Description of the condition
Undergoing surgery is a stressful experience. Many patients are understandably anxious about unfamiliar experiences, such as: anaesthesia; the need to stay away from home; possible pain and discomfort; and the risk of complications. Studies of preoperative patients have found that almost a quarter of patients experience high levels of anxiety (Caumo 2001; Roomruangwong 2012), measured on recognised anxiety questionnaires, such as the State Trait Anxiety Index or the Hospital Anxiety and Depression Scale. As well as the distress experienced by patients, anxiety may increase their experience of pain, and impair their coping skills and ability to follow instructions. There is evidence that high levels of anxiety are associated with increased risk of complications and adverse outcomes (Rosenberger 2006; Williams 2013). Reducing anxiety around the time of surgery is an important goal for compassionate, high-quality patient care.
Description of the intervention and how it might work
Educational interventions aim to reduce perioperative anxiety by giving the patient information about what will happen to them when they are in hospital. The content of educational interventions falls into three categories: procedural information about their condition, the planned procedure, postoperative care and arrangements for discharge; sensory information about what the patient is likely to experience; and behavioural/coping information such as suggested preparation and postoperative exercises (Guo 2012). The link between increased knowledge and reduced anxiety has been described using various theoretical models such as reducing unfamiliarity (Spalding 2003) and increasing self-efficacy - empowerment (Heikkinen 2008). Psychological interventions, such as relaxation techniques, which are aimed at enhancing an exploration of a patient’s attitudes and feelings directly (Hathaway 1986) will not be included in this review.
Format of delivery and timing
Information needs to be presented in a way which is clear and easy to understand but also which aids information retention. Preoperative education is often delivered verbally by medical or nursing staff but data suggest this verbal information is poorly retained, with only 25% of preoperative information spontaneously recalled (Sandberg 2012). This is often supplemented by written information such as pamphlets or booklets. Cochrane reviews have shown that written information in addition to verbal information improves knowledge about medications and advice on discharge from hospital (Johnson 2003; Nicolson 2009). Rapid technological change over the last ten years has increased the ways in which this information can be provided – including videos and DVDs, audio files or tapes and computer-guided learning via the internet. Other Cochrane and non-Cochrane reviews have considered the impact of multimedia delivery on health-related information with a range of comparison groups including none/usual care, verbal and written information (Ciciriello 2013; Jeste 2008). Investigating knowledge gain and skill acquisitions about medication use, Ciciriello 2013 demonstrated inconsistent benefit for multimedia format rather than usual care, written information or verbal information. Another narrative review was supportive of multimedia interventions to increase knowledge of illness management and treatment conditions but did not consider different comparison groups separately (Jeste 2008). A review focusing on knowledge retention after education supported the use of pamphlets and videos but the authors found no studies of the impact of computer-based material (Stern 2005).The issue of format needs to be addressed for interventions aimed at reducing perioperative anxiety.
The increase in day case or same-day admission surgery has reduced the time available for education within the hospital, making education before admission more important. Preoperative assessment visits are often used for education but the optimal timing of these visits in order to reduce perioperative anxiety is not known.
User perspective and variation
Educational programmes are often standardised in content and format, but people preparing for surgery will have a range of learning and coping styles which may affect their response to an intervention. Information that is helpful to some people may cause distress to others. Hathaway found a greater reduction of anxiety in people with higher baseline anxiety (Hathaway 1986) and other studies have looked at the influence of coping styles such as blunting/monitoring (Miller 1983; van Zuuren 2006). In addition to individual variability in the optimal content of an intervention, the acceptability of different formats is likely to vary enormously with age and educational background. People who have spent longer in education may be more accustomed to assimilating information through different media. Literacy levels and access to computers and the internet may limit the reach of written information and web-based resources (Bozionelos 2004; Wright 2009). There is a risk of some more vulnerable user groups being disadvantaged by the use of new formats. Neither individual nor cultural and international differences in the impact of different formats of educational interventions on perioperative anxiety have been considered in existing reviews.
Why it is important to do this review
There has been considerable interest in the effects of educational interventions on perioperative anxiety, with reviews and meta-analyses dating back to the 1980s (Devine 1983; Devine 1992; Hathaway 1986). These older reviews reported significant reductions in postoperative anxiety but had limitations including mixed patient populations, the inclusion of observational studies and the inclusion of psychological as well as educational content. More recent meta-analyses have been restricted to randomised controlled trials (RCTs). A Cochrane review of studies using a wider range of educational interventions in hip and knee replacement patients reported inconsistent findings, with anxiety reduced pre- but not post-operatively (McDonald 2004). Other reviews have found no clear effect of education on perioperative anxiety (Johansson 2005; Ronco 2012). An ongoing Cochrane review is assessing the effects of educational interventions on perioperative anxiety (Powell 2010) but this review is not considering different formats or timing of delivery.
