Surgical-site infections and the NNIS SSI Risk Index: room for improvement

Development and Validation of a Nomogram Based on Geriatric Nutritional Risk Index to Predict Surgical Site Infection Among Gynecologic Oncology Patients

Background

The geriatric nutritional risk index (GNRI) is a commonly used method to assess nutritional risk for predicting potential surgical site infections (SSI) in cancer patients. This study aims to create and verify a simple nomogram and a dynamic web-based calculator for predicting the risk of SSI among gynecologic oncology patients.

Methods

A retrospective evaluation was conducted on patients who were admitted into a tertiary hospital in China with confirmed diagnosis of gynecologic cancer between 01 August 2017 and 30 November 2021. A two-piecewise linear regression model with a smoothing function was used to investigate the non-linear association between GNRI and SSI to determine the ideal cut-off point. Three models were developed on the basis of different variables to predict SSI in gynecologic oncology patients. Through a nomogram the concordance index (C-index), the Akaike information criterion (AIC), and the integrated discrimination index (IDI) were used to determine the final model. Finally, the performance of the nomogram was validated using the 1,000-bootstrap resamples method and analyzed using C-index, GiViTI calibration belts, and decision curve. Also, a user-friendly dynamic web-based calculator was developed.

Results

A total of 1,221 patients were included in the analysis. A non-linear association could be observed between GNRI and SSI risk with a GNRI cut-off value of 101.7. After adding GNRI to Model 2 (which comprised Morse Fall Scale score, preoperative length of stay, operation time, and estimated blood loss), the AIC value decreased, the C-index value increased and IDI increased significantly. The nomogram C-index in the development cohort and internal validation cohort demonstrates a moderate-high degree of discrimination. The GiViTI calibrated belt showed a good agreement between the observed and predicted probabilities of SSI. The decision curve validates the clinical feasibility of the nomogram with a threshold value between 0 and 49%.

Conclusion

The GNRI cut-off value of 101.7 allowed for appropriate stratification of patients into distinct SSI risk groups. This study found that including GNRI in the above nomogram (Model 2) would enhance its potential to predict SSI in gynecologic oncology patients.

Management of superficial and deep surgical site infection: an international multidisciplinary consensus

Surgical site infections represent a considerable burden for healthcare systems. To obtain a consensus on the impact and future clinical and economic needs regarding SSI management in an era of multidrug resistance. A modified Delphi method was used to obtain consensus among experts from five European countries. The Delphi questionnaire was assembled by a steering committee, verified by a panel of experts and administered to 90 experts in 8 different surgical specialities (Abdominal, Cancer, Cardiac, General surgery, Orthopaedic, Thoracic, Transplant and Vascular and three other specialities (infectious disease, internal medicine microbiology). Respondents (n = 52) reached consensus on 62/73 items including that resistant pathogens are an increasing matter of concern and increase both treatment complexity and the length of hospital stay. There was strong positive consensus on the cost-effectiveness of early discharge (ED) programs, improvement of quality of life with ED and association between increased length of stay and economic burden to the hospital. However, established ED protocols were not widely available in their hospitals. Respondents expressed a positive consensus on the usefulness of antibiotics that allow ED. Surgeons are aware of their responsibility in an interdisciplinary team for the treatment of SSI, and of the impact of multidrug-resistant bacteria in the context of SSI. Reducing the length of hospital stays by applying ED protocols and implementing new treatment alternatives is crucial to reduce harm to patients and costs for the hospital.

Is antibiotic prophylaxis expendable in parotid gland surgery? A retrospective analysis of surgical site infection rates

OBJECTIVES

To evaluate the rate of surgical site infection (SSI) and associated risk factors after parotid gland surgery including the impact of antibiotic prophylaxis.

DESIGN

Retrospective single-centre clinical study.

SETTING

Tertiary referral centre for head and neck surgery.

PARTICIPANTS

Seven hundred and fifty four patients who underwent parotid gland surgery at the University Hospital Heidelberg, Germany, between 2007 and 2014 were enrolled in this study. Data on patient age, American Society of Anesthesiologists (ASA) classification system, smoking status, diabetes mellitus, operation time, and antibiotic prophylaxis were collected. Additionally, the National Healthcare Safety Network (NHSN) risk index was calculated. Association of these factors with SSI was evaluated in univariate analyses and a multivariate logistic regression model.

MAIN OUTCOME MEASURES

Rate of SSI.

RESULTS

Twenty four patients (3.2%) had an SSI according to the NHSN definition. In univariate analyses, only smokers (P = .048) and male patients (P = .01) had a significantly higher rate of SSI. Since the majority of smokers were men (62.3%), the effect of male gender, smoking, together with the NHSN risk index was further investigated as predictors of SSI within a logistic regression model. All three predictors showed a significant effect on SSI.

CONCLUSIONS

Parotid gland surgery has a low rate of SSI. In our cohort, male gender, smoking and high NHSN risk index scores were significantly associated with SSI, whereas antibiotic prophylaxis had no protective effect.

