What is the aim of this overview of reviews?
To identify and summarise all evidence from Cochrane Reviews on interventions to prevent surgical site infections (SSIs) that are delivered while surgery is taking place (during the intraoperative period).
We cannot be certain about the effectiveness in preventing SSI of the majority of intraoperative interventions, as we judged the certainty of the evidence to be generally low or very low. In some circumstances (listed below), antibiotics were effective for the prevention of SSI. There is no high- or moderate-certainty evidence for the relative effects of intraoperative interventions on mortality, and no data at all for quality of life or costs. For these reasons, we cannot be certain whether these antibiotics, which are effective at preventing SSI, have any negative effects on mortality or quality of life. Larger trials with appropriate methods are needed to measure the outcomes that are important to both patients and health professionals.
What was studied in the overview?
If bacteria get into a surgical cut during surgery, this can result in a wound infection commonly called an SSI. SSIs are one of the most common forms of healthcare-associated infections, with around 1 in 20 surgical patients developing an SSI in hospital. SSIs can also develop after people have left hospital. SSIs can result in delayed wound healing, increased hospital stays, increased use of antibiotics, unnecessary pain and, in extreme cases, death. Their prevention is therefore a key aim for health services. Many interventions are used to reduce the risk of SSI in people having surgery. These interventions can be delivered at three stages: before, during and after the operation. It is therefore important to identify interventions that can reduce the incidence of SSIs. This overview focuses only on interventions delivered during surgery.
What are the main results of the overview?
In July 2017 we searched for Cochrane Reviews involving interventions for preventing SSIs during surgery. We found a total of 32 Cochrane Reviews that could be included in this overview. Two reviews had no relevant data to extract so we extracted data from 30 reviews with 349 included trials, totaling 73,053 participants. Interventions assessed included use of disposable face masks and surgical gloves, the use of oxygen during surgery, antiseptics for hand washing, patient skin preparation and cleaning the vagina before caesarean section, methods of surgical incision and skin closure and use of antibiotics to prevent infection.
Evidence of at least moderate certainty indicates that the following interventions reduce SSI risk: (1) antibiotics administered via drip before caesarean incision reduce SSI risk compared with administration after cord clamping (high-certainty evidence); (2) giving antibiotics before surgery reduces SSI risk compared with placebo after breast cancer surgery (high-certainty evidence); (3) antibiotics used to prevent wound infections probably reduce SSIs for caesarean section compared with no antibiotics (moderate-certainty evidence); (4) antibiotics used to prevent wound infections probably reduce SSI risk for hernia repair compared with placebo or no treatment (moderate-certainty evidence); (5) iodine-impregnated adhesive drapes probably make no difference to SSI risk compared with no adhesive drapes (moderate-certainty evidence); (6) there is probably no difference in SSI risk when antibiotics are given in the short-term compared to the long-term during colorectal surgery (moderate-certainty evidence). One comparison showed that adhesive drapes increase the SSI risk compared with no drapes (high-certainty evidence). Overall, we judged the certainty of evidence for our primary outcomes (SSIs and death) to be low or very low.
Clinicians can use the evidence summarised in this overview to choose the best intervention for people having surgery. However, many of the comparisons were supported by low- or very low-certainty evidence and so require further evidence to support future decision making. This overview can also be used by policymakers in developing local and regional protocols or guidelines and can reveal knowledge gaps for future research.
How up to date is this overview?
We searched for reviews that had been published up to July 2017. Of the 32 reviews included in this overview, 13 reviews had not been updated in the past three years.
This overview provides the most up-to-date evidence on use of intraoperative treatments for the prevention of SSIs from all currently published Cochrane Reviews. There is evidence that some interventions are useful in reducing SSI risk for people undergoing surgery, such as antibiotic prophylaxis for caesarean section and hernia repair, and also the timing of prophylactic intravenous antibiotics administered before caesarean incision. Also, there is evidence that adhesive drapes increase SSI risk. Evidence for the many other treatment choices is largely of low or very low certainty and no quality-of-life or cost-effectiveness data were reported. Future trials should elucidate the relative effects of some treatments. These studies should focus on increasing participant numbers, using robust methodology and being of sufficient duration to adequately assess SSI. Assessment of other outcomes such as mortality might also be investigated as part of non-experimental prospective follow-up of people with SSI of different severity, so the risk of death for different subgroups can be better understood.
