Prophylactic Negative Pressure Wound Therapy in Reducing Surgical Site Infections in Closed Abdominal Incision: A Randomized Controlled Trial

Abstract

Objective:

This study aimed to evaluate the efficacy of prophylactic negative pressure wound therapy (PNPWT) in reducing the incidence of surgical site infection (SSI) and other wound complications in closed abdominal incisions.

Approach:

This was a prospective, single-center, open-label parallel arm superiority randomized controlled trial conducted over 2 years. Participants were randomly assigned to PNPWT and standard surgical dressing (SSD) group. The occurrence of postoperative SSI within 30 days, other wound-related complications, length of hospital (LOH) stay, and readmission within 1 month among both the study group were studied.

Results:

A total of 140 participants were included, with 70 each randomized to the PNPWT and SSD groups. In this study, 28.5% and 5.8% developed SSI in the SSD and PNPWT groups, respectively (relative risk = 0.26; 95% confidence interval = 0.08–0.80; p = 0.001). Similarly, the incidence of seroma (7.2% vs. 18.5%, p = 0.016), wound dehiscence (0% vs. 4.2%, p = 0.244), superficial and deep SSI (5.7% vs. 24.3%, p = 0.001) and (0% vs. 4.2%, p = 0.244), and LOH stay (days) (9 vs. 10.5, p = 0.07) were less in PNPWT compared to SSD group.

Innovation:

Despite the advances in surgical care, SSI rates continue to be high. The present findings might facilitate the use of PNPWT as a novel preventive strategy to reduce SSI in closed abdominal incision.

Conclusion:

The PNPWT in closed incisions following elective laparotomy can reduce the incidence of SSI when compared to SSD. The use of PNPWT was associated with a lower incidence of superficial SSI and seroma but without significant reduction in hospital stay.

Clinical Trial Registry India:

CTRI/2020/11/028795

Amaranathan Anandhi, MS, FAIS, FMAS, FCLS, FIAGES, EFIAGES, Dip, Lap., FICS, FALS, FISCP

INTRODUCTION

Health care-associated infections are a subject of great concern. Postabdominal surgery, operative wound complications are common, including surgical site infections (SSIs), seroma, hematoma formation, and wound dehiscence. Among these, SSIs are the most common occurring in 5–15% of the patients.¹ SSIs are linked to significant morbidity, including extended hospital stays, lower quality of life, higher health care expenses, and delay in adjuvant therapy in cancer patients. SSI and associated wound complications pose a considerable burden to patients and health care systems.² The cause is multifactorial, including patient-related factors such as obesity, diabetes mellitus, age, gender, and smoking, and treatment-related factors such as operative procedures, prophylactic antibiotics, and postoperative interventions. Several measures are practiced to prevent SSI, which range from simple conventional wound dressing with sterile dry gauze to more advanced wound dressings stimulating the proliferative phase of wound healing like hydrocolloids, topical application of autologous blood products, growth factors, cultured skin, and prophylactic negative pressure wound therapy (PNPWT). Although evidence-based SSI care bundles have been implemented globally, the incidence of SSI, its morbidity, and mortality rates continue to be high.

Thus, using PNPWT as a preventative measure emerged as a promising notion. Using PNPWT in closed surgical incisions may reduce fluid accumulation in the avascular dead space, that is seroma and thereby reducing the chance of infection. It also increases blood flow around the closed incisions, reduces shearing stress at suture lines, and increases lymphatic drainage, thereby improving wound healing and preventing associated complications.³ Though studies have demonstrated a decreased incidence of SSI by PNPWT in closed incisions in orthopedics, thoracic, and vascular surgery, the benefits of PNPWT in avoiding SSIs in high-risk closed abdominal incisions remain unclear.⁴ In a study that compared the effect of PNPWT with standard sterile dressing in patients undergoing pancreaticoduodenectomy, the incidence of SSI was 9.7% in the PNPWT group against 31.1% in the standard dressing group.⁵

Several meta-analyses have reported the benefits of PNPWT in closed incisions; however, these have either included patients undergoing a wide range of procedures or have included both observational studies and randomized trials. Since there is a paucity of data using PNPWT in an elective abdominal closed incision to prevent wound complications, especially SSI, we intent to the study the same.

