Philip L. Russo

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

BACKGROUND The Victorian Infection Control Surveillance Project (VICSP) is a multicenter collaborative surveillance project established by infection control practitioners. Five public hospitals contributed data for patients undergoing coronary artery bypass graft (CABG) surgery. OBJECTIVE To determine the aggregate and comparative interhospital surgical-site infection (SSI) rates for patients undergoing CABG surgery and the risk factors for SSI in this patient group. METHOD Each institution used standardized definitions of SSI, risk adjustment, and reporting methodology according to the National Nosocomial Infections Surveillance System of the Centers for Disease Control and Prevention. Data on potential risk factors were prospectively collected. RESULTS For 4,474 patients undergoing CABG surgery, the aggregate SSI rate was 7.8 infections per 100 procedures (95% confidence interval [CI95], 7.0-8.5), with individual institutions ranging between 4.5 and 10.7 infections per 100 procedures. Multivariate risk factor analysis demonstrated age (odds ratio [OR], 1.02; CI95, 1.01-1.04; P < .001), obesity (OR, 1.8; CI95, 1.4-2.3; P < .001), and diabetes mellitus (OR, 1.6; CI95, 1.2-2.1; P < .001) as independent predictors of SSI. Three hundred thirty-four organisms were isolated from 296 SSIs. Of the total SSIs, methicillin-resistant Staphylococcus aureus was isolated from 32%, methicillin-sensitive S. aureus from 24%, gram-negative bacilli (eg, Enterobacter and Escherichia coli) from 18%, and miscellaneous organisms from the remainder. CONCLUSION We documented aggregate and comparative SSI rates among five Victorian public hospitals performing CABG surgery and defined specific independent risk factors for SSI. VICSP data offer opportunities for targeted interventions to reduce SSI following cardiac surgery.

Outcomes from the first 2 years of the Australian National Hand Hygiene Initiative.

Objective: To report outcomes from the first 2 years of the National Hand Hygiene Initiative (NHHI), a hand hygiene (HH) culture‐change program implemented in all Australian hospitals to improve health care workers’ HH compliance, increase use of alcohol‐based hand rub and reduce the risk of health care‐associated infections.

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

OBJECTIVES To develop a new, simple, and practical risk index for patients undergoing coronary artery bypass graft (CABG) surgery, to develop a preoperative risk index that is predictive of surgical-site infection (SSI), and to compare the new risk indices with the National Nosocomial Infections Surveillance (NNIS) System risk index. DESIGN Potential risk factor and infection data were collected prospectively and analyzed by multivariate analysis. Two new risk indices were constructed and then compared with the NNIS System risk index for predictive power for SSI. SETTING Alfred Hospital is a 350-bed, university-affiliated, tertiary-care referral center. The cardiothoracic unit performs approximately 650 CABG procedures per year. PATIENTS All patients undergoing CABG surgery within the cardiothoracic unit at Alfred Hospital between December 1, 1996, and September 29, 2000, were included. RESULTS Potential risk factor data were complete for 2,345 patients. There were 199 SSIs. Obesity (odds ratio [OR], 1.78; 95% confidence interval [CI95], 1.24 to 2.55), peripheral or cerebrovascular disease (OR, 1.64; CI95, 1.16 to 2.33), insulin-dependent diabetes mellitus (OR, 2.29; CI95, 1.15 to 4.54), and a procedure lasting longer than 5 hours (OR, 1.75; CI95, 1.18 to 2.58) were identified as independent risk factors for SSI. With the use of a different combination of these risk factors, two risk indices were constructed and compared using the Goodman-Kruskal nonparametric correlation coefficient (G). kisk index B had the highest G value (0.3405; CI95, 0.2245 to 0.4565), compared with the NNIS System risk index G value (0.3142; CI95, 0.1462 to 0.4822). The G value for risk index A, constructed from preoperative variables only, was 0.3299 (CI9,, 0.2039 to 0.4559). CONCLUSION Two new risk indices have been developed. Both indices are as predictive as the NNIS System risk index. One of the new risk indices can also be applied preoperatively.

Cost of surgical site infections following coronary artery bypass surgery

Background:  Little information is available on the financial impact of surgical site infections (SSI) after major surgery. In order to calculate the cost of SSI following coronary artery bypass graft surgery (CABGs), a 2‐year retrospective case‐control study was undertaken at Alfred Hospital, a university‐affiliated tertiary referral centre.

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

OBJECTIVE To analyze the risk factors for surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery and to create an alternative SSI risk score based on the results of multivariate analysis. METHODS A prospective cohort study involving inpatient and laboratory-based surveillance of patients who underwent CABG surgery over a 27-month period from January 1, 2003 through March 31, 2005. Data were obtained from 6 acute care hospitals in Victoria, Australia, that contributed surveillance data for SSI complicating CABG surgery to the Victorian Hospital Acquired Infection Surveillance System Coordinating Centre and the Australasian Society of Cardiac and Thoracic Surgeons, also in Victoria. RESULTS A total of 4,633 (93%) of the 4,987 patients who underwent CABG surgery during this period were matched in the 2 systems databases. There were 286 SSIs and 62 deep or organ space sternal SSIs (deep or organ space sternal SSI rate, 1.33%). Univariate analysis revealed that diabetes mellitus, body mass index (BMI) greater than 35, and receipt of blood transfusion were risk factors for all types of SSI complicating CABG surgery. Six multivariate analysis models were created to examine either preoperative factors alone or preoperative factors combined with operative factors. All models revealed diabetes and BMI of 30 or greater as risk factors for SSI complicating CABG surgery. A new preoperative scoring system was devised to predict sternal SSI, which assigned 1 point for diabetes, 1 point for BMI of 30 or greater but less than 35, and 2 points for BMI of 35 or greater. Each point in the scoring system represented approximately a doubling of risk of SSI. The new scoring system performed better than the National Nosocomial Infections Surveillance System (NNIS) risk index at predicting SSI. CONCLUSION A new weighted scoring system based on preoperative risk factors was created to predict sternal SSI risk following CABG surgery. The new scoring system outperformed the NNIS risk index. Future studies are needed to validate this scoring system.

