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Delirium after cardiac surgery: risk factors, assessment methods and costs
Umeå University, Faculty of Medicine, Department of Nursing. Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Cardiac surgery is considered safe, but postoperative delirium (POD) remains frequently reported. Delirium is characterised by fluctuations in consciousness and cognition, and can be subdivided into disturbed psychomotoric activity (hyperactive and hypoactive) and psychiatric symptom profiles (psychotic and emotional). Delirium has an underlying cause that can be prevented and treated, provided the condition is detected. Undetected delirium could lead to serious consequences for the patient.

Aim: This thesis aims to understand the underlying risk factors of delirium, to compare different assessment methods and documentation, and to understand its effects on hospitalisation costs after cardiac surgery.

Methods: Two cohorts of patients undergoing cardiac surgery at the Heart Centre, Umeå University Hospital, Sweden were analysed. Cohort-A (Studies I-IV) enrolled 142 patients, ≥70 years of age, scheduled in 2009 for surgery with cardiopulmonary bypass (CPB). POD was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders 4th ed, text rev (DSM-IV-TR), based on repetitive assessments with the Mini-Mental State Examination (MMSE) and the Organic Brain Syndrome (OBS) scale. This method was considered as reference. Predisposing and precipitating risk factors were explored (Study I), and a separate analysis was conducted with focus on CPB parameters (Study II). Patients were also assessed for POD with the Confusion Assessment Method (CAM), which was validated versus the reference method (Study III). Additionally in Study IV, data about how nurses assessed patients for POD symptoms using the Nursing Delirium Screening Scale (Nu-DESC) were analysed together with information extracted from the clinical database. Moreover, discharge summaries from both nurses and physicians were retrospectively reviewed for key words and expression associated with delirium. Cohort-B (Study V) included 1879 routine cardiac surgery patients (2014-2017) retrospectively extracted from the clinical database with concomitant Nu-DESC scoring. The association between the Nu-DESC and postoperative hospitalization costs was analysed.

Results: In cohort-A, 54.9% (78/142) patients developed POD. Both predisposing and precipitating risk factors were significantly associated with POD, of which the ‘volume load during operation’ had the strongest predictive influence (Study I). Among CPB variables the ‘duration of mixed-venous oxygen saturation <75%’ predicted POD (Study II). Hypoactive was more common than hyperactive delirium. Those with hypoactive delirium were less likely to be detected by the CAM method (Study III), an observation also demonstrated from information found in the clinical database and in discharge summaries. Nu-DESC did not detect all patients with POD, but significantly increased the detection rate (Study IV). The major hospitalisation costs associated with Nu-DESC ≥2 occurred in the ICU and independently of the surgical procedure performed. There were no significant differences in costs among patients with Nu-DESC ≥2, between age groups (70-year cut-off) or genders (Study V).

Conclusions: Both predisposing and precipitating risk factors contributed to POD and should be considered in future guidelines to prevent delirium after cardiac surgery. Hypoactive delirium was most common, but was the most difficult to detect without screening scales. Systematic assessment with Nu-DESC improved the detection rate of POD. Delirium after cardiac surgery has consequences on healthcare and is associated with increased costs.

Abstract [sv]

Bakgrund: Hjärtkirurgi anses idag vara en säker metod men det förkommer frekventa rapporter om postoperativt delirium (POD). Delirium kännetecknas av fluktuationer i medvetandet och kognition och kan delas in i störd psykomotorisk aktivitet (hyperaktiva och hypoaktiva) och psykiatriska symtomprofiler (psykotiska och emotionella). Delirium har underliggande orsaker som kan förebyggas och behandlas, förutsatt att tillståndet upptäcks. Ett oupptäckt delirium kan leda till allvarliga konsekvenser för patienten.

Syfte: Denna avhandling syftar till att förstå de underliggande riskfaktorerna för delirium, jämföra olika bedömningsmetoder och dokumentation samt förstå effekterna på vårdkostnaderna efter hjärtkirurgi.

