Surgical site infections after coronary artery bypass graft surgery: incidence, perioperative hospital stay, readmissions, and revision surgeries

Healthcare costs and outcomes associated with surgical site infections after coronary artery bypass grafting surgeries in Oman

BACKGROUND

Surgical site infection (SSI) after coronary artery bypass graft (CABG) surgeries is considered a key indicator of the quality of healthcare services.

OBJECTIVE

This study aimed to estimate the healthcare outcomes associated with SSIs after CABG surgeries in Oman in terms of mortality rate, case-fatality rate, LOS, readmission rate and healthcare costs.

METHODS

The nested case-control study design was used based on retrospective data, which was conducted from 2016 to 2017. The case group encompassed all CABG patients with confirmed SSIs within 30 days of the surgery (n = 104) while controls were CABG patients without SSIs (n = 404).

RESULTS

Forty-four (42.3%) of the SSI patients were readmitted to the hospital compared to eight (2%) of the control group (p < .001). Patients in the case group had a longer LOS (M = 24.4, SD = 44.6 days) compared to those in the control group (M = 11, SD = 21 days, p = .003). The mean healthcare costs of cases (M = Omani Rial [OMR] 3823, SD = OMR 2516) were significantly greater than controls (M = OMR 3154, SD = OMR 1415, p = .010).

CONCLUSION

Results from this study can be baseline data for formulating new hypotheses and testing the causal relationship between SSIs after CABG surgeries and the readmission rate, LOS and health care costs.Key messagesSurgical Site Infections (SSIs) are still a major complication after cardiac surgeries in Oman.SSIs after cardiac surgeries are associated with substantially increased healthcare costs and length of stay.SSIs after cardiac surgeries are associated with negative outcomes such as mortality and case-fatality rates.

Delayed Ventricular Septal Rupture Repair After Myocardial Infarction: An Updated Review

Ventricular septal rupture (VSR) is a rare but serious complication that can occur after myocardial infarction (MI) and is associated with significant morbidity and mortality. The optimal management approach for VSR remains a topic of debate, with considerations including early versus delayed surgery, risk stratification, pharmacological interventions, minimally invasive techniques, and tissue engineering. The pathophysiology of VSR involves myocardial necrosis, inflammatory response, and enzymatic degradation of the extracellular matrix (ECM), particularly mediated by matrix metalloproteinases (MMPs). These processes lead to structural weakening and subsequent rupture of the ventricular septum. Hemodynamically, VSR results in left-to-right shunting, increased pulmonary blood flow, and potentially hemodynamic instability. The early surgical repair offers the advantages of immediate closure of the defect, prevention of complications, and potentially improved outcomes. However, it is associated with higher surgical risk and limited myocardial recovery potential during the waiting period. In contrast, delayed surgery allows for a period of myocardial recovery, risk stratification, and optimization of surgical outcomes. However, it carries the risk of ongoing complications and progression of ventricular remodeling. Risk stratification plays a crucial role in determining the optimal timing for surgery and tailoring treatment plans. Various clinical factors, imaging assessments, scoring systems, biomarkers, and hemodynamic parameters aid in risk assessment and guide decision-making. Pharmacological interventions, including vasopressors, diuretics, angiotensin-converting enzyme inhibitors, beta-blockers, antiplatelet agents, and antiarrhythmic drugs, are employed to stabilize hemodynamics, prevent complications, promote myocardial healing, and improve outcomes in VSR patients. Advancements in minimally invasive techniques, such as percutaneous device closure, and tissue engineering hold promise for less invasive interventions and better outcomes. These approaches aim to minimize surgical morbidity, optimize healing, and enhance patient recovery. In conclusion, the management of VSR after MI requires a multidimensional approach that considers various aspects, including risk stratification, surgical timing, pharmacological interventions, minimally invasive techniques, and tissue engineering.

Negative pressure wound therapy for surgical wounds healing by primary closure

BACKGROUND

Indications for the use of negative pressure wound therapy (NPWT) are broad and include prophylaxis for surgical site infections (SSIs). Existing evidence for the effectiveness of NPWT on postoperative wounds healing by primary closure remains uncertain.

