Awareness and wound assesment decrease surgical site infections

Abstract

Objective: Various surveillance methods have been described for surveillance of surgical site infections (SSI). The aim of this study was to examine prac- ticality of SSI risk assessment methods (SENIC and NNIS) with a postoperative wound monitoring scale (ASEPSIS) as an outcome assessment measure and evaluation of the contribution of wound assesment to the reduction of wound infection.

Material and Methods: Patients were followed with a prospective data chart through four year. Correlation of SENIC and NNIS together with ASEPSIS were performed.

Results: During the study period, 275 SSI occurred. SSIs were determined within the 21 days-period after operations. Correlation between SENIC with ASEPSIS (rs= 0.41, p< 0.001) was found better than that for NNIS with ASEPSIS (rs= 0.37, p< 0.001). Type of operation (emergency vs. elective), body mass index, operation class and American Society of Anesthesiologists scores were found independently predictive factors for SSI. The forth year SSI rate was found to be significantly lower than the other years (p< 0.001).

Conclusion: This study indicates weak but significant correlation between preoperative risk assessment methods for SSI and ASEPSIS method. In addi- tion, surgical wound assesment and awarness of the wound infection rates, have decreased the SSI rates over the years.

Keywords: Asepsis, senic, SSI, nnis

Introduction

Surgical site infection (SSI) continue to be the one of the most common nosocomial infection, accounting for more than 20% of all hospital-acquired infections (1). The incidence of SSI is 2% to 5% in patients undergoing surgery, which is the most common nosocomial infection in surgical patients, accounting for 38% of nosocomial infections in this patient population (2,3). Surgical site infections are associated with increased length of stay results in an additional cost and a 2- to 11-fold increase in the risk of mortality. Since SSIs can be preventable up to 60% by using evidence-based measures, accurate surveillance of wound complications has become a pay-for-performance metric and a target of quality-improvement efforts.

For this purpose, The Study on the Efficacy of Nosocomial Infection Control (SENIC) and the National Nosocomial Infections Surveillance (NNIS) system methods have been used predominantly for risk assessment of surgical wounds postoperative wound monitoring (4,5). Since the most important step in surgical site infections is the recognition and definition of the infection; standardized, objective, traceable and easily applicable survaillance systems are required. It has been revealed that the scoring system with all these features is the “ASEPSIS” scoring defined by Wilson (6,7). The main objective of this study was to examine corelation of NNIS and SENIC methods with ASEPSIS wound scoring method as an outcome assessment measure. In addition, factors affecting development of SSIs in different types of general surgical operations were investigated.

Material and Methods

A total of 2339 surgical procedures, excluding local and proctological procedures, were performed in our clinic (First Department of Surgery) in Ankara Numune Training and Research Hospital within four years. Prospective wound surveillance has been practiced for all patients having a surgical operation. The study protocol was approved by the local ethics committee.

A data chart including patient’s risk index and postoperative wound monitoring is used to follow all surgical wounds. All charts are followed and completed by a senior resident and a senior staff surgeon in our department.

SENIC and NNIS indexes were used together for risk assessment of SSI. The SENIC risk index includes measurement of wound contamination and a proxy for the patient’s susceptibility to infection. The NNIS risk index quantifies intrinsic and extrinsic measures of patient risk for developing an SSI. Both SENIC and NNIS indexes were eveluated according to the Table 1 and 2.

Table 1. SENIC SSI risk index

During wound surveillance, operations are classified into four categories according to their invasiveness. Surgical procedures in which the abdominal cavity is not entered (group 1); abdominal operations (excluding liver and major retroperitoneal operations) (group 2); thoracic operations (group 3); liver surgery and retroperitoneal operations (group 4) (9).

SSIs were evaluated according to the latest modifications of the Centers for Disease Control and Prevention (CDC) and ASEPSIS method (6,7,10). The wound of each patient was evaluated daily by the surgeon and recorded. The wound was evaluated at 14., 17. and 21. days postoperatively in the absence of significant wound infection. Patients discharged without SSI, were checked by the resident surgeon in the postoperative first month and third month at the outpatient clinic.

Postoperative wound evaluation was made using the ASEPSIS method (Table 3). While scores between 0 and 5 were given for erythema and serous discharge in the wound; Scores between 0 and 10 were given for purulent discharge and wound dehiscence. Scoring was made according to the ratio of the present symptom to the wound area. This scoring was made for five days of the first seven days postoperatively. Extra points for five-day scoring in cases of antibiotic use (10 points), drainage with local anesthesia (5 points), debridement under general anesthesia (10 points), wound culture positiveness (10 points) and no wound healing in 14 days (5 points) was added (6,7,11). The wounds are classified into five categories according to overall scores (Table 3). When the total score score was above 20, it was considered to have wound infection. Infected wounds were followed up until surgical infection regressed.