Epidemiology of Surgical Site Infections Considering the NHSN Standardized Infection Ratio in Hip and Knee Arthroplasties

Introduction Surgical site infections (SSIs) are a predominant form of hospital-acquired infections in surgical wards. The objective of the study was analysis of the incidence of SSI in, both primary and revision, hip and knee arthroplasties. Material and methods: The study was conducted in 2012–2018 in a Trauma and Orthopedics Ward in Tarnów according to the methodology of the Healthcare-Associated Infections Surveillance Network (HAI-Net), European Centre for Disease Prevention and Control (ECDC). Results: The surveillance comprised 2340 surgery patients, including: 1756 Hip Arthroplasties (HPRO) and 584 Knee Arthroplasties (KPRO). In the group of patients under study, 37 cases of SSI were detected, including: 26 cases of SSI after HPRO and 11 cases in KPRO. The average incidence of SSI amounted to 1.6% (1.5% HPRO and 1.9% KPRO) and in-hospital incidence density rates were 1.23 and 1.53 per 1000 patient-days, respectively. Median age of surgical patients in both HPRO and KPRO was 70 years. Women were undergoing arthroplasty surgery more often than men, HPRO (p < 0.05) and KPRO (p < 0.001). Patients with SSI stayed in the ward longer (SSI-HPRO, p < 0.001) (SSI-KPRO p < 0.01). In KPRO operations, the incidence of SSI was higher than expected, calculated according to the Standardized Infection Ratio (SIR). The most common etiologic agents isolated from SSIs in both HPRO and KPRO were coagulase-negative staphylococci. Conclusions: Establishing a thorough surveillance of hospital-acquired infections that takes into consideration epidemiological indicators is indispensable to properly assess the epidemiological situation in the ward. The optimal solution is to carry out long-term and multi-center surveillance in the framework of a uniform program, however, even results of single-center studies provide valuable data indicating challenges and needs in improving patient safety.

Post-Caesarean Section Surgical Site Infection Surveillance Using an Online Database and Mobile Phone Technology

BACKGROUND

Obstetric surgical site infections (SSIs) are common and expensive to the health care system but remain under reported given shorter postoperative hospital stays and suboptimal post-discharge surveillance systems. SSIs, for the purpose of this paper, are defined according to the Center for Disease Control and Prevention (1999) as infection incurring within 30 days of the operative procedure (in this case, Caesarean section [CS]).

PRIMARY OBJECTIVE

Demonstrate the feasibility of real-life use of a patient driven SSIs post-discharge surveillance system consisting of an online database and mobile phone technology (surgical mobile app - how2trak) among women undergoing CS in a Canadian urban centre.

SECONDARY OBJECTIVE

Estimate the rate of SSIs and associated predisposing factors.

METHODS

Prospective cohort of consecutive women delivering by CS at one urban Canadian hospital. Using surgical mobile app-how2trak-predetermined demographics, comorbidities, procedure characteristics, and self-reported symptoms and signs of infection were collected and linked to patients' incision self-portraits (photos) on postpartum days 3, 7, 10, and 30.

RESULTS

A total of 105 patients were enrolled over a 5-month period. Mean age was 31 years, 13% were diabetic, and most were at low risk of surgical complications. Forty-six percent of surgeries were emergency CSs, and 104/105 received antibiotic prophylaxis. Forty-five percent of patients (47/105) submitted at least one photo, and among those, one surgical site infection was detected by photo appearance and self-reported symptoms by postpartum day 10. The majority of patients whom uploaded photos did so multiple times and 43% of them submitted photos up to day 30. Patients with either a diagnosis of diabetes or self-reported Asian ethnicity were less likely to submit photos.

CONCLUSIONS

Post-discharge surveillance for CS-related SSIs using surgical mobile app how2trak is feasible and deserves further study in the post-discharge setting.

Epidemiology and risk factors associated with surgical site infection following surgery on thoracic aorta

Surgical site infection (SSI) following cardiovascular surgery has been well documented, possibly owing to its highly invasive nature, but SSI following surgery on the thoracic aorta has not. This study aimed to describe the epidemiology and assess risk factors associated with the latter in Japan using a national database for SSI. Data on surgery on thoracic aorta performed between 2012 and 2014 were extracted from the Japan Nosocomial Infections Surveillance (JANIS) database. Risk factors were assessed initially by univariate analysis, and then entered into a logistic regression model for final evaluation. The cumulative incidence of SSI was 4.1% (146/3538) and staphylococci were the most frequent pathogens isolated. Factors such as the duration of operation, emergency surgery and male gender were significantly associated with SSI. These findings differ from previous studies on open heart and coronary artery bypass surgery, in which the American Society of Anesthesiologists (ASA) score was significantly associated with SSI, but gender was not. This study suggests that risk stratification in the JANIS system might be improved by incorporating additionally identified factors for risk adjustment, when comparing the incidence of SSI between hospitals.

Clinical relevance and effect of surgical wound classification in appendicitis: Retrospective evaluation of wound classification discrepancies between surgeons, Swissnoso-trained infection control nurse, and histology as well as surgical site infection rates by wound class

BACKGROUND

Surgical wound classification (SWC) is used for risk stratification of surgical site infection (SSI) and serves as the basis for measuring quality of care. The objective was to examine the accuracy and reliability of SWC. This study was purposed to evaluate the discrepancies in SWC as assessed by three groups: surgeons, an infection control nurse, and histopathologic evaluation. The secondary aim was to compare the risk-stratified SSI rates using the different SWC methods for 30 d postoperatively.

METHODS

An analysis was performed of the appendectomies from January 2013 to June 2014 in the Cantonal Hospital of Schaffhausen. SWC was assigned by the operating surgeon at the end of the procedure and retrospectively reviewed by a Swissnoso-trained infection control nurse after reading the operative and pathology report. The level of agreement among the three different SWC assessment groups was determined using kappa statistic. SSI rates were analyzed using a chi-square test.

RESULTS

In 246 evaluated cases, the kappa scores for interrater reliability among the SWC assessments across the three groups ranged from 0.05 to 0.2 signifying slight agreement between the groups. SSIs were more frequently associated with trained infection control nurse-assigned SWC than with surgeons based SWC.

CONCLUSIONS

Our study demonstrated a considerable discordance in the SWC assessments performed by the three groups. Unfortunately, the currently practiced SWC system suffers from ambiguity in definition and/or implementation of these definitions is not clearly stated. This lack of reliability is problematic and may lead to inappropriate comparisons within and between hospitals and surgeons.

