Surgical-Site Infection Rates and Risk Factor Analysis in Coronary Artery Bypass Graft Surgery

Surgical Site Infection Prevention: A Review

IMPORTANCE

Approximately 0.5% to 3% of patients undergoing surgery will experience infection at or adjacent to the surgical incision site. Compared with patients undergoing surgery who do not have a surgical site infection, those with a surgical site infection are hospitalized approximately 7 to 11 days longer.

OBSERVATIONS

Most surgical site infections can be prevented if appropriate strategies are implemented. These infections are typically caused when bacteria from the patient's endogenous flora are inoculated into the surgical site at the time of surgery. Development of an infection depends on various factors such as the health of the patient's immune system, presence of foreign material, degree of bacterial wound contamination, and use of antibiotic prophylaxis. Although numerous strategies are recommended by international organizations to decrease surgical site infection, only 6 general strategies are supported by randomized trials. Interventions that are associated with lower rates of infection include avoiding razors for hair removal (4.4% with razors vs 2.5% with clippers); decolonization with intranasal antistaphylococcal agents and antistaphylococcal skin antiseptics for high-risk procedures (0.8% with decolonization vs 2% without); use of chlorhexidine gluconate and alcohol-based skin preparation (4.0% with chlorhexidine gluconate plus alcohol vs 6.5% with povidone iodine plus alcohol); maintaining normothermia with active warming such as warmed intravenous fluids, skin warming, and warm forced air to keep the body temperature warmer than 36 °C (4.7% with active warming vs 13% without); perioperative glycemic control (9.4% with glucose <150 mg/dL vs 16% with glucose >150 mg/dL); and use of negative pressure wound therapy (9.7% with vs 15% without). Guidelines recommend appropriate dosing, timing, and choice of preoperative parenteral antimicrobial prophylaxis.

CONCLUSIONS AND RELEVANCE

Surgical site infections affect approximately 0.5% to 3% of patients undergoing surgery and are associated with longer hospital stays than patients with no surgical site infections. Avoiding razors for hair removal, maintaining normothermia, use of chlorhexidine gluconate plus alcohol-based skin preparation agents, decolonization with intranasal antistaphylococcal agents and antistaphylococcal skin antiseptics for high-risk procedures, controlling for perioperative glucose concentrations, and using negative pressure wound therapy can reduce the rate of surgical site infections.

Twenty-year experience with skeletonized bilateral internal thoracic arteries for surgical myocardial revascularization. A single center experience

BACKGROUND AND AIM OF THE STUDY

The mammary artery shows excellent long-term patency and encourages the use of skeletonized bilateral internal thoracic arteries (BITA) for coronary surgery. We analyzed the long-term outcome of patients operated for myocardial revascularization with BITA in a single center.

MATERIALS AND METHODS

Clinical data and surgical details of patients undergoing coronary surgery with BITA were prospectively collected and retrospectively analyzed. Selected variables were studied as risk factors for sternal wound complication and a subanalysis of clinical outcome for patients aged 70 years or greater was performed. A long-term follow-up of the study group is provided.

RESULTS

From January 2001 to November 2021, 750 patients underwent myocardial revascularization using BITA grafts (mean age: 61 ± 9.5 years; males: 91%) at our institute. Patients with triple-vessel disease were 81%, 15.3% of all procedures were performed off-pump and 3.6% were urgent cases. Hospital mortality was 0.5%. Sternal wound complication was observed in 67 patients (9.0%) with 7 deep sternal wound infections (0.9%). Female gender (odds ratios [OR]: 3.7, p < 0.01), BMI >30 (OR: 1.8, p = 0.04), smoking (OR: 1.8, p = 0.02), and chronic kidney failure (OR: 3.7, p = 0.05) were independent predictors for sternal complications. During a mean follow-up time of 8.7 ± 5.3 years, 34 patients (4.5%) underwent a repeated myocardial revascularization, and there were 89 all-cause deaths (11.9%) and the cumulative survival at 5, 10, 15, and 20 years was 97%, 89%, 76%, and 60% for the whole study group 92%, 74%, 47%, and 43% for the subgroup of elderly patients (mean age: 74 ± 3.5 years).

CONCLUSIONS

Use of skeletonized bilateral thoracic arteries shows low-rate of wound infection and good long-term outcome with low risk of repeated revascularizations, regardless of patients' age.

Surgical Site Infection in Cardiac Surgery

Surgical site infections (SSIs) are one of the most significant complications in surgical patients and are strongly associated with poorer prognosis. Due to their aggressive character, cardiac surgical procedures carry a particular high risk of postoperative infection, with infection incidence rates ranging from a reported 3.5% and 26.8% in cardiac surgery patients. Given the specific nature of cardiac surgical procedures, sternal wound and graft harvesting site infections are the most common SSIs. Undoubtedly, DSWIs, including mediastinitis, in cardiac surgery patients remain a significant clinical problem as they are associated with increased hospital stay, substantial medical costs and high mortality, ranging from 3% to 20%. In SSI prevention, it is important to implement procedures reducing preoperative risk factors, such as: obesity, hypoalbuminemia, abnormal glucose levels, smoking and S. aureus carriage. For decolonisation of S. aureus carriers prior to cardiac surgery, it is recommended to administer nasal mupirocin, together with baths using chlorhexidine-based agents. Perioperative management also involves antibiotic prophylaxis, surgical site preparation, topical antibiotic administration and the maintenance of normal glucose levels. SSI treatment involves surgical intervention, NPWT application and antibiotic therapy.

Risk Factors for Post-cardiac Surgery Infections

Background Cardiac surgery infection is a life-threatening complication associated with high morbidity and mortality. One of the main types of these infections, surgical site infections (SSIs), also called postoperative wound infections basically delayed the post-surgical recovery in many patients. These infections rarely happen within 30 days after surgery due to different risk factors. Objectives The purpose of this study is to determine the risk factors that are involved in causing post-cardiac surgical infections. Methods This study was a retrospective study. The data of postoperative cardiac patients was obtained from the Cardiology and Cardiac Surgery Center in King Fahad Armed Force Hospital, Jeddah. Data on the patients were collected from 2016 to 2021. Eligible patients were those of age 18 and greater. These patients were evaluated on basis of the pre and postoperative risk factors and were analyzed for 30 days after discharge and those that developed SSIs were identified. Results Out of the total number of 2366 patients, 151 patients (6.4%) were identified with post-surgery infections out of which 107 (4.5%) had developed superficial wound infections (SSWIs) and 44 (1.9%) had developed deep wound infections (DSWIs). Infection mainly occurs in the male population (n=88, 58.3%). Major risk factors that were the main cause of post-cardiac surgery infections were diabetes (61.5%), hypertension (56.9%), smoking (38.4%), renal failure (27.1%), and re-do operation (25.1%). Conclusion Our study has demonstrated major risk factors that are involved in the occurrence of post-cardiac surgery infections like smoking, diabetes mellitus, sex, more than one operation during a single stay, etc. In the future, the contribution of various other factors involved in the occurrence of surgical site infections and best practices and methods should be studied and implemented to prevent the occurrence of post-cardiac surgery infections. Various simple techniques can still be utilized to prevent these sorts of infections, which will decrease the mortality rate.