Table 2. NNIS SSI risk index

Table 3. Brief description of the ASEPSIS method

Statistical Analysis

Patients were divided into two groups as those with and without SSI, and bivariate analysis was performed, and all significance tests were performed with two-tailed. Comparative analysis of variables was done using the χ² test. Correlation analysis between SENIC, NNIS, ASEPSIS methods was performed using Spearman correlation coefficient. The development of SSI was accepted as the dependent variable and multivariate analysis was performed by applying logistic regression using Wald statistics. In the multivariate analysis, those with a p value under 0.25 among the independent variables effective in the development of SSI, which were previously determined in the bivariate analysis, were used. All logistic regression results are given as odds ratio (OR) and with a 95% confidence interval (CI). All p values were two-tailed and p≤ 0.05 values were considered significant.

Results

During the study, a total of 2339 patients, 1108 (47.4%) male and 1231 (52.7%) female, were operated. The average age of the patients was 47.9 (range 6 to 95) years. All patients were followed for 21 days. This rate was 95% at 30-day follow-up, and 86% at three-month follow-up. Average BMI was 25.9 (range 15.6 to 55.5). Of all operations, 88.4% were elective. During the study, 19 different operations were performed. Most operations were included in group 2 (49%, n= 1147) (Table 4).

Table 4. Class of operation

Approximately 90% of the patients were scored as ASA II or ASA III. 84.7% of the operations were performed under general anesthesia. During the study, 275 SSIs were occured (11.8% of 2339 operations). All SSIs developed within the postoperative 21-day period. SSI rates through years has shown at figure 1 and the decrease at forth year was statistically significant. While the SSI rate was 9.5% at elective operations, it was 28.3% for emergency operations (p< 0.001). SSI occurred in 1.7% in group 1 operations, 16.4% in group 2 operations, and 37.2% in group 4 operations (p< 0.001 among all groups). 134 of 275 patients had culture positive SSI (48.7%). While this rate was 4.6% in elective operations, it was 13.6% in emergency operations. In general, a single microorganism isolated from the wound (75.1%), and most of them were Escherichia coli (45.5%) (Table 5).

Table 5. Microbial isolates from surgical wound infections

Figure 1. SSI rates through years.

Patients were compared as with and without SSI. As BMI, age, and ASA scores increased, SSI rates also increased (Table 6). However, there was no difference in SSIs between men and women. Class of operation (group 1, 2 or 4), type of operation (elective or emergency), and type of anesthesia also affected the development of SSI. NNIS and SENIC risk indexes were assigned in the preoperative period. Correlation between the SENIC risk index with the ASEPSIS (rs= 0.41, p< 0.001) and a correlation between the NNIS risk index with the ASEPSIS (rs= 0.37, p< 0.001) were found to be statistically significant.

Table 6. Bivariate analysis of the parameters according to status of infection

After bivariate analysis, BMI, age, ASA score, type and class of operation were selected as variables, since p values were <0.25 in the SSI development association, for logistic regression analysis. In this study, type of operation (emergency versus elective), BMI, operation class and ASA score were found to be independent variables in SSI development (Table 7).

Table 7. Multivariate logistic regression analyses of output parameters (SSI)

Discussion

Postoperative SSI is the most serious cause of morbidity and sometimes mortality. Comparison of the quality of surgical care provided among all health institutions is often made by considering the infection rates. Such comparisons are only valid if standard SSI definitions are made and permanent follow-up methods are used. Indexes indicating the risk of developing SSI, such as SENIC and NNIS, have been developed to compare patients’ intrinsic and extrinsic risk factors between hospitals (12,13). The SENIC risk index alone determines SSI risk better than wound classification. However, the SENIC index alone cannot determine the risk according to the type of operation. The NNIS risk index is a modification of the SENIC risk index. Some deficiencies in the SENIC system are corrected with the NNIS index. These two indexes can be used individually in studies on SSI or together, as in this study (14,15).

The diagnosis of SSI is a routine part of clinical practice. However, it is much more important to determine the severity of the infection. Recognizing the wound infection alone may be sufficient to treat the patient, but some standard criteria are needed in order to be able to take prophylactic measures and to be objective in wound follow-up. In the surgical ward, many wounds that drain “serous fluid” with wound edge separation may not be recorded as SSIs, particularly if no cultures were taken. Therefore, more objective and realistic wound assessment methods were needed. The advantages of the ASEPSIS method are that it is objective, realistic and productive, and can determine the severity of the SSI. A valid infection comparison between hospitals can be made with the ASEPSIS method (11,16).