Metod: Två kohorter av patienter som genomgått hjärtkirurgi vid Hjärtcentrum, Umeå Universitetssjukhus, Sverige analyserades. I kohort-A (Studie I-IV) inkluderades 142 patienter, ≥70 år planerade för operation med hjärt-lungmaskin under 2009. POD diagnostiserades enligt Diagnostic and Statistical Manual of Mental Disorders 4th ed, text rev (DSM-IV-TR), baserat på upprepade skattningar med Mini Mental State Examination (MMSE) och Organic Brain Syndrom(OBS) scale. Denna metod betraktas som referens. Predisponerande och utlösande riskfaktorer analyserades (Studie I), och en separat analys genomfördes med fokus på hjärt-lungmaskinens parametrar (Studie II). Patienterna bedömdes också för POD med Confusion Assessment Method (CAM), vilken validerades mot referensmetoden (Studie III). Vidare analyserades uppgifter om hur sjuksköterskor skattade patienterna för POD symtom med Nursing Delirium Screening Scale (Nu-DESC) tillsammans med information hämtad från den kliniska databasen. Dessutom granskades både sjuksköterskornas och läkarnas epikriser retrospektivt för nyckelord och uttryck associerade med delirium. Kohort-B (Studie V) inkluderade 1879 rutinmässiga hjärtkirurgiska patienter (2014-2017) som extraherades retrospektivt från den kliniska databasen med samtidiga Nu-DESC-poäng. Sambandet mellan Nu-DESC och de postoperativa vårdkostnaderna analyserades.

Resultat: I kohort-A, utvecklade 54,9% (78/142) av patienterna POD. Både predisponerande och utlösande riskfaktorer var signifikant associerade med POD, varav ’volymbelastningen under operation’ hade det starkaste prediktiva inflytandet (Studie I). Bland hjärt-lungmaskinens variabler bidrog ’duration av blandad venös syremättnad <75%’ till POD (Studie II). Hypoaktivt delirium var vanligare än hyperaktivt. Patienter med hypoaktiv delirium upptäcktes i mindre utsträckning med CAM (Studie III), en observation som också visade sig i information från den kliniska databasen och i epikriserna. Nu-DESC upptäckte inte alla patienter med POD men ökade detekteringsgraden signifikant (Studie IV). De största vårdkostnaderna i samband med Nu-DESC-poäng ≥2 inträffade på intensivvårdsavdelningen oberoende av kirurgiskt ingrepp som utförts. Det fanns inga signifikanta skillnader i kostnaderna mellan åldersgrupper (70-års brytpunkt) eller mellan män och kvinnor med Nu-DESC ≥2 (Studie V).

Slutsatser: Både predisponerande och utlösande riskfaktorer bidrar till POD och bör övervägas i framtida riktlinjer för att förhindra delirium efter hjärtkirurgi. Hypoaktivt delirium var vanligast men också svåraste att upptäcka utan bedömningsskalor. Systematisk bedömning med Nu-DESC förbättrade upptäckten av POD. Delirium efter hjärtkirurgi har konsekvenser för vården och är förknippad med ökade kostnader.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2018. , p. 55
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1967
Keywords [en]
Cardiac surgery, Cardiopulmonary bypass, Consequences, Delirium, Detection, Documentation, Economical aspect, Hospitalisation, Risk factors, Screening scales
National Category
Surgery Nursing
Research subject
Thoracic and Cardivascular Suregery; Caring Sciences
Identifiers
URN: urn:nbn:se:umu:diva-151414ISBN: 978-91-7601-909-2 (print)OAI: oai:DiVA.org:umu-151414DiVA, id: diva2:1244604
Public defence
2018-09-28, Aulan, Vårdvetarhuset, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2018-09-07 Created: 2018-09-03 Last updated: 2019-03-11Bibliographically approved
List of papers
1. Delirium after cardiac surgery: incidence and risk factors
Open this publication in new window or tab >>Delirium after cardiac surgery: incidence and risk factors
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2013 (English)In: Interactive Cardiovascular and Thoracic Surgery, ISSN 1569-9293, E-ISSN 1569-9285, Vol. 17, no 5, p. 790-796Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: Delirium after cardiac surgery is a problem with consequences for patients and healthcare. Preventive strategies from known risk factors may reduce the incidence and severity of delirium. The present aim was to explore risk factors behind delirium in older patients undergoing cardiac surgery with cardiopulmonary bypass.

METHODS: Patients (≥70 years) scheduled for routine cardiac surgery were included (n = 142). The patients were assessed and monitored pre-/postoperatively, and delirium was diagnosed from repeated assessments with the Mini-Mental State Examination and the Organic Brain Syndrome Scale, using the DSM-IV-TR criteria. Variables were analysed by uni-/multivariable logistic regression, including both preoperative variables (predisposing) and those extracted during surgery and in the early postoperative period (precipitating).