Prevention, Diagnosis and Management of Post-Surgical Mediastinitis in Adults Consensus Guidelines of the Spanish Society of Cardiovascular Infections (SEICAV), the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) and the Biomedical Research Centre Network for Respiratory Diseases (CIBERES)

This is a consensus document of the Spanish Society of Cardiovascular Infections (SEICAV), the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) and the Biomedical Research Centre Network for Respiratory Diseases (CIBERES). These three entities have brought together a multidisciplinary group of experts that includes anaesthesiologists, cardiac and cardiothoracic surgeons, clinical microbiologists, infectious diseases and intensive care specialists, internal medicine doctors and radiologists. Despite the clinical and economic consequences of sternal wound infections, to date, there are no specific guidelines for the prevention, diagnosis and management of mediastinitis based on a multidisciplinary consensus. The purpose of the present document is to provide evidence-based guidance on the most effective diagnosis and management of patients who have experienced or are at risk of developing a post-surgical mediastinitis infection in order to optimise patient outcomes and the process of care. The intended users of the document are health care providers who help patients make decisions regarding their treatment, aiming to optimise the benefits and minimise any harm as well as the workload.

Surgical Site Infections

Surgical site infections (SSIs) are among the most common and most costly health care-associated infections, leading to adverse patient outcomes and death. Wound contamination occurs with each incision, but proven strategies exist to decrease the risk of SSI. In particular, improved adherence to evidence-based preventive measures related to appropriate antimicrobial prophylaxis can decrease the rate of SSI. Aggressive surgical debridement and effective antimicrobial therapy are needed to optimize the treatment of SSI.

The Economic Implications of Introducing Single-Patient ECG Systems for Cardiac Surgery in Australia

Introduction

Sternal wound infections (SWIs) are severe adverse events of cardiac surgery. This study aimed to estimate the economic burden of SWIs following coronary artery bypass grafts (CABG) in Australia. It also aimed to estimate the national and hospital cost-benefit of adopting single-patient electrocardiograph (spECG) systems for CABG monitoring, a measure that reduces the rate of surgical site infections (SSIs).

Material and Methods

A literature review, which focused on CABG-related SSIs, was conducted to identify data which were then used to adapt a published Markov cost-effectiveness model. The model adopted an Australian hospital perspective.

Results

The average SWI-related cost of care increase per patient was estimated at 1022 Australian dollars (AUD), and the annual burden to the Australian health care system at AUD 9.2 million. SWI burden comprised 360 additional intensive care unit (ICU) days; 1979 additional general ward (GW) days; and 186 readmissions. Implementing spECG resulted in 103 fewer ICU days, 565 fewer GW days, 48 avoided readmissions, and a total national cost saving of AUD 2.5 million, annually. A hospital performing 200 yearly CABGs was estimated to save AUD 54,830.

Conclusion

SWIs cause substantial costs to the Australian health care system. Implementing new technologies shown to reduce the SWI rate is likely to benefit patients and reduce costs.

The relationship between diabetes and surgical site infection following coronary artery bypass graft surgery in current-era models of care

BACKGROUND

Although diabetes is a recognized risk factor for postoperative infections, the seminal Portland Diabetic Project studies in cardiac surgery demonstrated intravenous insulin infusions following open-cardiac surgery achieved near normal glycaemia and decreased deep sternal wound infection to similar rates to those without diabetes.

AIM

We sought to examine a contemporary cohort of patients undergoing coronary artery bypass graft surgery (CABGS) to evaluate the relationship between diabetes, hyperglycaemia and risk of surgical site infection (SSI) in current-era models of care.

METHODS

Consecutive patients who underwent CABGS between 2016 and 2018 were identified through a state-wide data repository for healthcare-associated infections. Clinical characteristics and records of postoperative SSIs were obtained from individual chart review. Type 2 diabetes (T2D), perioperative glycaemia and other clinical characteristics were analysed in relation to the development of SSI.

FINDINGS

Of the 953 patients evaluated, 11% developed SSIs a median eight days post CABGS, with few cases of deep SSIs (<1%). T2D was evident in 41% and more prevalent in those who developed SSIs (51%). On multivariate analysis T2D was not significantly associated with development of SSI (odds ratio (OR) 1.35; P=0.174) but body mass index (BMI) remained a significant risk factor (OR 1.07, P<0.001). In patients with T2D, perioperative glycaemia was not significantly associated with SSI.

CONCLUSION

In a specialist cardiac surgery centre using perioperative intravenous insulin infusions and antibiotic prophylaxis, deep SSIs were uncommon; however, approximately one in 10 patients developed superficial SSIs. T2D was not independently associated with SSI yet BMI was independently associated with SSI post CABGS.

The impact of obesity on immune response to infection: Plausible mechanisms and outcomes

Emerging data suggest an association between obesity and infectious diseases. Although the mechanisms underlying this link are not well established, a number of potential factors may be involved. Indeed, the obesity-related vulnerability to infectious diseases could be due to chronic low-grade inflammation, hyperglycemia, hyperinsulinemia, and hyperleptinemia, which lead to a weakening of both the innate and adaptive immune responses. In addition, obesity results in anatomical-functional changes by the mechanical obstacle of excessive adipose tissue that blunt the respiratory mechanisms and predisposing to respiratory infections. Subjects with obesity are also at risk of skin folds and sweat more profusely due to the thick layers of subcutaneous fat, favoring the proliferation of microorganisms and slowing the repair of wounds down. All these factors make subjects with obesity more prone to develop nosocomial infections, surgical site, skin and soft tissue infections, bacteremia, urinary tract infections, and mycosis. Furthermore, infections in subjects with obesity have a worse prognosis, frequently prolonging hospitalization time as demonstrated for several flu viruses and recently for COVID-19. Thus, the aim of this manuscript is to provide an overview of the current clinical evidence on the associations between obesity and infectious diseases highlighting physio pathological insights involved in this link.

The Impact of Obesity on Left Ventricular Assist Device Outcomes

Background and Objectives: The understanding of high body mass index (BMI) and outcomes after Left Ventricular Assist Device (LVAD) implantation continues to evolve and the relationship has not been established yet. In this study, we investigated the effects of obesity (BMI > 30 kg/m²) on post–LVAD implantation outcomes. HeartWare LVAD and Heart Mate III LVAD were implanted. The primary outcome that was measured was mortality (in-hospital and on follow-up). The secondary outcomes that were measured were major adverse events. Materials and Methods: At our institution, the West German Heart and Vascular Center (Essen, Germany), from August 2010 to January 2020, a total of 210 patients received a long-term LVAD. Patients were stratified according to BMI ≥ 30 kg/m² representing the obesity threshold. The first group (n = 162) had an average BMI of 24.2 kg/m² (±2.9), and the second group (n = 48) had an average BMI of 33.9 kg/m² (±3.2). Baseline demographics were analysed alongside comorbidities per group. Results: Overall mortality was not significantly different between the obese group (51.1% n = 24) and the nonobese group (55.2%, n = 85) (p = 0.619). The difference between the mean duration of survival of patients who expired after hospital discharge was insignificant (2.1 years ± 1.6, group 1; 2.6 years ± 1.5, group 2; p = 0.29). In-hospital mortality was unvaried between the two groups: group 1: n = 34 (44% out of overall group 1 deaths); group 2: n = 11 (45.8% out of overall group 2 deaths) (p > 0.05). Postoperative complications were unvaried between the obese and the non-obese group (all with p > 0.05). However, a significant difference was found with regards to follow-up neurological complications (18.5% vs. 37.8%, p = 0.01) and LVAD thrombosis (14.7% vs. 33.3%, p = 0.01), as both were higher in the obese population. Conclusion: Obesity does not form a barrier for LVAD implantation in terms of mortality (in-hospital and on follow up). However, a significantly higher incidence of follow-up LVAD thrombosis and neurological complications has been found in the obese group of patients.