Reducing surgical site infections following total hip and knee arthroplasty: an Israeli experience

PURPOSE

To assess the changes observed in surgical site infection (SSI) rates following total joint arthroplasty (TJA) after the introduction of an infection control programme and evaluate the risk factors for the development of these infections.

DESIGN

Prospective cohort study.

SETTING

Large tertiary medical centre in Israel.

METHODS

Data about SSIs and potential prophylaxis-, patient-, and procedure-related risk factors were collected for all patients who underwent elective total hip and total knee arthroplasty during the study period. Multivariant analyses were conducted to determine which significant covariates affected the outcome.

RESULTS

During the 76-month study period, SSIs (superficial and deep) occurred in 64 (4.4%) of 1554 patients. As compared with the 34 (7.7%) SSIs that occurred in the first 25 months, there were 23 (4.7%) SSIs in the following 25 months, and only 7 (1.3%) SSIs in the last third of the study (p = 0.058 and <0.001, respectively). A multiple logistic regression model indicated that risk factors for prosthetic joint infection were a National Nosocomial Infections Surveillance (NNIS) System surgical patient risk index score of 1 (OR 1.8; 95% CI 1.1-3.1) or 2 (OR 2.8; 95% CI 1.2-11.8). The incidence of SSI was not correlated with the timing, nor the duration of antibiotic prophylaxis.

CONCLUSIONS

The introduction of preventive measures and surveillance coincided with a significant reduction in SSIs following TJA in our institution. The risk of infection correlated with higher scores in the NNIS System surgical patient risk.

Risk of surgical site infection in older patients in a cohort survey: targets for quality improvement in antibiotic prophylaxis

The aims of the present study were to: (1) assess surgical site infection (SSI) incidence in a cohort of surgical patients and (2) estimate the compliance with national guidelines for perioperative antibiotic prophylaxis (PAP). SSIs, among the most common health care-associated infections, are an important target for surveillance and an official priority in several European countries. SSI commonly complicates surgical procedures in older people and is associated with substantial attributable mortality and costs. The implementation of PAP guidelines is difficult among surgeons, and failure to comply with the standard of care has been widely reported. A 12-month prospective survey was performed in accordance with the methods, protocols, and definitions of the Hospital in Europe Link for Infection Control through Surveillance (HELICS) protocol. The compliance of the current PAP practices with the published national guidelines was assessed. A total of 249 patients were enrolled. The cumulative SSI incidence was 3.2 per 100 operative procedures. Cumulative compliance for PAP was 12.4%. Overall, only infection risk index ≥ 1 was confirmed as a significant risk factor for SSI (odds ratio, 6.65; 95% confidence interval, 1.04-42.59; P = 0.045). When only older patients (age >65 years) were considered, no significant risk factors for SSI were identified. Our study indicates an overall inadequate compliance with PAP recommendations, thus highlighting the need to develop multimodal and targeted intervention programs to improve compliance with PAP guidelines.

Antibiotic prophylaxis in open inguinal hernia repair: a literature review and summary of current knowledge

More than 1 million inguinal hernia repairs are performed in Europe and the US annually. Although antibiotic prophylaxis is not required in clean, elective procedures, the routine use of implants (90% of inguinal hernia repairs are performed with mesh) makes the topic controversial. The European Hernia Society does not recommend routine antibiotic prophylaxis for elective inguinal hernia repairs. However, the latest randomized controlled trial, published by Mazaki et al., indicates that the use of prophylaxis is effective for the prevention of surgical site infection. Unnecessary prophylaxis contributes to the development of bacterial resistance and significantly increases healthcare costs. This review documents clinical trials on inguinal hernia repairs with mesh and summarizes the current knowledge. It also tries to solve certain problems, namely: what constitutes a real risk factor, late-onset infection, and how the "surgical environment" impacts on the need to use antibiotic prophylaxis.

Prophylactic negative pressure wound therapy in colorectal surgery. Effects on surgical site events: current status and call to action

Surgical site events, including surgical site infections (SSI), represent a major problem in general surgery. SSI are responsible of nuisance for patients, and can lead to important complications and disability, often needing prolonged postoperative stay with specific treatment and recovery in Intensive Care Units. These justify the higher costs due to SSI. Despite the growing body of evidence concerning SSI in general surgery, literature dealing with SSI after colorectal surgery is scarce, reflecting in suboptimal perception of such a relevant issue by colorectal surgeons and health authorities in Italy, though colorectal surgery is associated with higher rates of SSI. The best strategy for reducing the impact of SSI on costs of care and patients quality of life would be the development of a preventive bundle, similar to that adopted in the US through the colorectal section of the National Surgery Quality Improvement Project of the American College of Surgeons (ACS-NSQIP). This policy has been showed to significantly reduce the rates of SSI. In this scenario, incisional negative pressure wound therapy (NPWT) is likely to play a pivotal role. We herein reviewed the literature to report on the current status of preventive NPWT on surgical wounds of patients undergoing colorectal procedures with primary wound closure, suggesting evidence-based measures to reduce the impact of SSI, and to contain the costs associated with conventional NPWT devices by means of newer available technologies. Some explicative real life cases are presented.

Differences in risk factors associated with surgical site infections following two types of cardiac surgery in Japanese patients

BACKGROUND

Differences in the risk factors for surgical site infection (SSI) following open heart surgery and coronary artery bypass graft surgery are not well described.

AIM

To identify and compare risk factors for SSI following open heart surgery and coronary artery bypass graft surgery.

METHODS

SSI surveillance data on open heart surgery (CARD) and coronary artery bypass graft surgery (CBGB) submitted to the Japan Nosocomial Infection Surveillance (JANIS) system between 2008 and 2010 were analysed. Factors associated with SSI were analysed using univariate modelling analysis followed by multi-variate logistic regression analysis. Non-binary variables were analysed initially to determine the most appropriate category.

