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Standards for definitions and use of outcome measures for clinical effectiveness research in perioperative medicine

European Perioperative Clinical Outcome (EPCO) definitions

A statement from the ESA-ESICM joint taskforce on perioperative outcome measures

Jammer, Ib; Wickboldt, Nadine; Sander, Michael; Smith, Andrew; Schultz, Marcus J.; Pelosi, Paolo; Leva, Brigitte; Rhodes, Andrew; Hoeft, Andreas; Walder, Bernhard; Chew, Michelle S.; Pearse, Rupert M.

European Journal of Anaesthesiology (EJA): February 2015 - Volume 32 - Issue 2 - p 88–105
doi: 10.1097/EJA.0000000000000118
Guidelines
Free

There is a need for large trials that test the clinical effectiveness of interventions in the field of perioperative medicine. Clinical outcome measures used in such trials must be robust, clearly defined and patient-relevant. Our objective was to develop standards for the use of clinical outcome measures to strengthen the methodological quality of perioperative medicine research. A literature search was conducted using PubMed and opinion leaders worldwide were invited to nominate papers that they believed the group should consider. The full texts of relevant articles were reviewed by the taskforce members and then discussed to reach a consensus on the required standards. The report was then circulated to opinion leaders for comment and review. This report describes definitions for 22 individual adverse events with a system of severity grading for each. In addition, four composite outcome measures were identified, which were designed to evaluate postoperative outcomes. The group also agreed on standards for four outcome measures for the evaluation of healthcare resource use and quality of life. Guidance for use of these outcome measures is provided, with particular emphasis on appropriate duration of follow-up. This report provides clearly defined and patient-relevant outcome measures for large clinical trials in perioperative medicine. These outcome measures may also be of use in clinical audit. This report is intended to complement and not replace other related work to improve assessment of clinical outcomes following specific surgical procedures.

From the Department of Clinical Medicine, University of Bergen, Bergen, Norway (IJ), Department of Anaesthesia and Intensive Care, Haukeland University Hospital, Bergen, Norway (IJ), Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Geneva, Geneva, Switzerland (NW, BW), Department of Anaesthesia and Intensive Care, Charite, Berlin, Germany (MS), Royal Lancaster Infirmary, Lancaster University, Lancaster, UK (AS), Department of Intensive Care Medicine, Academic Medical Centre, Amsterdam, The Netherlands (MJS), Department of Surgical Sciences and Integrated Diagnostics, IRCCS San Martino Hospital, University of Genoa, Genoa, Italy (PP), European Society of Anaesthesiology, Brussels, Belgium (BL), Critical Care, St George's Hospital, London, UK (AR), Department of Anaesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany (AH), Department of Anaesthesia and Intensive Care Medicine, Hallands Sjukhus Halmstad, Halmstad, Sweden (MSC), Institute of Clinical Sciences, Lund University, Sweden (MSC) and Queen Mary University of London, London, UK (RMP)

Correspondence to Rupert M. Pearse, Adult Critical Care Unit, Royal London Hospital, London E1 1BB, UK Tel: +44 20 3594 0346; e-mail: r.pearse@qmul.ac.uk

Published online 23 July 2014

This article is accompanied by the following Invited Commentary:

Grocott MPW. Standardisation of perioperative outcome measures. Eur J Anaesthesiol 2015; 32:83–84.

Index

Introduction 90

Material and Methods 90

Results 90

Individual adverse event definitions 91

Composite outcome measures 92

Quality of life measures 92

Healthcare resource use 92

Duration of follow-up 93

Discussion 93

Conclusions 94

Acknowledgements relating to this article 94

Appendix 1. Abbreviations 94

Appendix 2. Detailed definitions 95

  1. Single organ outcome measures 95
    1. 1.1 Acute Kidney Injury (AKI) 95
    2. 1.2 Acute Respiratory Distress Syndrome (ARDS) 95
    3. 1.3 Anastomotic breakdown 95
    4. 1.4 Arrhythmia 96
    5. 1.5 Cardiac arrest 96
    6. 1.6 Cardiogenic pulmonary oedema 96
    7. 1.7 Deep vein thrombosis (DVT) 96
    8. 1.8 Delirium 97
    9. 1.9 Gastrointestinal bleed 97
    10. 1.10 Infection, source uncertain 97
    11. 1.11 Laboratory confirmed bloodstream infection 97
    12. 1.12 Myocardial infarction 98
    13. 1.13 Myocardial injury after non-cardiac surgery (MINS) 98
    14. 1.14 Pneumonia 98
    15. 1.15 Paralytic ileus 99
    16. 1.16 Postoperative haemorrhage 99
    17. 1.17 Pulmonary embolism (PE) 99
    18. 1.18 Stroke 99
    19. 1.19 Surgical site infection (superficial) 100
    20. 1.20 Surgical site infection (deep) 100
    21. 1.21 Surgical site infection (organ/space) 100
    22. 1.22 Urinary tract infection 101
  2. Composite outcome measures 101
    1. 2.1 Major Adverse Cardiac Events (MACE) 101
    2. 2.2 Postoperative pulmonary complications 102
    3. 2.3 PostOperative Morbidity Survey (POMS) 102
    4. 2.4 Quality of Recovery (QoR) 103
  3. Grading of complications 103
    1. 3.1 Pragmatic severity grading 103
    2. 3.2 Clavien-Dindo grading of complications 104
  4. Health-related quality of life (HRQL) 104

References 105

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Introduction

In excess of 230 million patients undergo surgery worldwide each year with reported hospital mortality rates of between 1 and 4%.1–3 Patients who develop complications but survive to leave hospital often suffer reductions in functional independence and long-term survival.4–6 Variations in mortality suggest that there is a potential to improve survival after surgery.2,7 With the high volumes of surgery performed, even a low rate of avoidable harm will be associated with a large number of preventable deaths. Improvements in perioperative medicine may therefore lead to substantial public health benefit.