Methicillin-resistant Staphylococcus aureus nasal colonization in cardiovascular surgery patients at a university hospital in Bogotá, Colombia

Introducción.

Staphylococcus aureus resistente a la meticilina (SARM) es un microorganismo que coloniza las fosas nasales y diferentes partes del cuerpo, lo cual se considera un factor de riesgo para adquirir infecciones invasivas, especialmente en pacientes sometidos a cirugía cardiovascular.

Objetivo.

Determinar la colonización nasal por SARM y establecer las características clínicas en pacientes programados para cirugía cardiovascular.

Materiales y métodos.

Se hizo un estudio descriptivo entre febrero y diciembre de 2015. Se incluyeron pacientes adultos programados para cirugía cardiovascular en el Hospital Universitario San Ignacio de Bogotá. La colonización se identificó mediante reacción en cadena de la polimerasa (Polymerase Chain Reaction, PCR) en tiempo real en muestras obtenidas mediante hisopados nasales. Los pacientes fueron descolonizados con mupirocina al 2,0 % intranasal dos veces al día y baños con gluconato de clorhexidina al 4 % del cuello hacía abajo durante cinco días, al cabo de lo cual se hizo una PCR de control.

Resultados.

Se incluyeron 141 pacientes, 52 hospitalizados y 89 ambulatorios. Del total, 19 (13,4 %) tenían colonización nasal por SARM, correspondientes a 9 (17,3 %) de los 52 hospitalizados y 10 (11,2 %) de los 89 ambulatorios. Todos los pacientes sometidos a descolonización tuvieron resultado negativo en la PCR al final del proceso y ninguno presentó infección del sitio operatorio por S. aureus.

Conclusiones.

Se demostró colonización nasal por SARM tanto en los pacientes hospitalizados como en los ambulatorios. La descolonización con mupirocina fue efectiva para erradicar el estado de portador a corto plazo, lo que podría tener efecto en las tasas de infección del sitio operatorio en las cirugías cardiovasculares.

Mediastinitis in open heart surgery: a systematic review and meta-analysis of risk factors

Objective. We aimed to summarize the evidence from observational studies examining the risk factors of the incidence of mediastinitis in open heart surgery. Design. The study was a systematic review and meta-analysis of cohorts and case-control studies. Material and methods. We searched the literature and 74 studies with at least one risk factor were identified. Both fixed and random effects models were used. Heterogeneity between studies was examined by subgroup and meta-regression analysis. Publication bias or small study effects were evaluated and corrected by limit meta-analysis. Results. When correcting for small study effect, presence of obesity as estimated from 43 studies had Odds Ratio OR = 2.26. (95% CI: 2.17-2.36). This risk was increasing with decreasing latitude of study place. Presence of diabetes mellitus from 63 studies carried an OR = 1.90 (95% CI: 1.59-2.27). Presence of Chronic Obstructive Pulmonary Disease (COPD) from 30 studies had an OR = 2.59 (95% CI: 2.22-2.85). Presence of bilateral intramammary graft (BIMA) from 23 studies carried an OR = 2.54 (95% CI: 2.07-3.13). This risk was increasing with increasing frequency of female patients in the study population. Conclusion. Evidence from this study showed the robustness of the risk factors in the pathogenesis of mediastinitis. Preventive measures can be implemented for reducing obesity, especially in lower latitude countries. Furthermore, it is mandatory to monitor perioperative hyperglycemias with continuous insulin infusion. Use of skeletonized BIMA carries higher risk of mediastinitis especially in female patients without evidence of beneficial effect on survival for the time being.

Preoperative cigarette smoking and short-term morbidity and mortality after cardiac surgery: a meta-analysis

Currently, the choice of whether or not to electively operate on current smokers is varied among cardiothoracic surgeons. This meta-analysis aims to determine whether preoperative current versus ex-smoking status is related to short-term postoperative morbidity and mortality in cardiac surgical patients. Systematic literature searches of the PubMed, MEDLINE and Cochrane databases were carried out to identify all studies in cardiac surgery that investigated the relationship between smoking status and postoperative outcomes. Extracted data were analysed by random effects models. Primary outcomes included 30-day or in-hospital all-cause mortality and pulmonary morbidity. Overall, 13 relevant studies were identified, with 34 230 patients in current or ex-smoking subgroups. There was no difference in mortality (p=0.93). Current smokers had significantly higher risk of overall pulmonary complications (OR 1.44; 95% CI 1.27 to 1.64; p<0.001) and postoperative pneumonia (OR 1.62; 95%  CI 1.27 to 2.06; p<0.001) as well as lower risk of postoperative renal complications (OR 0.82; 95%  CI 0.70 to 0.96; p=0.01) compared with ex-smokers. There was a trend towards an increased risk of postoperative MI (OR 1.29; 95%  CI 0.95 to 1.75; p=0.10). No difference in postoperative neurological complications (p=0.15), postoperative sternal surgical site infections (p=0.20) or postoperative length of intensive care unit stay (p=0.86) was seen. Cardiac surgical patients who are current smokers at the time of operation do not have an increased 30-day mortality risk compared with ex-smokers, although they are at significantly increased risk of postoperative pulmonary complications.

Spinal Cord Stimulation Infection Rate and Risk Factors: Results From a United States Payer Database

Objective

Surgical site infections can cause negative clinical and economic outcomes. A recent international survey on Spinal Cord Stimulation (SCS) infection control practices demonstrated low compliance with evidence‐based guidelines. This study defines infection rate for SCS implants and identifies infection risk factors.

Materials and Methods

A retrospective analysis of the MarketScan® Databases identified patients with SCS implant (2009–2014) and continuous health plan enrollment for ≥12‐months (12 m) preimplant. For logistic regression analysis, patients were enrolled for 12 m postimplant. Kaplan–Meier and Cox Proportional Hazard survival analyses assessed time to infection, with infection rate reported at 12 m postimplant. Logistic regression characterized risk factors based on demographics, comorbidities, and clinical characteristics.

Results

In the logistic regression (n = 6615), 12 m device‐related infection rate was 3.11%. Infection risk factors included peripheral vascular disease (OR, 1.784; 95% CI: 1.011–3.149; p = 0.0457) and infection in 12 m before implant (OR, 1.518; 95% CI: 1.022–2.254; p = 0.0386). The odds of patients experiencing an infection decreased by 3.2% with each additional year of age (OR, 0.968; 95% CI: 0.952–0.984; p < 0.0001). Survival analysis (n = 13,214) identified prior infection (HR, 1.770; 95% CI: 1.342–2.336; p < 0.0001) as a risk factor. Infection was less likely in older patients (HR, 0.974; 95% CI: 0.962–0.986; p < 0.0001). Expected risk factors including obesity, diabetes, and smoking were not identified as risk factors in this analysis. There was no significant difference between infection rate for initial and replacement implants.