OBJECTIVES

To assess the effects of NPWT for preventing SSI in wounds healing through primary closure, and to assess the cost-effectiveness of NPWT in wounds healing through primary closure.

SEARCH METHODS

In January 2021, we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries and references of included studies, systematic reviews and health technology reports. There were no restrictions on language, publication date or study setting.

SELECTION CRITERIA

We included trials if they allocated participants to treatment randomly and compared NPWT with any other type of wound dressing, or compared one type of NPWT with another.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed trials using predetermined inclusion criteria. We carried out data extraction, assessment using the Cochrane risk of bias tool, and quality assessment according to Grading of Recommendations, Assessment, Development and Evaluations methodology. Our primary outcomes were SSI, mortality, and wound dehiscence.

MAIN RESULTS

In this fourth update, we added 18 new randomised controlled trials (RCTs) and one new economic study, resulting in a total of 62 RCTs (13,340 included participants) and six economic studies. Studies evaluated NPWT in a wide range of surgeries, including orthopaedic, obstetric, vascular and general procedures. All studies compared NPWT with standard dressings. Most studies had unclear or high risk of bias for at least one key domain. Primary outcomes Eleven studies (6384 participants) which reported mortality were pooled. There is low-certainty evidence showing there may be a reduced risk of death after surgery for people treated with NPWT (0.84%) compared with standard dressings (1.17%) but there is uncertainty around this as confidence intervals include risk of benefits and harm; risk ratio (RR) 0.78 (95% CI 0.47 to 1.30; I² = 0%). Fifty-four studies reported SSI; 44 studies (11,403 participants) were pooled. There is moderate-certainty evidence that NPWT probably results in fewer SSIs (8.7% of participants) than treatment with standard dressings (11.75%) after surgery; RR 0.73 (95% CI 0.63 to 0.85; I² = 29%). Thirty studies reported wound dehiscence; 23 studies (8724 participants) were pooled. There is moderate-certainty evidence that there is probably little or no difference in dehiscence between people treated with NPWT (6.62%) and those treated with standard dressing (6.97%), although there is imprecision around the estimate that includes risk of benefit and harms; RR 0.97 (95% CI 0.82 to 1.16; I² = 4%). Evidence was downgraded for imprecision, risk of bias, or a combination of these. Secondary outcomes There is low-certainty evidence for the outcomes of reoperation and seroma; in each case, confidence intervals included both benefit and harm. There may be a reduced risk of reoperation favouring the standard dressing arm, but this was imprecise: RR 1.13 (95% CI 0.91 to 1.41; I² = 2%; 18 trials; 6272 participants). There may be a reduced risk of seroma for people treated with NPWT but this is imprecise: the RR was 0.82 (95% CI 0.65 to 1.05; I² = 0%; 15 trials; 5436 participants). For skin blisters, there is low-certainty evidence that people treated with NPWT may be more likely to develop skin blisters compared with those treated with standard dressing (RR 3.55; 95% CI 1.43 to 8.77; I² = 74%; 11 trials; 5015 participants). The effect of NPWT on haematoma is uncertain (RR 0.79; 95 % CI 0.48 to 1.30; I² = 0%; 17 trials; 5909 participants; very low-certainty evidence). There is low-certainty evidence of little to no difference in reported pain between groups. Pain was measured in different ways and most studies could not be pooled; this GRADE assessment is based on all fourteen trials reporting pain; the pooled RR for the proportion of participants who experienced pain was 1.52 (95% CI 0.20, 11.31; I² = 34%; two studies; 632 participants). Cost-effectiveness Six economic studies, based wholly or partially on trials in our review, assessed the cost-effectiveness of NPWT compared with standard care. They considered NPWT in five indications: caesarean sections in obese women; surgery for lower limb fracture; knee/hip arthroplasty; coronary artery bypass grafts; and vascular surgery with inguinal incisions. They calculated quality-adjusted life-years or an equivalent, and produced estimates of the treatments' relative cost-effectiveness. The reporting quality was good but the evidence certainty varied from moderate to very low. There is moderate-certainty evidence that NPWT in surgery for lower limb fracture was not cost-effective at any threshold of willingness-to-pay and that NPWT is probably cost-effective in obese women undergoing caesarean section. Other studies found low or very low-certainty evidence indicating that NPWT may be cost-effective for the indications assessed.