One review of media-based interventions providing information about anaesthesia across all surgical disciplines found a small reduction in anxiety with uncertain clinical relevance, but the authors were unable to assess the impact of different formats of delivery or timing of education on anxiety, due to a lack of studies (Lee 2003; Lee 2005). In a time of rapid technological change it is important to review all available data and to consider the interventions' effects in different user groups.
To assess the effects of different formats or media of delivery and timing of preoperative educational interventions on the anxiety experienced by adult surgical patients before, during and after surgery. We will consider the effects of different formats and timing on other patient-reported outcomes including anxiety caused by the educational intervention, postoperative pain, knowledge, satisfaction with surgery and satisfaction with the educational intervention. We will also include data on service-delivery oriented outcomes such cancellation of surgery by patient, length of hospital stay and the cost of educational intervention.
A secondary objective is to investigate whether the preferred format or timing varies with individual or cultural characteristics including age, gender, educational level, baseline anxiety, coping style or type of surgery.
Criteria for considering studies for this review
Types of studies
We will consider all randomised controlled trials (RCTs) and quasi-randomised studies, as we anticipate that there may not be many properly randomised controlled trials looking at different intervention formats. Quasi-randomised trials are those in which randomisation is attempted but subject to potential manipulation, such as allocating participants by day of the week, date of birth, or sequence of entry into trial.
We will also include cluster-randomised studies in which groups of individuals rather than individuals are randomised. The groups or clusters may be formed by different hospitals or different surgeons.
Types of participants
We will include trials of people aged over 16 years undergoing elective surgery requiring general, spinal or epidural anaesthesia. Studies will be eligible for inclusion if the majority of the participants were aged over 16 years. Trials of people undergoing emergency surgery will not be included as the time and planning of any educational intervention will be limited. We are restricting the study population to those undergoing surgical operations requiring general, spinal or epidural anaesthesia as the process of anaesthesia itself is a source of anxiety and we wish to minimise the differences between studies.
Types of interventions
We will include studies delivering an educational intervention within three months before the planned surgery in one of the following formats:
- printed written material
- audio intervention or telephone call
- video/digital video disc (DVD)
- computer - web-based learning
- mobile-phone based - text message
The educational intervention should provide procedural or sensory information about the planned surgery, anaesthetic, the expected postoperative course and symptoms to be expected. The information delivered may also include behavioural instruction such as suggestions of physical exercises. This information may be in combination with other psychological interventions but we will not include any intervention offering only psychological skills training.
The main aim of the review is to consider how factual information is best delivered. Comparison groups should include the same core content but vary in:
1. Different or additional format of delivery used
Comparison groups may include face-to-face verbal information if the content is the same as in the intervention. We will exclude studies involving a usual care comparison group which provide no details of educational information given to the control group. We will include direct comparisons replacing different formats such as printed written material versus video, or website versus printed written material. We will also include studies in which one format has been used in addition to another format e.g. verbal instruction plus written material versus verbal instruction.
We will exclude studies in which the content of the intervention differs between the intervention and comparison groups. Differences could include different educational material or additional domains such as psychological training.
2. Timing of information prior to surgery
In studies of different timing the content and format of delivery must be the same in both groups but with different timing, e.g. 1 week versus 3 weeks before surgery.
Types of outcome measures
- Preoperative anxiety – measured between receiving the intervention and undergoing the surgery, using a validated or widely-used scale such as the State Trait Anxiety Index (STAI) or the Hospital Anxiety and Depression Scale (HADS).
- Postoperative anxiety – measured within first week after surgery, using scales as above.
- Preoperative anxiety due to information received, measured between receiving intervention and undergoing operation, using a validated or widely-used scale or one devised by the investigators.
- Postoperative pain - measured within the first week after surgery, using a visual analogue or other validated or widely-used scale.
- Length of stay in hospital.
- Cancellation of surgery by patient.
- Patient satisfaction with surgery or anaesthetic - measured within first week after operation, using a visual analogue or other validated or widely-used scale. We will accept locally-derived scales as well as appropriate validated measures such as the Pickering Patient Experience Questionnaire (PPE-15 - Jenkinson 2002) or the Heidelberg Peri-anaesthetic Questionnaire (Schiff 2008).