Conclusions

The 3.11% SCS‐related infection rate within 12 m of implant emphasizes the need for improved infection control practices. Research is needed to limit SCS infections in younger patients and those with infection history.

An Assessment Scale for Patients with Postoperative Superficial Incisional Surgical Site Infection: a Cross-Sectional Study

Superficial incisional surgical site infection (SSI) is a common postoperative complication in surgical patients. The aim of this study was to assess the predictive power of an assessment scale for identifying patients at risk of superficial incisional SSI. A cross-sectional survey was conducted at the Department of Surgery at the Medical Research Institute Hospital, Alexandria University. A sample of 150 adult patients aged from 18 to 65 years, who undergoing general surgeries that had clean sutured surgical wounds, was randomly selected. Forty-six patients (30.7%) had SSI. The total score can significantly discriminate between positive and negative superficial incisional SSI patients with diagnostic accuracy of AUC (SE) = 0.66 (0.048). Each score more than the cutoff point (11.5) will increase the risk of surgical site infection development by 2.5 times (OR (95% CI) = 2.5 (1.26-3.1)). The developed assessment scale can discriminate between patients who are at risk of superficial incisional SSI and those who are not. It can be used as a preliminary screening tool for subsequent investigation for the presence of infection.

Population Pharmacokinetic Model for Vancomycin Used in Open Heart Surgery: Model-Based Evaluation of Standard Dosing Regimens

The purpose of this study was to investigate the population pharmacokinetics of vancomycin in patients undergoing open heart surgery. In this observational pharmacokinetic study, multiple blood samples were drawn over a 48-h period of intravenous vancomycin in patients who were undergoing open heart surgery. Blood samples were analyzed using an Architect i4000SR immunoassay analyzer. Population pharmacokinetic models were developed using Monolix 4.4 software. Pharmacokinetic-pharmacodynamic (PK-PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets. A total of 168 blood samples were analyzed from 28 patients. The pharmacokinetics of vancomycin are best described by a two-compartment model with between-subject variability in clearance (CL), the volume of distribution of the central compartment (V₁), and volume of distribution of the peripheral compartment (V₂). The CL and the V₁ of vancomycin were related to creatinine CL (CL_CR), body weight, and albumin concentration. Dosing simulations showed that standard dosing regimens of 1 and 1.5 g failed to achieve the PK-PD target of AUC_0-24/MIC > 400 for an MIC of 1 mg/liter, while high weight-based dosing regimens were able to achieve the PK-PD target. In summary, the administration of standard doses of 1 and 1.5 g of vancomycin two times daily provided inadequate antibiotic prophylaxis in patients undergoing open heart surgery. The same findings were obtained when 15- and 20-mg/kg doses of vancomycin were administered. Achieving the PK-PD target required higher doses (25 and 30 mg/kg) of vancomycin.

Multi-centre prospective internal and external evaluation of the Brompton Harefield Infection Score (BHIS)

BACKGROUND

Previously, we reported that the Brompton Harefield Infection Score (BHIS) accurately predicts surgical site infection (SSI) after coronary artery bypass grafting (CABG). The BHIS was developed using two-centre data and stratifies SSI risk into three groups based on female gender, diabetes or HbA1c > 7.5%, body mass index ≥ 35, left ventricular ejection fraction < 45% and emergency surgery. The purpose of this study was to prospectively evaluate BHIS internally as well as externally.

METHODS

Multi-centre prospective evaluation involving three tertiary centres took place between October 2012 and November 2015. SSI was classified using the Public Health England protocol. Receiver operating characteristic (ROC) curves assessed predictive accuracy.

RESULTS

Across the four hospital sites, 168 of 4308 (3.9%) CABG patients had a SSI. Categorising the hospitals by BHIS score revealed that 65% of all patients were low risk (BHIS 0-1), 26% were medium risk (BHIS 2-3) and 8% were high risk (BHIS ≥ 4). The area under the ROC curve was in the range of 0.702-0.785. Overall area under the ROC curve was 0.709.

CONCLUSIONS

BHIS provides a novel, internally and externally evaluated score for a patient's risk of SSI after CABG. It enables clinicians to focus on strategies to prospectively identify high-risk patients and improve outcomes.

Population Pharmacokinetic Model-Based Evaluation of Standard Dosing Regimens for Cefuroxime Used in Coronary Artery Bypass Graft Surgery with Cardiopulmonary Bypass

The purpose of this study was to investigate the population pharmacokinetics (PK) of cefuroxime in patients undergoing coronary artery bypass graft (CABG) surgery. In this observational pharmacokinetic study, multiple blood samples were collected over a 48-h interval of intravenous cefuroxime administration. The samples were analyzed by using a validated high-performance liquid chromatography (HPLC) method. Population pharmacokinetic models were developed using Monolix (version 4.4) software. Pharmacokinetic-pharmacodynamic (PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets. A total of 468 blood samples from 78 patients were analyzed. The PK for cefuroxime were best described by a two-compartment model with between-subject variability on clearance, the volume of distribution of the central compartment, and the volume of distribution of the peripheral compartment. The clearance of cefuroxime was related to creatinine clearance (CL_CR). Dosing simulations showed that standard dosing regimens of 1.5 g could achieve the PK-PD target of the percentage of the time that the free concentration is maintained above the MIC during a dosing interval (fT_MIC) of 65% for an MIC of 8 mg/liter in patients with a CL_CR of 30, 60, or 90 ml/min, whereas this dosing regimen failed to achieve the PK-PD target in patients with a CL_CR of ≥125 ml/min. In conclusion, administration of standard doses of 1.5 g three times daily provided adequate antibiotic prophylaxis in patients undergoing CABG surgery. Lower doses failed to achieve the PK-PD target. Patients with high CL_CR values required either higher doses or shorter intervals of cefuroxime dosing. On the other hand, lower doses (1 g three times daily) produced adequate target attainment for patients with low CL_CR values (≤30 ml/min).

Development and Validation of a Stratification Tool for Predicting Risk of Deep Sternal Wound Infection after Coronary Artery Bypass Grafting at a Brazilian Hospital

Objective

Deep sternal wound infection following coronary artery bypass grafting is a serious complication associated with significant morbidity and mortality. Despite the substantial impact of deep sternal wound infection, there is a lack of specific risk stratification tools to predict this complication after coronary artery bypass grafting. This study was undertaken to develop a specific prognostic scoring system for the development of deep sternal wound infection that could risk-stratify patients undergoing coronary artery bypass grafting and be applied right after the surgical procedure.

Methods

Between March 2007 and August 2016, continuous, prospective surveillance data on deep sternal wound infection and a set of 27 variables of 1500 patients were collected. Using binary logistic regression analysis, we identified independent predictors of deep sternal wound infection. Initially we developed a predictive model in a subset of 500 patients. Dataset was expanded to other 1000 consecutive cases and a final model and risk score were derived. Calibration of the scores was performed using the Hosmer-Lemeshow test.