AUTHORS' CONCLUSIONS

People with primary closure of their surgical wound and treated prophylactically with NPWT following surgery probably experience fewer SSIs  than people treated with standard dressings but there is probably no difference in wound dehiscence (moderate-certainty evidence). There may be a reduced risk of death after surgery for people treated with NPWT compared with standard dressings but there is uncertainty around this as confidence intervals include risk of benefit and harm (low-certainty evidence). People treated with NPWT may experience more instances of skin blistering compared with standard dressing treatment (low-certainty evidence). There are no clear differences in other secondary outcomes where most evidence is low or very low-certainty. Assessments of cost-effectiveness of NPWT produced differing results in different indications. There is a large number of ongoing studies, the results of which may change the findings of this review. Decisions about use of NPWT should take into account surgical indication and setting and consider evidence for all outcomes.

Surgical Site Infection Affects Length of Stay After Complex Head and Neck Procedures

OBJECTIVES/HYPOTHESIS

Quality improvement (QI) initiatives emphasize a need for reduction in hospital length of stay (LOS). We sought to determine the impact of surgical site infections (SSIs) on LOS after complex head and neck surgery (HNS).

STUDY DESIGN

Retrospective cohort analysis.

METHODS

An analysis of the American College of Surgeons National Surgical Quality Improvement Program was undertaken. All adult patients undergoing complex HNS from 2005 to 2016 were included in the analysis. Our main outcomes were SSI incidence and increase in hospital LOS attributable to SSI.

RESULTS

Of 4,014 patients identified, 16.5% developed SSI. History of smoking, diabetes, preoperative wound infection, contaminated or dirty wound classes, and prolonged operative time were found to significantly predict postoperative SSI. Adjusting for significant pre- and postoperative factors, SSI was associated with significantly increased LOS (hazard ratio = 0.486, 95% confidence interval: 0.419-0.522).

CONCLUSIONS

SSI following complex HNS is associated with significantly increased hospital LOS. This result supports the need for institutional QI strategies that target SSIs after head and neck procedures in an effort to provide the highest quality care at the lowest possible cost. Our analysis identifies risk factors that can allow identification of patients at high risk of SSI and prolonged hospitalization.

LEVEL OF EVIDENCE

2b Laryngoscope, 2020.

The Impacts of Deep Surgical Site Infections on Readmissions, Length of Stay, and Costs: A Matched Case-Control Study Conducted in an Academic Hospital in the Netherlands

OBJECTIVE

This study aimed to evaluate the impacts of deep surgical site infections (dSSIs) regarding hospital readmissions, prolonged length of stay (LoS), and estimated costs.

PATIENTS AND METHODS

We designed and applied a matched case-control observational study using the electronic health records at the University Medical Center Groningen in the Netherlands. We compared patients with dSSI and non-SSI, matched on the basis of having similar procedures. A prevailing topology of surgeries categorized as clean, clean-contaminated, contaminated, and dirty was applied.

RESULTS

Out of a total of 12,285 patients, 393 dSSI were identified as cases, and 2864 patients without SSIs were selected as controls. A total of 343 dSSI patients (87%) and 2307 (81%) controls required hospital readmissions. The median LoS was 7 days (P₂₅-P₇₅: 2.5-14.5) for dSSI patients and 5 days (P₂₅-P₇₅: 1-9) for controls (p-value: <0.001). The estimated mean cost per hospital admission was €9,016 (SE±343) for dSSI patients and €5,409 (SE±120) for controls (p<0.001). Independent variables associated with dSSI were patient's age ≥65 years (OR: 1.334; 95% CI: 1.036-1.720), the use of prophylactic antibiotics (OR: 0.424; 95% CI: 0.344-0.537), and neoplasms (OR: 2.050; 95% CI: 1.473-2.854).

