Post-discharge surveillance to identify colorectal surgical site infection rates and related costs

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Summary

A growing number of surveillance studies have highlighted concerns with relying only on data from inpatients. Without post-discharge surveillance (PDS) data, the rate and burden of surgical site infections (SSIs) are underestimated. PDS data for colorectal surgery in the UK remains to be published. This is an important specialty to study since it is considered to have the highest SSI rate and is among the most expensive to treat. This study of colorectal SSI used a 30 day surveillance programme with telephone interviews and home visits. Each additional healthcare resource used by patients with SSI was documented and costed. Of the 105 patients who met the inclusion criteria and completed the 30 day follow-up, 29 (27%) developed SSI, of which 12 were diagnosed after discharge. The mean number of days to presentation of SSI was 13. Multivariable logistic analysis identified body mass index as the only significant risk factor. The additional cost of treating each infected patient was £10,523, although 15% of these additional costs were met by primary care. The 5 month surveillance programme cost £5,200 to run. An analysis of the surveillance nurse's workload showed that the nurse could be replaced by a healthcare assistant. PDS to detect SSI after colorectal surgery is necessary to provide complete data with accurate additional costs.

Introduction

Surveillance of surgical site infections (SSIs) is undertaken to enable hospitals to measure and evaluate their own practice. Sharing surveillance data through national programmes, such as the Health Protection Agency (HPA) in the UK, allows comparisons to be made both between hospitals and between different countries.

Traditionally, surveillance has been passive and retrospective, relying on infections being identified by staff not employed for surveillance and captured through casenote review. Surveillance has largely focused on inpatients and usually ends when patients are discharged. A number of studies have identified weaknesses with relying only on data from inpatients.1 A major concern is that inpatient surveillance underestimates infection rates by failing to identify infections after hospital discharge. This will increase as inpatient lengths of stay decrease, giving the illusion that SSI rates are falling. Studies have shown that up to 89% of infections occur following discharge.2

A major reason for collecting post-discharge surveillance (PDS) data is to identify accurate SSI rates so that accurate costings can be made. Additionally, there is a suggestion that risk factors associated with SSI detected after discharge are different from risk factors associated with infections detected during inpatient stays.3 This may have implications for the National Nosocomial Infection Surveillance (NNIS) risk score.4 The NNIS score is widely used to predict each patient's risk of developing an SSI and is calculated from the American Society of Anesthesiology (ASA) score, duration of operation and wound classification. Recent studies suggest that whereas the NNIS score correlates positively with inpatient infections, discrepancies have been shown in the ability of the NNIS score to predict post-discharge infections.3

Few studies have looked specifically at PDS in colorectal surgery. This is an important surgical specialty to explore as it has the highest rate of SSI and is one of the most expensive SSIs to treat. Data extrapolated from German and Dutch national surveillance programmes, which include PDS, reveal colorectal SSI rates of 7% and 11%, respectively.5 This compares with two American studies and one Italian study which found post-discharge colorectal SSI rates of 20%, 26% and 18.9%, respectively.6, 7, 8 No UK-based studies of colorectal PDS appear to have been published and the national UK surveillance programme only collects inpatient data. In 2007 the UK national inpatient colorectal SSI rate was 8.4%.9 One study in 2004 estimated the mean additional cost of treating a colorectal SSI at US $6,200.7

The aims of this study were to determine SSI rates for colorectal surgery using PDS, to identify factors which increased the risk of infection, and to provide an accurate cost for treating patients with SSI.

Section snippets

Surveillance programme

From January until April 2008, all patients requiring colorectal surgery undergoing anterior resection, anterior–posterior resection, Hartmann's procedure, hemicolectomy, and subtotal colectomy at University Hospitals Leicester NHS Trust were entered into a SSI surveillance programme.

The design of the surveillance programme was derived from studies showing that telephone interviews and direct observation by independent observers provided the most accurate data.10 Patients were followed up for

Results

A total of 126 patients had colorectal surgery during the 4 month surveillance period. Twenty-one of these patients did not meet the eligibility criteria for inclusion; eight were lost to follow-up, six died and seven had further surgery after 72 h. The findings presented are for the 105 patients who met the surveillance inclusion criteria and completed the full 30 day follow-up.

Discussion

At 27% the SSI rate was similar to, though slightly higher than, the American and Italian colorectal studies which also used a 30 day follow-up programme.6, 7, 8 However, the rates from this study and these other studies are two to three times higher than the rates found in national surveillance programmes which also included post-discharge data.5 These differences may be due to variations in data collection methods, differences in patient demographics between countries or differences in

Acknowledgements

We would like to acknowledge the contribution of I. Jones, K. Weafer and Dr D. Jenkins, University Hospital Leicester NHS Trust.

References (18)

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    They are associated with increased hospital stay, readmission, and cost utilization.36 Given the oftentimes contaminated nature of colorectal surgeries, these surgeries have high rates of SSI, ranging from 5% to 30%.37 Patient and disease factors that contribute to SSI include higher ASA class, obesity, tobacco use, chronic obstructive pulmonary disease (COPD), diabetes, age, and IBD.

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