Surgical site infection (SSI) rates vary from 1% to 5% in the month following surgery. Due to the large number of surgical procedures conducted annually, the costs of these SSIs can be considerable in financial and social terms. Many interventions are used with the aim of reducing the risk of SSI in people undergoing surgery. These interventions can be broadly delivered at three stages: preoperatively, intraoperatively and postoperatively. The intraoperative interventions are largely focused on decontamination of skin using soap and antiseptics; the use of barriers to prevent movement of micro-organisms into incisions; and optimising the patient's own bodily functions to promote best recovery. Both decontamination and barrier methods can be aimed at people undergoing surgery and operating staff. Other interventions focused on SSI prevention may be aimed at the surgical environment and include methods of theatre cleansing and approaches to managing theatre traffic.
To present an overview of Cochrane Reviews of the effectiveness and safety of interventions, delivered during the intraoperative period, aimed at preventing SSIs in all populations undergoing surgery in an operating theatre.
Published Cochrane systematic reviews reporting the effectiveness of interventions delivered during the intraoperative period in terms of SSI prevention were eligible for inclusion in this overview. We also identified Cochrane protocols and title registrations for future inclusion into the overview. We searched the Cochrane Library on 01 July 2017. Two review authors independently screened search results and undertook data extraction and 'Risk of bias' and certainty assessment. We used the ROBIS (risk of bias in systematic reviews) tool to assess the quality of included reviews, and we used GRADE methods to assess the certainty of the evidence for each outcome. We summarised the characteristics of included reviews in the text and in additional tables.
We included 32 Cochrane Reviews in this overview: we judged 30 reviews as being at low risk of bias and two at unclear risk of bias. Thirteen reviews had not been updated in the past three years. Two reviews had no relevant data to extract. We extracted data from 30 reviews with 349 included trials, totaling 73,053 participants. Interventions assessed included gloving, use of disposable face masks, patient oxygenation protocols, use of skin antiseptics for hand washing and patient skin preparation, vaginal preparation, microbial sealants, methods of surgical incision, antibiotic prophylaxis and methods of skin closure. Overall, the GRADE certainty of evidence for outcomes was low or very low. Of the 77 comparisons providing evidence for the outcome of SSI, seven provided high- or moderate-certainty evidence, 39 provided low-certainty evidence and 31 very low-certainty evidence. Of the nine comparisons that provided evidence for the outcome of mortality, five provided low-certainty evidence and four very low-certainty evidence.
There is high- or moderate-certainty evidence for the following outcomes for these intraoperative interventions. (1) Prophylactic intravenous antibiotics administered before caesarean incision reduce SSI risk compared with administration after cord clamping (10 trials, 5041 participants; risk ratio (RR) 0.59, 95% confidence interval (CI) 0.44 to 0.81; high-certainty evidence - assessed by review authors). (2) Preoperative antibiotics reduce SSI risk compared with placebo after breast cancer surgery (6 trials, 1708 participants; RR 0.74, 95% CI 0.56 to 0.98; high-certainty evidence - assessed by overview authors). (3) Antibiotic prophylaxis probably reduce SSI risk in caesarean sections compared with no antibiotics (82 relevant trials, 14,407 participants; RR 0.40, 95% CI 0.35 to 0.46; moderate-certainty evidence; downgraded once for risk of bias - assessed by review authors). (4) Antibiotic prophylaxis probably reduces SSI risk for hernia repair compared with placebo or no treatment (17 trials, 7843 participants; RR 0.67, 95% CI 0.54 to 0.84; moderate-certainty evidence; downgraded once for risk of bias - assessed by overview authors); (5) There is currently no clear difference in the risk of SSI between iodine-impregnated adhesive drapes compared with no adhesive drapes (2 trials, 1113 participants; RR 1.03, 95% CI 0.66 to 1.60; moderate-certainty evidence; downgraded once for imprecision - assessed by review authors); (6) There is currently no clear difference in SSI risk between short-term compared with long-term duration antibiotics in colorectal surgery (7 trials; 1484 participants; RR 1.05 95% CI 0.78 to 1.40; moderate-certainty evidence; downgraded once for imprecision - assessed by overview authors). There was only one comparison showing negative effects associated with the intervention: adhesive drapes increase the risk of SSI compared with no drapes (5 trials; 3082 participants; RR 1.23, 95% CI 1.02 to 1.48; high-certainty evidence - rated by review authors).