Case-Control Study of Risk Factors for Mediastinitis After Cardiovascular Surgery

Risk factors for sternal wound infection after open-heart operations: A systematic review and meta-analysis

We aimed to quantitatively and systematically elucidate the rationality of the examined variables as independent risk factors for sternal wound infection. We searched databases to screen studies, ascertained the variables to be analysed, extracted the data and applied meta-analysis to each qualified variable. Odds ratios and mean differences were considered to be the effect sizes for binary and continuous variables, respectively. A random-effects model was used for these procedures. The source of heterogeneity was evaluated using a meta-regression. Publication bias was tested by funnel plot and Egger's test, the significant results of which were then calculated using trim and fill analysis. We used a sensitivity analysis and bubble chart to describe their robustness. After screening all variables in the eligible literature, we excluded 55 because only one or no research found them significant after multivariate analysis, leaving 33 variables for synthesis. Two binary variables (age over 65 years, NYHA class >2) and a continuous variable (preoperative stay) were not significant after the meta-analysis. The most robust independent risk factors in our study were diabetes mellitus, obesity, use of bilateral internal thoracic arteries, chronic obstructive pulmonary disease, prolonged surgery time, prolonged ventilation and critical preoperative state, followed by congestive heart failure, atrial fibrillation, renal insufficiency, stroke, peripheral vascular disease and use of an intra-aortic balloon pump. Relatively low-risk factors were emergent/urgent surgery, smoking, myocardial infarction, combined surgery and coronary artery bypass grafting. Sternal wound infection after open-heart surgery is a multifactorial disease. The detected risk factors significantly affected the wound healing process, but some were different in strength. Anything that affects wound healing and antibacterial ability, such as lack of oxygen, local haemodynamic disorders, malnutrition condition and compromised immune system will increase the risk, and this reminds us of comprehensive treatment during the perioperative period.

Incidence and predictors of sternal surgical wound infection in cardiac surgery: A prospective study

Sternal surgical wound infection (SSWI) in cardiac surgery is associated with increased morbidity. We investigated the incidence of SSWI, the main germs implicated and predictors of SSWI. Prospective study including patients undergoing full median sternotomy between January 2017 and December 2019. Patients were followed-up for 3 months after hospital discharge. All sternal wound infections up to 90 days after discharge were considered SSWI. 1004 patients were included. During follow-up, 68 (6.8%) patients presented SSWI. Patients with SSWI had a higher incidence of postoperative renal failure (29.4% vs 17.1%, P = .007), a higher incidence of early postoperative reoperation for non-infectious causes (42.6% vs 9.1%, P < .001), longer ICU stay (3 [2-9] days vs 2 [2-4] days, P = .006), and longer hospital stay (24.5 [14.8-38.3] days vs 10 [7-18] days, P < .001). Gram-positive germs were presented in 49% of the cultures, and gram-negative bacteria in 35%. Early reoperation for non-infectious causes (OR 4.90, 95% CI 1.03-23.7), and a longer ICU stay (OR 1.37 95% CI 1.10-1.72) were independent predictors of SSWI. SSWI is rare but leads to more postoperative complications. The need for early reoperation because of non-infectious cause and a longer ICU stay were independently associated with SSWI.

The association between preoperative length of hospital stay and deep sternal wound infection: A scoping review

BACKGROUND

Deep sternal wound infection (DSWI) is a serious complication of cardiac surgery, associated with a significantly longer hospital stay, an increased mortality, and an almost doubling of treatment costs. The preoperative length of hospital stay has been suggested in a small number of studies as a modifiable risk factor yet is not included in surgical site infection prevention guidelines. The aim of this scoping review was to review the existing evidence on the association between preoperative length of hospital stay and DSWI, and to identify established risk factors for DSWI.

METHODS

A literature search of six electronic databases yielded 2297 results. Titles concerning risk factors for DSWI, sternal or surgical wound infection, or poststernotomy complications were included. Abstracts relating to preoperative length of stay as a risk factor for DSWI proceeded to full article review. Articles regarding paediatric surgery, DSWI management or unavailable in English were excluded.

