Optimal methods for the use of 'pain' as an outcome in systematic reviews of postoperative pain management

Background and introduction

Pain is a common primary or secondary outcome in systematic reviews of perioperative anaesthesia and postoperative care. How methods are applied and outcomes are managed varies substantially across published reviews and this can create problems when trying to interpret their findings. Indeed, while it can appear to be simple, managing pain as an outcome presents us with a number of interesting challenges.

At the Cochrane Pain, Palliative and Supportive Care (PaPaS) Review Group we have developed the resources presented here to help to guide review authors and people who are using systematic reviews in this field towards optimal methods in this field. This project was supported by a Cochrane Network Innovation Fund, and the resources were developed in consultation with the Cochrane Musculoskeletal, Oral, Skin and Sensory (MOSS) Network and other key contacts in this topic area.

In this project we established an expert group of editors and authors to distil and synthesise evidence-based best practice guidance on the management of pain as an outcome in systematic review of perioperative anaesthesia and postoperative care. We reviewed the evidence to support best practice, elucidated examples, and provide some recommendations and considerations (see resources below). Discussion is presented on areas of uncertainty where further research is needed, how to incorporate this practice into systemic reviews, and on transferable learnings to systematic review practice in general.

On this website you will find a checklist of critical items that authors of reviews in this field should consider when designing and conducting their review. The checklist also serves as a guide to optimal methods for people who are trying to make sense of a systematic review that has postoperative pain as an important outcome. We have also developed a series of short presentations outlining the evidence underpinning the issues covered in the checklist [coming soon].

Through this project our hope is that we have provided resources to drive improvement in the standard of systematic reviews in this field, and also a useful guide for those seeking to use systematic reviews to guide clinical decisions.

For any queries, please contact Dr Neil O'Connell at neil.oconnell@brunel.ac.uk.

Resources for systematic reviewers and Cochrane Review Groups

The Checklist

Performing a systematic review and/or meta-analysis of studies reporting results for acute postoperative pain in adults: a quick check of some critical elements for pain reporting and analysis. Download the Checklist here.

Series of Powerpoint slides

1. Introduction to acute postoperative pain download Slideset 1 here

This presentation offers an introduction to the topic and covers the following: background; definitions of acute and chronic pain; prevalence of acute pain and postoperative pain; importance of acute postoperative pain; a look at patient perspectives; and acute versus chronic pain after surgery.

• Accompanying reference list available here Slideset 1 Ref list

2. Measuring postoperative pain download Slideset 2 here

This presentation provides the following information: background to measurements; categorical pain intensity and pain relief scales; visual analogue and composite pain scales; patients must measure their own pain; how pain scores are expressed and calculated; time to remedication and other measures.

• Accompanying reference list available here Slideset 2 Ref list

3. Looking at outcomes download Slideset 3 here

This presentation covers the following: what is an outcome?; postoperative pain related outcomes; time to remedication; opioid or analgesic requirement; adverse events; length of hospital stay; readmission.

• Accompanying reference list available here Slideset 3 Ref list

4. Some fundamentals of acute pain studies download Slideset 4 here

This presentation introduces the following: randomisation; double blinding; initial pain intensity; dealing with dropouts; remedication; imputation.

• Accompanying reference list available here Slideset 4 Ref list

5. Considerations of study size download Slideset 5 here

This presentation covers: background to study size; examples of treatment group sizes in acute pain; examining random variations with small group size; what is small, and problems with small studies; examples of problems with small studies.

• Accompanying reference list available here Slideset 5 Ref list

6. Dealing with publication bias download Slideset 6 here

This presentation provides some background and information on the following: susceptibility to publication bias; examples with and without susceptibility; how susceptibility works; calculating susceptibility – method and worked example.

• Accompanying reference list available here Slideset 6 Ref list
• We are also able to provide on request an Excel spreadsheet and a PDF of the book chapter explaining how the method was derived.

7. Applying lessons in practice download Slideset 7 here

This presentation provides a worked example from a PaPaS Review (Perioperative intravenous ketamine for acute postoperative pain in adults, Brinck 2018), including the following: looking at data in practice, and methods; pain at rest - effect of size; pain at rest - effect of pain level with control; opioid consumption - effect of size; opioid consumption - effect of consumption with control.

• Accompanying reference list available here Slideset 7 Ref list

Acknowledgements

Thank you to the Cochrane Network Innovation Fund for investing in this project.

Thank you to Mohammed A. Abusayed (University Hospitals of Derby and Burton, UK) for auditing reviews of interventions for pain in the Cochrane Library in 2016.

Thank you to all the project team members, advisers, and MOSS key contacts: Joanne Abbott; Geert Crombez; Rob Dellavalle; Christopher Eccleston; Anna Erskine; Emma Fisher; Kerry Harding; Jennifer Hilgart; John Lawrenson; Hopin Lee; Nuala Livingstone; Lara Maxwell; Andrew Moore; Gill Norman; Neil O'Connell; Roses Parker; Phil Riley; Kate Seers; Teo Aminah Wasteneys Quay; Andrew Smith; Martin Tramèr; Peter Tugwell; Katie Webster; Amanda C de C Williams.

Free to use and share

These resources are freely available to use and share. If you would like to acknowledge the use of these resources in your published Cochrane Review, you are welcome to use the following suggested text in the 'Acknowledgements' section: We acknowledge the Cochrane Pain, Palliative and Supportive Care (PaPaS) Review Group's resources for systematic reviews of studies reporting results for acute postoperative pain in adults, which informed this [protocol / review]; the resources were produced with the support of a Cochrane Network Innovation Fund and in consultation with the Musculoskeletal, Oral, Skin and Sensory (MOSS) Network.