Impact of closed-incision negative pressure wound dressings on surgical site infection following groin incisions in vascular surgery;a single-centre experience

Abstract

Objectives

Surgical site infection (SSI) is a common complication in vascular surgery, and is associated with increased patient morbidity, readmission and reintervention. The aim of this study was to assess the impact of closed-incision negative pressure wound therapy (CiNPWT) upon rate of SSI and length of hospital stay.

Methods

This study was reported in line with the STROBE guidelines. We assessed the baseline incidence of SSI from a 12-month retrospective cohort and, following a change in practice intervention with CiNPWT, compared to a 6-month prospective cohort. The primary endpoint was incidence of SSI (according to CDC-NHSN guidelines) while secondary endpoints included length of hospital stay, readmission, reintervention and Days Alive and Out of Hospital (DAOH) to 90-days.

Results

A total of 127 groin incisions were performed: 76 (65 patients) within the retrospective analysis and 51 (42 patients) within the prospective analysis (of whom 69% received CiNPWT). The primary endpoint of SSI was seen in 21.1% of the retrospective cohort and 9.8% of the prospective cohort (p = .099). Readmission was found to be significantly associated with the retrospective cohort (p = .016) while total admission (inclusive of re-admission) was significantly longer in those in the retrospective cohort (p = .013). DAOH-90 was 83 days (77–85) following introduction of the CiNPWT protocol as compared to the retrospective cohort (77 days (64–83), p = .04).

Conclusion

Introduction of CiNPWT was associated with a reduced length of hospital stay and improved DAOH-90. Further trials on CINPWT should include patient-centred outcomes and healthcare cost analysis.

Keywords

Closed-incisions negative pressure wound therapy closed-incision negative pressure wound therapy vascular vascular surgery surgical site infection groin incision

Background

Surgical Site Infection (SSI) is a common complication after surgery and is associated with poorer patient outcomes. In Australia, where about 2.5 million operations are performed annually, the overall incidence of SSI is approximately 3%.¹ Patient factors such as diabetes, cardiac disease and obesity increase the risk of SSI.² Additionally, the nature and type of operation performed affect the rate of SSI (25–40% of patients undergoing emergency abdominal surgery develop an SSI compared to 6–30% of patients undergoing vascular surgery).^3–6

Vascular surgery is particularly prone to SSI as patients frequently have multiple comorbidities including chronic kidney disease, malnutrition and anaemia.⁷ The surgery is often emergent, the operations themselves frequently involve the groin (for femoral artery exposure) and the procedures can be lengthy. SSI in vascular patients are associated with increased length of hospital stay (LOS), reintervention, vascular graft failure and increased patient mortality.^7–10 Such events lead to a substantial increase in medical costs.^7,11 Strategies to reduce SSI and prevent hospital readmission have focused on antisepsis washes, multi-resistant staphylococcus aureus (MRSA) decolonisation programmes, pre-operative nutritional optimisation and the delivery of perioperative antibiotics immediately prior to surgical incision.¹²

Closed-incision Negative Pressure Wound Therapy (CiNPWT) has been associated with reduced SSI in orthopaedic, obstetric and general surgery.^13–15 However, as superficial SSI can be subjective, Cochrane called for differentiation between deep and superficial SSI as well as the need for patient-centred outcome data.¹⁶ In Vascular Surgery, a meta-analysis of several small RCTs also suggested that CiNPWT reduces SSI. However, due to heterogenous inclusion criteria, SSI definitions and short duration follow-up,^17–22 patient outcomes such as LOS, readmission or reintervention could not be assessed.²³ Another patient-centred outcome which has not previously been utilised in the assessment of the impact of CiNPWT in vascular surgery is Days Alive and Out of Hospital.²⁴

The aim of this study was to assess the use of CiNPWT in patients undergoing vascular surgery and the associated impact upon SSI rate, LOS, unplanned readmission, reintervention and DAOH at 90 days.

Methods

Study design and setting

This study was undertaken at a single-centre tertiary unit in Western Australia with 783 beds, serving 647,754 people, across a catchment area of 3300 square kilometres. Its overall workload was 888 arterial procedures in 2018, shared between five independent vascular surgeons (Department of Health ID 29271: 26/02/2019).

A quazi-experimental design compared both retrospective and prospective data capture, reported in line with STROBE guidelines.²⁵ Initially, a baseline retrospective review of patients undergoing open vascular surgery involving a groin incision, across a 12-month time period (1 January 2018 to 31 December 2018) with 90-day follow-up, was performed (‘retrospective cohort’). This was followed by an institutional change in practice, training and implementation of CiNPWT dressings. Subsequently, a prospective analysis was performed as part of a multi-centre observational cohort study (Groin wound Infection after Vascular Exposure audit; GIVE)²⁶ over a 6-month timeframe (6 March 2019 to 6 September 2019) with 90-day follow-up completed (‘prospective cohort’).