The impact of a large clinical trial is critically dependent on the use of well defined outcome measures, which must be patient-centred and important as well as potentially modifiable by the trial intervention. Thirty-day mortality is often regarded as the most important outcome measure but may not be the most relevant. Patients are more likely to develop short-term complications from surgery that may lead to loss of function and possibly death within the first year.4–6 However, it seems likely that most patients who choose to undergo surgery do so in the hope of long-term survival with good quality of life. Clinical effectiveness trials should therefore be designed to test whether perioperative interventions can improve these outcomes. However, at present, there is no standard approach to the evaluation of complications, quality of life or survival in clinical trials in the field of perioperative medicine.

There is a clear need for a standardised list of clearly defined clinical outcome measures for use in large, pragmatic clinical trials in this field. This would help investigators to improve the design of clinical trials through the use of recognised reference standards. This should lead to a stronger evidence base to inform clinical practice and improve long-term outcomes after surgery. The European Society of Anaesthesiology (ESA) and the European Society of Intensive Care Medicine (ESICM) therefore funded a joint task force to evaluate the literature and create standards for the definition and use of outcome measures in clinical effectiveness research in perioperative medicine. A full list of abbreviations used in this statement is contained in Appendix 1.

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Materials and methods

The members of the taskforce were appointed through an open application process in each society administered by the ESA Research Committee and the ESICM Executive Committee. There was some dialogue between the two Societies and R.P. as chair, to ensure a balance of experience. The statement was written by this expert group after a literature review. We agreed that the guidelines should complement existing systems to evaluate outcomes after surgery. The objective was not to provide an exhaustive account of all alternative definitions but to provide a methodological standard for use in large, pragmatic clinical studies designed to improve patient outcomes after surgery. The statement is not intended to influence the design of smaller translational studies or evaluations of individual technical complications of anaesthesia or surgery, wherein more specific definitions may have greater utility.

To identify relevant publications, an electronic search of the PubMed database was performed on 23 January 2013 using the following search string: ‘Perioperative Period’ [Mesh] AND ‘Postoperative Complications’ [Mesh] OR ‘Outcome Assessment (Healthcare)’ [Mesh] OR ‘Morbidity’ [Mesh], including publications pertaining to humans written in English, French or German languages. Publication titles were first reviewed by two task force members (I.J. and R.P.). Disputes were resolved by discussion and, if necessary, reference to a third member who arbitrated. The abstracts of the remaining publications were then reviewed by all taskforce members and the full text was acquired for the selected articles. In addition, taskforce members, members of the two societies and key opinion leaders in perioperative medicine worldwide were invited to nominate relevant publications. The taskforce members appraised the full-text versions of the selected articles, which were categorised as relevant, not relevant or potentially relevant. In a face-to-face meeting, the final list of definitions was then selected.

Outcome measure definitions were arranged into four categories: individual adverse event definitions, composite outcome measures, healthcare resource use and quality of life measures. In addition, opinion on methodological best practice was identified in terms of duration of follow-up and the combined use of outcome measures. The group agreed a priori on specific adverse events for which a definition was important. Outcome measures were excluded where the taskforce members agreed that the risk of subjective assessment was too great. Where alternative valid definitions were identified, the taskforce reached a consensus on the optimal candidate for this specific application but included references to the alternative(s). Where no valid definition could be identified, we contacted recognised experts for further guidance. The final manuscript was circulated to key opinion leaders for comment and suggestions. Decisions were reached through discussion and informal consensus. We did not use a formal voting or Delphi methodology.

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Results

The literature search identified 11 478 articles, but few had direct relevance to our objective (Fig. 1). From these, 31 articles were chosen for the analysis. There was consensus amongst the group that not all potential perioperative adverse events could be defined in a way that would be suitable for use in a large pragmatic clinical trial. The list of definitions is provided in Appendix 2. Two additional articles were included following review by international opinion leaders, resulting in 33 articles being included finally for the qualitative analysis.

Fig. 1

Fig. 1

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Individual adverse event definitions

Definitions were included for 22 individual complications. Most adverse events occur as a consequence of tissue injury due to surgery or anaesthesia, in combination with patient age, frailty and comorbid disease, rather than as a result of technical failure or medical error. In terms of infection, the United States of America Centers for Disease Control (CDC) definitions of infection were recommended. However, some simplifications to the CDC criteria are possible when intended for use solely in the postoperative population. Existing definitions for acute respiratory distress syndrome, acute kidney injury and myocardial injury after noncardiac surgery were adopted unchanged. Some individual adverse events as outcome measures are listed below:

  1. Grading of severity reduces subjectivity
  2. Assessors may be blinded even with open study group allocation
  3. Biological mechanisms should be considered when choosing outcome measures
  4. Report harm as well as benefits of trial interventions using separate outcome measures

In randomised trials, it is likely that the intervention may have both harmful and beneficial effects. It is appropriate to use separate outcome measures for benefit and harm in this context. Fully blinded study group allocation may not be possible in large pragmatic trials, but it is usually possible to blind the assessor of clinical outcomes and staff responsible for data entry and data management. The group agreed that it was very important to grade the severity of adverse events because this may vary widely. In some cases, this grading was integral to the definition selected, but in others, a simple system of grading was adopted. A small number of definitions did not permit severity grading. An important feature of the grading systems is that they do not define severity according to medical or surgical treatments, which may prove arbitrary in the context of international trials. However, where this is not a concern, the Clavien-Dindo grading system may be preferable.8 During the final review process, a number of opinion leaders recommended including a standard definition of myocardial infarction as well as the recently developed definition of Myocardial Injury after Noncardiac Surgery (MINS).9,10

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Composite outcome measures

A number of composite outcome measures were identified that focus on specific categories of outcome (e.g. postoperative pulmonary complications). Other composites deal with the need to systematically screen for mild postoperative morbidity such as that caused by immobility, pain or nausea and vomiting (e.g. Quality of Recovery scale, postoperative morbidity survey). Composite outcome systems offer a number of benefits, most notably an increased event rate helping to ensure adequate statistical power, which are listed as follows:

  1. May increase event rate and improve statistical power
  2. Differ in structure and may provide categorical or continuous variables
  3. May conceal differential weighting (frequency and severity) of component variables
  4. Function best when components focus on linked aspects of clinical problems
  5. Early postoperative mortality represents a composite of serious adverse events

It is logical to combine related outcomes that represent different aspects of a single underlying pathophysiological process. However, there are potential limitations to the use of this approach. It is of particular importance to select only those outcomes that may plausibly be modified by the intervention. The component variables of a composite outcome measure should not differ too widely in terms of severity and frequency. Differences in the frequency of component variables in a composite outcome may be obscured, particularly where the outcome is reported in a binary fashion (i.e. positive or negative). Some composites allow a severity grading, but this may not accurately reflect differential weightings that should be applied to each component outcome, for example postoperative morbidity survey. The group noted that in the context of postoperative outcomes, short-term mortality simply represents a composite of the most serious complications.

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Quality of life measures

Major surgery may often be followed by deteriorations in quality of life which are important to patients. Quality of life data place the value of surgery and any perioperative trial intervention into context. The quality of life outcome measures are listed as follows:

  1. Reflect important aspects of outcome that matter most to surviving patients
  2. Composites of survival and good function or quality of life may be ideal outcome
  3. Often required for health economics analyses
  4. Data collection and analysis should take into account patients who are unable to respond

No measures were identified that had been specifically designed to assess quality of life after surgery. However, there are a number of established and well validated tools that allow for the evaluation of quality of life in various levels of detail. The design of some recent perioperative medicine trials has utilised survival with good function or good quality of life as an outcome. Examples include death or inability to walk following proximal femoral fracture repair and survival with good quality of life.11,12 EQ-5D provides a simple evaluation that is also useful for health economics analyses. The WHO Disability Assessment Schedule is useful where a simple measure of quality of life is all that is required, whilst the Short-form 36 (SF-36) provides a much more detailed evaluation of quality of life but is more time-consuming to perform and may be best used where quality of life is the central focus of the research.13 When collecting quality of life data in surgical populations with mortality or cognitive decline, it is important to develop systems to exclude bias associated with nonresponders. This may involve inviting a surrogate to provide this information on the patient's behalf, for example a family member. During the final review process by opinion leaders, the PQRS scale and the SF-8 were both identified as potentially useful measures that have been incorporated into the standards document.14,15

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Healthcare resource use

Most reports of clinical effectiveness research in perioperative medicine describe one or more measures of healthcare resource use. The most common examples include duration of hospital and critical care stay. These measures are important for health economics evaluations but are not reliable surrogate markers of clinical outcome because they are affected by hospital and healthcare policy as well as by clinician behaviour. The measures of healthcare resource use are listed below:

  1. Affected by how healthcare systems function
  2. Poor surrogate for complications or other patient-centred outcomes
  3. Important in health economics analyses

There may be exceptions in which measures of resource use can be argued to provide an indication of clinical need rather than physician discretion in treatment or hospital policy, an example being tracheal intubation for respiratory failure. During the final review process by opinion leaders, hospital readmission was also suggested as a suitable measure of healthcare resource use.

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Duration of follow-up

For adverse events, 30 days is recommended as the most appropriate follow-up period, although some composite outcomes may be reported on a prespecified postoperative day. However, mortality at 30 days does not provide an adequate measure of the clinical effectiveness of a treatment designed to improve patient-centred outcomes. Many patients who develop severe complications may survive to 30 days only to die in the weeks that follow.4,5 In addition, the event rate for 30-day mortality may be too low, creating methodological problems in terms of sample size. The group agreed that most patients undergo surgery in the hope of long-term survival with a good functional outcome, and therefore recommended that all trials should report mortality at a minimum of 90 days after surgery and ideally 1 year, although short-term mortality may remain relevant as a treatment safety outcome.

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Discussion

This work has provided the first standards for use of outcome measures in clinical effectiveness research in perioperative medicine and may also be of use in clinical audit. By providing guidance on the choice of outcome measures and the optimal time frame for use, the standards will enable researchers to develop high-quality research methodologies that meet an internationally agreed benchmark. The standards are designed to complement rather than replace existing definitions, many of which have been incorporated into this report. It is also recognised that adaptations may be required for specific research questions.

The adverse events identified do not represent a comprehensive list of all that may occur. Instead, we have focused on those considered most important in a mixed population of surgical patients and relevant to perioperative care as opposed to specific technical complications of surgery or anaesthesia. We have not included some adverse events with definitions that are highly subjective (e.g. pleural effusion). In several cases, the group drew a distinction between physiological derangement and discrete adverse events (e.g. atelectasis). However, some composite outcomes incorporate such events (e.g. postoperative pulmonary complications). The group agreed that composite outcomes should be included because their use is generally confined to observational or interventional research relating to an individual organ system. Many outcome measures were originally developed outside the perioperative context, for example acute kidney injury. The advantage of these definitions is that they have been developed by experts in the relevant field. However, some are less suitable for use as outcome measures in the perioperative period. A particular example is venous thromboembolism (deep vein thrombosis and pulmonary embolism); these adverse events can be detected reliably only through screening of all patients and this may prove impractical where the outcome is not a central focus of the research. Some screening tools are not appropriate for use following surgery, for example D-dimer measurement.16 The physiological changes that follow surgery and anaesthesia, including the systemic inflammatory response, may result in partial compliance with the criteria for a number of outcome measures, for example infection. It is of particular importance to grade the severity of complications to minimise this problem. The taskforce group and several opinion leaders noted that the definition of postoperative myocardial infarction remains a subject of debate.

