Post-Appendectomy Surgical Site Infection Rate after Using an Antimicrobial Film Incise Drape: A Prospective Study

Abstract

Background:

An appendectomy is a contaminated or potentially dirty surgical procedure that can be associated with surgical site infection (SSI).

Methods:

A single-center unblinded prospective cohort study examined the role of antimicrobial incise film drapes in lowering the rate of SSI after appendectomy. Any patient aged 12 years or older who was scheduled for open appendectomy for acute appendicitis was included. Patients were assigned to two groups. Group 1 (n=52) had the standard five-minute skin preparation with 10% povidone-iodine soap followed by the application of an antimicrobial film incise drape, and group 2 (n=39) had the standard skin preparation alone.

Results:

Six (11.5%) of the 52 patients who had the antimicrobial film incise drape and two (5.1%) of the 39 patients who did not have the drape developed SSI (p=NS). Of the six patients in the antimicrobial film group with post-operative SSI, three had a perforated appendix, two had a gangrenous appendix, and one had an inflamed appendix. In group 2, one patient had an inflamed appendix and the other had a perforated appendix. The median length of stay in the hospital was two days (range 1–11 days) for both groups.

Conclusion:

Our study did not support the view that antimicrobial film incise drapes can lower the rate of post-appendectomy SSI. Moreover, the length of stay was not minimized by the use of these drapes.

Appendectomy is regarded as a contaminated or potentially dirty procedure that is associated with a substantial post-operative surgical site infection (SSI) rate: Rates as high as 40% have been reported [1]. Several factors are associated with postoperative infection, such as surgery performed in the presence of an established infection, surgical complexity, and diabetes mellitus [2].

Antimicrobial film incise drapes are plastic adhesion iodine-coated skin drapes claimed by the manufacturer to provide a sterile surface to the wound edge and continuous antimicrobial activity throughout the procedure [3]. This study was conducted to assess the role of antimicrobial film incise drape in lowering the rate of SSI after appendectomy.

Patients and Methods

The Department of Surgery at King Fahd General Hospital conducted a single-center unblinded prospective cohort study to assess the role of antimicrobial film incise drapes in lowering the rate of SSI after appendectomy. This drape has an iodophor complex containing povidone-iodine incorporated into the adhesive that provides continuous antimicrobial activity [3]. These drapes (Loban™ 2 incise drapes; 3M Co., St. Paul, MN) were provided gratis by the 3M Company for the purpose of this study.

Patients

The approval of the hospital Research Ethics Board was obtained for the conduct of this trial. The population included patients aged 12 years or older presenting to the emergency department with signs of acute appendicitis who were scheduled for open appendectomy. Both males and females were enrolled. Recruitment of the patients started on January 17, 2012, and ended in December 2012.

At the time of admission, eligible patients were recruited, and informed consent was obtained. Patients were assigned to two groups by the research assistant. Group 1 had the standard five-minute skin preparation with 10% povidone–iodine soap followed by the application of the antimicrobial film incise drape, and group 2 had the standard five-minute skin preparation alone. We used a pseudo-randomization method for treatment allocation. That is, patient assignment was done initially on an alternating-day schedule. However, we encountered difficulty when the patient stayed overnight, and the surgery was performed the next day, so we began assigning patients to groups on a weekly basis. That is, patients admitted in the first and third weeks of the month were assigned to group 1, and patients admitted in the second and fourth weeks were assigned to group 2. For each patient, a case report form was completed collecting the patient's age and gender, duration of symptoms, body mass index (BMI), presence of fever (temperature ≥38°C), and the white blood cell (WBC) count. Prophylactic antibiotics were given to all patients as 1.5 g of cefuroxime and 1 g of metronidazole pre-operatively.

Technique

Both groups had the standard five-minute skin preparation with povidone–iodine; group 1 had the incise drape applied after drying of the prepared skin. The drape was placed as recommended by the manufacturer, starting at the center of the incision area and going outward to prevent non-adhesiveness caused by air bubbles between the sheet and the skin. Appendectomy was carried out in the standard way by the assigned surgical team. The degree of inflammation of the appendix was documented, as well as the presence of perforation, gangrene, or fluid collection. A closed-system pelvic drain was inserted in the presence of any collection. In all cases, incision closure was carried out in layers with braided polyglactin absorbable sutures, and the skin was closed interruptedly with nylon monofilament nonabsorbable sutures. Post-operatively, the prophylactic antibiotics were administered intravenously for each patient every 8 h. On discharge, oral cefuroxime (500 mg) and metronidazole (500 mg) were to be taken every 12 and 8 h, respectively, for five days.