RESULTS: Delirium was diagnosed in 78 patients (54.9%). Delirium was independently associated with both predisposing and precipitating factors (P-value, odds ratio, upper/lower confidence interval): age (0.036, 1.1, 1.0/1.2), diabetes (0.032, 3.5, 1.1/11.0), gastritis/ulcer problems (0.050, 4.0, 1.0/16.1), volume load during operation (0.001, 2.8, 1.5/5.1), ventilator time in ICU (0.042, 1.2, 1.0/1.4), highest temperature recorded in ICU (0.044, 2.2, 1.0/4.8) and sodium concentration in ICU (0.038, 1.2, 1.0/1.4).

CONCLUSIONS: Delirium was common among older patients undergoing cardiac surgery. Both predisposing and precipitating factors contributed to delirium. When combined, the predictive strength of the model improved. Preventive strategies may be considered, in particular among the precipitating factors. Of interest, delirium was strongly associated with an increased volume load during surgery.

Place, publisher, year, edition, pages
Oxford University Press, 2013
Keywords
cardiac surgery, delayed, early, hemispheric, stroke survival
National Category
Surgery Cardiac and Cardiovascular Systems Nursing
Identifiers
urn:nbn:se:umu:diva-86091 (URN)10.1093/icvts/ivt323 (DOI)000326725300011 ()23887126 (PubMedID)
Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2018-09-03Bibliographically approved
2. Disturbances in Oxygen Balance During Cardiopulmonary Bypass: A Risk Factor for Postoperative Delirium
Open this publication in new window or tab >>Disturbances in Oxygen Balance During Cardiopulmonary Bypass: A Risk Factor for Postoperative Delirium
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2018 (English)In: Journal of Cardiothoracic and Vascular Anesthesia, ISSN 1053-0770, E-ISSN 1532-8422, Vol. 32, no 2, p. 684-690Article in journal (Refereed) Published
Abstract [en]

Objective: The aim of this study was to determine risk factors for postoperative delirium after cardiac surgery, specifically associated with the conduct of cardiopulmonary bypass (CPB).

Design: Prospective observational study.

Setting: Heart Centre, University Hospital.

Participants: The study included 142 patients aged 70 years and older scheduled for elective cardiac surgery with CPB.

Interventions: Risk factor analysis comprised information collected from the hospital clinical and CPB dedicated databases in addition to the medical chart. Delirium was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision criterion using the Mini Mental State Examination and the Organic Brain Syndrome scale.

Measurements and Main Results: Assessments of delirium diagnosis were executed preoperatively and on the following first and fourth postoperative days. Delirium occurred in 55% (78/142) of the patients. Patients with delirium were identified with significantly higher body weight and body surface area preoperatively, accompanied with longer CPB time, higher positive fluid balance per CPB, and lower systemic pump flow related to body surface area. Furthermore, the duration of the mixed venous oxygen saturation (SvO2) below 75% was significantly longer during CPB. The result from the multivariable logistic regression analysis included the duration of SvO2 below 75%, fluid balance per CPB and patient age as independent risk factors for postoperative delirium.

Conclusions: The influence of the SvO2 level during CPB, fluid balance, and patient age should be recognized as risk factors for postoperative delirium after cardiac surgery in patients 70 years and older.

Place, publisher, year, edition, pages
Saunders Elsevier, 2018
Keywords
cardiac surgery, cardiopulmonary bypass, mixed venous oxygen saturation, postoperative delirium, risk factors
National Category
Nursing Cardiac and Cardiovascular Systems Respiratory Medicine and Allergy Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-144659 (URN)10.1053/j.jvca.2017.08.035 (DOI)000429083200014 ()29153931 (PubMedID)
Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2019-05-22Bibliographically approved
3. Validation of the confusion assessment method in detecting postoperative delirium in cardiac surgery patients
Open this publication in new window or tab >>Validation of the confusion assessment method in detecting postoperative delirium in cardiac surgery patients
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2015 (English)In: American Journal of Critical Care, ISSN 1062-3264, E-ISSN 1937-710X, Vol. 24, no 6, p. 480-487Article in journal (Refereed) Published
Abstract [en]

Background: Early detection, prevention, and treatment of delirium after cardiac surgery are important for quick postoperative recovery. The Confusion Assessment Method (CAM) may be an easy-to-use instrument for detecting delirium in clinical practice.