We are not aware of any previous standards that meet the particular need addressed by this document. However, we recognise that this first endeavour has both strengths and limitations. Our literature search included manuscripts in English, German and French. However, reports relating to perioperative medicine are not easily identified through a literature search because there is no standard approach to the use of MeSH terms by authors of perioperative medicine research articles. There is an argument to create a new MeSH heading of ‘perioperative medicine’ to ensure that trials in this field are more easily identified. To address this limitation, we contacted key opinion leaders in perioperative medicine research worldwide to suggest articles that we should consider. This approach did allow us to identify additional relevant outcome measures, but it remains possible that we did not identify relevant information from outside our research community. The group considered the collated evidence and discussed definitions on an individual basis. However, we did not adopt a formal voting system or a Delphi consensus process. In seeking the views of international opinion leaders, we have sought to produce a document that will be widely accepted and adopted. This collaborative approach is intended to promote the wider use of valid outcome measures rather than to prioritise and rank the alternative measures available. This document will also promote discussion and define the context for further methodology research to improve outcome measure definitions for perioperative medicine research.

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Conclusion

We have provided standards for the use of outcome measures in clinical effectiveness research in perioperative medicine. This will enable researchers to develop high-quality research methodologies that meet an internationally agreed standard. Further work may improve the definitions provided and broaden the scope to include risk adjustment scores and tackle the diagnostic challenges of some adverse events that occur after surgery.

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Acknowledgements relating to this article

Assistance with the Guidelines: we are grateful to the following opinion leaders who commented on the draft manuscript; Bruce Biccard, Durban, South Africa; Wolfgang Buhre, Maastricht, Netherlands; Jaume Canet, Barcelona, Spain; Matthew Chan, Hong Kong, China; Pierre-Alain Clavien, Zurich, Switzerland; Kees Dejong, Maastricht, Netherlands; Giorgio Della Rocca, Udine, Italy; Nicolas Demartines, Lausanne, Switzerland; Omar Faiz, London, UK; Emmanuel Futier, Clermont-Ferrand, France; Mike Grocott, Southampton, UK; Robert Hahn, Stockholm, Sweden; Peter Holt, London, UK; Mikhail Kirov, Arkhangelsk, Russia; Olle Ljungqvist, Örebro, Sweden; Suzanna Lobo, São José do Rio Preto, Brazil; Donald Low, Seattle, USA; Ramani Moonesinghe, London, UK; Paul Myles, Melbourne, Australia; Monty Mythen, London, UK; Lars Rasmussen, Copenhagen, Denmark; Toby Richards, London, UK; Reitze Rodseth, Pietermaritzburg, South Africa; Colin Royse, Melbourne, Australia; Andrew Shaw, Nashville, USA; Duminda Wijeysundera, Toronto, Canada; Hannah Wunsch, New York, USA.

Financial support and sponsorship: support and funding were provided by the European Society of Anaesthesiology (ESA) and the European Society of Intensive Care Medicine (ESICM).

Conflicts of interest: all authors received support and funding by ESA and ESICM in planning and designing this article.

ACS-NSQIP American College of Surgeons’ National Surgical Quality Improvement Program

AKI Acute kidney injury

AKIN Acute kidney injury network

ARDS Acute respiratory distress syndrome

CAM-ICU Confusion assessment method for the intensive care unit

CDC Centers for Disease Control

CPAP Continuous Positive Airways Pressure

CT Computed Tomography

DVT Deep Vein Thrombosis

ECG Electrocardiogram

eGFR Estimated glomerular filtration rate

EQ-5D EuroQol: A standardised instrument for use as a measure of health outcome

ESA European Society of Anaesthesiology

ESICM European Society of Intensive Care Medicine

HRQL Health Related Quality of Life

KIDGO Kidney disease improving global outcomes guidelines

MACCE Major adverse cardiac and cerebrovascular events

MACE Major adverse cardiac events

MINS Myocardial injury after non-cardiac surgery

MRI Magnetic resonance imaging

PE Pulmonary embolism

PEEP Positive end-expiratory pressure

POMS Postoperative morbidity survey

PQRS Postoperative quality recovery scale

QoR-15 Quality of recovery, a 15-item questionnaire

QoR-40 Quality of recovery, a 40-item questionnaire

SF-8 Short form 8

SF-12 Short-form 12

SF-36 Short-form 36

T92 Toronto 92 severity grading system

TnT Troponin T

WHO World Health Organisation

WHODAS 2.0 World Health Organisation Disability Assessment

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Appendix 1. Abbreviations Appendix 2. Detailed definitions

1. Single organ outcome measures

1.1 Acute Kidney Injury (AKI)

Definition. Kidney Disease Improving Global Outcomes (KDIGO) guidelines17 (Table A2.1.1).

Table A2.1.1 Kidney Disease Improving Global Outcomes Guidelines (KIDGO)

Table

Table

Guidance. Baseline serum creatinine concentration must be measured before surgery. When preoperative data are unavailable, an estimated value can be used if there is no evidence of chronic kidney disease.

Severity grading. Integrated in the above definition.

Alternatives. RIFLE grading of acute kidney injury18 or AKIN staging for acute kidney injury.19

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1.2 Acute Respiratory Distress Syndrome (ARDS)

Definition. The Berlin definition of Respiratory Distress Syndrome.20

  • Timing. Within one week of a known clinical insult or new or worsening respiratory symptoms
  • and
  • Chest imaging.a Bilateral opacities not fully explained by effusions, lobar/lung collapse or nodules
  • and
  • Origin of oedema. Respiratory failure not fully explained by cardiac failure or fluid overload. Need objective assessment (e.g. echocardiography) to exclude hydrostatic oedema if no risk factor present
  • and
    • Mild. PaO2:FIO2 between 26.7 and 40.0 kPa (200–300 mmHg) with PEEP or CPAP ≥5 cmH2O.c
    • Moderate. PaO2:FIO2 between 13.3 and 26.6 kPa (100–200 mmHg) with PEEP ≥5 cmH2O
    • Severe. PaO2:FIO2 ≤ 13.3 kPa (100 mmHg) with PEEP ≥5 cmH2O

aChest radiograph or computed tomography scan.

bIf altitude is higher than 1000 m, a correction factor should be calculated (PaO2:FiO2 x [barometric pressure/101 kPa]).

cThis may be delivered non-invasively in the mild acute respiratory distress syndrome group.