FINDINGS

The cumulative incidence rates of SSI for CARD and CBGB were 2.6% (151/5895) and 4.1% (160/3884), respectively. In both groups, the duration of the operation and a high American Society of Anesthesiologists' (ASA) score were significant in predicting SSI risk in the model. Wound class was independently associated with SSI in CARD but not in CBGB. Implants, multiple procedures and emergency operations predicted SSI in CARD, but none of these factors predicted SSI in CBGB.

CONCLUSIONS

There was a remarkable difference in the prediction of risk for SSI between the two types of cardiac surgery. Risk stratification in CARD could be improved by incorporating variables currently available in the existing surveillance systems. Risk index stratification in CBGB could be enhanced by collecting additional variables, because only two of the current variables were found to be significant for the prediction of SSI.

Validation of a Modified Version of the National Nosocomial Infections Surveillance System Risk Index for Health Services Research

Objective.

To validate the National Nosocomial Infections Surveillance system risk index through administrative data to predict surgical site infections.

Design.

Retrospective cohort study.

Setting.

Population-based analysis in Ontario, Canada.

Patients.

All elderly patients who underwent elective surgery from April 1, 1992, through March 31, 2006 (n = 469,349).

Methods.

Data on procedural and patient outcomes were gathered from linked population-wide hospital discharge records and physician claims. The 75th percentile of surgical duration was estimated through anesthesiologist billing fees recorded in 15-minute increments; the American Society of Anesthesiology score of at least 3 out of 5 was estimated by diagnostic codes for severe systemic illness; and all surgeries were classified as clean or clean-contaminated because of their elective nature (thus, the maximum score on the modified index was 2).

Results.

A total of 147,216 surgeries (31%) had a score of 0;246,592 (53%) had a score of 1; and 75,541 (16%) had a score of 2 on the modified index. The 30-day risk of surgical site infection increased with each increment in the modified index (score of 0, 5.4%; score of 1, 8.0%; score of 2, 14.3%; P < .001). The association was evident for surgical site infection diagnosed during the index admission (score of 0, 2.0%; score of 1, 3.7%; score of 2, 8.9%; P < .001), as well as that associated with reoperation or death (score of 0, 0.04%; score of 1, 0.23%; score of 2, 0.73%; P < .001). The modified index predicted increases in surgical site infection risk within each of 11 surgical subgroups. In accord with past research, the modified index had modest discrimination (C statistic, 0.59), and the majority of surgical site infections (72%) occurred within lower risk strata.

Conclusions.

The modified index predicts surgical site infection in population-based analyses and is associated with incremental increases in risk.

The Surgical Site Infection Risk Score (SSIRS): A Model to Predict the Risk of Surgical Site Infections

Background

Surgical site infections (SSI) are an important cause of peri-surgical morbidity with risks that vary extensively between patients and surgeries. Quantifying SSI risk would help identify candidates most likely to benefit from interventions to decrease the risk of SSI.

Methods

We randomly divided all surgeries recorded in the National Surgical Quality Improvement Program from 2010 into a derivation and validation population. We used multivariate logistic regression to determine the independent association of patient and surgical covariates with the risk of any SSI (including superficial, deep, and organ space SSI) within 30 days of surgery. To capture factors particular to specific surgeries, we developed a surgical risk score specific to all surgeries having a common first 3 numbers of their CPT code.

Results

Derivation (n = 181 894) and validation (n = 181 146) patients were similar for all demographics, past medical history, and surgical factors. Overall SSI risk was 3.9%. The SSI Risk Score (SSIRS) found that risk increased with patient factors (smoking, increased body mass index), certain comorbidities (peripheral vascular disease, metastatic cancer, chronic steroid use, recent sepsis), and operative characteristics (surgical urgency; increased ASA class; longer operation duration; infected wounds; general anaesthesia; performance of more than one procedure; and CPT score). In the validation population, the SSIRS had good discrimination (c-statistic 0.800, 95% CI 0.795–0.805) and calibration.

Conclusion

SSIRS can be calculated using patient and surgery information to estimate individual risk of SSI for a broad range of surgery types.

Efficacy of preparation solutions and cleansing techniques on contamination of the skin in foot and ankle surgery

We report a systematic review and meta-analysis of published randomised and quasi-randomised trials evaluating the efficacy of pre-operative skin antisepsis and cleansing techniques in reducing foot and ankle skin flora. The post-preparation culture number (Post-PCN) was the primary outcome. The data were evaluated using a modified version of the Cochrane Collaboration’s tool. We identified eight trials (560 participants, 716 feet) that met the inclusion criteria. There was a significant difference in the proportions of Post-PCN between hallux nailfold (HNF) and toe web spaces (TWS) sites: 0.47 vs 0.22, respectively (95% confidence interval (CI) 0.182937 to 0.304097; p < 0.0001).

Meta-analyses showed that alcoholic chlorhexidine had better efficacy than alcoholic povidone-iodine (PI) at HNF sites (risk difference 0.19 (95% CI 0.08 to 0.30); p = 0.0005); a two-step intervention using PI scrub and paint (S& P) followed by alcohol showed significantly better efficacy over PI (S& P) alone at TWS sites (risk difference 0.13 (95% CI 0.02 to 0.24); p = 0.0169); and a two-step intervention using chlorhexidine scrub followed by alcohol showed significantly better efficacy over PI (S& P) alone at the combined (HNF with TWS) sites (risk difference 0.27 (95% CI 0.13 to 0.40); p < 0.0001). No significant difference was found between cleansing techniques.

Cite this article: Bone Joint J 2013;95-B:498–503.

Decreasing time trend in SSI incidence for orthopaedic procedures: surveillance matters!

BACKGROUND

Infection is the most common reason for early revision after hip and knee arthroplasty, and the revision rate is increasing. Surgical site infection (SSI) surveillance data are important to assess the true infection rate. There is little information regarding the potential time trend in SSI incidence following orthopaedic surgery.