CLINICAL PROBLEM ADDRESSED

Despite the various advances in the medical field, SSI rates are still high with significant morbidity and mortality. Particularly, abdominal surgeries tend to have high chance of developing SSI because of the high bacterial concentrations in the intestines and more likely bacterial contamination in abdominal operations than others.⁵ In India, SSI rates vary widely ranging from 1.6% to 38% depending on the setting.⁶

PNPWT is a noninvasive system in which negative pressure is exerted over a closed wound using an adhesive semiocclusive dressing connected by a tubing to a suction apparatus. The role of negative pressure wound therapy (NPWT) in preventing SSI has been explored previously in various subspecialties and has reported promising results.⁷ The data on role of PNPWT in preventing wounds complications in closed abdominal incisions is still lacking. Therefore, we aim to study the effect of PNPWT on the incidence of SSIs as the primary objective and the incidence of other wound complications such as seroma, wound dehiscence, duration of dressing, number of dressings changed, length of hospital (LOH) stay, and readmission within 30 days postsurgery as secondary objective.

MATERIALS AND METHODS

Study design

This study was an open-label parallel arm superiority randomized controlled trial (RCT) conducted in the Department of General Surgery in a tertiary care hospital from November 2020 to June 2022. The study was approved by the Institute of Human Ethics Committee and was registered in Clinical Trial Registry India (CTRI) India (https://ctri.nic.in/Clinicaltrials/advsearch2.php) with registration number CTRI/2020/11/028795. The nature, methodology, and risk involved in the study were explained to the patient. All the information collected was kept confidential, and the patients were free to withdraw from the study at any time.

Study participants

All patients over 18 years of age undergoing elective midline laparotomy under Type II clean contaminated wound were included. We have excluded the laparotomy wounds which were not closed primarily for some reason, laparoscopic-assisted procedures and patients planned for a second look laparotomy within the same admission for causes other than SSI. Meanwhile, in patients who developed an allergic reaction to the dressing material or did not tolerate the NPWT, the intervention was stopped, and the standard surgical dressing (SSD) was applied.

Sample size

The sample size was calculated using OpenEpi software version 3.1, considering the expected rate of SSI in the control arm and in the intervention arm as 31% and 9.7%, respectively, with 95% confidence interval, power of 80% in both the arms, the sample size was calculated to be 128; 64 participants in each arm.³ Considering a dropout rate of 10%, the final sample size was estimated to be 140, with 70 participants in each arm.

Study procedure

Patients planned for elective laparotomy were assessed for eligibility and recruited for the study after obtaining informed consent. Preoperative antibiotic of intravenous Ceftriaxone 1 gm was given 1 h before incision and was continued for the first postoperative day (POD) as 1 gm 12 h apart. The abdomen was prepped using a 1% povidone iodine preparation and alcohol-based solution. After the definitive procedure, rectus was closed using an interrupted 1/0 polypropylene suture. Skin incision closure was done with either sutures or staplers according to the operating surgeon's practice. After which the patients were randomized in a 1:1 ratio into either SSD or NPWT groups. Stratified permuted block randomization was done using a computer program with randomly selected block sizes of 4 and 6. Allocation concealment was carried out by serially numbered opaque sealed envelopes.

Patients randomized to the control group received a routine SSD which consists of dressing using sterile gauze with adhesive tape. Patients randomized to the experimental arm received NPWT dressing immediately after skin closure. Sterile absorbent gauze/foam was used in the dressing, and a transparent adhesive drape was used to create an air-tight seal with a suction tube kept inside, which was connected to a suction device set to provide 125 mmHg of continuous negative pressure. The NPWT system was applied over the surgical wound for a minimum of 3 days and a maximum of 10 days. The dressing was inspected daily by the investigator. If the NPWT system was soiled or dislodged, it was removed and reapplied to ensure coverage of the wound for a maximum of 10 days after the operation or till the discharge of the patient, whichever was earlier.