Severity grading. Integrated in the above definition.

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1.3 Anastomotic breakdown

Definition. Leak of luminal contents from a surgical connection between two hollow viscera. The luminal contents may emerge either through the wound or at the drain site, or they may collect near the anastomosis, causing fever, abscess, septicaemia, metabolic disturbance and/or multiple organ failure. The escape of luminal contents from the site of the anastomosis into an adjacent localised area, detected by imaging, in the absence of clinical symptoms and signs should be recorded as a subclinical leak.21

Guidance. There is a lack of consensus regarding the definition of anastomotic leakage.22 It is important to use this definition together with a grading system to measure the impact of the anastomotic breakdown on patient outcome.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.4 Arrhythmia

Definition. Arrhythmia is defined as electrocardiograph (ECG) evidence of cardiac rhythm disturbance.

Guidance. The use of severity grading for arrhythmia is of particular importance. Variations in clinical treatment may introduce bias if this is used as the sole index of severity.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.5 Cardiac arrest

Definition. The International Liaison Committee on Resuscitation defines cardiac arrest as the cessation of cardiac mechanical activity, as confirmed by the absence of signs of circulation.23

Guidance. ECG changes may corroborate the presence of cardiac arrest.

Severity. Binary outcome.

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1.6 Cardiogenic pulmonary oedema

Definition. Cardiogenic pulmonary oedema is defined as evidence of fluid accumulation in the alveoli due to poor cardiac function.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.7 Deep vein thrombosis (DVT)

Definition. A new blood clot or thrombus within the venous system.

Guidance. We did not identify any specific definition for DVT in the literature. Treatment is often determined by clinical risk of DVT rather than a definitive diagnosis. Systematic screening is required in trials in which DVT is an important outcome measure. Appropriate diagnostic tests include ultrasound, venography, CT or MRI venography. Plasma D-dimer measurement is not recommended as a diagnostic test in the first three weeks following surgery.16

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.8 Delirium

Definition. Delirium may be identified using the Intensive Care Delirium Screening Checklist.24 Patients are first evaluated for an altered level of consciousness. Those with a response to mild or moderate stimulation, an exaggerated response to stimulation or normal wakefulness are evaluated fully. Patients receive one point for each of the following criteria: inattention, disorientation, hallucination-delusion-psychosis, psychomotor agitation or retardation, inappropriate speech or mood, sleep/wake cycle disturbance or symptom fluctuation. Delirium is diagnosed with a score ≥4.

Guidance. Delirium screening tools have most widely been validated in the critical care setting and are not routinely used in a ward setting. Pain and underlying causes or agitation should be treated before applying the test.

Severity grading. Integrated into definition.

Alternatives. Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).25

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1.9 Gastrointestinal bleed

Definition. Gastrointestinal bleed is defined as unambiguous clinical or endoscopic evidence of blood in the gastrointestinal tract. Upper gastrointestinal bleeding (or haemorrhage) is that originating proximal to the ligament of Treitz, in practice from the oesophagus, stomach and duodenum. Lower gastrointestinal bleeding is that originating from the small bowel or colon.26

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.10 Infection, source uncertain

Definition. The CDC defines infection, source uncertain as one where there is strong clinical suspicion of infection but the source has not been confirmed because clinical information suggests more than one possible site, meeting two or more of the following criteria:27 core temperature < 36°C or >38°C; white cell count >12 × 109 l−1 or < 4 × 109 l−1, respiratory rate >20 breaths per minute or PaCO2 < 4.7 kPa (35 mmHg); pulse rate >90 beats per minute

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.11 Laboratory confirmed bloodstream infection

Definition. The CDC defines laboratory confirmed bloodstream infection as one which meets at least one of the following criteria which should not be related to infection at another site:27

  1. Patient has a recognised pathogen cultured from one or more blood cultures and the organism cultured from blood is not related to an infection at another site
  2. Patient has at least one of the following signs or symptoms: fever >38°C, chills or hypotension, and at least one of the following:
    1. Common skin contaminant cultured from two or more blood cultures drawn on separate occasions
    2. Common skin contaminant cultured from at least one blood culture from a patient with an intravascular line, and the physician institutes appropriate antimicrobial therapy
    3. Positive blood antigen test.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.12 Myocardial infarction

Definition. Increase in serum cardiac biomarker values (preferably cardiac troponin) with at least one value above the 99th percentile upper reference limit and at least one of the following criteria:10 symptoms of ischaemia; new or presumed new significant ST segment or T wave ECG changes or new left bundle branch block; development of pathological Q waves on ECG; radiological or echocardiographic evidence of new loss of viable myocardium or new regional wall motion abnormality; identification of an intracoronary thrombus at angiography or autopsy.

Guidance. The definition of postoperative myocardial infarction remains under debate. Investigators should consider using either the definition of myocardial injury after non-cardiac surgery (MINS) or myocardial infarction, or both.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.13 Myocardial injury after non-cardiac surgery (MINS)

Definition. Peak troponin T (TnT) ≥0.03 ng ml−1 judged due to myocardial ischaemia (i.e. no evidence of a non-ischaemic aetiology causing the TnT elevation). This criterion excludes troponin abnormalities related to other causes e.g. sepsis.9

Guidance. The definition of postoperative myocardial infarction remains under debate. Investigators should consider using either the definition of MINS or myocardial infarction, or both. In evaluating MINS, troponin concentration should be measured daily for the first three days after surgery. Patients who fulfil the criterion do not necessarily present with an ischaemic feature but should be followed up with ECG recordings.

Severity. Binary outcome.

