Surgical site infection (SSI) contributes to a significant proportion of post-operative morbidity in patients undergoing emergency laparotomy (EL). SSIs cause significant patient burden, increased length of stay and have economic implications.
We undertook a registry-based, prospective cohort study, using data from National Emergency Laparotomy Audit (NELA) database between January 2014 and December 2019. This study aims to compare rates of SSI between patients receiving ciNPT and standard surgical dressing following emergency laparotomy through a propensity matched analysis.
Prophylactic ciNPWT was applied to the midline laparotomy incision under sterile conditions. Negative pressure consisted of continuous -125 mmHg for 7 days. The control group consisted of patients undergoing a standard surgical dressing. In this patient population, prophylactic ciNPWT in emergency laparotomy patients was associated with a reduction in SSI rates.
Aims and objectives
The sixth NELA report documented just under 25000 patients undergoing an emergency laparotomy in 2018-19 in England and Wales. Post-operative complications and death are unfortunately common; the most recent report has shown that 9.6% of all patients die within a month of having an emergency laparotomy.
Concerns about the quality and consistency of care received by patients requiring an emergency laparotomy have been raised culminating in the publication of a variety of multidisciplinary recommendations, standards and process measures that are intended to safeguard the quality of care of all patients undergoing emergency laparotomy.
The aim of this project was to ensure that all standards, including NICE guidance, were adhered to safeguarding the quality of life of patients receiving an EL. The aim was to compare the rates of SSI between patients receiving ciNPWT and standard surgical dressing following EL through a propensity matched analysis.
The study methodology references several key recommendations made in NICE guideline NG125. These include pre-operative phase considerations such as appropriate resuscitation and antibiotic prophylaxis, intra-operative considerations such as antiseptic skin preparation and specified wound closure techniques. Finally, it specifically addresses the necessity for surgical site wound classification, post-operative morbidity and 30-day complication rates as part of its post-operative phase recommendations.
In addition, this study also refers to recommendations expressed in NICE guideline MTG43, advising that evidence supports the case for adopting PICO negative pressure wound dressings for closed surgical incisions in the NHS. They are associated with fewer SSIs and seromas compared with standard wound dressings. NICE evidence reviews within MTG43 identified age, underlying illness, obesity, smoking, wound classification, and complexity of procedure as the main risk factors for SSI. All risk factors were considered for each patient as part of the pre-operative assessment and consent process for this study.
In this project we used the PREVENA™ Incision Management System, also recommended for use in a NICE MedTech Innovation Briefing: MIB173. The main points from the evidence summarised in MIB173 show that Prevena is more effective at reducing complications than standard care in people with closed surgical incisions.
Reasons for implementing your project
The project was undertaken in a high-volume emergency laparotomy teaching hospital (200-250 cases per year according to NELA data). It was recognised that the SSI rates for this cohort of patients was high with well reported implications for cost, length of stay, incisional hernia rates and longer-term outcome.
The NHS Getting it Right First Time (GIRFT) initiative reported that less than 10% of units were aware of their SSI rates in elective surgery let alone emergency surgery. The surgeons in this project were keen to document the unit morbidity as well as working with ciNPWT technology with the aim of reducing SSI rates for their population.
A snapshot audit carried out before implementation showed an SSI rate of 20% which was well within the reported spectrum in the literature but still high. Emergency laparotomy is considered a high-risk procedure for SSI often due to a combination of a physiological unwell patient and a septic source within the abdomen.
The catchment area is approximately 300,000 for secondary care and there is significant deprivation within this area with the North-east containing some of the most deprived areas in England. A smaller number of emergency laparotomy patients would come from further afield with particularly complex needs requiring the expertise of the regional teaching hospital.
The cost of a major SSI after emergency laparotomy was estimated to cost £10,000-£15,000 resulting form months of dressings, packing and significant on-going community costs. The costs of the Prevena dressing at approximately £300 would potentially pay for itself if it prevented 2-3 major wound infections per year.
The group noted that the dressings had been found to be acceptable to post-sternotomy cardiac patients within the hospital and reviewing both the dressing and published data in the literature the group could find no concerns regarding causing harm.
How did you implement the project
The NELA was established to examine the inpatient care and outcomes of patients undergoing emergency laparotomy in England and Wales and to then provide comparative data to hospitals, thereby promoting local quality improvement.