AIM

To evaluate whether a time trend exists in SSI incidence due to surveillance following orthopaedic surgery.

METHODS

The SSI rates after hip and knee replacements and osteosynthesis of trochanteric femoral fractures and ankle fractures were recorded prospectively from May 1998 to October 2008 according to the criteria of the US Centers for Disease Control and Prevention. In total, 4177 procedures were analysed, 65.8% of which were performed on female patients. Linear regression was used to analyse trends in SSI rates.

FINDINGS

SSI incidence decreased significantly from 7% in the first year to 3% in the last year; a 57% relative reduction. The duration of surgery was the only significant predictor for infection (P < 0.001) in a logistic regression model that also included age, American Society of Anesthesiologists' score and level of emergency.

CONCLUSION

Surveillance following orthopaedic procedures showed a significant decrease in SSI incidence over the 11-year surveillance period. The causality between surveillance and SSI incidence is difficult to prove, but surveillance with feedback probably influences several procedures that affect the quality of health care, even if duration of surgery is the only significant predictor of this effect.

"But my patients are different!": risk adjustment in 2012 and beyond

Feedback of surgical site infection (SSI) rates to surgeons improves patient outcomes and should be considered a cornerstone of any infection control program. For as long as feedback of SSI data has occurred, those in infection control have often heard a searing retort from indignant surgeons: “But my patients are different!”

Fortunately, epidemiologists have several tools to use in response. One of the most commonly used approaches involves risk adjustment for differences in case mix between the group of interest (eg, a surgeon's patients) and a comparator. In other words, risk adjustment levels the playing field.

Formal risk adjustment for rates of SSI has existed for almost 50 years but is still an imperfect science. In fact, risk adjustment for different variables can lead to different conclusions. Over the past 2 decades, the National Healthcare Safety Network (NHSN) risk index has been used by many hospitals to perform risk adjustment for rates of SSI. The NHSN risk index is simple and effective but has undergone considerable scrutiny. Numerous investigators have described scenarios and/or procedures for which the risk index performed poorly and have offered suggestions for improvement. Indeed, Robert Gaynes summarized some of the shortcomings of the NHSN risk index in 2 editorials 10 years ago, stating, “A composite risk index that captures the joint influence of [intrinsic patient risk] and other risk factors is required before meaningful comparisons of SSI rates can be made by surgeons, among institutions, or across time.”

Validating a 3-point prediction rule for surgical site infection after coronary artery bypass surgery

BACKGROUND

Surgical site infection (SSI) after coronary artery bypass graft (CABG) surgery is an increasing healthcare problem. Investigators from Australia proposed a new, 3-point scale that assesses SSI risk on the basis of diagnosis of diabetes mellitus and body mass index.

OBJECTIVE

To validate the Australian Clinical Risk Index among patients undergoing CABG surgery in the United States.

DESIGN AND SETTING

Nested case-control study involving patients undergoing CABG surgery at 9 hospitals during 1991-2002.

PATIENTS

Case patients were those who developed SSIs after CABG surgery. Control subjects were matched to case patients on the basis of hospital, age, and procedure date.

METHODS

Odds ratios (ORs) for SSIs were calculated for the comparison of case patients with control subjects for all risk categories determined using the Australian Clinical Risk Index and National Nosocomial Infections Surveillance System (NNIS) risk index. An adjusted area under the curve was used to compare predictive values among risk indices.

RESULTS

Four hundred sixty patients were studied, including 269 patients with SSI and 191 control subjects. NNIS risk group 2 was associated with increased rate of SSI (OR, 1.79; 95% confidence interval [CI], 1.19-2.67). No patient had an NNIS risk index of 3. The remaining NNIS categories were not predictive of infection. In contrast, an increase in Australian Clinical Risk Index was associated with an increase in risk of SSI (category 2: OR, 2.39 [95% CI, 1.33-4.29]; category 3: OR, 4.46 [95% CI, 1.83-10.85]).

CONCLUSIONS

The NNIS risk index predicts the risk of SSI associated with many procedures, but it has limited use in predicting the risk of SSI after CABG surgery. The new Australian Clinical Risk Index stratified patients into discrete groups associated with increased risk of SSI. Data from our study support the use of this new risk index in the US population.

Developing a risk stratification model for surgical site infection after abdominal hysterectomy

OBJECTIVE

The incidence of surgical site infection (SSI) after hysterectomy ranges widely from 2% to 21%. A specific risk stratification index could help to predict more accurately the risk of incisional SSI following abdominal hysterectomy and would help determine the reasons for the wide range of reported SSI rates in individual studies. To increase our understanding of the risk factors needed to build a specific risk stratification index, we performed a retrospective multihospital analysis of risk factors for SSI after abdominal hysterectomy.

METHODS

Retrospective case-control study of 545 abdominal and 275 vaginal hysterectomies from July 1, 2003, to June 30, 2005, at 4 institutions. SSIs were defined by using Centers for Disease Control and Prevention/National Nosocomial Infections Surveillance criteria. Independent risk factors for abdominal hysterectomy were identified by using logistic regression.

RESULTS

There were 13 deep incisional, 53 superficial incisional, and 18 organ-space SSIs after abdominal hysterectomy and 14 organ-space SSIs after vaginal hysterectomy. Because risk factors for organ-space SSI were different according to univariate analysis, we focused further analyses on incisional SSI after abdominal hysterectomy. The maximum serum glucose level within 5 days after operation was highest in patients with deep incisional SSI, lower in patients with superficial incisional SSI, and lowest in uninfected patients (median, 189, 156, and 141 mg/dL, respectively; P = .005). Independent risk factors for incisional SSI included blood transfusion (odds ratio [OR], 2.4) and morbid obesity (body mass index [BMI], >35; OR, 5.7). Duration of operation greater than the 75th percentile (OR, 1.7), obesity (BMI, 30-35; OR, 3.0), and lack of private health insurance (OR, 1.7) were marginally associated with increased odds of SSI.