The number of times the dressings changed was recorded. The reasons were documented if the operating team decided on the definitive removal of the PNPWT system during the postoperative period. The LOH in days and postoperative pain on the 3rd and 5th PODs measured using the visual analog scale (VAS) from 1 to 10 were recorded. Data missing due to death or re-laparotomy were counted as SSIs in both groups. Data missing for other reasons (e.g., lost to follow-up) weren't counted as SSIs in either group. Patients were discharged according to the discretion of the operating surgeon. The patients were explained the signs and symptoms of SSI during discharge, and the same was enquired about over the phone on the 30th day of surgery, and information was recorded.

Outcome measures

Demographic data such as age, sex, body mass index (BMI), and telephone number, the clinical data such as American Society of Anesthesiologists (ASA) class, comorbidities, smoking, neoadjuvant therapy, preoperative blood sugar, hemoglobin, and albumin were recorded from a prospectively collected database, and electronic laboratory notebook was not used. Operative details such as type of surgery, wound class, duration of surgery, amount of blood loss, number of blood transfusions were collected.

The primary end point of this study was to assess the incidence of SSI from randomization to 30 days postsurgery, while secondary points were the rates of wound complications such as seroma, wound dehiscence, different classes of SSI, duration of dressing, number of dressings changed, LOH stay, and readmission within 30 days postsurgery were collected.⁸ Further, signs and symptoms of SSIs were interviewed over the phone on the 30th day postsurgery and were recorded. Participants before discharge were educated about the signs of SSI such as swelling around the surgical site, redness, warmth, and discharge.

Statistical analysis

The continuous variables were summarized as a mean and standard deviation and median with interquartile range (IQR) depending on the normality of the distribution. Categorical variables such as age, sex, wound category, type of surgery, and comorbidities were summarized as frequencies and percentage. The pain scale measured using VAS were summarized as median with IQR. The unpaired t-test, and the Mann–Whitney test were used to check for significant difference between the groups for quantitative variables and the Chi-square, or Fisher exact test was used to analyze categorical variables.

A two-sided p-value of <0.05 was considered significant. STATA 14 was used for statistical analysis. Holm–Bonferroni correction method was used to adjust for the multiplicity of statistical testing in regard to the incidence of superficial and deep SSI. A p-value of 0.049 and 0.005 were considered statistically significant in regard to the statistical significance of deep and superficial SSI among two groups, respectively.

RESULTS

The flow chart Figure 1 shows the patient enrolment, randomization, allocation, follow-up, and analysis throughout the trial according to the CONSORT protocol. A total of 155 patients who underwent laparotomy were assessed for eligibility based on inclusion and exclusion criteria. Out of those, 140 patients were recruited for the study and randomly allocated in a 1:1 ratio to SSD group and PNPWT group, with 70 participants each. There was no lost to follow-up in the study population. One participant in PNPWT developed an allergic reaction on POD-3 after applying PNPWT dressing and was excluded from the study. Thus, a modified intention to treat analysis was performed after exclusion of the participant from the intervention arm due to the development of allergy during the follow-up period.

Figure 1.

CONSORT flow chart.

Demographic profile

The overall mean age was 55.1 ± 11.13 in the SSD group and 51.7 ± 13.05 years in PNPWT. The basic demographic characteristics such as age of patients, male-to-female ratio, and BMI were comparable between the two groups. Also, the comorbidities, tobacco habituation, ASA grade, serum fasting blood sugars, albumin, and hemoglobin levels were comparable between the groups (Table 1).

Table 1.

Comparison of demographic characteristics between the study groups

Variables	SSD (N = 70) (%), Mean (SD)	PNPWT (N = 69) (%), Mean (SD)
Age (years)	55.1 ± 11.13	51.7 ± 13.05
BMI (kg/m²)	17.94 ± 3.26	18.30 ± 3.34
Gender
Male	37 (52.8%)	41 (59.4%)
Female	33 (47.1%)	28 (40.5%)
Hypertension	11 (15.7)	11 (15.9)
Diabetes	8 (11.4)	11 (15.9)
Both HTN and DM	1 (1.4)	3 (4.35)
Others	4 (5.7)	2 (2.9)
Smoking	19 (27.1)	25 (36.2)
Neoadjuvant therapy	13 (18.5)	8 (11.5)
ASA class
I	0 (0.0)	1 (1.5)
III	48 (68.5)	45 (65.2)
IV	22 (31.4)	23 (33.3)
FBS	107.5 ± 20.75	112.2 ± 18.0
Albumin	3.23 ± 1.35	3.11 ± 0.52
Hemoglobin	10.6 ± 1.77	10.3 ± 2.19
Types of surgeries
Upper GI	20 (28.5)	18 (26)
Colorectal	19 (27.1)	17 (24.6)
Hepatobiliary	1 (1.4)	6 (8.6)
Feeding procedures	28 (40)	24 (34.7)
Stoma	2 (2.8)	4 (5.7)