The primary outcome measure was SSI. The status of the incision was documented at the time of discharge and in the outpatient clinic. Patients who did not show up for two weeks were called and asked to attend the clinic. Incision assessment was continued for six weeks after discharge. Any evidence of SSI was documented and classified according to the U.S. Centers for Disease Control and Prevention criteria as superficial, deep, or organ/space SSI [4]. The patient's length of stay in the hospital was recorded as a secondary outcome measure.

Statistical Analysis

Descriptive analysis was performed. Categorical variables were reported as frequencies or relative frequencies and compared using the X² or Fisher exact test as appropriate. Continuous variables were reported as means with standard deviations and medians with minimum and maximum values and compared using the Student t-test or the Mann-Whitney U test if not distributed normally. Post-appendectomy SSI was compared in the two study groups, and relative risk (RR) with the corresponding 95% confidence interval (CI) was calculated as the measure of treatment effect. All tests were two-sided, and a p value of 0.05 was considered statistically significant. The SPSS software (IBM Inc., Armonk, NY) was used for statistical analysis.

Results

There were 195 cases of appendectomy performed during the study period; only 91 cases were included in this study, as we excluded cases that were done laparoscopically or by a different surgical team. We also excluded cases in which the research criteria were breached, such as use of a different antibiotic regimen or incision closure in a different way.

Of 91 patients, 52 received antimicrobial film incise drapes and 39 did not. There were no statistically significant differences in the baseline characteristics of the study groups (Table 1). Only nine (10%) of 91 cases had associated fever (temperature ≥38°C), but 65 (71%) of 91 had associated elevation of the WBC count (WBC >11×10⁹/L).

Table 1.

Baseline Characteristics by Treatment

	Group 1 with drape (n=52)	Group 2 without drape (n=39)	p
Mean age (years) (SD)	23.3 (9.2)	24.0 (12.0)	0.732
Mean duration of symptoms (days) (SD)	34.8 (20.0)	32.6 (17.4)	0.604
Mean weight (kg) (SD)	61.8 (14.6)	61.5 (14.3)	0.925
Mean height (cm) (SD)	161.3 (13.5)	157.8 (29.5)	0.495
Mean body mass index (kg/m²) (SD)	23.0 (4.5)	23.6 (5.0)	0.981
Mean white blood count (x 13,000 mcL) (SD)	13.0 (4.2)	14.5 (3.7)	0.097
Female (%)	19.0 (36.5)	10 (25.6)	0.270
No patient risk factor (%)	51.0 (98.1)	37 (94.1)	0.574
Temperature ≥38°C (%)	6.0 (11.5)	3 (7.7)	0.727

SD=standard deviation.

Table 2 compares the operating room variables by treatment group. There were no statistically significant differences in intraoperative factors between groups. Eight (8.8%) of the 91 patients developed SSI (superficial type): Six (11.5%) of 52 patients who had the antimicrobial drape and two (5.1%) of the 39 patients who did not (p=0.459) with an RR of 2.2 (95% CI 0.50–10.5). Of the six patients in the drape group who had a postoperative SSI, three had a perforated appendix, two had a gangrenous appendix, and one had an inflamed appendix. In the non-drape group, one patient with SSI had an inflamed appendix, and the other patient had a perforated appendix. None of the patients with SSI in either group had diabetes mellitus or was immunocompromised. Four (50%) of the eight patients with a postoperative SSI had pelvic drain insertion, whereas only 11 (13%) of the 83 patients without SSI had pelvic drain insertion (p=0.007). The median length of stay in the hospital was two days (range 1–11 days) for both groups. Incise drapes were easy to use, and there were no reported sensitivity reactions.

Table 2.