- Patient knowledge - measured at any time between receiving the intervention to the end of the first week after surgery, using a standard tool or locally-derived scale.
- Patient satisfaction with information - measured anytime between receiving the intervention to the end of the first week after surgery, using a visual analogue or other validated or widely-used scale.
- Cost of educational intervention.
- Long-term patient outcomes such as mental health conditions or anxiety on subsequent admissions.
If data allow, we will subdivide outcomes measured preoperatively into short-term (on admission to hospital, in anaesthetic preparation room), mid-term (up to one week before surgery), and long-term (more than one week before surgery). We will subdivide outcomes measured postoperatively into immediate (in recovery or post-anaesthesia care unit (PACU)), short-term (postoperative day (POD) 0 and1), and longer term (POD 2 to 7).
If a study reports data at multiple time points for a single outcome measure, we will select only one data point for each interval (short-, mid- or long-term) and will report this in the text.
Main outcomes for 'Summary of findings' table
We will report the outcomes listed at Primary outcomes in a 'Summary of findings' table.
Search methods for identification of studies
We will search the following electronic databases:
- The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, latest issue);
- MEDLINE (OvidSP) (1980 to present);
- EMBASE (OvidSP) (1980 to present);
- CINAHL (EBSCO) (1980 to present).
- PsycINFO (EBSCO) (1980 to present).
- ProQuest Dissertations & Theses (1980 to present)
We present the strategy for MEDLINE (OvidSP) in Appendix 1. We will tailor this strategy to other databases and report them in the review.
We will include any publication that reports study data, including abstracts, letters and articles. There will be no language restrictions but we will start searching from 1980 onwards. We do not think that earlier studies will be relevant due to restricted range of possible formats before 1980. Changes in health service delivery since 1980 mean that studies of different timing of interventions may not be applicable to the current healthcare situation with its emphasis on day surgery.
Searching other resources
We will also search trial registers such as www.clinicaltrials.gov, Current Controlled Trials (http://www.controlled-trials.com/) and the International Clinical Trials Registry Platform (http://apps.who.int/trialsearch/) for ongoing trials and recently completed studies. We will undertake forward citation tracking for key review articles and eligible articles identified from the electronic resources using IS Web of Science. We will also carry out backward citation tracking by checking the reference lists of key review articles and eligible articles. We will contact experts in the field and authors of included studies for advice as to other relevant studies.
Data collection and analysis
Selection of studies
Results of the searches will be collated and duplicates removed. The selection of eligible articles will take place in two stages.
All titles and abstracts will be screened by Amanda Nicholson (AN) and Sharon Lewis (SL) to remove studies that are very unlikely to be eligible. A pilot of 100 titles will be performed before all titles are reviewed in order to clarify criteria for discarding articles at this stage. If no abstract is available but the title may be relevant, we will obtain the full text of the article.
When all titles and abstracts have been screened, the full text of potentially-relevant studies will be assessed by two of the five investigators and recorded on the study eligibility form. A pilot of 10 papers will be read and then the investigators will meet to compare results and modify the form as required. All potentially-relevant papers will then be read and the two investigators will meet to compare results. Differences that cannot be resolved will be referred to Anna Lee (AL)/Andrew Smith (AS)/Chris Coldwell (CC). The numbers of papers retrieved and exclusions at each stage – with reasons for those reviewed in full text – will be recorded in a PRISMA flowchart (Liberati 2009). Reasons for excluding ineligible papers which are well-known or might appear to be eligible will be summarised in the Characteristics of Excluded Studies table.
Data extraction and management
Data will be extracted from eligible studies by two investigators working independently using a paper extraction form developed and piloted using the Cochrane Consumers and Communication Review Group Data Extraction Template (available at: http://cccrg.cochrane.org/author-resources). This form will be reviewed after data from the first three papers have been entered, and modified as required. If there are duplicate publications from the same study, we will create a composite dataset from all the eligible publications. Data to be extracted will include the following items:
- Study design: randomisation unit, cluster or patient; sequence generation or other randomisation method.
- Power calculations, baseline risk and effect size assumed.
- Patient group: age, demographic, type of surgical operation, baseline anxiety and other coping styles.
- Content of educational intervention (classified as procedural information, sensory information and/or behavioural information)
- Intervention group format and timing details such as duration of video, size of pamphlet, format and timing, training of any staff delivering interventions.