ASA, American Society of Anesthesiologists; BMI, body mass index; DM, diabetes mellitus; FBS, fasting blood sugar; GI, gastrointestinal; HTN, hypertension; PNPWT, prophylactic negative pressure wound therapy; SSD, standard surgical dressing.

Primary outcome

On comparing the incidence of SSI, 20 patients (28.5%) in the SSD group and 4 patients (5.8%) in the PNPWT group developed SSI (p = 0.001).

A total of 24 participants developed SSI of which 21 had superficial SSI, 3 had deep SSI and none of the participants in both groups developed organ space SSI.

On subgroup analysis, 17 participants in the SSD group and 4 participants in the PNPWT group were noted to have developed superficial SSI (p = 0.001). All the 3 participants who developed deep SSI belonged to SSD group, while none of the participants in the PNPWT group had deep SSI (p = 0.244) (Table 2).

Table 2.

Comparison of incidence, types of surgical site infection, and wound-related complications among the study groups

Variable	SSD (N = 70)		PNPWT (N = 69)		p
Variable	n	%	n	%	p
Incidence of SSI
Yes	20	28.5	4	5.8	0.001^a
No	50	71.4	65	94.2	0.001^a
Types of SSI
Superficial SSI	17	24.3	4	5.7	0.001^b
Deep SSI	3	4.2	—	—	0.244^b
Complication other than SSI
Seroma	13	18.5	5	7.2	0.016^b
Dehiscence	3	4.2	—	—	0.244^b

Chi-square test.

Fisher's test.

SSI, surgical site infection.

Secondary outcome

On comparing other wound-related complications, 13 patients (18.5%) in the SSD group and 5 patients (7.2%) in the PNPWT developed seroma (p = 0.016). Wound dehiscence was noted in three participants (4.2%) in the SSD group, while none of the participants in the PNPWT developed wound dehiscence (p = 0.244) (Table 2).

The median LOH stay among the participants in the SSD group was 10.5 days with an IQR of 8–13 days compared to 9 days with an IQR of 7–11 days among the PNPWT group (p = 0.07). On assessing the patients' postoperative pain using the VAS score, we found that the score on the third POD was significantly lower among PNPWT (p = 0.02), with no significant difference on the fifth POD between the groups. The mean number of dressings applied in the SSD group was 3.8 (standard deviation [SD] ±0.95), and in the PNPWT group was 2.6 (SD ±0.56) (p = 0.001). The mean duration of dressings applied in the SSD group was 5.7 days (SD ±1.2), and in the PNPWT group was 5.6 days (SD ±1.3) (p = 0.61). The readmission rates within 1 month after surgery showed no statistically significant difference between the two groups (Table 3).

Table 3.

Comparison of secondary outcomes between the study groups

Variables	SSD (n = 70)	PNPWT (n = 69)	p
Length of hospital stay, median (IQR)	10.5 (8–13)	9.0 (7–11)	0.07
Pain (VAS) on 3rd POD, median (IQR)	1.0 (1–2)	1.0 (1–1)	0.02
Pain (VAS) on 5th POD, median (IQR)	1 (0–1)	0 (0–1)	0.2
Number of dressings	3.8 ± 0.95	2.66 ± 0.56	0.001^a
Duration of dressing (days)	5.7 ± 1.2	5.6 ± 1.3	0.61^a
Readmitted patients within 1 month, n (%)	2 (2.8)	1 (1.4)	1.0^b

Unpaired t-test.

Fisher's exact.