CONCLUSIONS

Incisional SSI after abdominal hysterectomy was associated with increased BMI and blood transfusion. Longer duration of operation and lack of private health insurance were marginally associated with SSI.

An alternative scoring system to predict risk for surgical site infection complicating coronary artery bypass graft surgery

OBJECTIVE

To analyze the risk factors for surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery and to create an alternative SSI risk score based on the results of multivariate analysis.

METHODS

A prospective cohort study involving inpatient and laboratory-based surveillance of patients who underwent CABG surgery over a 27-month period from January 1, 2003 through March 31, 2005. Data were obtained from 6 acute care hospitals in Victoria, Australia, that contributed surveillance data for SSI complicating CABG surgery to the Victorian Hospital Acquired Infection Surveillance System Coordinating Centre and the Australasian Society of Cardiac and Thoracic Surgeons, also in Victoria.

RESULTS

A total of 4,633 (93%) of the 4,987 patients who underwent CABG surgery during this period were matched in the 2 systems databases. There were 286 SSIs and 62 deep or organ space sternal SSIs (deep or organ space sternal SSI rate, 1.33%). Univariate analysis revealed that diabetes mellitus, body mass index (BMI) greater than 35, and receipt of blood transfusion were risk factors for all types of SSI complicating CABG surgery. Six multivariate analysis models were created to examine either preoperative factors alone or preoperative factors combined with operative factors. All models revealed diabetes and BMI of 30 or greater as risk factors for SSI complicating CABG surgery. A new preoperative scoring system was devised to predict sternal SSI, which assigned 1 point for diabetes, 1 point for BMI of 30 or greater but less than 35, and 2 points for BMI of 35 or greater. Each point in the scoring system represented approximately a doubling of risk of SSI. The new scoring system performed better than the National Nosocomial Infections Surveillance System (NNIS) risk index at predicting SSI.

CONCLUSION

A new weighted scoring system based on preoperative risk factors was created to predict sternal SSI risk following CABG surgery. The new scoring system outperformed the NNIS risk index. Future studies are needed to validate this scoring system.

Improved risk adjustment for comparison of surgical site infection rates

OBJECTIVE

To develop prognostic models for improved risk adjustment in surgical site infection surveillance for 5 surgical procedures and to compare these models with the National Nosocomial Infection Surveillance system (NNIS) risk index.

DESIGN

In a multicenter cohort study, prospective assessment of surgical site infection and risk factors was performed from 1996 to 2000. In addition, risk factors abstracted from patient files, available in a national medical register, were used. The c-index was used to measure the ability of procedure-specific logistic regression models to predict surgical site infection and to compare these models with models based on the NNIS risk index. A c-index of 0.5 indicates no predictive power, and 1.0 indicates perfect predictive power.

SETTING

Sixty-two acute care hospitals in the Dutch national surveillance network for nosocomial infections.

PARTICIPANTS

Patients who underwent 1 of 5 procedures for which the predictive ability of the NNIS risk index was moderate: reconstruction of the aorta (n=875), femoropopliteal or femorotibial bypass (n=641), colectomy (n=1,142), primary total hip prosthesis (n=13,770), and cesarean section (n=2,962).

RESULTS

The predictive power of the new model versus the NNIS index was 0.75 versus 0.62 for reconstruction of the aorta (P<.01), 0.78 versus 0.58 for femoropopliteal or femorotibial bypass (P<.001), 0.69 versus 0.62 for colectomy (P<.001), 0.64 versus 0.56 for primary total hip prosthesis arthroplasty (P<.001), and 0.70 versus 0.54 for cesarean section (P<.001).

CONCLUSION

Data available from hospital information systems can be used to develop models that are better at predicting the risk of surgical site infection than the NNIS risk index. Additional data collection may be indicated for certain procedures--for example, total hip prosthesis arthroplasty.

The establishment of a statewide surveillance program for hospital-acquired infections in large Victorian public hospitals: a report from the VICNISS Coordinating Centre

BACKGROUND

A 1998 survey of acute Victorian public hospitals (VPH) revealed that surveillance of hospital-acquired infections (HAI) was underdeveloped, definitions and methodology varied considerably, and results disseminated inconsistently. The survey identified the need for an effective surveillance system for HAI.

OBJECTIVE

To develop and support a standardized surveillance program for HAIs in large acute VPH and to provide risk-adjusted, procedure-specific, HAI rates.

METHODS

In 2002, the independent Victorian Nosocomial Infection Surveillance System (VICNISS) Coordinating Centre (VCC) was established to develop and support the standardized surveillance program. A multidisciplinary team was recruited. A communication strategy, surveillance manual, user groups, and Web site were developed. Formal education sessions were provided to participating infection control nurse consultants (ICCs). Surveillance activities were based on the US Centers for Diseases Control and Prevention's National Nosocomial Infection Surveillance System (NNIS) surgical site infection and intensive care unit (ICU) components. NNIS methods were modified to suit local needs. Data collection was paper based or through existing hospital software. An advisory committee of key stakeholders met every second month.

RESULTS

The surveillance program was rolled out over 12 months to all 28 large adult VPH. Data on over 20,000 surgical procedures performed at participating sites between November 11, 2002, and December 31, 2004, were submitted. Thirteen hospitals contributed to the ICU surveillance activities. Following aggregation and analysis by the VCC, hospital- and state-level results were posted on the Web page for hospitals to review.

CONCLUSION

A standardized approach for surveillance of HAI was established in a short time frame in over 28 VPH. VICNISS is a tool that will continue to provide participating hospitals with a basis for continuous quality improvement.