CONCLUSION

dSSI is associated with increased costs, prolonged LoS, and increased readmission rates. Elevated risks were seen for elderly patients and those with neoplasms. Additionally, a protective effect of prophylactic antibiotics was found.

Implications of Methicillin-Resistant Staphylococcus aureus Carriage on Cardiac Surgical Outcomes

BACKGROUND

Staphylococcus aureus remains the most common cause of sternal surgical site infections (SSIs). Opinions on the postoperative implications of preoperative methicillin-resistant S aureus (MRSA) colonization currently differ. This study aimed to investigate whether MRSA carriage affects postoperative outcomes and safety of operation.

METHODS

A total of 1,774,811 cardiac surgical patients from 2009 to 2014 were identified from the National Inpatient Sample database. Among these patients, 5798 (0.33%) were MRSA carriers. Propensity-score matching was used to determine the effect of MRSA colonization on outcomes.

RESULTS

MRSA carriers did not differ in age or sex from noncarriers, but they more often presented for urgent surgery (P < .001). Among matched pairs, there was no difference in mortality (P = .76), stroke, SSIs, pneumonia, renal failure, cardiac complications, respiratory failure, or prolonged mechanical ventilation. MRSA infection (P < .001), MRSA septicemia (P = 0.03), and blood transfusion (P = .003) occurred more often among MRSA carriers. There was no increase in cost (P = .12), but the hospital length of stay was longer (P = .005). Predictors of MRSA infection among carriers included age older than 85 years, rural hospital location, and diabetes. Carriers with endocarditis and drug abuse were at highest risk for MRSA infection.

CONCLUSIONS

MRSA carriers undergoing cardiac surgery are not at higher risk for mortality or SSIs and can expect outcomes similar to those of noncarriers. Higher rates of postoperative MRSA infection and septicemia among carriers, although still very low, support the need for selective preoperative screening and prophylaxis when possible.

History of Depression and Increased Risk of Sternal Wound Infection After Cardiothoracic Surgery: A Novel and Potentially Modifiable Risk Factor

Background

Sternal wound infection (SWI) is a leading cause of postoperative disease and death; the risk factors for SWI remain incompletely understood. The goal of the current study was to investigate the relationship between a preoperative history of depression and the risk of SWI after cardiothoracic surgery.

Methods

Among patients undergoing cardiothoracic surgery in a major academic medical center between 2007 and 2012, those in whom SWI developed (n = 129) were matched, by date of surgery, with those in whom it did not (n = 258). Multivariable logistic regression was used to examine the strength of relationships between risk factors and development of infection. History of depression was defined as a composite variable to increase the sensitivity of detection.

Results

History of depression as defined by our composite variable was associated with increased risk of SWI (adjusted odds ratio, 2.4; 95% confidence interval, 1.2–4.7; P = .01). Staphylococcus aureus was the most common organism isolated.

Conclusions

History of depression was associated with increased risk of SWI. Future prospective studies are warranted to further investigate this relationship. Depression is highly treatable, and increased efforts to identify and treat depression preoperatively may be a critical step toward preventing infection-related disease and death.

Cost-effectiveness analysis of single use negative pressure wound therapy dressings (sNPWT) compared to standard of care in reducing surgical site complications (SSC) in patients undergoing coronary artery bypass grafting surgery

Background

There is a growing interest in using negative pressure wound therapy in closed surgical incision to prevent wound complications which continue to persist following surgery despite advances in infection measures.

Objectives

To estimate the cost-effectiveness of single use negative pressure wound therapy (sNPWT) compared to standard of care in patients following coronary artery bypass grafting surgery (CABG) procedure to reduce surgical site complications (SSC) defined as dehiscence and sternotomy infections.

Method

A decision analytic model was developed from the Germany Statutory Health Insurance payer’s perspective over a 12-week time horizon. Baseline data on SSC, revision operations, length of stay, and readmissions were obtained from a prospective observational study of 2621 CABG patients in Germany. Effectiveness data for sNPWT was taken from a randomised open label trial conducted in Poland which randomised 80 patients to treatment with either sNPWT or standard care. Cost data (in Euros) were taken from the relevant diagnostic related groups and published literature.