IQR, interquartile range; PNPWT, prophylactic negative pressure wound therapy; POD, postoperative day; SSD, standard surgical dressing; VAS, visual analogue scale.

DISCUSSION

PNPWT is a promising trend in the management of closed surgical incisions to prevent wound-related complications, notably SSI. Studies have demonstrated a decreased incidence of SSI by PNPWT in orthopedics, thoracic, and vascular surgery, but its benefit in preventing SSIs in high-risk closed abdominal incisions remain unclear.⁴ The benefits of PNPWT in patients undergoing abdominal surgery are supported by mostly retrospective and observational studies, and there are only a few randomized control trails exploring this aspect.^9

–13

Several meta-analyses have reported the benefits of PNPWT in closed incisions; however, these have either included patients undergoing a wide range of procedures or have included both observational studies and randomized trials.^14,15 Thus, the present study was conducted as a prospective RCT comparing SSD and PNPWT among the patients undergoing elective laparotomy.

This RCT demonstrated a statistically significant reduction in the incidence of SSI and other wound complications, such as seroma formation and wound dehiscence, in patients undergoing PNPWT compared to SSD. Also, patients who received PNPWT for abdominal incisions had a shorter hospital stay, lower VAS score on the early PODs, and a fewer wound dressing changes during their stay. This substantiates the benefit of PNPWT in closed laparotomy wounds in an elective setting.

PNPWT is suggested to reduce the risk of SSI by decreasing bacterial contamination and fluid accumulation and increasing the microvascular blood flow in the closed incision.¹ A study done by Malmsjö et al. suggested that both hypo- and hyperperfusion mechanism may have a role in the wound healing in NPWT group.¹⁶ Our study showed a significant decrease in the incidence of SSI among the patients in the PNPWT. Similar to our study, few RCTs also showed a significant decrease in the incidence of SSI in the PNPWT group compared to the control group.^14,17

In addition to SSI, other wound complications such as seroma, hematoma, and wound dehiscence pose a tremendous burden on the treating surgeon. In our study, apart from the decreased incidence of SSI, we also found that seroma rates were significantly lower among patients randomized to the PNPWT group. But the rate of wound dehiscence was found to be same in both the group which was similar to the results of few systematic reviews.^14,18 Considering this, our study highlights the importance of further adequately powered studies to explore the role of PNPWT in mitigating these wound-related complications other than SSI.

The diagnosis, course, and management of three subtypes of SSI (superficial, deep, and organ space) are varied.⁸ The protective role of PNPWT against each subtype remains unclear. We have many conflicting results in the literature. A meta-analysis showed that the superficial SSI rate was reduced in the PNPWT group with no effect on deep or organ/space SSI. Similarly, another study by Patrick found that the incidence of deep SSI incidence remained the same in both PNPWT and SSD groups.¹⁸ Likewise in another study, no significant difference in the prevention of both superficial and deep SSI by PNPWT was observed.¹⁹ But in our current study, we have observed that PNPWT can significantly reduce rates of superficial SSI, but not deep SSI. Further adequately powered studies are essential to enumerate the effect of NPWT on the various classes of SSI.

The LOH stay is an essential metric of health care delivery and is often used as an efficiency indicator. Despite a decrease in the incidence of SSI in the PNPWT group, there was no statistically significant decrease in the LOH. Similar results were seen in an RCT and a meta-analysis where PNPWT did not affect the LOH stay.^15,20 This is because, in our study, most of the SSI in the SSD group was superficial SSI (85%) which required minimal additional interventions and discharge criteria were not dependent on it.

In concordance with previous studies, our study demonstrated a significantly decreased number of dressings in PNPWT than in SSD.²¹ Although not significant, PNPWT had fewer duration of dressings. We also found that the postoperative pain scores (VAS scale) on POD-3 were significantly less in the PNPWT group than in SSD. This is because of faster growth of granulation tissue covering the raw wound area following PNPWT along with fewer wound manipulation while changing the dressings.²¹

In the era of limited literature on negative pressure wound therapy, we conducted an open-label parallel arm superiority RCT between the SSD group and the PNPWT group. In our study, homogenous distribution of the patients was observed with strict adherence to the inclusion and exclusion criteria. The strength of our study is the homogeneity of the population, where the confounding factors, quantitative variables, and qualitative variables studied among the two groups were similar. On the other hand, our study included only clean-contaminated wounds, which have a low-to-moderate risk for SSI.