RESULTS

The review identified 11 observational cohort studies. DSWI prevalence was between 0.9% and 6.8%. Preoperative length of stay ranged from 0-15.5 days and was found to be associated with DSWI in all studies. Preoperative length of stay and DSWI were inconsistently defined. Other risk factors for DSWI included diabetes, obesity, respiratory disease, heart failure, renal impairment, complex surgery, and reoperation (p < 0.05).

CONCLUSION

In this scoping review, an association between preoperative length of stay and the development of DSWI following cardiac surgery was identified. Thus, preoperative length of stay as a modifiable risk factor for DSWI should be considered for inclusion in cardiothoracic surgical infection prevention guidelines.

Eradication of Staphylococcus aureus post-sternotomy mediastinitis following the implementation of universal pre-operative nasal decontamination with mupirocin: an interrupted time-series analysis

BACKGROUND

Although pre-surgical nasal decontamination with mupirocin (NDM) has been advocated as a measure for preventing post-surgical mediastinitis (PSM) due to Staphylococcus aureus, this strategy is not universally recommended due to the lack of robust supporting evidence. We aimed to evaluate the role of pre-operative NDM in the annual incidence of S. aureus PSM at our institution.

METHODS

An interrupted time-series analysis, with autoregressive error model, was applied to our single-center cohort by comparing pre-intervention (1990-2003) and post-intervention period (2005 to 2018). Logistic regression was performed to analyze risk factors for S. aureus PSM.

FINDINGS

12,236 sternotomy procedures were analyzed (6,370 [52.1%] and 5,866 [47.9%] in the pre-intervention and post-intervention periods, respectively). The mean annual percentage adherence to NDM estimated over the post-interventional period was 90.2%. Only four out of 127 total cases of S. aureus PSM occurred during the 14-years post-intervention period (0.68/1,000 sternotomies vs. 19.31/1,000 in pre-interventional period [p<0.0001]). Interrupted time-series analysis demonstrated a statistically significant annual reduction of S. aureus PSM trend of -9.85 cases per 1,000 sternotomies (-13.17 to -6.5, P-value< 0·0001) in 2005, with a decreasing trend maintained over the following five years with an estimated relative reduction of 84.8% (95% CI: 89·25 to 74·09). Chronic obstructive pulmonary disease was the single independent risk factor for S. aureus PSM (odds ratio: 3.7; 95% CI: 1.72-7.93) and was equally distributed in patients undergoing sternotomy during pre or post-intervention periods.

INTERPRETATION

Our experience suggests that the implementation of pre-operative NDM reduces significantly the incidence of S. aureus PSM.

Enterobacteriaceae surgical site infection after cardiac surgery: the hypothetical role of vancomycin

BACKGROUND

In the middle of October 2011, the Hygiene Department of Caen University Hospital suspected an outbreak of surgical site infections (SSI) after open-heart operations with an unusually high proportion of microorganisms belonging to the Enterobacteriaceae family. The attack rate was 3.8%, significantly different (p = 0.035) from the attack rate of 1.2% in 2010 over the equivalent period. A case-control study was conducted to search specifically for risk factors for Enterobacteriaceae infections after median sternotomy in cardiac patients.

METHODS

Case patients were defined retrospectively as patients with superficial or deep surgical site infection with Enterobacteriaceae within 30 days of median sternotomy. Four control patients were selected per case patient from patients matched for date of operation (± 15 days) and European System for Cardiac Operative Risk Evaluation (<5, [5-10], >10).

RESULTS

Univariate analysis identified the following risk factors: inappropriate skin preparation on the morning of the intervention (p = 0.046), use of vancomycin (p = 0.030), and number of sternotomy dressings (p = 0.033). A multivariate logistic regression analysis found that vancomycin use was independently associated with an increased risk of postoperative SSI with Enterobacteriaceae (p = 0.019; odds ratio = 7.4).