Results

The model had area under Receiver Operating Characteristic (ROC) curve of 0.729 (0.821 for preliminary dataset). Baseline risk score incorporated independent predictors of deep sternal wound infection: obesity (P=0.046; OR 2.58; 95% CI 1.11-6.68), diabetes (P=0.046; OR 2.61; 95% CI 1.12-6.63), smoking (P=0.008; OR 2.10; 95% CI 1.12-4.67), pedicled internal thoracic artery (P=0.012; OR 5.11; 95% CI 1.42-18.40), and on-pump coronary artery bypass grafting (P=0.042; OR 2.20; 95% CI 1.13-5.81). A risk stratification system was, then, developed.

Conclusion

This tool effectively predicts deep sternal wound infection risk at our center and may help with risk stratification in relation to public reporting and targeted prevention strategies in patients undergoing coronary artery bypass grafting.

A perioperative care map improves outcomes in patients with morbid obesity undergoing major surgery

BACKGROUND

The surgical management of patients with morbid obesity (body mass index ≥ 40) is notable for a relatively high risk of complications. To address this problem, a perioperative care map was developed using precautions and best practices commonly employed in bariatric surgery. It requires additional medical assessments, sleep apnea surveillance, more stringent guidelines for anesthetic management, and readily available bariatric operating room equipment, among other items. This care map was implemented in 2013 at 4 major urban teaching hospitals for use in patients undergoing all types of nonambulatory surgery with a body mass index greater than 40 kg/m². The impact on patient outcomes was evaluated.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was used to compare 30-day outcomes of morbidly obese patients before the year 2013 and after the years 2015 care-map implementation. In addition, trends in 30-day outcomes for morbidly obese patients were compared with those for non-obese patients.

RESULTS

Morbidly obese patients, between 2013 and 2015, saw an adjusted decrease in the rate of unplanned return to the operating room (OR = 0.49; P = .039), unplanned readmission (OR = 0.57; P = .006), total duration of stay (-0.87 days; P = .009), and postoperative duration of stay (-0.69 days; P = .007). Of these, total duration of stay (-0.86 days; P = .015), and postoperative duration of stay (-0.69 days; P = .012) improved significantly more for morbidly obese patients than for nonmorbidly obese patients.

CONCLUSION

Outcomes in morbidly obese patients improved from 2013 to 2015. Implementation of a perioperative care map may have contributed to these improvements. The care map should be further investigated and considered for more widespread use.

European Association for Cardio-Thoracic Surgery expert consensus statement on the prevention and management of mediastinitis

Mediastinitis continues to be an important and life-threatening complication after median sternotomy despite advances in prevention and treatment strategies, with an incidence of 0.25-5%. It can also occur as extension of infection from adjacent structures such as the oesophagus, airways and lungs, or as descending necrotizing infection from the head and neck. In addition, there is a chronic form of 'chronic fibrosing mediastinitis' usually caused by granulomatous infections. In this expert consensus, the evidence for strategies for treatment and prevention of mediatinitis is reviewed in detail aiming at reducing the incidence and optimizing the management of this serious condition.

Safety, tolerability, and immunogenicity of a single dose 4-antigen or 3-antigen Staphylococcus aureus vaccine in healthy older adults: Results of a randomised trial

BACKGROUND

The decline in immune function with age is a challenge to vaccine development. Following an initial study in adults aged 18-64years, this study evaluated the safety and immunogenicity of Staphylococcus aureus (S. aureus) 4-antigen (SA4Ag) and 3-antigen (SA3Ag) vaccine in older adults. SA3Ag included capsular polysaccharide serotypes 5 and 8 (CP5 and CP8) conjugated to the nontoxic mutant form of diphtheria toxin (CRM₁₉₇) and a recombinant version of clumping factor A (ClfA). SA4Ag included these antigens, with the addition of a recombinant manganese transporter C (rP305A or MntC). Both vaccines were unadjuvanted.

METHODS

In this double-blind, sponsor-unblinded, placebo-controlled, phase 1/2 study, 284 healthy adults (aged 65-85years) were randomised to receive a single dose of one of three formulations of SA4Ag with escalating dose levels of rP305A, SA3Ag, or placebo. Functional immune responses were measured using opsonophagocytic activity (OPA) killing and fibrinogen-binding inhibition (FBI) assays; immunogenicity was also assessed using a competitive Luminex® immunoassay (cLIA). T-cell responses were measured in a small subgroup of subjects using intracellular cytokine staining (ICS) assays.

RESULTS

The results demonstrated rapid and robust functional immune responses to all antigens in healthy older adults. A high proportion of active vaccine recipients met the pre-defined antibody thresholds for each antigen at Day 29. SA4Ag elicited a dose-level response to rP305A with up to a 13-fold rise in cLIA titres at Day 29. Opsonophagocytic activity (OPA) assays showed >50- and >20-fold rises in functional titres using S. aureus strains expressing CP5 and CP8, respectively, at Day 29. T-cell cytokine responses were not substantially above background levels. There were no safety concerns in this study population and no increases in adverse events with higher rP305A dose levels.

CONCLUSIONS

Single-dose vaccination of SA4Ag and SA3Ag in healthy adults aged 65-85years safely induced rapid and robust functional immune responses, supporting further development of SA4Ag for the prevention of S. aureus disease in adults up to age 85years.

TRIAL REGISTRATION NUMBER

NCT01643941.

Development and Validation of a Preoperative Surgical Site Infection Risk Score for Primary or Revision Knee and Hip Arthroplasty

BACKGROUND

Surgical site infection (SSI) is a major complication following total joint arthroplasty. Host susceptibility to infection has emerged as an important predictor of SSI. The purpose of this study was to develop and validate a preoperative SSI risk-assessment tool for primary or revision knee and hip arthroplasty.

METHODS

Data for 6,789 patients who underwent total joint arthroplasty (from the years 2000 to 2011) were obtained from a single hospital system. SSI was defined as a superficial infection within 30 days or deep infection within 1 year. Logistic regression modeling was utilized to create a risk scoring system for a derivation sample (n = 5,789; 199 SSIs), with validation performed on a hold-out sample (a subset of observations chosen randomly from the initial sample to form a testing set; n = 1,000; 41 SSIs).

RESULTS

On the basis of logistic regression modeling, we created a scoring system to assess SSI risk (range, 0 to 35 points) that is the point sum of the following: primary hip arthroplasty (0 points); primary knee (1); revision hip (3); revision knee (3); non-insulin-dependent diabetes (1); insulin-dependent diabetes (1.5); chronic obstructive pulmonary disease (COPD) (1); inflammatory arthropathy (1.5); tobacco use (1.5); lower-extremity osteomyelitis or pyogenic arthritis (2); pelvis, thigh, or leg traumatic fracture (2); lower-extremity pathologic fracture (2.5); morbid obesity (2.5); primary bone cancer (4); reaction to prosthesis in the last 3 years (4); and history of staphylococcal septicemia (4.5). The risk score had good discriminatory capability (area under the ROC [receiver operating characteristic] curve = 0.77) and calibration (Hosmer-Lemeshow chi-square test, p = 0.34) and was validated using the independent sample (area under the ROC curve = 0.72). A small subset of patients (5.9%) had a >10% estimated infection risk.

CONCLUSIONS

The patient comorbidities composing the risk score heavily influenced SSI risk for primary or revision knee and hip arthroplasty. We believe that infection risk can be objectively determined in a preoperative setting with the proposed SSI risk score.