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1.14 Pneumonia

Definition. The CDC defines pneumonia as follows:27

Two or more serial chest radiographs with at least one of the following (one radiograph is sufficient for patients with no underlying pulmonary or cardiac disease):

  1. new or progressive and persistent infiltrates
  2. consolidation
  3. cavitation;

at least one of the following

  1. fever (>38°C) with no other recognised cause
  2. leucopaenia (white cell count < 4 × 109 l−1) or leucocytosis (white cell count >12 × 109 l−1)
  3. for adults >70 years old, altered mental status with no other recognised cause;

and at least two of the following

  1. new onset of purulent sputum or change in character of sputum, or increased respiratory secretions, or increased suctioning requirements
  2. new onset or worsening cough, or dyspnoea, or tachypnoea
  3. râles or bronchial breath sounds
  4. worsening gas exchange (hypoxaemia, increased oxygen requirement, increased ventilator demand).

Guidance. The definition may also be used to identify ventilator-associated pneumonia.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.15 Paralytic ileus

Definition. Failure to tolerate solid food or defecate for three or more days after surgery.28

Guidance. There is a lack of agreement about the definition of paralytic ileus in the literature.29

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

Alternative. Gastrointestinal failure score.30

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1.16 Postoperative haemorrhage

Definition. The ACS-NSQIP defines postoperative haemorrhage as blood loss within 72 h after the start of surgery which would normally result in transfusion of blood.31

Severity grading

Mild. Not applicable

Moderate. Complication which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.17 Pulmonary embolism (PE)

Definition. A new blood clot or thrombus within the pulmonary arterial system.

Guidance. We did not identify a suitable definition for postoperative PE in the literature. Treatment is often determined by clinical risk of PE rather than a definitive diagnosis. Systematic screening is required in trials where PE is an important outcome measure. Appropriate diagnostic tests include scintigraphy and CT angiography. Plasma D-dimer measurement is not recommended as a diagnostic test in the first three weeks following surgery.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.18 Stroke

Definition. The ACS-NSQIP defines stroke as an embolic, thrombotic or haemorrhagic cerebral event with persistent residual motor, sensory or cognitive dysfunction (e.g. hemiplegia, hemiparesis, aphasia, sensory deficit, impaired memory).31

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.19 Surgical site infection (superficial)

Definition. The CDC defines a superficial incisional surgical site infection as one which meets the following criteria.27

  1. Infection occurs within 30 days after surgery and
  2. Involves only skin and subcutaneous tissue of the incision and
  3. The patient has at least one of the following:
    1. purulent drainage from the superficial incision
    2. organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial incision
    3. at least one of the following symptoms or signs of infection: pain or tenderness, localised swelling, redness or heat, and superficial incision is deliberately opened by surgeon and is culture positive or not cultured. A culture-negative finding does not meet this criterion.
    4. diagnosis of an incisional surgical site infection by a surgeon or attending physician.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.20 Surgical site infection (deep)

Definition. The CDC defines a deep incisional surgical site infection as one which meets the following criteria.27

  1. Infection occurs within 30 days after surgery if no implant is left in place or 1 year if implant is in place.
  2. Involves deep soft tissues (e.g. fascial and muscle layers) of the incision.
  3. The patient has at least one of the following:
    1. purulent drainage from the deep incision but not from the organ/space component of the surgical site
    2. a deep incision spontaneously dehisces or is deliberately opened by a surgeon and is culture-positive or not cultured when the patient has at least one of the following symptoms or signs: fever (>38°C), or localised pain or tenderness. A culture-negative finding does not meet this criterion.
    3. an abscess or other evidence of infection involving the deep incision is found on direct examination, during surgery, or by histopathological or radiological examination
    4. diagnosis of an incisional surgical site infection by a surgeon or attending physician.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.21 Surgical site infection (organ/space)

Definition. The CDC defines an organ/space surgical site infection as one which involves any part of the body excluding the fascia or muscle layers and meets the following criteria.27

  1. Infection occurs within 30 days after surgery.
  2. The infection appears to be related to the surgical procedure and involves any part of the body, excluding the skin incision, fascia or muscle layers opened or manipulated during the operative procedure.
  3. The patient has at least one of the following:
    1. purulent drainage from a drain that is placed through a stab wound into the organ/space
    2. organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space
    3. an abscess or other evidence of infection involving the organ/space that is found on direct examination, during reoperation or by histopathological or radiological examination
    4. diagnosis of an organ/space surgical site infection by a surgeon or attending physician.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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1.22 Urinary tract infection

Definition. A simplified version of the CDC recommendations defines a urinary tract infection as follows: a positive urine culture of ≥105 colony forming units ml−1 with no more than two species of micro-organisms, and with at least one of the following symptoms or signs: fever (>38°C), urgency, frequency, dysuria, suprapubic tenderness, costovertebral angle pain or tenderness with no other recognised cause.27

Guidance. Each of these criteria should be identified within a 24-h period.

Severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

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2. Composite outcome measures

2.1 Major Adverse Cardiac Events (MACE)

Definition. Major adverse cardiac and cerebrovascular events definition. MACE is defined as one or more of the following.32

  • Non-fatal cardiac arrest. An absence of cardiac rhythm or presence of chaotic rhythm requiring any component of basic or advanced cardiac life support.
  • Acute myocardial infarction. Increase and gradual decrease in troponin level or a faster increase and decrease of creatine kinase isoenzyme as markers of myocardial necrosis in the company of at least one of the following: ischaemic symptoms, abnormal Q waves on the ECG, ST segment elevation or depression; coronary artery intervention (e.g. coronary angioplasty) or a typical decrease in an elevated troponin level detected at its peak after surgery in a patient without a documented alternative explanation for the troponin elevation.
  • Congestive heart failure. New in-hospital signs or symptoms of dyspnoea or fatigue, orthopnoea, paroxysmal nocturnal dyspnoea, increased jugular venous pressure, pulmonary râles on physical examination, cardiomegaly or pulmonary vascular engorgement.
  • New cardiac arrhythmia. ECG evidence of atrial flutter, atrial fibrillation, or second- or third-degree atrioventricular conduction block.
  • Angina. Dull diffuse substernal chest discomfort precipitated by exertion or emotion and relieved by rest or glyceryl trinitrate.