Consecutive adult patients (18 years-of-age and over) undergoing elective or emergency surgery with a groin incision for lower limb vascular surgery were assessed, involving both longitudinal and transverse incisions for procedures including femoral exposure or endarterectomy and lower limb bypass. Groin incisions were extended down the leg (i.e., lower limb bypass) or above the groin (i.e., for iliac vessel exposure) as required. Groin incisions excluded were those for arterial exposure as part of a cardiac procedure, that is, trans catheter aortic valve implantation (TAVI), endovascular aneurysm repair (EVAR) access, venous access (i.e., high tie, ligation and stripping of the long saphenous vein) and known infected wounds.

Departmental change in practice involved the introduction of CiNPWT dressings for groin incisions (Prevena Incision management system; Acelity™), although the final decision regarding primary post-operative dressing remained at the discretion of the operating surgeon. Training was undertaken for medical and nursing staff via multiple sessions demonstrating appropriate application as well as the desired duration of application without interruption. Specific queries were answered while, to ensure uniformity, a dedicated single-applicator for the CiNPWT was identified. The device was applied following wound closure in theatre by one individual with additional adhesive dressings utilised to obtain a seal as required. The device was connected to a portable suction canister which was pre-programmed to maintain suction at 125 mmHg. In the event of a groin incision being extended down the leg (i.e., for vein harvest) or above the groin (i.e., for iliac vessel exposure), either individual groin CiNPWT with a standard dressing was sited or a long contiguous CiNPWT device was placed as demonstrated in Figure 1. Dressings were kept in place for a planned minimum of 5 days or until discharge from hospital. There were no changes to either perioperative antibiotic regimen or mechanism of wound closure.

Figure 1

. Contiguous CiNPWT device application following lower extremity bypass.

Outcomes

The primary outcome was rate of groin wound SSI per groin from day of surgery to 90 days. SSI was defined, in accordance with the CDC-NHSN guidelines (Supplementary material 1), as infection occurring after surgery in the part of the body where the surgery took place.²⁷ Secondary outcomes within 90-days of surgery were; initial LOS, unplanned readmission due to SSI, reintervention due to SSI (surgical ± radiological), total LOS (incident admission ± readmission) and DAOH-90. DAOH-90 was calculated from the date of index surgery (Day 0) using hospitalization and mortality data.²⁴ The date of surgery and hospital discharge date were used to calculate LOS (ignoring any days in hospital prior to the index surgery). If a patient died in hospital, or after discharge on any day within the first 90 days after surgery, the patient was assigned 0 DAOH-90. If a patient was discharged from hospital on Day 10 after surgery but was subsequently readmitted for 10 days before their second hospital discharge, then the patient would be assigned 70 DAOH-90. Post-operative days in a post-discharge nursing facility were not counted as days at home.

Data collection, management and validation

The local study team, comprising the primary author and supervising consultant, was responsible for data collection. Information technology systems were used to screen for eligible patients in both the ‘retrospective cohort’ and ‘prospective cohort’. Data points consisted of key demographics, baseline and intra-operative variables. A data collection proforma was utilised comprising baseline demographic data, operative data and follow-up information (Supplementary Material 2). Definitions of comorbidities and specific outcomes are given in Supplementary Material 3. Post-operative sequelae data points were collected as soon as the 90-day follow-up period was reached. In the incidence of an SSI, further details were required with respect to the extent of the infection, magnitude of additional management and resultant patient outcome. Data were obtained using both the patient’s medical notes and electronic records. The information collected included the assessment of pre-operative assessment documentation, theatre information technology systems, discharge letters, clinic letters as well as accident and emergency department records. No changes to normal patient follow-up were made. Data were collected retrospectively and prospectively on an anonymised data collection tool, which was held electronically on a single secure hospital computer, in accordance with local guidelines.

Statistical analysis

The two cohorts were compared by total number of patients on an intention-to-treat basis and as-treated population, with primary analysis focused upon intent-to-treat. Continuous variables were tested for normality and analysed using parametric or non-parametric tests as appropriate. A p-value <.05 was considered statistically significant. Percentages were calculated using the total number of patients (for patient-specific variables) or total number of groins (for operative and post-operative variables and outcomes) as a denominator, as appropriate. Data were analysed in SPSS (IBM™, Armonk, USA; version 25).