Results

The clinical study reported an increase in wounds that healed without complications 37/40 (92.5%) in the sNPWT compared to 30/40 (75%) patients in the SC group p = 0.03. The model estimated sNPWT resulted in 0.989 complications avoided compared to 0.952 and the estimated quality adjusted life years were 0.8904 and 0.8593 per patient compared to standard care. The estimated mean cost per patient was €19,986 for sNPWT compared to €20,572 for SC resulting in cost-saving of €586. The findings were robust to a range of sensitivity analyses.

Conclusion

The sNPWT can be considered a cost saving intervention that reduces surgical site complications following CABG surgery compared to standard care. We however recommend that additional economic studies should be conducted as new evidence on the use of sNPWT in CABG patients becomes available to validate the results of this economic analysis.

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.

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).

Surgical site infection with extended-spectrum β-lactamase-producing Enterobacteriaceae after cardiac surgery: incidence and risk factors

OBJECTIVE

To determine the incidence, microbiology and risk factors for sternal wound infection (SWI) with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE) following cardiac surgery.

METHODS

We performed a retrospective analysis between January 2006 and December 2015 of prospective surveillance of a cohort of patients with cardiac surgery at a single centre (Paris, France). SWI was defined as the need for reoperation due to sternal infection. All patients with an initial surgery under extracorporeal circulation and diagnosed with an SWI caused by Enterobacteriaceae isolates were included. We compared patients infected with at least one ESBL-PE with those with SWI due to other Enterobacteriaceae by logistic regression analysis.

RESULTS

Of the 11 167 patients who underwent cardiac surgery, 412 (3.7%) developed SWI, among which Enterobacteriaceae were isolated in 150 patients (36.5%), including 29 ESBL-PE. The main Enterobacteriaceae (n = 171) were Escherichia coli in 49 patients (29%) and Enterobacter cloacae in 26 (15%). Risk factors for SWI with ESBL-PE in the multivariate logistic regression were previous intensive care unit admission during the preceding 6 months (adjusted odds ratio (aOR) 12.2; 95% CI 3.3-44.8), postoperative intensive care unit stay before surgery for SWI longer than 5 days (aOR 4.6; 95% CI 1.7-11.9) and being born outside France (aOR 3.2; 95% CI 1.2-8.3).

CONCLUSIONS

Our results suggest that SWI due to ESBL-PE was associated with preoperative and postoperative unstable state, requiring an intensive care unit stay longer than the usual 24 or 48 postoperative hours, whereas being born outside France may indicate ESBL-PE carriage before hospital admission.

Ability to predict the development of surgical site infection in cardiac surgery using the Australian Clinical Risk Index versus the National Nosocomial Infections Surveillance-derived Risk Index

Surgical site infection (SSI) is a major infectious complication that increases mortality, morbidity, and healthcare costs. There are scores attempting to classify patients for calculating SSI risk. Our objectives were to validate the Australian Clinical Risk Index (ACRI) in a European population after cardiac surgery, comparing it against the National Nosocomial Infections Surveillance-derived risk index (NNIS) and analyzing the predictive power of ACRI for SSI in valvular patients. All the patients that who underwent cardiac surgery in a tertiary university hospital between 2011 and 2015 were analyzed. The patients were divided into valvular and coronary groups, excluding mixed patients. The ACRI score was validated in both groups and its ability to predict SSI was compared to the NNIS risk index. We analyzed 1,657 procedures. In the valvular patient group (n: 1119), a correlation between the ACRI score and SSI development (p < 0.05) was found; there was no such correlation with the NNIS index. The area under the receiver-operating characteristic curve (AUC) was 0.64 (confidence interval [CI] 95%, 0.5-0.7) for ACRI and 0.62 (95% CI, 0.5-0.7) for NNIS. In the coronary group (n: 281), there was a correlation between ACRI and SSI but no between NNIS and SSI. The ACRI AUC was 0.70 (95% CI, 0.5-0.8) and the NNIS AUC was 0.60 (95% CI, 0.4-0.7). The ACRI score has insufficient predictive power, although it predicts SSI development better than the NNIS index, fundamentally in coronary artery bypass grafting (CABG). Further studies analyzing determining factors are needed.