- Comparison group: format and timing of intervention, additional features.
- Co-interventions; other training given alongside educational intervention.
- Outcomes: outcomes and timepoints i. collected, ii. reported. For each outcome: definition, unit of measurement, timing.
- Subgroups measured and reported.
- Results: numbers of participants (and number of clusters) assigned to each intervention group. For each outcome: sample size, summary data for each intervention (two by two table where possible for dichotomous data, means and standard deviations for continuous data), P values and confidence intervals. If results are reported separately for subgroups, data will be extracted.
- Funding sources and declarations of interests.
All extracted data will be entered into RevMan (Review Manager 2012) by one review author, and will be checked for accuracy against the data extraction sheets by a second review author working independently. If relevant information or data are not available in the paper, we will contact the lead author to request the additional details. Disagreements will be resolved by discussion and if necessary by consultation with AL/AS. We will display the different formats, components and timepoints of the educational interventions within included studies in an additional table to allow an overview across studies.
Assessment of risk of bias in included studies
We will assess and report on the methodological risk of bias of included studies in accordance with the Cochrane Handbook (Higgins 2011) and the guidelines of the Cochrane Consumers and Communication Review Group (Ryan 2011), which recommend the explicit reporting of the following individual elements for RCTs: random sequence generation; allocation sequence concealment; blinding (participants, personnel); blinding (outcome assessment); completeness of outcome data, selective outcome reporting; and other sources of bias. We will consider blinding separately for different outcomes where appropriate (for example, blinding may have the potential to affect subjective versus objective outcome measures differently). We will judge each item as being at high, low or unclear risk of bias as set out in the criteria provided by Higgins 2011, and provide a quote from the study report and a justification for our judgement for each item in the 'Risk of bias' table.
Studies will be deemed to be at the highest risk of bias if they are scored as being at high or unclear risk of bias for either the sequence generation, allocation concealment or performance bias domains, based on growing empirical evidence that these factors are particularly important potential sources of bias (Higgins 2011). We will assess and report quasi-RCTs as being at a high risk of bias on the random sequence generation item of the 'Risk of bias' tool. For cluster-RCTs we will also assess and report on the risk of bias associated with an additional domain: selective recruitment of cluster participants. It is impossible for participants in these studies to be blinded to their allocation so when assessing performance bias we will pay particular attention to the content of the educational intervention and whether this was likely to have varied between different formats or timings. Studies where we felt there was a high risk that the content of intervention differed between formats will be considered to be at high risk of bias.
In all cases, two authors will independently assess the risk of bias of included studies, with any disagreements resolved by discussion to reach consensus. We will contact study authors for additional information about the included studies, or for clarification of the study methods as required. We will incorporate the results of the 'Risk of bias' assessment into the review through standard tables, and systematic narrative description and commentary about each of the elements, leading to an overall assessment of the risk of bias of included studies and a judgment about the internal validity of the review’s results.
Measures of treatment effect
Many of the outcomes for this review are continuous measures, measured on validated or widely-used scales such as the STAI for anxiety and visual analogue scales for pain or satisfaction. For continuous measures, we will analyse data based on the mean, standard deviation (SD) and number of people assessed for both the intervention and comparison groups to calculate mean difference (MD) and 95% confidence interval (CI). If the MD is reported without individual group data, we will use this to report the study results. For anxiety we will analyse studies which have used the same scale together initially. If more than one study measures the same outcome using different tools, we will calculate the standardised mean difference (SMD) and 95% CI using the inverse variance method in Review Manager 5 (Review Manager 2012). Costs of the educational intervention will be standardised to UK pounds in 2012 using the Cochrane ‘CCEMG – EPPI-Centre Cost Converter’ (v.1.2) and the standardised values used in the review (http://eppi.ioe.ac.uk/costconversion/default.aspx).
Some studies may use scales for anxiety or knowledge to create binary outcomes by classifying all participants above or below a certain level as high and/or low. For these and other dichotomous outcomes, such as cancellation, we will analyse data based on the number of events and the number of people assessed in the intervention and comparison groups. We will use these to calculate the risk ratio (RR) and 95% CI.
Unit of analysis issues
For any cluster trials included in the review, we will extract data directly from the publication only if the analysis used accounts for the cluster design with a method such as multi-level modelling or generalised estimating equations. If these adjustments are not made within the report, we will undertake approximate analyses by recalculating standard errors or sample sizes based on the design effect and intraclass correlation (ICC). We will obtain estimates of the ICC by contacting authors of included studies, or impute them using estimates from external sources. The resulting effect estimates and their standard errors will be analysed using the generic inverse variance method in RevMan. If it is not possible to obtain sufficient information to reanalyse the data we will report effect estimates and annotate with ‘unit-of-analysis error'.