The infection rate seen in group 1 (1.68%) can be compared with other reports. In the report published by NNIS in 2001, median rates of wound infection for mastectomy ranged from 0.72% to 1.65%, and those for herniorrhaphy ranged from 0.64% to 3.33% (3). In group 2 operations, the SSI rates (16.4%) in this study were found to be higher than the NNIS reports. According to NNIS, the lowest infection rate in this group was seen in cholecystectomies (0.00%-3.08%), whereas the highest rate was observed in colon surgery (3.57% -12.88%). In group 4 operations, the rate of SSI was found higher than both NNIS and other reports (37.2%) (3,18).

During the study, all SSI’s occurred within 21 days. In the literature, follow-up time varies in different studies. Some authors recommend at least 30 days for a close follow-up period (18,19). Others propose limited surveillance of wound status (20–22). In this study, ASEPSIS method was applied according to Wilson’s original definition (7). The main reason of our limited follow-up period is the improvement on the cost-effectiveness of wound surveillance. The patient concordance to the follow-up program is also another problem, as observed in our study. A similar description of SSI status, after percutaneous endoscopic gastrostomy, was reported in a recent study from United Kingdom (20). In this report, the authors followed surgical wounds up to 28 days using the ASEPSIS method, which has been discussed in the surgical literature since the first report in 1986. In the articles published by Smyth and Emmerson (21) and another one published by Mangram (22) the follow-up period was proposed 21 days, (3-weeks). Therefore, the time points for wound control in the current study were chosen based on these papers (23). A 21-day surveillance period for SSIs seems adequate for a wide range of general surgical procedures.

In this study, the significance of age, BMI, ASA score, class and type of operation and type of anesthesia in relation to the development of SSI was clearly shown in bivariate analysis. BMI, ASA score and class and type of operation were found as independent risk factors for according to logistic regression analysis. These results are concordant with other studies. The relationship between emergency operations and SSI has been also shown in a study from Denmark (24). In their study, less SSI (6%) was found in elective GIS operations compared to emergency GIS operations (16%) . The relationship between obesity and SSI is well documented (25,26). Age and ASA score are considered as independent variables in the development of SSI (18). The role of general anesthesia on SSI pathogenesis is not fully understood yet. Untill recent studies, a negative effect of general anesthesia on wound healing was not shown, however, recent studies have shown that general anesthesia may be a risk factor for the development of SSI (27,28). In this study, the low number of patients undergoing regional anesthesia led to bias among type of anesthesia.

With the SENIC project that started in 1974, it has been shown that nasocomial infections decreased by one third by following up nosocomial infections and informing the hospital staff of their results (6). As in the study of Haley et al., in our study compering the SSI rates of first year with the increased rates of second and third year was because of the correct recognition of SSI; And the decrease in the fourth year has been thought as a result of the clinical physicians’ more careful, in terms of SSI in the peroperative period. During this study we also recognised that especially at education hospitals postoperative wound assement must be the one of the main subjects to be tought to surgical residents, as SSIs can be preventible more than 50% just with assesment. In this sense, we believe that it will be beneficial for surgical units to share their own SSI results with clinical or hospital staff, and to reduce SSI rates by both continuing awareness and monitoring risk factors by reminding them.

In our study, the SENIC risk index was found to have a better correlation with the ASEPSIS wound tracking scale than the NNIS risk index. However, rs values of both indexes are below 0.75. This shows a weak relationship between parameters. New studies should be conducted to increase the sensitivity and specificity of these indexes. The number of wound infections calculated according to the ASEPSIS method includes delay in wound healing, minor, moderate and severe wound infections. Depending on these differences, the calculated number of SSIs may be higher than other SSI classification systems.

In conclusion, higher than expected rate of surgical wound infection for group 2 and 4 classes of operations were found in this study. This difference is due to intrinsic and extrinsic conditions of the study era. A weak correlation was found between the preoperative risk index scales for SSI (NNIS and SENIC) and the ASEPSIS method. In fact, the SENIC index has been modified with NNIS, but the fact that the ASEPSIS method has a weaker correlation with NNIS has shown the necessity of developing NNIS. The application of ASEPSIS method to postoperative patients is found simple and repeatable. Surveillance tasks with feedback to clinical surgery staff are considered to be important in the care of patients.

The approval for this study was obtained from Ankara City Hospital No. 1 Clinical Research Ethics Committee (Decision No: E1-21-1643, Date: 17.03.2021).

Externally peer-reviewed.

Concept - M.A., S.T.; Design - S.T., M.A., E.P.; Supervision - S.T., F.M.A., S.H.; Materials - M.A., T.A.; Data Collection and/or Processing - M.A., E.P.; Analysis and/or Interpratation - E.K. Literature Review - M.A.; Writing Manuscript - M.A., S.T.; Critical Reviews - S.T., S.H.

The authors declare that they have no conflict of interest.

The authors declared that this study has received no financial support.

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