Results

Overall, 107 patients underwent 127 groin incisions with 65 patients (76 incisions) in the retrospective cohort and 42 (51 incisions) in the prospective cohort. Most patients (29/42) in the prospective cohort received CiNPWT. However, 13 patients received an adhesive absorbent (Tegaderm™) dressing due to either administrative reasons, lack of availability of the dressing, or ‘out of hours’ provision.

Overall median age was 69 years (IQR 61–76) and the majority of cases were male (73.4%). Most patients had an ASA of either two or three while the majority of groin incisions were for endarterectomy and/or bypass (59.1%). There were no significant differences in baseline demographics or type of operative intervention between the two cohorts (Table 1).

Table 1.

Baseline demographics and operative data.

	Retrospective(%/IQR)	Prospective(%/IQR)	p-value
N cases (N incisions)	65 (76)	42 (51)	—
Age (years)	66 (57–76)	72.5 (65–78)	0.171
Sex – Male	50 (76.9)	25 (59.5)	0.055
Caucasian	62 (95.4)	37 (88.1)	0.162
ASA	3.08 (SD 0.44)	3.12 (SD 0.67)	0.696
Emergency	31 (47.7)	25 (59.5)	0.232
Operation
Common femoral endarterectomy	19 (29.2)	12 (28.5)	0.942
Femoral-popliteal bypass	19 (29.2)	7 (16.7)	0.139
Femoral-distal bypass	12 (18.5)	4 (9.5)	0.206
Femoral-femoral bypass	3 (4.6)	1 (2.4)	0.552
Axillo-bi-femoral bypass	2 (3.1)	2 (4.8)	0.654
Aorto-bi-femoral bypass	6 (9.2)	1 (2.4)	0.162
Iatrogenic pseudoaneurysm repair	4 (6.2)	9 (21.4)	0.018
Ilio-femoral bypass	—	1 (2.4)	—
Other	—	5 (11.9)	—
Longitudinal incisions	—	48 (94.1)	—
Oblique incisions	—	3 (5.9)	—
Bilateral groin incisions	11 (16.9)	9 (21.4)	0.491
Procedure length (mins)	247 (201–309)	259 (171–333)	0.788

Continuous data are presented as means ± standard deviations (SD), inter-quartile range (IQR). Categorical data are given as the counts (percentage). ASA: American Society of Anesthesiology score, mins: minutes. Other: common femoral artery exposure for thrombectomy (iliac ± femoral ± popliteal).

Outcomes

Overall rate of SSI was 19.6% with 16 cases (21%) in the retrospective cohort compared to 5 cases (9.8%) in the prospective cohort (OR: 0.41, 95% CI: 0.14 to 1.20, p = .10) (Table 2). Most SSI were superficial; 13 cases (81%) in the retrospective cohort and 4 cases (80%) in the prospective cohort.

Table 2.

Impact of SSI at 90-day follow-up per groin incision.

Outcome	Retrospective	Prospective	p-value
Outcome	N = 76	N = 51	p-value
Surgical site infection (per groin incision)	16 (21.1)	5 (9.8)	0.099
CDC classification (%)
Superficial	13	4
Deep/Organ space	3	1
Unplanned readmission due to SSI	14 (21.5)	2 (4.7)	0.016
Reoperation due to SSI	9 (11.8)	1 (2.0)	0.017
Total LOS (initial ± re-admission) following SSI (days)	23 (16–42)	17 (7–29)	0.198
DAOH-90 following SSI (days)	61 (43–74)	76 (73–84)	0.014

Continuous data are presented as means ± standard deviations (SD), inter-quartile range (IQR). Categorical data are given as the counts (%: percentage). CDC: Centers for Disease Control and Prevention, SSI: surgical site infection, LOS: length of stay, DAOH-90: days alive and out of hospital at 90 days.

Secondary endpoints

Initial LOS was reduced following the introduction of CiNPWT from a median (95% CI) of 10 days (7–19) to 7 days (5–12) (p = .04) (Table 3). Readmission to hospital for SSI occurred in 14 patients in the retrospective cohort and two patients in the prospective cohort (p = .016). Reintervention was required in nine patients within the retrospective cohort compared to one in the prospective cohort (OR: 6.6, 95% CI: 0.80 to 54.10, p = .10). No patient had reintervention during their initial stay.

Table 3.

LOS and DAOH at 90-day follow-up per patient.

Outcome	Retrospective	Prospective	p-value
Outcome	N = 65 (IQR)	N = 42 (IQR)	p-value
LOS (days)
Initial	10 (7–19)	7 (5–12)	0.042
Re-admission	12 (6–24)	14 (6–21)	0.757
Total LOS (initial ± re-admission)	13 (7–23)	7 (5–12)	0.013
DAOH-90	77 (64–83)	83 (77–85)	0.043

Continuous data are presented as means ± standard deviations (SD), inter-quartile range (IQR). LOS: length of stay, DAOH-90: days alive and out of hospital at 90 days.