Dealing with missing data
We will attempt to contact study authors to obtain missing data (participant, outcome, or summary data). For participant data, we will, where possible, conduct analysis on an intention-to-treat basis; otherwise data will be analysed as reported. We will report on the levels of loss to follow-up and assess this as a source of potential bias. If data allow, we will perform sensitivity analyses to compare the effect of complete case analysis, worst case scenario and last observation carried forward options on the results of individual studies and any meta-analyses.
Assessment of heterogeneity
For each comparison, for example video versus written material, we expect that the findings for any given outcome may differ between studies included in the review. This heterogeneity may be due to:
- Differences in the study population, including age, geographical and cultural context, literacy and familiarity with digital technology, baseline anxiety and coping style, type of operation
- Details of format, e.g. differences in duration of video, size of pamphlet
- Content of educational intervention (classified as procedural information, sensory information and behavioural information) and co-interventions
- Timing of intervention (for studies of different format)
- Format of intervention (for studies of different timing)
Where studies are considered similar enough on the above factors to allow pooling of data using meta-analysis, we will assess the degree of heterogeneity by visual inspection of forest plots and by examining the Chi
Where we detect substantial clinical, methodological or statistical heterogeneity across included studies we will not report pooled results from meta-analysis but will instead use a narrative approach to data synthesis. In this event we will attempt to explore possible clinical or methodological reasons for this variation by grouping studies that are similar in terms of study population and content and precise format details of the intervention features to explore differences in intervention effects.
Assessment of reporting biases
We will assess reporting bias qualitatively based on the characteristics of the included studies (e.g. if only small studies that indicate positive findings are identified for inclusion), and if information that we obtain from contacting experts and authors of studies suggests that there are relevant unpublished studies.
If we identify sufficient studies (at least 10) for inclusion in the review we will construct a funnel plot to investigate small study effects, which may indicate the presence of publication bias. We will formally test for funnel plot asymmetry, with the choice of test made based on advice in Higgins 2011. Heterogeneity between studies may lead to asymmetry and we will consider this possibility when reviewing results.
The comparisons included in the review will depend on the final included studies. For each format group considered, such as printed written material, we will not pool studies with different comparison groups. For example, studies in which written material was replaced by video will not be pooled with studies in which video was used in addition to written material. For each comparison, we will pool data only if the included trials are similar enough to ensure meaningful conclusions from a statistically pooled result. We will consider variation in participants, settings, intervention, comparison and outcome measures as well as statistical measures of heterogeneity described above (Assessment of heterogeneity). Due to the anticipated variability in the populations of included studies, we will use a random-effects model for meta-analysis.
If we do not have adequate comparable data to pool the data statistically using meta-analysis for some comparisons, we will present a narrative synthesis of results. We will present the major outcomes and results, organised by intervention/comparison categories.
Subgroup analysis and investigation of heterogeneity
The acceptability of different formats and delivery will vary across different groups of participants. The content of education material will vary between surgical procedures, and visual information or diagrams may be more important in some topics than others. We will consider the effect of the intervention on subgroups organised by:
- content of educational intervention (classified as procedural information, sensory information and behavioural information)
- age and gender
- educational level
- type of surgery
We will use subgroup data as reported by study authors but will note whether subgroups were specified a priori and whether the randomisation was stratified on the subgroup variable. We will investigate heterogeneity and the difference in effect sizes between subgroups using the test for heterogeneity between groups in RevMan software. If we have sufficient data we will investigate further using random-effects meta-regression.
We will assess the robustness of our results using sensitivity analyses. We will assess the impact of studies assessed as being as high risk of bias on our results by removing them from pooled analyses, paying particular attention to studies at high risk of bias for sequence generation. If we have made assumptions about missing outcome data, we will run analyses with alternative assumptions to compare results.
Assessing the quality of the evidence
We will assess and report the quality of the evidence, using the GRADE system to assess the quality of the evidence for each outcome on each of the following domains: study limitations, consistency, imprecision, indirectness and publication bias. Two authors will independently assess the quality of the evidence as implemented and described in the GRADEprofiler (GRADEpro) software (Schünemann 2011).
