurmans MJ, van der Palen J. Prediction of delirium after cardiac surgery and the use of a risk checklist. European Journal of Cardiovascular Nursing. 2012; 12(3): 284-292. doi: 10.1177/1474515112450244
  4. Robinson TN, Eiseman B. Postoperative delirium in the elderly: diagnosis and management. Clinical Interventions in Aging. 2008; 3(2): 351-355.
  5. Norkiene I, Ringaitiene D, Misiuriene I, et al. Incidence and precipitating factors of delirium after coronary artery bypass grafting. Scandanavian Cardiovascular Journal. 2007; 41: 180-185. doi:10.1080/14017430701302490
  6. Böhner H, Hummel TC, Habel U, et al. Predicting Delirium After Vascular Surgery: A Model Based on Pre- and Intraoperative Data. Annals of Surgery. 2003; 238(1): 149-156. doi:10.1097/01.sla.0000077920.38307.5f
  7. Chang Y, Tsai Y, Lin P, Chen M, Liu C. Prevalence and Risk Factors for Post-Operative Delirium in a Cardiovascular Intensive Care Unit. American Journal of Critical Care. 2008; 17(6): 567-575.
  8. Pol RA, van Leeuwen BL, Visser L, et al. Standardised Frailty Indicator as Predictor for Postoperative Delirium after Vascular Surgery: A Prospective Cohort Study. European Journal of Vascular and Endovascular Surgery. 2011; 42: 824-830. doi: 10.1016/j.ejvs.2011.07.006
  9. Oldham MA, Hawkins KA, Yuh DD, et al. Cognitive and functional status predictors of delirium and delirium severity after coronary artery bypass graft surgery: an interim analysis of the Neuropsychiatric Outcomes After Heart Surgery study. International Psychogeriatrics. 2015; 27(12): 1929-38. doi: 10.1017/S1041610215001477
  10. Visser L, Prent A, van der Laan MJ, et al. Predicting postoperative delirium after vascular surgical procedures. Journal of Vascular Surgery. 2015; 62(1): 183-189. doi: 10.1016/j.jvs.2015.01.041
  11. Bakker RC, Osse RJ, Tulen JHM, Kappetein AP, Bogers JJC. Preoperative and operative predictors of delirium after cardiac surgery in elderly patients. European Journal of Cardio-Thoracic Surgery. 2012; 41: 544-549. doi: 10.1093/ejcts/ezr031
  12. Rudolph JL, Jones RN, Levkoff SE, et al. Derivation and Validation of a Preoperative Prediction Rule for Delirium After Cardiac Surgery. Circulation. 2009; 119: 229-236. doi: 10.1161/CIRCULATIONAHA.108.795260
  13. Abawi M, Nijhoff F, Emmelot-Vonk MH, et al. Incidence, predictive factors, and effect of delirium after transcatheter aortic valve replacement. JCC: Cardiovascular Interventions. 2016; 9(2): 160-168. Doi: 10.1016/j.jcin.2015.09.037
  14. van Meenen LCC, van Meenen DMP, de Rooji SE, ter Riet G. Risk Prediction Models for Postoperative Delirium: A Systematic Review and Meta-Analysis. Journal of American Geriatrics Society. 2014; 62: 2383-2390. doi: 10.1111/jgs.13138