Comparing Intraoperative Factors by Treatment

	Group 1 with drape (n=52)	Group 2 without drape (n=39)	p
Duration of operation (min) (SD)	89.0 (36.2)	90.7 (51.0)	0.840
Post-operative antibiotics (days) (SD)	3.1 (4.1)	2.8 (2.8)	0.697
When infection appeared (days) (SD)	9.8 (5.1)	8.5 (7.7)	0.782
Training of surgeon (%)
Junior resident	15 (29.0)	10 (25.6)	0.601
Senior resident	33 (63.4)	24 (61.5)
Specialist/consultant	4 (7.6)	5 (12.8)
Timing of prophylactic antibiotics (%)
At induction	4 (7.7)	5 (12.8)	0.605
<2 h	11 (21.2)	10 (25.6)
>2 h	37 (71.2)	24 (61.5)
Intraoperative status of the appendix (%)
Normal	5 (9.6)	0	0.275
Inflamed	37 (71.2)	30 (76.9)
Perforated	5 (9.6)	4 (10.3)
Gangrenous	5 (9.6)	5 (12.8)
Intraoperative collection (%)
Localized, sero-purulent	32 (65.3)	26 (66.7)	0.629
Diffuse (free), sero-purulent	6 (12.2)	4 (10.3)
Localized, pus	4 (8.2)	6 (15.4)
Diffuse (free), pus	7 (14.3)	3 (7.7)
Pelvic drain inserted (%)	10 (19.2)	7 (17.9)	0.877

SD=standard deviation.

Discussion

Our findings do not support the value of Ioban incise drapes in lowering the rate of post-operative SSI. In a meta-analysis done by Webster et al., iodine-impregnated adhesive drapes had no effect on the SSI rate (RR 1.03; 95% CI 0.064–1.66; p=0.89) [5]. As described by the manufacturer, the Ioban 2 incise drape helps reduce the risk of surgical site contamination by providing a physical barrier to skin bacteria [3]. Dewan et al. found no difference between the SSI rates for the patients on whom the iodophor drape was used and those patients on whom the drape was not used. However, they found that isolates of normal skin organisms were less frequent when the drape was used in clean and clean-contaminated procedures [6]. In the guideline for prevention of SSI published by the Hospital Infection Control Practices Advisory Committee, there was no evidence that specific reductions in microbial counts on the skin (obtained with use of common preoperative skin-preparation products) lowered the incidence of SSI [7]. In a procedure such as appendectomy, bacterial contamination of the incision with colonic flora during surgery is the major factor in the subsequent development of SSI [8]. Thus, using a product such as an antimicrobial film incise drape will not help in reducing site contamination and infection.

In the drape group, six patients developed SSI. Five of them had complicated appendicitis with perforation or gangrene. These cases are expected to have a higher rate of SSI than in a patient with uncomplicated appendicitis. Morbidity rates associated with appendectomy (mostly related to infection) increase with rupture of the appendix, ranging from 3%–5% in non-perforated appendix to 30%–47% in cases of perforation [9, 10]. Another study found that SSI had an incidence rate of 3.0% in the simple appendicitis group vs. 4.5% in the gangrenous or perforated appendicitis group. (p=0.407) [11]. We had a similar number of cases of perforated and gangrenous appendix in both groups (Table 2); however, the SSI rate was no higher in the undrape group. Webster et al. found a significantly higher proportion of patients in the adhesive drape group developed an SSI [5].

All patients in this study received the same regimen of antibiotic prophylaxis (cefuroxime and metronidazole). Antibiotic prophylaxis is effective in the prevention of post-operative infectious complications in appendectomized patients, whether the drugs are given before, during, or after the operation [1]. Factors such as the skill of the surgeon, prophylactic antibiotics, and time and duration of the procedure were similar in the two groups and did not affect the rate of incision infection (Table 2).

Patients with pelvic collections had drains inserted at the time of appendectomy. Four of the eight patients with postoperative SSI had pelvic drains, whereas only 11 (13%) of the 83 patients without postoperative SSI had a pelvic drain (p=0.007). Although the drain will provide a channel of communication between the infected pelvic cavity and the subcutaneous tissue, which may facilitate contamination of the incision, the higher SSI rate is related to the presence of the collection rather than of the drain, especially when the drain exits through a separate opening, usually away from the appendectomy incision.

In all cases, wounds were closed in layers with braided polyglactin absorbable sutures, and the skin was closed interruptedly with nylon (monofilament non-absorbable) sutures. There are many reports about the advantage of delayed primary closure in complicated appendicitis in reducing the rate of incision infection [8, 13]. A meta-analysis of 2,532 patients conducted by Rucinski et al. concluded that in gangrenous and perforated appendicitis, the incision should be closed primarily regardless of the type of closure. They explained that with the proper use of antimicrobial therapy and avoidance of drains that exit through the same incision, primary closure of contaminated appendectomy incisions can be permitted with a low rate of incision infection [14].