Surgical Site Infection After Cardiac Surgery: A Simplified Surveillance Method

We report the results of a 2-year, 7-center program of surveillance of deep sternal wound infection (DSWI) after cardiac surgery. DSWI was defined as the need for reoperation. Stratification data were abstracted from computerized files. The incidence of DSWI was 2.2% (198 of 8,816 cardiac surgery procedures). The risk factors identified were obesity, age, coronary artery bypass grafting, postoperative mechanical ventilation, and early surgical reexploration. The resource efficiency of this simplified surveillance method is discussed.

Latitude of the study place and age of the patient are associated with incidence of mediastinitis and microbiology in open-heart surgery: a systematic review and meta-analysis

Objective

We aimed to summarize the pooled frequency of mediastinitis following open-heart surgery caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria.

Design

This study was a systematic review and a meta-analysis of prospective and retrospective cohort studies.

Materials and methods

We searched the literature, and a total of 97 cohort studies were identified. Random-effect model was used to synthesize the results. Heterogeneity between studies was examined by subgroup and meta-regression analyses, considering study and patient-level variables. Small-study effect was evaluated.

Results

Substantial heterogeneity was present. The estimated incidence of mediastinitis evaluated from 97 studies was 1.58% (95% confidence intervals [CI] 1.42, 1.75) and that of Gram-positive bacteria, Gram-negative bacteria, and MRSA bacteria evaluated from 63 studies was 0.90% (95% CI 0.81, 1.21), 0.24% (95% CI 0.18, 0.32), and 0.08% (95% CI 0.05, 0.12), respectively. A meta-regression pinpointed negative association between the frequency of mediastinitis and latitude of study place and positive association between the frequency of mediastinitis and the age of the patient at operation. Multivariate meta-regression showed that prospective cohort design and age of the patients and latitude of study place together or in combination accounted for 17% of heterogeneity for end point frequency of mediastinitis, 16.3% for Gram-positive bacteria, 14.7% for Gram-negative bacteria, and 23.3% for MRSA bacteria.

Conclusion

Evidence from this study suggests the importance of latitude of study place and advanced age as risk factors of mediastinitis. Latitude is a marker of thermally regulated bacterial virulence and other local surgical practice. There is concern of increasing risk of mediastinitis and of MRSA in elderly patients undergoing sternotomy.

Closed incision negative pressure therapy: international multidisciplinary consensus recommendations

Surgical site occurrences (SSOs) affect up to or over 25% of patients undergoing operative procedures, with the subset of surgical site infections (SSIs) being the most common. Commercially available closed incision negative pressure therapy (ciNPT) may offer surgeons an additional option to manage clean, closed surgical incisions. We conducted an extensive literature search for studies describing ciNPT use and assembled a diverse panel of experts to create consensus recommendations for when using ciNPT may be appropriate. A literature search of MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials using key words ‘prevention’, ‘negative pressure wound therapy (NPWT)’, ‘active incisional management’, ‘incisional vacuum therapy’, ‘incisional NPWT’, ‘incisional wound VAC’, ‘closed incisional NPWT’, ‘wound infection’, and ‘SSIs’ identified peer‐reviewed studies published from 2000 to 2015. During a multidisciplinary consensus meeting, the 12 experts reviewed the literature, presented their own ciNPT experiences, identified risk factors for SSOs and developed comprehensive consensus recommendations. A total of 100 publications satisfied the search requirements for ciNPT use. A majority presented data supporting ciNPT use. Numerous publications reported SSI risk factors, with the most common including obesity (body mass index ≥30 kg/m²); diabetes mellitus; tobacco use; or prolonged surgical time. We recommend that the surgeon assess the individual patient's risk factors and surgical risks. Surgeons should consider using ciNPT for patients at high risk for developing SSOs or who are undergoing a high‐risk procedure or a procedure that would have highly morbid consequences if an SSI occurred.

Effect of Preoperative Antibiotic Prophylaxis on Surgical Site Infections Complicating Cardiac Surgery

Objective.

To evaluate the effect of an optimized policy for antibiotic prophylaxis on surgical site infection (SSI) rates in cardiac surgery.

Design.

Prospective cohort study.

Setting.

Tertiary medical center in Israel.

Methods.

SSIs were recorded during a 10-year study period and ascertained through routine surveillance using the National Healthcare Safety Network (NHSN) methodology. Multivariable analyses were conducted to determine which significant covariates, including the administration of preoperative prophylaxis, affected these outcomes.

Results.

A total of 2,637 of 3,170 evaluated patients were included, and the overall SSI rate was 8.4%. A greater than 50% reduction in SSI rates was observed in the last 4 years of the study. Overall and site-specific infection rates were similar for patients receiving cefazolin or vancomycin. SSIs developed in 206 (8.1%) of the 2,536 patients who received preoperative prophylaxis (within 2 hours of the first incision) compared with 14 (13.9%) of 101 patients who received antibiotic prophylaxis at a different time (P= .04; odds ratio [OR], 1.8; 95% confidence interval [CI], 1.0–3.3). After accounting for covariates, preoperative hospital stay (5 days or more), an NHSN risk category (2 or 3), age (60 years or more), surgeon's role, and the period of measurement were significantly associated with SSIs. Emergency surgery, age, surgeon's role, and nonpreoperative prophylaxis were found to be independent predictors of superficial SSI.

Conclusions.

We observed a progressive and significant decrease in SSI rates after the implementation of an infection control program that included an optimized policy of preoperative prophylaxis in cardiac surgery.

An experimental assessment of catheter trackability forces with tortuosity parameters along patient-specific coronary phantoms

Coronary artery disease is one of the leading causes of cardiovascular deaths worldwide. Approximately 70% of patients requiring coronary revascularisation receive endovascular stents. The endovascular procedure is the preferred option due to its minimally invasive nature when compared to open heart surgery. Stent delivery is paramount for the success of the endovascular procedure. Catheter delivery forces within tortuous blood vessels can produce vasoconstriction and injury, resulting in reactive intimal proliferation or distal embolisation associated with end-organ ischaemia and infarction. Trackability is evaluated by most medical device companies for further development of their delivery systems. Relevant device design attributes must be tested in settings which simulate aspects of the intended use conditions, such as vessel geometry and compliance. Various tortuosity parameters are used to facilitate endovascular intervention planning. This study assessed the significance and correlation between the trackability forces for a coronary stent system with various geometrical parameters based on patient-specific geometries. A motorised delivery system delivered a commercially available coronary stent system and monitored the trackability forces along three phantom patient-specific thin-walled, compliant coronary vessels supported by a cardiac phantom model. The maximum trackability forces, curvature and torsion values ranged from 0.31 to 0.87 N, 0.06 to 0.22 mm(-1) and -11.1 to 5.8 mm(-1), respectively. The trackability forces were significantly different between all vessels (p < 0.002), while the tortuosity parameters were not significantly different (p > 0.05). A new tortuosity parameter-coined tracking curvature which considers the lumen radius as well as the curvature along the centreline was statistically different (p < 0.002) for all vessels and correlated with the trackability forces. There was a strong correlation between the cumulative trackability force and the cumulative tracking curvature. Tracking curvature could be used as a predictive clinical tool to aid stent delivery to the vicinity of the lesion.