Epidemiological Surveillance of Surgical Site Infection and its Risk Factors in Cardiac Surgery: A Prospective Cohort Study

INTRODUCTION AND OBJECTIVES

Surgical site infection in cardiac surgery is uncommon. The aim of the present study was to examine the incidence of this infection, compare it with national and international data, and evaluate its risk factors.

METHODS

This prospective cohort study included patients who underwent valve surgery or coronary revascularization during a 6-year period. The incidence of surgical site infection was studied. Associations between risk factors and infection were evaluated using odds ratios (OR). The infection rate was compared with Spanish and American data using the standardized infection ratio.

RESULTS

A total of 1557 patients were included. The overall cumulative incidence of infection was 4% (95% confidence interval [95%CI], 3.6%-5.6%), 3.6% in valve surgery (95%CI, 2.5%-4.7%) and 4.3% in coronary revascularization (95%CI, 2.3%-6.3%). Risk factors for surgical site infection in valve surgery were diabetes mellitus (OR=2.8; P<.05) and obesity (OR=6.6; P<.05). Risk factors for surgical site infection in coronary revascularization were diabetes mellitus (OR=2.9; P<.05) and reoperation for bleeding (OR=8.8; P<.05).

CONCLUSIONS

Diabetes mellitus and obesity favor surgical site infection in valve surgery, whereas diabetes mellitus and reoperation for bleeding favor surgical site infection in coronary revascularization. Infection surveillance and control programs permit evaluation and comparison of infection rates in cardiac surgery.

From Cues to Nudge: A Knowledge-Based Framework for Surveillance of Healthcare-Associated Infections

We propose an integrated semantic web framework consisting of formal ontologies, web services, a reasoner and a rule engine that together recommend appropriate level of patient-care based on the defined semantic rules and guidelines. The classification of healthcare-associated infections within the HAIKU (Hospital Acquired Infections - Knowledge in Use) framework enables hospitals to consistently follow the standards along with their routine clinical practice and diagnosis coding to improve quality of care and patient safety. The HAI ontology (HAIO) groups over thousands of codes into a consistent hierarchy of concepts, along with relationships and axioms to capture knowledge on hospital-associated infections and complications with focus on the big four types, surgical site infections (SSIs), catheter-associated urinary tract infection (CAUTI); hospital-acquired pneumonia, and blood stream infection. By employing statistical inferencing in our study we use a set of heuristics to define the rule axioms to improve the SSI case detection. We also demonstrate how the occurrence of an SSI is identified using semantic e-triggers. The e-triggers will be used to improve our risk assessment of post-operative surgical site infections (SSIs) for patients undergoing certain type of surgeries (e.g., coronary artery bypass graft surgery (CABG)).

Sources of Variation in Hospital-Level Infection Rates After Coronary Artery Bypass Grafting: An Analysis of The Society of Thoracic Surgeons Adult Heart Surgery Database

BACKGROUND

Patients undergoing coronary artery bypass grafting (CABG) are at risk for a variety of infections. Investigators have focused on predictors of these adverse sequelae, but less attention has been focused on characterizing hospital-level variability in these outcomes.

METHODS

Between July 2011 and December 2013, The Society of Thoracic Surgeons Adult Cardiac Surgery Database shows 365,686 patients underwent isolated CABG in 1,084 hospitals. Hospital-acquired infections (HAIs) were defined as pneumonia, sepsis/septicemia, deep sternal wound infection/mediastinitis, vein harvest/cannulation site infection, or thoracotomy infection. Hospitals were ranked by their HAI rate as low (≤ 10th percentile), medium (10th to 90th percentile), and high (>90th percentile). Differences in perioperative factors and composite morbidity and mortality end points across these groups were determined using the Wilcoxon rank sum and χ(2) tests.