It remains unclear if PNPWT improves the SSI rates associated with all wound types. Thus, further studies are needed to evaluate the role of PNPWT in emergency surgeries. Also, the LOH stay is multifactorial, which depends on not only the midline wound but also the type of surgery, presence of drains, mobilization out of bed, and other surgical complications. These factors need to be studied while exploring the effects of PNPWT on LOH. An economic evaluation was not performed to determine the cost-effectiveness of PNPWT compared with SSDs.

In conclusion, the prophylactic use of negative pressure wound therapy (PNPWT) in closed incisions following elective laparotomy can reduce the incidence of SSI significantly when compared to traditional surgical dressings. PNPWT was associated with a lower incidence of superficial SSI, seroma, and fewer dressing changes during hospitalization. Even though there is no significant reduction in the LOH stay, patients had a significant reduction in early postoperative pain score.

Therefore, this study opens up the scope for further research in the use of PNPWT in other procedures also to reduce SSI and its associated with morbidity and mortality.

INNOVATION

The use of negative pressure wound therapy in preventing SSI is an emerging idea and has been reported across various specialties. Its role in preventing the occurrence of SSI in closed abdominal incision is still unclear. Here we focused on comparing the effects of PNPWT versus SSD on the incidence of SSI and other wound complications among patients undergoing elective abdominal surgeries. Application of NPWT prophylactically on closed abdominal incisions should reduce the incidence of SSI and other wound complications, thereby reducing the LOH in patients with closed incisions following laparotomy.

KEY FINDINGS

Incidence of SSI was lower in the PNPWT than in SSD (5.8% vs. 28.5%, respectively) (relative risk = 0.26; 95% confidence interval = 0.08–0.80; p = 0.001).

Other wound complications such as the incidence of seroma (7.2% vs. 18.5%, p = 0.016), wound dehiscence (0% vs. 4.2%, p = 0.244), superficial, and deep SSI (5.7% vs. 24.3%, p = 0.001) and (0% vs. 4.25%, p = 0.244) were lower in the PNPWT group.

The LOH stay showed a decreasing trend among the patients who received PNPWT, though it was not significant (9 vs. 10.5, p = 0.07).

Footnotes

ACKNOWLEDGMENTS AND FUNDING SOURCES

The authors would like to thank Dr. Subitha Lakshminarayanan, additional professor, Department of Preventive and Social Medicine (PSM), Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India, for her help in the statistical analysis. This study was not funded.

AUTHOR DISCLOSURE AND GHOSTWRITING

The authors report no conflict of interests in this work. The content of this article was written by the authors listed. No ghost-writers were used to write this article.

AUTHORs' CONTRIBUTIONS

M.M.: Data curation (lead), methodology and project administration (lead). A.A.: Conceptualization (lead), data curation, methodology writing–original draft (lead), formal analysis and review and editing. S.S.: Methodology writing–original draft and review and editing (equal). A.R.K.: Formal analysis, supervision, manuscript writing and review and editing (equal). M.S.: Writing–review and editing (equal). V.K.: Conceptualization (supporting); writing–original draft (supporting), and writing–review and editing (equal).

ABOUT THE AUTHORS

Maharjan Manik, MBBS, MS, is a junior resident in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India. Amaranathan Anandhi, MS, FAIS, FMAS, FCLS, FIAGES, EFIAGES, Dip, Lap., FICS, FALS, FISCP, is a additional professor in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India. Sathasivam Sureshkumar, MS, DNB, MNAMS, FICS, FMAS, is a professor in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India. Andi Rajendharan Keerthi, MBBS, MS, DNB, is a senior resident in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India.

Mahalingam Sudharshan, MBBS, MS, is a senior resident in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India. Vikram Kate, MS, FRCS (Eng.), FRCS (Ed.), FRCS (Glasg.), PhD (Surg. Gastro.), MAMS, MASCRS, FACS, FACG, FFST (Ed.), is a professor of surgery in the Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, India.

Abbreviations and Acronyms

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