Although there was no difference in LOS if readmitted, the total LOS (inclusive of readmission) was reduced following the introduction of CiNPWT (13 days (7–23) vs. 7 days (5–12), p = .01). The introduction of a CiNPWT protocol was also associated with increased DAOH-90 with a median (95% CI) of 83 days (77–85) compared to the pre-protocol retrospective cohort of 77 days (64–83), p = .04).

Discussion

This study showed that a protocol incorporating CiNPWT for groin incisions following vascular surgery could be successfully implemented to a tertiary teaching hospital. Although introduction of CiNPWT was not associated with an overall reduced rate of SSI, there were meaningful improvements in patient related outcomes with an average of five additional Days Alive and Out of hospital at 90 days. Specifically, introduction of CiNPWT was associated with reduced LOS, reduced readmissions to hospital and reduced need for reintervention.

Previous studies on the role of CiNPWT following groin incisions have focused on overall rates of SSI with improvements in the incidence.^19,20,22 However, these studies incorporated heterogenous endpoints while follow-up was limited to 30 days. While most SSI may occur within the first 30 days after surgery, the CDC defines deep/organ space SSI as any occurring up to 90-days post-operatively.²⁷ In our data, three patients presented with deep SSI between 30 and 90 days, all of whom required reintervention.

A key aspect of our study was the duration of patient follow-up to 90 days. This revealed the impact of SSI on overall length of stay in hospital with a reduction in readmission and reintervention rates following introduction of CiNPWT. Kwon et al. (2018) was one of the few studies that examined a patient-centred outcome following the utilisation of CiNPWT with a reduction in reoperation observed, although there was no impact on overall length of stay.²¹ This improvement may be explained by the increased sterility of the wound environment secondary to negative pressure application. Aligned to this, the cost associated with CiNPWT devices also discourages frequent dressing changes, in comparison to the relatively cheap absorbent adhesive dressings, which may result in wound contamination.

To date patient-centred clinical outcomes or healthcare cost analyses have not been assessed in randomised controlled trials of CiNPWT.¹⁵ While our data suggest a reduction in initial and overall LOS to 90 days, the use of DAOH-90 has been shown to accurately predict patient outcomes.²⁴ In our analysis, DAOH-90 improved by an average of 5 days following introduction of CiNPWT (2 days is considered a minimal clinically important difference). These data could also contribute to assess healthcare cost utililisation for these, more expensive, initial dressings.

This analysis has several important limitations that are associated with any observational study. Firstly, the selection and reporting bias inherent within any single-centre study is a significant factor. Retrospective analysis is limited by available data (inclusive of patient demographics and concomitant co-morbidity burden which were not routinely documented within this cohort), that may lead to underreporting of adverse events while comparisons generated are restricted by the lack of a randomly matched prospective cohort. The study team also made the decision to include only SSIs that became evident to the relevant vascular centre. It is acknowledged that this may miss milder infections treated in the community or at other centres. Although the true incidence of SSI might be higher, this would be unlikely to impact upon deep/organ space infections that required reintervention.

Overall, previous studies have concentrated on the overall incidence of SSI between patient groups, comparing CiNPWT to standard of care. However, the definition of superficial SSI can be subjective and impacted by coverage of the wound, via the CiNPWT dressing, for the first 5 days. Data from this study suggest that patient related data such as LOS, readmissions, need for reintervention and DAOH can be reliably collected to 90 days after surgery. A future RCT could focus on DAOH-90 and associated healthcare cost utilisation.

Conclusion

Introduction of CiNPWT in patients undergoing groin incisions in vascular surgery was associated with a reduction in LOS, with reduced rates of readmission and reintervention to 90 days. Further trials on CINPWT should include patient-centred outcomes such as LOS and DAOH-90 while also analysing healthcare costs.

Supplemental material

Supplemental Material - Impact of closed-incision negative pressure wound dressings on surgical site infection following groin Incisions in vascular Surgery; a Single-centre experience

Supplemental Material for Impact of closed incision negative pressure wound dressings on surgical site infection following groin Incisions in vascular Surgery; a Single-centre experience by Ian Patrick Barry, Luke P Turley, Brenig L Gwilym, David C Bosanquet and Toby Richards in Vascular

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Data availability

The data that support the findings of this study are available on request from the corresponding author.

ORCID iD

Ian Patrick Barry

Supplemental material

Supplemental material for this article is available online.

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Supplementary Material

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