RESULTS

HAIs occurred among 3.97% of patients overall, but rates varied across hospital groups (low: <0.84%, medium: 0.84% to 8.41%, high: >8.41%). Pneumonia (2.98%) was the most common HAI, followed by sepsis/septicemia (0.84%). Patients at high-rate hospitals more often smoked, had diabetes, chronic lung disease, New York Heart Association Functional Classification III to IV, and received blood products (p < 0.001); however, they less often were prescribed the appropriate antibiotics (p < 0.001). Major morbidity and mortality occurred among 12.3% of patients, although this varied by hospital group (low: 8.6%, medium: 12.3%, high: 17.9%; p < 0.001).

CONCLUSIONS

Substantial hospital-level variation exists in postoperative HAIs among patients undergoing CABG, driven predominantly by pneumonia. Given the relatively small absolute differences in comorbidities across hospital groups, our findings suggest factors other than case mix may explain the observed variation in HAI rates.

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.

Center-level variation in infection rates after coronary artery bypass grafting

BACKGROUND

Health-care-acquired infections (HAIs) are a leading cause of morbidity and mortality after cardiac surgery. Prior work has identified several patient-related risk factors associated with HAIs. We hypothesized that rates of HAIs would differ across institutions, in part attributed to differences in case mix.

METHODS AND RESULTS

We analyzed 20 896 patients undergoing isolated coronary artery bypass grafting surgery at 33 medical centers in Michigan between January 1, 2009, and June 30, 2012. Overall HAIs included pneumonia, sepsis/septicemia, and surgical site infections, including deep sternal wound, thoracotomy, and harvest/cannulation site infections. We excluded patients presenting with endocarditis. Predicted rates of HAIs were estimated using multivariable logistic regression. Overall rate of HAI was 5.1% (1071 of 20 896; isolated pneumonia, 3.1% [n=644]; isolated sepsis/septicemia, 0.5% [n=99]; isolated deep sternal wound infection, 0.5% [n=96]; isolated harvest/cannulation site, 0.5% [n=97]; isolated thoracotomy, 0.02% [n=5]; multiple infections, 0.6% [n=130]). HAI subtypes differed across strata of center-level HAI rates. Although predicted risk of HAI differed in absolute terms by 2.8% across centers (3.9-6.7%; min:max), observed rates varied by 18.2% (0.9-19.1%).

CONCLUSIONS

There was a 18.2% difference in observed HAI rates across medical centers among patients undergoing isolated coronary artery bypass grafting surgery. This variability could not be explained by patient case mix. Future work should focus on the impact of other factors (eg, organizational and systems of clinical care) on risk of HAIs.

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.

Epidemiology and outcomes of deep surgical site infections following lung transplantation

We conducted a retrospective study of deep surgical site infections (SSIs) among consecutive patients who underwent lung transplantation (LTx) at a single center from 2006 through 2010. Thirty-one patients (5%) developed SSIs at median 25 days after LTx. Empyema was most common (42%), followed by surgical wound infections (29%), mediastinitis (16%), sternal osteomyelitis (6%), and pericarditis (6%). Pathogens included Gram-positive bacteria (41%), Gram-negative bacteria (41%), fungi (10%) and Mycobacterium abscessus, Mycoplasma hominis and Lactobacillus sp. (one each). Twenty-three percent of SSIs were due to pathogens colonizing recipients' native lungs at time of LTx, suggesting surgical seeding as a source. Patient-related independent risk factors for SSIs were diabetes and prior cardiothoracic surgery; procedure-related independent risk factors were LTx from a female donor, prolonged ischemic time and number of perioperative red blood cell transfusions. Mediastinitis and sternal infections were not observed among patients undergoing minimally invasive LTx. SSIs were associated with 35% mortality at 1 year post-LTx. Lengths of stay and mortality in-hospital and at 6 months and 1 year were significantly greater for patients with SSIs other than empyema. In conclusion, deep SSIs were uncommon, but important complications in LTx recipients because of their diverse microbiology and association with increased mortality.