Guidance. Some investigators use only cardiac complications as a composite of Major Adverse Cardiac Events (MACE) whilst others add stroke to create a composite of Major Adverse Cardiac and Cerebrovascular Events (MACCE).

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2.2 Postoperative pulmonary complications

Definition: Definitions of postoperative pulmonary complications are shown in Table A2.2.2.33

Table A2.2.2 Postoperative pulmonary complications

Table

Table

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2.3 PostOperative Morbidity Survey (POMS)

Definition. POMS is defined as positive where the criteria for any one of the 20 items shown in Table A2.2.3 are met (clarification provided for some specific situations).34,35

Table A2.2.3 Items of the PostOperative Morbidity Survey (POMS)

Table

Table

Guidance. POMS consists of 20 items that address ten domains of postoperative morbidity. For each domain, either the presence or absence of morbidity is recorded on the basis of objective criteria. POMS does not produce a score for morbidity but instead the results are used to report the presence of morbidity overall or by categories. Completion of POMS is based on clinical information from the 24 h preceding the time of POMS assessment. For the morbidity to be present, it must have developed following surgery and have the capacity to prevent hospital discharge. Any pre-existing morbidities should be recorded as absent. POMS may be used on days 3, 7 and 15 after surgery.

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2.4 Quality of Recovery (QoR)

Definition. QoR-15 describes items on a visual analogue scale from 0 to 10, as shown in Table A2.2.4.36

Table A2.2.4 Quality of recovery items

Table

Table

Guidance. Patients should complete the QoR-15 questionnaire before surgery to provide baseline data. The questionnaire is then repeated 24 h after surgery, at which time the patient also rates overall postoperative recovery using a 100-mm visual analogue scale marked from ‘poor recovery’ to ‘excellent recovery’.

Alternative. QoR-40 is a 40-item questionnaire that provides a global score and separate scores across five dimensions: patient support, comfort, emotions, physical independence and pain.37,38

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3. Grading of complications

3.1 Pragmatic severity grading

Mild. Results in only temporary harm and would not usually require specific clinical treatment.

Moderate. More serious complication but one which does not usually result in permanent harm or functional limitation. Usually requires clinical treatment.

Severe. Results in significant prolongation of hospital stay and/or permanent functional limitation or death. Almost always requires clinical treatment.

Alternatives. We developed a simple grading system which is recommended for individual complications described above. This is suitable for very pragmatic trials, in particular international trials. The Clavien-Dindo grading system is a widely used and valid alternative.

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3.2 Clavien-Dindo grading of complications

Definition. Classification of surgical complications as shown in Table A2.3.2.8

Table A2.3.2 Clavien-Dindo grading of complications

Table

Table

Alternative. The Toronto 92 Severity Grading system (T92), the Accordion classification and the revised Accordion classification.39,40

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4. Health-related quality of life (HRQL)

Definition. HRQL is a broad construct, referring to ‘the physical, psychological and social domains of health, seen as distinct areas that are influenced by a person's experiences, beliefs, expectations and perceptions’.41 The assessment of HRQL is an essential element of healthcare evaluation. Generic or specific instruments can be used to measure HRQL: generic HRQL instruments are designed to be applicable across a wide range of populations and interventions; specific HRQL measures are designed to be relevant to particular interventions or in certain subpopulations (e.g. individuals with rheumatoid arthritis).

Guidance. See Table A2.4. EQ-5D (various versions available) is recommended as a simple and effective tool to assess HRQL and also provides important data for health economics analyses. The Short-Forms 8, 12 and 36 and the World Health Organisation Disability Assessment Schedule are also widely used and valid options depending on the specific needs of the research.14,42–44 The Postoperative Quality Recovery Scale (PQRS) was designed specifically to evaluate and track multiple domains of recovery from surgery and anaesthesia from the time of surgery until several months into the postoperative period.15