CONCLUSIONS

Although vancomycin is known to be effective for preventing infection with methicillin-sensitive organisms, our results suggest that it was associated with a risk for the development of SSI with gram-negative organisms after median sternotomy. This study led to a multidisciplinary meeting that defined new guidelines for prophylactic antibiotic therapy before open-heart operations.

Risk factors for surgical site infection in cardiac surgery

OBJECTIVE: To analyze the occurrence of surgical site infection (SSI) in patients undergoing cardiac surgery in the period between July 2005, and July 2010. METHODS: A quantitative, historical cohort study that evaluated 384 patients in a public teaching hospital. The Statistical Package for the Social Sciences software was used for data analysis and for descriptive analysis, measures of association in contigency tables and logistic regression were used. RESULTS: It was found that 36 (9.4%) patients developed a SSI and that mortality occurred in 14 (38.9%). Staphylococcus aureus was the prevalent microorganism (12, 27.3%) In the multivariate analysis, the risk factors identified as predictors of SSI were male gender, intubation for more than 24 hours, and reintubation. CONCLUSION: The risk factors predictive of the occurence of SSI (p<0.05) were: male gender, reintubation, and intubation for more than 24 hours.

Treatment of gram-positive deep sternal wound infections in cardiac surgery--experiences with daptomycin

The reported incidence of deep sternal wound infection (DSWI) after cardiac surgery is 0.4-5% with Staphylococcus aureus being the most common pathogen isolated from infected wound sternotomies and bacteraemic blood cultures. This infection is associated with a higher morbidity and mortality than other known aetiologies. Little is reported about the optimal antibiotic management. The aim of the study is to quantify the application of daptomycin treatment of DSWI due to gram-positive organisms post cardiac surgery. We performed an observational analysis in 23 cases of post sternotomy DSWI with gram-positive organisms February 2009 and September 2010. When the wound appeared viable and the microbiological cultures were negative, the technique of chest closure was individualised to the patient. The incidence of DSWI was 1.46%. The mean dose of daptomycin application was 4.4 ± 0.9 mg/kg/d and the average duration of the daptomycin application was 14.47 ± 7.33 days. In 89% of the patients VAC therapy was used. The duration from daptomycin application to sternal closure was 18 ± 13.9 days. The parameters of infection including, fibrinogen (p = 0.03), white blood cell count (p = 0.001) and C-reactive protein (p = 0.0001) were significantly reduced after daptomycin application. We had no mortality and wound healing was successfully achieved in all patients. Treatment of DSWI due to gram-positive organisms with a daptomycin-containing antibiotic regimen is safe, effective and promotes immediate improvement of local wound conditions.Based on these observations, daptomycin may offer a new treatment option for expediting surgical management of DSWI after cardiac surgery.

Surgical site infections--economic consequences for the health care system

PURPOSES

Unfortunately, surgical site infections (SSIs) are a quite common complication and represent one of the major causes of postoperative morbidity and mortality, and may furthermore lead to enormous additional costs for hospitals and health care systems.

METHODS

In order to determine the estimated costs due to SSIs, a MEDLINE search was performed to identify articles that provide data on economic aspects of SSIs and compared to findings from a matched case-control study on costs of SSIs after coronary bypass grafting (CABG) in a German tertiary care university hospital.

RESULTS

A total of 14 studies on costs were found. The additional costs of SSI vary between $3,859 (mean) and $40,559 (median). Median costs of a single CABG case in the recently published study were $49,449 (€36,261) vs. $18,218 (€13,356) in controls lacking infection (p < 0.0001). The median reimbursement from health care insurance companies was $36,962 (€27,107) leading to a financial loss of $12,482 (€9,154) each.

CONCLUSION

Costs of SSIs may almost triple the individual overall health care costs and those additional charges may not be sufficiently covered. Appropriate measures to reduce SSI rates must be taken to improve the patient's safety. This should also diminish costs for health care systems which benefits the entire community.