Surgical-site infections after orthopaedic surgery: statewide surveillance using linked administrative databases

Prospective surveillance programmes to monitor the incidence of surgical-site infection (SSI) in patients who have had orthopaedic implant surgery can be difficult to implement due to limited human and technical resources. In addition, prolonged patient follow-up, up to one year, may be required. Traditional methods of surveillance can be enhanced by using administrative databases to assist in case finding and facilitate overall surveillance activities. The aim of this study was to identify the incidence of SSI in patients who had undergone total hip replacement (THR) or total knee replacement (TKR) surgery in all Western Australian (WA) hospitals during 1999 using the Western Australian Data Linkage System. The WA Data Linkage System links several population-based administrative health datasets within the state, including the Hospital Morbidity Data System (HMDS), containing International Classification of Disease-coded discharge information, and mortality records. A total of 1476 THR and 1875 TKR procedures was identified from 21 WA hospitals during 1999. The incidence of SSI after these procedures was 5% (95% CI 4.3-5.7) [THR (4.86%, 95% CI 3.77-5.95) and TKR (5.15%, 95% CI 4.15-6.15)]. The incidence was 33.72 infections per 1000 person-years. Patients aged over 80 years experienced a significantly higher rate of infection after THR compared with patients aged 80 or less (z-test, z = 2.56, P = 0.015), but not for TKR. No patients with an SSI died during follow-up. The WA Data Linkage System provided a unique opportunity to review the incidence of SSIs in patients undergoing THR or TKR surgery in WA hospitals.

Monitoring patient safety in health care: building the case for surrogate measures

BACKGROUND

Objective measurements are notably lacking for many adverse events in health care. A new approach to monitoring such events is based on the experience in measuring hospital-associated infections.

DEVELOPING OBJECTIVE AND UNIVERSAL MEASURES

An essential tenet of the current goal of surveillance-focusing only on rigorously confirmed adverse events-is neither necessary nor achievable across the entire health care system. Efforts should be directed instead to creating objective measures of quality of care and of outcomes that can be used by all health care facilities. Adopting objective measures would be easier if health care was open to surrogate measures of important outcomes. Surrogate measures of interest for infection surveillance are used to identify objective, readily ascertained events that are sufficiently correlated with infections to provide useful information about organizations' infection rates. For example, the surgical site infection rate following coronary artery bypass appears to correlate closely enough with the proportion of patients who receive extended courses of inpatient antibiotics to be a useful indicator of a hospital's outcomes for the procedure.

CONCLUSION

Developing clinically relevant process or surrogate measures that clinicians would use to improve patient outcomes is essential. These measures could be relevant not only to hospital-acquired infections but other health care-related adverse events that are relatively common yet require substantial resources to identify.

Antimicrobial prophylaxis in clean surgery with special focus on inguinal hernia repair with mesh

Until recently, antimicrobial prophylaxis was thought to be unnecessary for clean surgery except when a foreign body is implanted or the presence of infection poses a significant risk to patients. However, the results of several trials support extending the administration of antimicrobial prophylaxis to other types of clean surgery such as inguinal hernia repair or breast surgery. A recent Cochrane meta-analysis concluded that antimicrobial prophylaxis for inguinal hernia repair with or without mesh cannot be recommended or discarded. Resolution of this problem is important because inguinal hernia repair with mesh is one of the most common procedures in general surgery, and antibiotic consumption for preventive purposes is becoming a serious problem due to the risk of contribution to development of bacterial resistance and the significant increase in healthcare costs. This review will document clinical trials and meta-analyses on clean surgery, and will focus on inguinal hernia repair with mesh.

Surgical-site infection after cardiac surgery: incidence, microbiology, and risk factors

OBJECTIVE

To identify risk factors associated with surgical-site infection according to the depth of infection, the cardiac procedure, and the National Nosocomial Infections Surveillance System risk index.

DESIGN

Prospective survey conducted during a 12-month period.

SETTING

A 48-bed cardiac surgical department in a teaching hospital.

PATIENTS

Patients admitted for cardiac surgery between February 2002 and January 2003.

RESULTS

Surgical-site infections were diagnosed in 3% of the patients (38 of 1,268). Of the 38 surgical-site infections, 20 were superficial incisional infections and 18 were mediastinitis for incidence rates of 1.6% and 1.4%, respectively. Cultures were positive in 28 cases and the most commonly isolated pathogen was Staphylococcus. A National Nosocomial Infections Surveillance System risk index score of 2 or greater was associated with a risk of surgical-site infection (relative risk, 2.4; P < .004). Heart transplantation, mechanical circulatory assistance, coronary artery bypass graft with the use of internal mammary artery, and reoperation for cardiac tamponade or pericard effusion were independent risk factors associated with surgical-site infection.

CONCLUSIONS

Data surveillance using incidence rates stratified by cardiac procedure and type of infection is relevant to improving infection control efforts. Risk factors in patients who developed superficial infection were different from those in patients who developed mediastinitis. Coronary artery bypass graft using internal mammary artery was associated with a high risk of surgical-site infection, and independent factors such as reoperation for cardiac tamponade or pericard effusion increased the risk of infection.

Surgical site infection after groin hernia repair

Background

Post-discharge surveillance for 30 days is needed to determine the true incidence of surgical site infection (SSI). This study was undertaken to determine the incidence of, and risk factors for, SSI after hernia repair.

Methods

A total of 3150 patients who had undergone groin hernia repair in 32 Scottish hospitals were telephoned 10, 20 and 30 days after operation to screen for SSI. Patients who believed the wound to be infected were seen by a healthcare worker to confirm the diagnosis. Details of operations and risk factors were obtained by case-note review.