Separation of polyethylene antimicrobial incise drapes from the skin during operation was associated with a six-fold increase in the infection rate compared with operations in which the incise drape did not lift [12]. Our study showed a twofold increase compared with placebo (RR=2.2; 95% CI 0.5–10.5) in incision infection by using antimicrobial film incise drape. We did not encounter an incident where the drape separated from the skin during the procedure; we actually had to remove it actively at the time of incision closure.

The length of hospital stay was similar in the drape and non-drape groups. In the meta-analysis conducted by Webster et al., no reduction in the length of the hospital stay was found when the Ioban incise drape was used [5].

Our study has certain limitations inherent to observational design. First, it was underpowered to reach a definitive conclusion. Although it was a prospective design and less prone to missing or inaccurate data collection, the treatment allocation was neither concealed nor blinded. We used a pseudo-randomization approach that resulted in different sample sizes in the study groups. Another limitation is that we did not use the National Healthcare Safety Network (NHSN) Risk Index for SSI risk adjustment. Our analyses would have been strengthened greatly if we had.

Conclusion

The findings from this study do not support the use of antimicrobial film incise drape for the prevention of post- appendectomy SSI. As well, length of hospital stay was not minimized by the use of these drapes. Because the purpose of these drapes is to provide a shield on the skin and prevent skin organisms from causing surgical incision infections, their benefit could be limited to clean procedures rather than contaminated or dirty operations such as appendectomy.

Footnotes

Author Disclosure

All authors declare that there is no conflict of interest, and this work received no type of funding other than the donation of the drapes from 3M.

References

Andersen

, Kallehave

, Andersen

. Antibiotics versus placebo for prevention of postoperative infection after appendectomy. Cochrane Database Syst Rev, 2005; 3:CD001439.

Rotermann

. Infection after cholecystectomy, hysterectomy or appendectomy. Health Rep, 2004; 15:11–23.

3M Company. Product package insert. Available at www.3m.com/product/information/ioban-2-antimicrobial-incise-drape.html Accessed May 6, 2013.

U.S. Centers for Disease Control and Prevention. Procedure-Associated Module: Surgical Site Infection Event. Available at www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf. Accessed January 29, 2014.

Webster

, Alghamdi

. Use of plastic adhesive drapes during surgery for preventing surgical site infection. Cochrane Database Syst Rev, 2007; 4:CD006353.

Dewan

, Van Rij

, Robinson

, et al. The use of an iodophor-impregnated plastic incise drape in abdominal surgery: A controlled clinical trial. Aust N Z J Surg, 1987; 57:859–863.

Mangram

, Horan

, Pearson

, et al. Guideline for prevention of surgical site infection. Hospital Infection Control Practice Advisory Committee. Infect Control Hosp Epidemiol, 1999; 20:250–278.

Lemieur

, Rodriguez

, Jacobs

, et al. Wound management in perforated appendicitis. Am Surg, 1999; 65:439–443.

Jaffe

, Berger

. The appendix. In: Brunicardi

, Andersen

, Billiar

, et al., eds. Schwartz's Principles of Surgery. Eighth Edition. New York. McGraw-Hill, 2005:1119–1137.

10.

Condon

, Telford

. Appendicitis. In: Townsend

Jr , Beauchamp

, Evers

, Mattox

, eds. Sabiston's Textbook of Surgery: The Biological Basis of Modern Surgical Practice. Fourteenth edition. Philadelphia. WB Saunders, 1991:884–898.

11.

Mehrabi Bahar

, Jangjoo

, Amouzeshi

, et al. Wound infection incidence in patients with simple and gangrenous or perforated appendicitis. Arch Iran Med, 2010; 13:13–16.

12.

Alexander

, Aerni

, Plettner

. Development of a safe and effective one-minute preoperative skin preparation. Arch Surg, 1985; 120:1357–1361.

13.

Cohn

, Giannotti

, Ong

, et al. Prospective randomized trial of two wound management strategies for dirty abdominal wounds. Ann Surg, 2001; 233:409–413.

14.

Rucinski

, Fabian

, Panagopoulos

, et al. Gangrenous and perforated appendicitis: A meta-analytic study of 2532 patients indicates that the incision should be closed primarily. Surgery, 2000; 127:136–141.