The Audit was commissioned by the Healthcare Quality Improvement Partnership (HQIP), funded by NHS England and the Welsh Government, and began in December 2012. In October 2013, Newcastle Hospitals NHS Foundation Trust began providing information to NELA regarding their structures and processes of care that relate to the treatment of patients undergoing emergency laparotomy.
We decided to focus upon reducing our in-house SSI rates and decided to augment our in-house SSI bundles by using ciNPWT in selected, high risk cases. We looked at the ciNPWT dressings available and the available evidence at the time including guidelines from NICE and WHO.
Funding was provided though our directorate budget with the anticipation of cost savings down the line. We planned to analyse our SSI outcomes by using prospectively-collected NELA data to see if the data in the literature was applicable to our local cohort. We put in place a protocol to carry out the study and engaged a team of medical students and junior doctors with data collection.
The key strength of our work is using the NELA dataset to identify all patients undergoing emergency laparotomy at our centre. This mandatory dataset reflects pragmatic, real-world data consisting of a heterogenous emergency surgery patient population. Additional supplementary data not routinely collected within NELA were collected including SSI rates, morbidity, and grade of morbidity to identify important outcomes.
Data was collected in the projected timescale according to our inclusion and exclusion criteria. The data was then analysed and written as a manuscript. The publication in the journal ‘Surgery’ can be accessed here.
The study is the largest to date to investigate the role of ciNPWT in the emergency laparotomy setting. It demonstrates the benefit of prophylactic use of ciNPWT in the acute setting; with reduced rates of overall SSI rates compared to standard surgical dressings in a matched cohort ; 16.9% vs 33.8% (p<0.001). Furthermore, there was an observed, statistically significant reduction in SSI rates across the superficial and deep CDC categories of SSI in the ciNPWT cohort.
Post-operative outcomes achieved:
The overall incidence of SSI was 25.3% (n=120). The rate of SSI in ciNPWT cohort was 16.9% compared to 33.8% in the standard surgical dressing cohort, p<0.001.
The rate of superficial and deep infections was higher in the standard dressing arm compared to the ciNPWT, p<0.001. We did however observe higher rates of organ space infection within the ciNPWT group compared to the standard dressing; 35.0% vs 21.2%, p<0.001. This reflects the mechanism of action of ciNPWT, which is targeted at the abdominal wall, and wouldn’t be expected to impact organ space infection rates.
There were no overall differences in 30-day morbidity, Clavien-Dindo grade, Comprehensive Complication Index (CCI) severity, length of hospital stays, re-operation rates and 30-day mortality between the two groups.
Predictors of SSI:
At bivariate logistic regression, the use of a standard surgical dressing (p=0.01) and undergoing an emergency colorectal procedure (p=0.01) were associated with a higher risk of developing an SSI. Patient factors such as smoking status, diabetes, CMI and American Society of
Anaesthesiologists (ASA) grade were not associated with SSI.
Peri-operative factors of preoperative antibiotic use and skin preparation types were not associated with SSI. The presence of peritoneal contamination was found not to be an independent predictor of SSI.
Being involved in introducing an intervention which improved outcomes for patients was incredibly satisfying for the medical and nursing teams involved. A formal cost analysis was not included in this piece of work and the group are planning to look at health-related quality of life (HRQoL) and patient reported outcomes (PROMs) in patients with ciNPWT.
Key learning points
SSI is a common complication after emergency laparotomy with significant implications for patients in both the short- and longer term and major cost implications for healthcare providers.
This project shows that the addition of a specialised, prophylactic ciNPWT dressing to a dedicated SSI-prevention bundle (covering pre-op, intra-op and post-op phases) reduces SSI incidence and is acceptable to patients and the extended healthcare team. Some staff training is necessary to deal with troubleshooting, but this was not a significant problem and the training is brief.
Some surgeons involved were sceptical of the intervention initially but more and more of them began to use in their practice across the directorate until it had near universal penetrance. This is likely to be the effects seen locally alongside increasing literature reporting favourable results.
Getting a robust business plan is likely to be important in other centres with accurate costings of SSI in their centre and a good baseline SSI calculation in this patient group. Prophylactic measures in the NHS are not always supported as the cost returns often come down the line and this reinforces the need for a robust business plan alongside review of the literature and guidelines (WHO guidelines state that ciNWPT should be considered in high-risk laparotomy cases).
If I was running this project again, I would have factored in some health-related quality of life assessment into the project as I think this will be key for our patients in the future. Patient-reported outcomes are becoming more and more important in surgery and we must do better in assessing and considering the views of our patients.