Results

One hundred and four patients (3·3 per cent) declined to give a contact telephone number, leaving 3046 patients who agreed to take part in the study. Some 108 patients (3·4 per cent) could not be contacted at any point, giving a response rate of 93·3 per cent. Complete data were available for 2665 patients (87·5 per cent); 140 (5·3 per cent) developed SSI and 57 (2·1 per cent) thought the wound infected but this was not confirmed by the healthcare worker. Patients given a prophylactic antibiotic had a lower incidence of SSI (P = 0·002), but neither increase in the American Society of Anesthesiologists grade of fitness for operation nor prolonged duration of operation was a significant risk factor for infection.

Conclusion

SSI after hernia repair is common and large clinical trials are required to determine whether the use of prophylactic antibiotics reduces the incidence of infection.

Incidence of surgical-site infections and the validity of the National Nosocomial Infections Surveillance System risk index in a general surgical ward in Santa Cruz, Bolivia

OBJECTIVES

To estimate the frequency of and risk factors for surgical-site infections (SSIs) in Bolivia, and to study the performance of the National Nosocomial Infections Surveillance (NNIS) System risk index in a developing country.

DESIGN

A prospective study with patient follow-up until the 30th postoperative day.

SETTING

A general surgical ward of a public hospital in Santa Cruz, Bolivia.

PATIENTS

Patients admitted to the ward between July 1998 and June 1999 on whom surgical procedures were performed.

RESULTS

Follow-up was complete for 91.5% of 376 surgical procedures. The overall SSI rate was 12%. Thirty-four (75.6%) of the 45 SSIs were culture positive. A logistic regression model retained an American Society of Anesthesiologists score of more than 1 (odds ratio [OR], 1.87), a not-clean wound class (OR, 2.28), a procedure duration of more than 1 hour (OR, 1.81), and drain (OR, 1.98) as independent risk factors for SSI. There was no significant association between the NNIS System risk index and SSI rates. However, a "local" risk index constructed with the above cutoff points showed a linear trend with SSI (P < .001) and a relative risk of 3.18 for risk class 3 versus a class of less than 3.

CONCLUSIONS

SSIs cause considerable morbidity in Santa Cruz. Appropriate nosocomial infection surveillance and control should be introduced. The NNIS System risk index did not discriminate between patients at low and high risk for SSI in this hospital setting, but a risk score based on local cutoff points performed substantially better.

A new surgical-site infection risk index using risk factors identified by multivariate analysis for patients undergoing coronary artery bypass graft surgery

OBJECTIVES

To develop a new, simple, and practical risk index for patients undergoing coronary artery bypass graft (CABG) surgery, to develop a preoperative risk index that is predictive of surgical-site infection (SSI), and to compare the new risk indices with the National Nosocomial Infections Surveillance (NNIS) System risk index.

DESIGN

Potential risk factor and infection data were collected prospectively and analyzed by multivariate analysis. Two new risk indices were constructed and then compared with the NNIS System risk index for predictive power for SSI.

SETTING

Alfred Hospital is a 350-bed, university-affiliated, tertiary-care referral center. The cardiothoracic unit performs approximately 650 CABG procedures per year.

PATIENTS

All patients undergoing CABG surgery within the cardiothoracic unit at Alfred Hospital between December 1, 1996, and September 29, 2000, were included.

RESULTS

Potential risk factor data were complete for 2,345 patients. There were 199 SSIs. Obesity (odds ratio [OR], 1.78; 95% confidence interval [CI95], 1.24 to 2.55), peripheral or cerebrovascular disease (OR, 1.64; CI95, 1.16 to 2.33), insulin-dependent diabetes mellitus (OR, 2.29; CI95, 1.15 to 4.54), and a procedure lasting longer than 5 hours (OR, 1.75; CI95, 1.18 to 2.58) were identified as independent risk factors for SSI. With the use of a different combination of these risk factors, two risk indices were constructed and compared using the Goodman-Kruskal nonparametric correlation coefficient (G). kisk index B had the highest G value (0.3405; CI95, 0.2245 to 0.4565), compared with the NNIS System risk index G value (0.3142; CI95, 0.1462 to 0.4822). The G value for risk index A, constructed from preoperative variables only, was 0.3299 (CI9,, 0.2039 to 0.4559).

CONCLUSION

Two new risk indices have been developed. Both indices are as predictive as the NNIS System risk index. One of the new risk indices can also be applied preoperatively.

Risk assessment for surgical site infections following total hip and total knee prostheses

The purpose of the study was to assess the relative importance of risk factors for surgical site infections (SSI) following total hip and total knee prostheses in The Netherlands. In the period 1996-99 63 hospitals in The Netherlands registered SSI after 36,629 orthopedic operations. Total hip and total knee prostheses were analyzed in detail. The results of our study showed that a long preoperative stay was a risk factor for deep SSIs after both procedures. A dirty or contaminated wound and a serious systemic condition were risk factors for deep SSIs after total hip prostheses. If post-discharge surveillance was carried out, more SSIs were found, for total knee prostheses more than twice as many. Independent risk factors for SSIs after total hip prostheses were a contaminated/dirty wound and for total knee prostheses a short operation duration. The authors conclude that surveillance of surgical site infections following total hip and total knee prostheses revealed different risk factors for (deep) SSIs.

Surveillance of hospital-acquired infection in England, Germany, and The Netherlands: will international comparison of rates be possible?

Three national surveillance systems for nosocomial infection have been developed independently and implemented successfully in England, Germany, and The Netherlands. All three are based on the American National Nosocomial Infections Surveillance System and have adopted a surveillance strategy that is targeted at specific infections or groups of patients for limited time periods. Case-finding methods, the minimum data set, and analysis of data are similar and could be standardized easily. Resolution of the differences in the definitions of infection, the study population, and follow-up should make possible the international comparison of infection rates. Such comparisons may identify differences in healthcare practices between countries and suggest areas for improvement.