Objectives: To compare the congruent validity of the CAM with the results from repeated assessments by using a combination of the Organic Brain Syndrome Scale and the Mini-Mental State Examination according to the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision) criteria for delirium.

Methods: Patients aged 70 years or older undergoing cardiac surgery were assessed on postoperative days 1 and 4, and the 2 diagnostic methods were compared. The sensitivity and specificity of the CAM were examined. The reference method allowed categorization of delirium into subgroups of psychomotor activities and psychiatric symptom profiles, which were compared with the CAM results.

Results: Postoperative delirium was diagnosed in 78 of 141 patients (55.3%). According to the CAM, 59 patients (41.8%) were categorized as delirious, 53 correctly. Thus, the sensitivity was 68% and the specificity was 90%, indicating false-negative rather than false-positive observations.

Conclusion: Patients with psychomotor hyperactivity and mixed psychotic-emotional symptoms were more likely to have delirium detected via the CAM than were patients with less obvious clinical manifestations of delirium. Repetitive cognitive testing and psychogeriatric experience are probably necessary to improve the results obtained with the CAM.

Place, publisher, year, edition, pages
American Association of Critical-Care Nurses, 2015
Keywords
mini-mental state, risk factors, hospital patients, elderly patients, older people, 3 scores, intervention, fracture, profile, screen
National Category
Nursing Surgery Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:umu:diva-111993 (URN)10.4037/ajcc2015551 (DOI)000364316700004 ()26523005 (PubMedID)
Available from: 2015-12-03 Created: 2015-11-30 Last updated: 2018-09-03Bibliographically approved
4. The use of a screening scale improves the recognition of delirium in older patients after cardiac surgery: a retrospective observational study
Open this publication in new window or tab >>The use of a screening scale improves the recognition of delirium in older patients after cardiac surgery: a retrospective observational study
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2019 (English)In: Journal of Clinical Nursing, ISSN 0962-1067, E-ISSN 1365-2702, Vol. 28, no 11-12, p. 2309-2318Article in journal (Refereed) Published
Abstract [en]

AIMS AND OBJECTIVES: This study analyzed postoperative delirium (POD) in clinical practice after cardiac surgery, how it is detected and documented and if the use of a screening scale improves the detection rate.

BACKGROUND: Cardiac surgery is considered a routine procedure with few complications. However, POD remains a concern, although often being overlooked in clinical practice.

DESIGN: Retrospective observational analysis.

METHODS: Patients 70 years and older with POD (n=78) undergoing cardiac surgery were included in the study. Discharge summaries of both nurses and physicians were reviewed together with the clinical database for information about POD, to be compared with symptom screening using the Nursing Delirium Screening Scale (Nu-DESC). A quantitative content analysis was used for the review of discharge summaries, with a coding scheme adopted from the Nu-DESC method. The STROBE checklist was followed.

RESULTS: In discharge summaries 41 of the 78 POD patients were correctly recognized, and 22 of these were identified in the clinical database. Screening by the Nu-DESC identified delirium at a measurably higher rate, 56/78 patients. The review of discharge summaries showed that patients expressing 'inappropriate behaviour' was the most easily identified sign for POD for both nurses and physicians.

CONCLUSIONS: Healthcare professionals underdiagnose delirium after cardiac surgery, with a low detection rate described in both discharge summaries and in the clinical database. Recognition of delirium improved when Nu-DESC was used for systematic screening.

RELEVANCE TO CLINICAL PRACTICE: This study emphasizes the need for better screening for the detection of delirium in daily clinical practice. This article is protected by copyright. All rights reserved.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
Assessments scales, Cardiac surgery, Clinical database, Documentation, Postoperative delirium
National Category
Nursing
Identifiers
urn:nbn:se:umu:diva-157010 (URN)10.1111/jocn.14838 (DOI)000467448000026 ()30791158 (PubMedID)2-s2.0-85062685218 (Scopus ID)
Note

Originally included in thesis in manuscript form

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-08-06Bibliographically approved
5. The association between delirium symptoms according to the Nursing Delirium Screening Scale and hospitalization costs after cardiac surgery
Open this publication in new window or tab >>The association between delirium symptoms according to the Nursing Delirium Screening Scale and hospitalization costs after cardiac surgery
(English)Manuscript (preprint) (Other academic)
Keywords
Cardiac surgery, Delirium, Economical outcome, Hospitalization costs, Length of Stay
National Category
Surgery Nursing
Identifiers
urn:nbn:se:umu:diva-151376 (URN)
Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-09-03

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