Introduction

Health care-associated infections (HAI) are acquired by patients while receiving care and represent the most frequent adverse event affecting patient safety worldwide.

Recent work by the World Health Organization (WHO) shows that surgical site infection (SSI) is the most surveyed and frequent type of HAI in low- and middle-income countries and affects up to one third of patients who have undergone a surgical procedure. Although SSI incidence is lower in high-income countries, it remains the second most frequent type of HAI in Europe and the United States of America (USA).

Many factors in the patient’s journey through surgery have been identified as contributing to the risk of SSI. Therefore, the prevention of these infections is complex and requires the integration of a range of preventive measures before, during and after surgery. However, the implementation of these measures is not standardized worldwide. No international guidelines are currently available and inconsistency in the interpretation of evidence and recommendations among national guidelines is frequently identified.

The aim of these guidelines is to provide a comprehensive range of evidence-based recommendations for interventions to be applied during the pre-, intra- and postoperative periods for the prevention of SSI, while also considering aspects related to resource availability and values and preferences.

Although the guidelines are intended for surgical patients of all ages, some recommendations do not apply to the paediatric population due to lack of evidence or inapplicability and this is clearly stated.

Target audience

The primary target audience for these guidelines is the surgical team, that is, surgeons, nurses, technical support staff, anaesthetists and any professionals directly providing surgical care. Pharmacists and sterilization unit staff will also be concerned by some aspects of these guidelines. The recommendations are also intended to be used by policy-makers, senior managers and infection prevention and control (IPC) professionals as the basis for developing national and local SSI protocols and policies, and supporting staff education and training.

Guideline development methods

The guidelines were developed according to the processes described in the WHO Handbook for guideline development issued in 2014. In summary, the process included:

(1)

identification of the primary critical outcomes and priority topics and formulation of a series of questions structured in a PICO (Population, Intervention, Comparison, Outcomes) format;

(2)

retrieval of the evidence through specific systematic reviews of each topic using a standardized agreed methodology;

(3)

assessment and synthesis of the evidence;

(4)

formulation of recommendations; and

(5)

writing of the guideline content and planning for its dissemination and associated implementation strategy.

The development of the guidelines involved the formation of four main groups to guide the process: the WHO Guideline Steering Group; the Guidelines Development Group (GDG); the Systematic Reviews Expert Group; and the External Review Group.

Using the list of priority topics, questions and critical outcomes identified by the WHO Guideline Steering Group, the GDG and the guideline methodologist in a scoping meeting convened by WHO in September 2013, the Systematic Reviews Expert Group conducted 27 systematic reviews to provide the supporting evidence for the development of the recommendations; summaries of the systematic reviews are available as web appendices of the guidelines. The scientific evidence was synthesized using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. WHO convened four GDG technical consultations between June 2014 and November 2015 to formulate and approve the recommendations based on the evidence profiles. In agreement with the methodologist and the WHO Guidelines Review Committee secretariat, five recommendations were re-discussed through GDG on-line consultations after the meetings and slightly modified, based on either comments by the external peer reviewers or emerging new evidence.

Following the issue of the guidelines in November 2016, some concerns were raised by experts and users during 2017 on the strong recommendation regarding the use of 80% fraction of inspired oxygen (high FiO₂) in surgical patients under general anaesthesia with tracheal intubation. The arguments were related to the analysis of the evidence on the benefit and safety of this intervention. Therefore, between 2017 and 2018 WHO re-assessed the evidence by updating the systematic review related to the effectiveness of high FiO₂ and commissioning an independent systematic review on adverse events potentially associated with the recommended use of high FiO₂. The GDG membership was also broadened to include an additional eight anaesthetists. Based on the evidence reviews up to April 2018, the GDG decided to revise the strength of the recommendation from strong to conditional and to update the chapter of the guidelines dedicated to this topic.

The guidelines consist of a core section including a dedicated chapter for each recommendation, which is divided into subsections according to their application in the pre-, intra- and postoperative periods. This is preceded by a section including other important issues in the approach to SSI prevention that were not the subject of recommendations, but of which users should be fully aware. A summary of main existing national guidelines on SSI prevention is also provided as a web appendix of the guidelines.

Recommendations

The WHO technical consultations led to the adoption of 29 recommendations covering 23 topics for the prevention of SSI in the pre-, intra- and postoperative periods (see Table). For four topics, the GDG considered that the available evidence was not sufficient to develop related recommendations. For each recommendation, the quality of evidence was graded as “very low”, “low”, “moderate” or “high”. The GDG qualified the direction and strength of each recommendation by considering the quality of evidence and other factors, including the balance between benefits and harms, the values and preferences of stakeholders and the resource implications of the intervention. To ensure that each recommendation is correctly understood and applied in practice, the GDG has provided additional remarks where needed. Guideline users should refer to these remarks, as well as to the summary of the evidence provided in each chapter of the recommendations. The summaries of the systematic reviews, including the risk of bias assessments and the GRADE tables, are available in full as on-line appendices of the guidelines. Each chapter also features a research agenda identified by the GDG for each topic.

The recommendations for the prevention of SSI to be applied or considered in the pre-, intra- and postoperative periods are summarized in the Table below, together with the associated PICO questions and their strength and evidence quality. In accordance with WHO guideline development procedures, these recommendations will be reviewed and updated following identification of new evidence at least every five years. WHO welcomes suggestions regarding additional questions for inclusion in future updates of the guidelines.

Table 1

Summary of core topics, research questions and recommendations for the prevention of surgical site infection.