Ensuring relevance to decisions in health care
The protocol and review will receive feedback from at least one consumer referee in addition to a health professional as part of the Cochrane Consumers and Communication Review Group’s standard editorial process.
We thank the editors and staff of the Cochrane Consumers and Communication Review Group, particularly our contact editor Dr Sandy Oliver for her input to this protocol. We thank Rachael Powell for helpful discussions to avoid overlap with the ongoing review (Powell 2010).
Appendix 1. Search strategy for MEDLINE
1. exp surgical procedures operative/
2. exp specialties surgical/
3. exp "anesthesia and analgesia"/
4. exp postoperative complications/
5. (surg* or operati* or presurg* or postsurg* or perioperat* or preoperat* or postoperat* or an?esthe*).mp.
9. exp fear/
10. stress psychological/
11. (anxious* or anxiet* or fear* or panic* or dread* or worry* or agitation or agitated or apprehensi* or nervous* or distress* or stress or stressed or stressful or psycholog* or catastrophiz* or catastrophis* or discomfort* or comfort* or pain or painful* or cope or coping).tw.
13. health knowledge attitudes practice/
14. ((patient* or client*) and knowledge).tw.
15. patient satisfaction/
16. ((patient* or client*) and (satisfied or satisfaction)).tw.
17. "quality of life"/
18. quality of life.tw.
19. "length of stay"/
20. length of stay.tw.
22. 12 or 21
23. 7 and 22
24. health education/
25. exp consumer health information/
26. patient education as topic/
28. access to information/
30. health communication/
31. information dissemination/
32. exp teaching materials/ or videorecording/
34. computer assisted instruction/
35. ((educat* or inform* or communicat* or instruct* or advis* or advice* or teach* or learn* or coach* or train*) adj5 (patient* or client*)).tw.
36. ((educat* or inform* or communicat* or instruct* or advis* or advice* or teach* or learn* or coach* or train* or written or print* or verbal or face-to-face or online or on-line or web* or internet or computer* or video* or audio* or dvd or multimedia or multi-media or telephone) adj3 (intervention* or session* or program* or material* or package* or provision or provid* or present* or deliver* or method* or process* or format*)).tw.
37. ((preoperative or pre-operative or written or print* or verbal or face-to-face or online or on-line or web* or internet or computer* or video* or audio* or dvd or multimedia or multi-media or telephone) adj3 (informati* or education* or instruction* or training)).tw.
39. 23 and 38
40. randomized controlled trial.pt.
41. controlled clinical trial.pt.
44. clinical trials as topic.sh.
48. exp animals/ not humans.sh.
49. 47 not 48
50. 39 and 49
Contributions of authors
Conceiving the review: Anna Lee (AL), Chris Coldwell (CC) and Andrew Smith (AS)
Co-ordinating the review: Amanda Nicholson (AN)
Undertaking manual searches: AN and Sharon Lewis (SL) - with support from CCCRG
Screening search results: AN and SL
Organizing retrieval of papers: SL and AN
Screening retrieved papers against inclusion criteria: AN, SL
Appraising quality of papers: Any two authors. AL and AS resolving disagreements
Abstracting data from papers: Any two authors. AL and AS resolving disagreements
Writing to authors of papers for additional information: AN and SL
Providing additional data about papers: AN and SL
Obtaining and screening data on unpublished studies: SL and AN
Data management for the review: AN
Entering data into Review Manager (RevMan 5.2): SL and AN
RevMan statistical data: AN
Other statistical analysis not using RevMan: AN
Interpretation of data: SL, AN, AL, CC and AS
Statistical inferences: AN, AL and AS
Writing the review: All authors
Securing funding for the review: AS
Performing previous work that was the foundation of the present study: N/A
Guarantor for the review (one author): AS
Person responsible for reading and checking review before submission: AN
Responsible for updates: all authors
Declarations of interest
From March to August 2011, AN worked for the Cardiff Research Consortium, which provided research and consultancy services to the pharmaceutical industry. Cardiff Research Consortium has no connection with AN's work with The Cochrane Collaboration. AN's husband has small direct holdings in several drug and biotech companies as part of a wider balanced share portfolio. See Sources of support.
Sources of support
- No sources of support supplied
- NIHR Cochrane Collaboration Programme Grant. Enhancing the safety, quality and productivity of perioperative care. Project Ref: 10/4001/04, UK.This grant funds the work of AN, SL and AS on this review.
This protocol is based on standard text and guidance provided by the Cochrane Consumers and Communication Review Group (CCCRG 2013).