Vaccines for Staphylococcus aureus and Target Populations

Staphylococcus aureus is a leading pathogen in surgical site, intensive care unit, and skin infections, as well as healthcare-associated pneumonias. These infections are associated with an enormous burden of morbidity, mortality, and increase of hospital length of stay and patient cost. S. aureus is impressively fast in acquiring antibiotic resistance, and multidrug-resistant strains are a serious threat to human health. Due to resistance or insufficient effectiveness, antibiotics and bundle measures leave a tremendous unmet medical need worldwide. There are no licensed vaccines on the market despite the significant efforts done by public and private initiatives. Indeed, vaccines tested in clinical trials in the last two decades have failed to show efficacy. However, they targeted single antigens and contained no adjuvants and efficacy trials were performed in severely ill subjects. Herein, we provide a comprehensive evaluation of potential target populations for efficacy trials taking into account key factors such as population size, incidence of S. aureus infection, disease outcome, primary endpoints, as well as practical advantages and disadvantages. We describe the whole-blood assay as a potential surrogate of protection, and we show the link between phase III clinical trial data of failed vaccines with their preclinical observations. Finally, we give our perspective on how new vaccine formulations and clinical development approaches may lead to successful S. aureus vaccines.

Demonstration of the preclinical correlate of protection for Staphylococcus aureus clumping factor A in a murine model of infection

The Staphylococcus aureus virulence factor clumping factor A (ClfA) is a component of an investigational S. aureus prophylactic vaccine. ClfA enables S. aureus to bind to fibrinogen and platelets during the initial stages of invasive disease. Here we demonstrate that ectopic expression of ClfA is sufficient to render nonpathogenic Lactococcus lactis lethal in a murine model of systemic infection. In contrast, L. lactis expressing ClfAY338A, which cannot bind fibrinogen, did not cause death in the mice. Pathogenicity was also prevented by immunization with ClfA. This model was then used to define a preclinical correlate of protection by measuring functional antibody in a S. aureus fibrinogen binding inhibition assay (FBI) and correlating that titer with protective outcomes. Although many humans have pre-existing antibodies that bind to ClfA, only sera with a threshold functional titer in the FBI were protective in this preclinical model. This confirms that fibrinogen binding is critical for ClfA-mediated pathogenesis and demonstrates that functional antibodies against ClfA are sufficient to protect against ClfA-mediated pathogenesis in vivo, enabling the definition of a preclinical correlate of protection for ClfA-containing vaccines based on FBI titer.

Diabetes mellitus is associated with increased risk of surgical site infections: A meta-analysis of prospective cohort studies

BACKGROUND AND OBJECTIVE

Observational studies have suggested an association between diabetes mellitus and the risk of surgical site infections (SSIs), but the results remain inconclusive. We conducted a meta-analysis of prospective cohort studies to elucidate the relationship between diabetes mellitus and SSIs.

METHODS

We searched PubMed, Embase, and Web of Science databases and reviewed the reference lists of the retrieved articles to identify relevant studies. Associations were tested in subgroups representing different patient characteristics and study quality criteria. The random-effect model was used to calculate the overall relative risk (RR).

RESULTS

Fourteen prospective cohort studies (N = 91,094 participants) were included in this meta-analysis, and the pooled crude RR was 2.02 (95% confidence interval, 1.68-2.43) with significant between-study heterogeneity observed (I(2) = 56.50%). Significant association was also detected after we derived adjusted RRs for studies not reporting the adjusted RRs and calculated the combined adjusted RR of the 14 studies (RR, 1.69; 95% confidence interval, 1.33-2.13). Results were consistent and statistically significant in all subgroups. Stratified analyses found the number of confounders adjusted for, sample size, and method of diabetes case ascertainment might be the potential sources of heterogeneity. Sensitivity analysis further demonstrated the robustness of the result.

CONCLUSIONS

This meta-analysis suggests diabetes mellitus is significantly associated with increased risk of SSIs. Future studies are encouraged to reveal the mechanisms underlying this association.

Impact of obesity on the risk of wound infection following surgery: results from a nationwide prospective multicentre cohort study in England

We sought to assess the impact of body mass index on the risk of surgical site infection in a prospective cohort study of 206 National Health Service (NHS) hospitals in England between 2007 and 2011. Body mass index was available for 159,720 of 350,089 operations among patients undergoing abdominal hysterectomy, coronary artery bypass graft, hip replacement, knee replacement, or large-bowel surgery. Among these patients, the risk of surgical site infection ranged from 0.65% for knee replacement to 11.04% for large-bowel surgery. Overall, 127,512 (79.8%) patients were overweight or obese (body mass index of ≥25 kg/m(2)). Obesity was associated with a 1.1-fold to 4.4-fold increase in the adjusted odds of developing surgical site infection as compared with normal weight, depending on the type of surgery. The population-attributable fraction (PAF) for body mass index was greatest in overweight (body mass index of 25.0-29.9 kg/m(2)) patients undergoing coronary artery bypass graft, accounting for 15% of their overall risk of surgical site infection (PAF 0.15; 95% CI 0.09-0.22). Being overweight or obese substantially increased the likelihood of patients developing surgical site infection. Given the increasingly high proportion of the surgical population who are overweight, this is likely to place a considerable additional burden on the NHS. Strategies for mitigating this excess risk need to be found.

Effect of perioperative mupirocin and antiseptic body wash on infection rate and causative pathogens in patients undergoing cardiac surgery

INTRODUCTION

Preoperative nasal mupirocin has been shown to reduce surgical site infections (SSIs) in patients undergoing cardiac surgery. We analyzed the effect of mupirocin plus antiseptic body wash on SSI rate and etiology.

METHODS

Prospective SSI surveillance was done for patients undergoing cardiac surgery before and after implementation of mupirocin nasal ointment and chlorhexidine/octenidine body wash.

RESULTS

Overall SSI rate was 8.6% (81 out of 945) for the control and 6.9% (58 out of 842) for the intervention cohort (P = .19). In multivariable analysis, the study protocol was associated with an odds ratio of 0.61 (95% confidence interval, 0.41-0.91; P = .015) with regard to any SSI. This effect was exclusively due to a reduction in superficial SSIs and was observed both in patients with preoperative and postoperative treatment initiation. Coagulase-negative staphylococci (CoNS), the most commonly isolated pathogen, were found in 37% and 48% (P = .19) of patients in the control and the intervention cohort, respectively. CoNS were methicillin resistant in 69% of cases.

CONCLUSIONS

Mupirocin and antiseptic body wash reduced the rate of superficial but not deep or organ/space SSIs. Postoperative patient treatment may be critical in reducing the risk for superficial SSI, presumably due to a reduction of bacterial skin load. A high proportion of SSI was due to methicillin-resistant CoNS and thus not covered by routine perioperative antimicrobial prophylaxis.

Which Kind of Provider's Operation Volumes Matters? Associations between CABG Surgical Site Infection Risk and Hospital and Surgeon Operation Volumes among Medical Centers in Taiwan

BACKGROUND

Volume-infection relationships have been examined for high-risk surgical procedures, but the conclusions remain controversial. The inconsistency might be due to inaccurate identification of cases of infection and different methods of categorizing service volumes. This study takes coronary artery bypass graft (CABG) surgical site infections (SSIs) as an example to examine whether a relationship exists between operation volumes and SSIs, when different SSIs case identification, definitions and categorization methods of operation volumes were implemented.