Table A2.4 Health-related quality of life assessment tools

Table

Table

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References

1. Weiser TG, Regenbogen SE, Thompson KD, et al. An estimation of the global volume of surgery: a modelling strategy based on available data. Lancet 2008; 372:139–144.
2. Pearse RM, Moreno RP, Bauer P, et al. Mortality after surgery in Europe: a 7 day cohort study. Lancet 2012; 380:1059–1065.
3. Findlay G, Goodwin A, Protopappa K, et al. Knowing the risk; a review of the peri-operative care of surgical patients. London: National Confidential Enquiry into Patient Outcome and Death; 2011.
4. Khuri SF, Henderson WG, DePalma RG, et al. Determinants of long-term survival after major surgery and the adverse effect of postoperative complications. Ann Surg 2005; 242:326–341.
5. Jencks SF, Williams MV, Coleman EA. Rehospitalizations among patients in the Medicare fee-for-service program. N Engl J Med 2009; 360:1418–1428.
6. Head J, Ferrie JE, Alexanderson K, et al. Diagnosis-specific sickness absence as a predictor of mortality: the Whitehall II prospective cohort study. BMJ 2008; 337:a1469.
7. Ghaferi AA, Birkmeyer JD, Dimick JB. Variation in hospital mortality associated with inpatient surgery. N Engl J Med 2009; 361:1368–1375.
8. Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240:205–213.
9. Botto F, Alonso-Coello P, Chan MT, et al. Myocardial injury after noncardiac surgery: a large, international, prospective cohort study establishing diagnostic criteria, characteristics, predictors, and 30-day outcomes. Anesthesiology 2014; 120:564–578.
10. Thygesen K, Alpert JS, Jaffe AS, et al. Third universal definition of myocardial infarction. Eur Heart J 2012; 33:2551–2567.
11. Carson JL, Terrin ML, Noveck H, et al. Liberal or restrictive transfusion in high-risk patients after hip surgery. N Engl J Med 2011; 365:2453–2462.
12. Myles PS. REstrictive versus LIbEral Fluid therapy in major abdominal surgery: RELIEF study. http://clinicaltrials.gov/show/NCT01424150 [Accessed 28 November 2013].
13. Bergman S, Feldman LS, Barkun JS. Evaluating surgical outcomes. Surg Clin North Am 2006; 86:129–149.
14. Valles J, Guilera M, Briones Z, et al. Validity of the Spanish 8-item short-form generic health-related quality-of-life questionnaire in surgical patients: a population-based study. Anesthesiology 2010; 112:1164–1174.
15. Royse CF, Newman S, Chung F, et al. Development and feasibility of a scale to assess postoperative recovery: the postoperative quality recovery scale. Anesthesiology 2010; 113:892–905.
16. Dindo D, Breitenstein S, Hahnloser D, et al. Kinetics of D-dimer after general surgery. Blood Coagul Fibrinolysis 2009; 20:347–352.
17. Khwaja A. KDIGO clinical practice guidelines for acute kidney injury. Nephron Clin Pract 2012; 120:179–184.
18. Borthwick E, Ferguson A. Perioperative acute kidney injury: risk factors, recognition, management, and outcomes. BMJ 2010; 341:c3365.
19. Mehta RL, Kellum JA, Shah SV, et al. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care 2007; 11:R31.
20. Force ADT, Ranieri VM, Rubenfeld GD, et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA 2012; 307:2526–2533.
21. Peel AL, Taylor EW. Proposed definitions for the audit of postoperative infection: a discussion paper. Surgical Infection Study Group. Ann R Coll Surg Engl 1991; 73:385–388.
22. Bruce J, Krukowski ZH, Al-Khairy G, et al. Systematic review of the definition and measurement of anastomotic leak after gastrointestinal surgery. Br J Surg 2001; 88:1157–1168.
23. Jacobs I, Nadkarni V, Bahr J, et al. Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries: a statement for healthcare professionals from a task force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian Resuscitation Council, New Zealand Resuscitation Council, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Councils of Southern Africa). Circulation 2004; 110:3385–3397.
24. Bergeron N, Dubois MJ, Dumont M, et al. Intensive Care Delirium Screening Checklist: evaluation of a new screening tool. Intensive Care Med 2001; 27:859–864.
25. Ely EW, Inouye SK, Bernard GR, et al. Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA 2001; 286:2703–2710.
26. Scottish Intercollegiate Guidelines Network. Management of acute upper and lower gastrointestinal bleeding, Guideline No. 105. Edinburgh: Scottish Intercollegiate Guidelines Network; 2008. http://www.sign.ac.uk/guidelines/fulltext/105/index.html. [Accessed 23 June 2014]
27. Horan TC, Andrus M, Dudeck MA. CDC/NHSN surveillance definition of healthcare-associated infection and criteria for specific types of infections in the acute care setting. Am J Infect Control 2008; 36:309–332.
28. van Bree SH, Bemelman WA, Hollmann MW, et al. Identification of clinical outcome measures for recovery of gastrointestinal motility in postoperative ileus. Ann Surg 2014; 259:708–714.
29. Ramirez JA, McIntosh AG, Strehlow R, et al. Definition, incidence, risk factors, and prevention of paralytic ileus following radical cystectomy: a systematic review. Eur Urol 2013; 64:588–597.
30. Reintam A, Parm P, Kitus R, et al. Gastrointestinal failure score in critically ill patients: a prospective observational study. Crit Care 2008; 12:R90.
31. American College of Surgeons. National Surgical Quality Improvement Program. Chicago, IL: American College of Surgeons; 2014. http://acsnsqip.org. [Accessed 23 June 2014]
32. Sabate S, Mases A, Guilera N, et al. Incidence and predictors of major perioperative adverse cardiac and cerebrovascular events in noncardiac surgery. Br J Anaesth 2011; 107:879–890.
33. Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology 2010; 113:1338–1350.
34. Grocott MP, Browne JP, Van der Meulen J, et al. The Postoperative Morbidity Survey was validated and used to describe morbidity after major surgery. J Clin Epidemiol 2007; 60:919–928.
35. Bennett-Guerrero E, Welsby I, Dunn TJ, et al. The use of a postoperative morbidity survey to evaluate patients with prolonged hospitalization after routine, moderate-risk, elective surgery. Anesth Analg 1999; 89:514–519.
36. Stark PA, Myles PS, Burke JA. Development and psychometric evaluation of a postoperative quality of recovery score: the QoR-15. Anesthesiology 2013; 118:1332–1340.
37. Gornall BF, Myles PS, Smith CL, et al. Measurement of quality of recovery using the QoR-40: a quantitative systematic review. Br J Anaesth 2013; 111:161–169.
38. Myles PS, Weitkamp B, Jones K, et al. Validity and reliability of a postoperative quality of recovery score: the QoR-40. Br J Anaesth 2000; 84:11–15.
39. Porembka MR, Hall BL, Hirbe M, Strasberg SM. Quantitative weighting of postoperative complications based on the Accordion severity grading system: demonstration of potential impact using the American College of Surgeons National Surgical Quality Improvement Program. J Am Coll Surg 2010; 210:286–298.
40. Strasberg SM, Linehan DC, Hawkins WG. The Accordion severity grading system of surgical complications. Ann Surg 2009; 250:177–186.
41. Testa MA, Simonson DC. Assesment of quality-of-life outcomes. N Engl J Med 1996; 334:835–840.
42. Ware JE Jr. SF-36 health survey update. Spine 2000; 25:3130–3139.
43. Ware J Jr, Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996; 34:220–233.
44. U[Combining Diaeresis]stu[Combining Diaeresis]n TB. Measuring health and disability: manual for WHO Disability Assessment Schedule WHODAS 2.0. Geneva: World Health Organization; 2010.
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