Enhanced surgical site infection surveillance following caesarean section: experience of a multicentre collaborative post-discharge system

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Summary

The caesarean section rate in the UK has more than doubled during the last two decades and is continuing to rise. The majority of studies carried out to determine the incidence of infection associated with this procedure have been restricted to the inpatient stay, which may give misleading results. Women undergoing caesarean section have routine contact with a community midwife after discharge. This provided an opportunity to assess whether a collaborative surveillance approach between hospital and community staff was feasible using routinely available information. Following a successful pilot study, 11 maternity units in the East Midlands participated in an extended study. Complete records were available for 5563 (88%) women. Overall, 758 (13.6%) wound problems were reported, 84% of which developed after discharge. Of these, 488 (8.9%) met national definitions for surgical site infection (SSI); however, there was a marked inter-unit difference in incidence, ranging from 2.9% to 17.9%. Statistical models were used to examine these differences using 12 possible risk factors. Five risk factors were found to be significantly associated with the development of a surgical site infection: body mass index, age, blood loss, method of wound closure and emergency procedures. These results suggest that caesarean section is associated with high infectious morbidity, the extent of which would have been considerably underestimated without post-discharge monitoring. Almost all women with wound problems were treated with antibiotics, regardless of how minor the problem, with 97% being prescribed in the community. This indicates a requirement for local review of antibiotic prescribing practice.

Introduction

In the past 15 years, the proportion of caesarean section births has been increasing steadily in England, and now accounts for 24% of all births.1 More than 150 000 women were delivered in this way in 2005, making this procedure one of the most commonly performed major operations.2 Although it has undoubtedly reduced infant and maternal mortality, studies have shown that the procedure is associated with significant infectious morbidity involving the operative site. Wound infection rates ranging between 7% and 41.1% have been reported.3, 4 Although this wide variation may be due to differences in the criteria used to diagnose infection, case-finding, and the use of antibiotic prophylaxis, the majority of studies have been restricted to the inpatient stay. Underestimation of the incidence of infection ranging from 20% to 70% has been reported in general surgery if patients are not monitored after they leave hospital.5 A National Audit Office report considered that post-discharge surveillance was important if National Health Service (NHS) Trusts were to understand the full extent of hospital-acquired infection, yet it had been attempted in only a quarter.6 Their recommendation, subsequently endorsed by the Committee of Public Accounts, was that post-discharge surveillance should be considered.7

It was decided to investigate the incidence of surgical site infection (SSI) in a one-year study that included post-discharge surveillance at a single maternity unit in the East Midlands during 2001–2002. This study used the fact that women undergoing caesarean section have routine contact with a community midwife for a minimum of 10 days after discharge, or longer if there are any wound or other obstetric-related problems. This provided an opportunity to assess whether a collaborative surveillance approach between infection control teams, and hospital and community midwives was feasible; and whether the incidence of infection following caesarean section and information on potential risk factors could be determined from routine records. Included in the risk factor data to be collected were factors shown to be independently important in predicting SSI in a multicentre prospective study carried out by the US Centers for Disease Control (CDC).8

Of the 1029 women who had caesarean deliveries, inpatient and community records were available for 896 (87%). Using the criteria of the study hospital, SSIs were classified as major if wounds were discharging pus or inflamed and required antibiotic therapy; or there was spreading cellulitis and fever (>38 °C), complete or partial (>50%) dehiscence, or required surgical revision/debridement. Wound problems that did not meet these definitions were classified as minor. A total of 213 (23.7%) wound infections were identified from the records, 111 of which were classified as major. The majority of infections (89%) were identified after discharge. All patients had been routinely prescribed antibiotic prophylaxis. These results confirmed that wound infection was a significant problem following caesarean section and that a combined hospital/community monitoring approach was feasible.

On the basis of these results, it was decided to extend the study to other maternity units in the same region. The primary objective of the main study was to prospectively study the occurrence of surgical wound and uterine infections following caesarean section in maternity units throughout the East Midlands region using a standardised approach with common case-definitions and case-finding methods. Factors associated with post-delivery infectious morbidity would also be identified and, because it had been ascertained that all units routinely gave antibiotic prophylaxis, compliance with policies would be assessed.

Eleven maternity units within the East Midlands region participated in the surveillance between July 2003 and March 2005, collecting data for varying periods of between three and 18 months. Initially, seven units undertook to collect data for 12 months, although two units in one Trust had to stop after six months due to staffing issues. Towards the end of the study period, four of the remaining five units within the region opted to take part, and the study period was extended for another six months.

Section snippets

Study design

This was a prospective multicentre study. Each unit nominated maternity and infection control staff to co-ordinate the study.

Study population

All women who underwent caesarean section at any of the participating units during the study period were included in the surveillance. Patients were followed up from the day of surgery until the date of last contact with the community midwife.

Definitions of infection

Based on the experience of the CDC, deep incisional infections involving the fascial and muscle layers rarely occur after caesarean

Results

Although inpatient information was available for the 6297 caesarean section procedures carried out during the study period, inclusion was dependent on the return of the community follow-up records to the hospital by the community midwives. Both hospital and community information was available for 5563 (88%) of the patients.

Discussion

This study has demonstrated the feasibility and usefulness of post-discharge surveillance in a group of patients undergoing one of the most commonly performed operative procedures. Hospital-acquired infections delay recovery, may increase the duration of hospital stay, and have economic consequences for the primary and secondary healthcare sectors.11, 12, 13 In a Department of Health (DH)-commissioned study undertaken in 1994–1995, it was estimated that the average additional inpatient cost of

Acknowledgements

We thank the staff of participating hospitals and the East Midlands Health Protection Unit for their help and support.

References (20)

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