METHODS

A population-based cross-sectional multilevel study was conducted. A total of 7,007 patients who received CABG surgery between 2006 and 2008 from 19 medical centers in Taiwan were recruited. SSIs associated with CABG surgery were identified using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9 CM) codes and a Classification and Regression Trees (CART) model. Two definitions of surgeon and hospital operation volumes were used: (1) the cumulative CABG operation volumes within the study period; and (2) the cumulative CABG operation volumes in the previous one year before each CABG surgery. Operation volumes were further treated in three different ways: (1) a continuous variable; (2) a categorical variable based on the quartile; and (3) a data-driven categorical variable based on k-means clustering algorithm. Furthermore, subgroup analysis for comorbidities was also conducted.

RESULTS

This study showed that hospital volumes were not significantly associated with SSIs, no matter which definitions or categorization methods of operation volume, or SSIs case identification approaches were used. On the contrary, the relationships between surgeon's volumes varied. Most of the models demonstrated that the low-volume surgeons had higher risk than high-volume surgeons.

CONCLUSION

Surgeon volumes were more important than hospital volumes in exploring the relationship between CABG operation volumes and SSIs in Taiwan. However, the relationships were not robust. Definitions and categorization methods of operation volume and correct identification of SSIs are important issues for future research.

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 Coronary Artery Bypass Graft Surgical Site Infection Surveillance Data From a Statewide Surveillance System in Australia

Objective.

To measure the accuracy and determine the positive predictive value (PPV) and negative predictive value (NPV) of data submitted to a statewide surveillance system for identifying surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery.

Design.

Retrospective review of hospital medical records comparing SSI data with surveillance data submitted by infection control consultants (ICCs).

Setting.

Victorian Hospital Acquired Infection Surveillance System (VICNISS) Coordinating Centre in Victoria, Australia.

Patients.

All patients reported to have an SSI following CABG surgery and a random sample of approximately 10% of patients reported not to have an SSI following CABG surgery.

Results.

The VICNISS ascertainment rate for CABG procedures in Victoria was 95%. One hundred sixty-nine medical records were reviewed, and reviewers agreed with ICCs about 46 (96%) of the patients reported as infected by the ICCs and 31 (91%) of the patients identified with a sternal SSI by the ICCs. In one-third of SSIs, the depth of SSI documented by ICCs was discordant with that documented by the reviewers. Disagreement about patients with donor site SSI was frequent. When the review findings were used as the reference standard, the PPV for ICC-reported SSI was 96% (95% confidence interval [CI], 86%-99%), and the NPV was 97% (95% CI, 92%-99%). For ICC-reported sternal SSI, the PPV was 91% (95% CI, 76%-98%) and the NPV was 98% (95% CI, 94%-100%).

Conclusions.

There was broad agreement on the number of infected patients and the number of patients with sternal SSI. However, discordance was frequent with respect to the depth of sternal SSI and the identification of donor site SSI. We recommend modifications to the methodology for National Noscomial Infection Surveillance System-based surveillance for SSI following CABG surgery.

Improving Risk-Adjusted Measures of Surgical Site Infection for the National Healthcare Safely Network

Background.

The National Healthcare Safety Network (NHSN) has provided simple risk adjustment of surgical site infection (SSI) rates to participating hospitals to facilitate quality improvement activities; improved risk models were developed and evaluated.

Methods.

Data reported to the NHSN for all operative procedures performed from January 1, 2006, through December 31, 2008, were analyzed. Only SSIs related to the primary incision site were included. A common set of patient- and hospital-specific variables were evaluated as potential SSI risk factors by univariate analysis. Some ific variables were available for inclusion. Stepwise logistic regression was used to develop the specific risk models by procedure category. Bootstrap resampling was used to validate the models, and the c-index was used to compare the predictive power of new procedure-specific risk models with that of the models with the NHSN risk index as the only variable (NHSN risk index model).

Results.

From January 1, 2006, through December 31, 2008, 847 hospitals in 43 states reported a total of 849,659 procedures and 16,147 primary incisional SSIs (risk, 1.90%) among 39 operative procedure categories. Overall, the median c-index of the new procedure-specific risk was greater (0.67 [range, 0.59–0.85]) than the median c-index of the NHSN risk index models (0.60 [range, 0.51–0.77]); for 33 of 39 procedures, the new procedure-specific models yielded a higher c-index than did the NHSN risk index models.

Conclusions.

A set of new risk models developed using existing data elements collected through the NHSN improves predictive performance, compared with the traditional NHSN risk index stratification.

Surgical site infections following coronary artery bypass graft procedures: 10 years of surveillance data

BACKGROUND

Surgical site infections following coronary artery bypass graft (CABG) procedures pose substantial burden on patients and healthcare systems. This study aims to describe the incidence of surgical site infections and causative pathogens following CABG surgery over the period 2003-2012, and to identify risk factors for complex sternal site infections.

METHODS

Routine computerised surveillance data were collected from three public hospitals in Queensland, Australia in which CABG surgery was performed between 2003 and 2012. Surgical site infection rates were calculated by types of infection (superficial/complex) and incision sites (sternal/harvest sites). Patient and procedural characteristics were evaluated as risk factors for complex sternal site infections using a logistic regression model.

RESULTS

There were 1,702 surgical site infections (518 at sternal sites and 1,184 at harvest sites) following 14,546 CABG procedures performed. Among 732 pathogens isolated, Methicillin-sensitive Staphylococcus aureus accounted for 28.3% of the isolates, Pseudomonas aeruginosa 18.3%, methicillin-resistant Staphylococcus aureus 14.6%, and Enterobacter species 6.7%. Proportions of Gram-negative bacteria elevated from 37.8% in 2003 to 61.8% in 2009, followed by a reduction to 42.4% in 2012. Crude rates of complex sternal site infections increased over the reporting period, ranging from 0.7% in 2004 to 2.6% in 2011. Two factors associated with increased risk of complex sternal site infections were identified: patients with an ASA (American Society of Anaesthesiologists) score of 4 or 5 (reference score of 3, OR 1.83, 95% CI 1.36-2.47) and absence of documentation of antibiotic prophylaxis (OR 2.03, 95% CI 1.12-3.69).

CONCLUSIONS

Compared with previous studies, our data indicate the importance of Gram-negative organisms as causative agents for surgical site infections following CABG surgery. An increase in complex sternal site infection rates can be partially explained by the increasing proportion of patients with more severe underlying disease.

Care bundle to prevent methicillin-resistant Staphylococcus aureus sternal wound infection after off-pump coronary artery bypass

Methicillin-resistant Staphylococcus aureus (MRSA) sternal wound infection (SWI) after cardiac surgery is endemic in our hospital. An infection control care bundle with preoperative chlorhexidine showering and povidone iodine paint before bathing was introduced in 2006. From 2001 to 2012, 23 (2.3%) of 1,010 patients undergoing off-pump coronary artery bypass had SWIs. SWI significantly decreased after 2006 (1.4% vs 3.4%, respectively; P = .03). Care bundle was more protective against MRSA infection (2.3% vs 0.5%, respectively; P = .021). SWI remained a common complication after off-pump coronary artery bypass. MRSA infection was most common, and the mortality was high. Care bundle can effectively decrease the incidence of SWI, especially infection caused by MRSA.