Validation of Statewide Surveillance System Data on Central Line–Associated Bloodstream Infection in Intensive Care Units in Australia

OBJECTIVE To measure the interobserver agreement, sensitivity, specificity, positive predictive value, and negative predictive value of data submitted to a statewide surveillance system for identifying central line-associated bloodstream infection (BSI). DESIGN Retrospective review of hospital medical records comparing reported data with gold standard according to definitions of central line-associated BSI. SETTING Six Victorian public hospitals with more than 100 beds. METHODS Reporting of surveillance outcomes was undertaken by infection control practitioners at the hospital sites. Retrospective evaluation of the surveillance process was carried out by independent infection control practitioners from the Victorian Hospital Acquired Infection Surveillance System (VICNISS). A sample of records of patients reported to have a central line-associated BSI were assessed to determine whether they met the definition of central line-associated BSI. A sample of records of patients with bacteremia in the intensive care unit during the assessment period who were not reported as having central line-associated BSI were also assessed to see whether they met the definition of central line-associated BSI. RESULTS Records of 108 patients were reviewed; the agreement between surveillance reports and the VICNISS assessment was 67.6% (k = 0.31). Of the 46 reported central line-associated BSIs, 27 were confirmed to be central line-associated BSIs, for a positive predictive value of 59% (95% confidence interval [CI], 43%-73%). Of the 62 cases of bacteremia reviewed that were not reported as central line-associated BSIs, 45 were not associated with a central line, for a negative predictive value of 73% (95% CI, 60%-83%). Estimated sensitivity was 35%, and specificity was 87%. The positive likelihood ratio was 3.0, and the negative likelihood ratio was 0.72. DISCUSSION The agreement between the reporting of central line-associated BSI and the gold standard application of definitions was unacceptably low. False-negative results were problematic; more than half of central line-associated BSIs may be missed in Victorian public hospitals.

Impact of revising the National Nosocomial Infection Surveillance System definition for catheter-related bloodstream infection in ICU: reproducibility of the National Healthcare Safety Network case definition in an Australian cohort of infection control professionals

BACKGROUND Effective and comparable surveillance for central venous catheter-related bloodstream infections (CLABSIs) in the intensive care unit requires a reproducible case definition that can be readily applied by infection control professionals. METHODS Using a questionnaire containing clinical cases, reproducibility of the National Nosocomial Infection Surveillance System (NNIS) surveillance definition for CLABSI was assessed in an Australian cohort of infection control professionals participating in the Victorian Hospital Acquired Infection Surveillance System (VICNISS). The same questionnaire was then used to evaluate the reproducibility of the National Healthcare Safety Network (NHSN) surveillance definition for CLABSI. Target hospitals were defined as large metropolitan (1A) or other large hospitals (non-1A), according to the Victorian Department of Human Services. Questionnaire responses of Centers for Disease Control and Prevention NHSN surveillance experts were used as gold standard comparator. RESULTS Eighteen of 21 eligible VICNISS centers participated in the survey. Overall concordance with the gold standard was 57.1%, and agreement was highest for 1A hospitals (60.6%). The proportion of congruently classified cases varied according to NNIS criteria: criterion 1 (recognized pathogen), 52.8%; criterion 2a (skin contaminant in 2 or more blood cultures), 83.3%; criterion 2b (skin contaminant in 1 blood culture and appropriate antimicrobial therapy instituted), 58.3%; non-CLABSI cases, 51.4%. When survey questions regarding identification of cases of CLABSI criterion 2b were removed (consistent with the current NHSN definition), overall percentage concordance increased to 62.5% (72.2% for 1A centers). CONCLUSION Further educational interventions are required to improve the discrimination of primary and secondary causes of bloodstream infection in Victorian intensive care units. Although reproducibility of the CLABSI case definition is relatively poor, adoption of the revised NHSN definition for CLABSI is likely to improve the concordance of Victorian data with international centers.

Performance of the National Nosocomial Infections Surveillance Risk Index in Predicting Surgical Site Infection in Australia

BACKGROUND The Victorian Hospital Acquired Infection Surveillance System (VICNISS) hospital-acquired infection surveillance system was established in 2002 in Victoria, Australia, and collates surgical site infection (SSI) surveillance data from public hospitals in Australia. OBJECTIVE To evaluate the association between the US National Nosocomial Infections Surveillance (NNIS) systems risk index and SSI rates for 7 surgical procedures. METHODS SSI surveillance was performed with NNIS definitions and methods for surgical procedures performed between November 2002 and September 2004. Correlations were assessed using the Goodman-Kruskal gamma statistic. RESULTS Data were submitted for the following numbers of procedures: appendectomy, 545; coronary artery bypass graft (CABG), 4,632; cholecystectomy, 1,001; colon surgery, 623; cesarean section, 4,857; hip arthroplasty, 3,825; and knee arthroplasty, 2,416. NNIS risk index and increasing SSI rate were moderately well correlated for appendectomy ( gamma =0.55), colon surgery ( gamma =0.48), and cesarean section ( gamma =0.42). A fairly positive correlation was found for cholecystectomy ( gamma =0.17), hip arthroplasty ( gamma =0.2), and knee arthroplasty ( gamma =0.16). However, for CABG surgery, a poor association was found ( gamma =0.02). CONCLUSIONS The NNIS risk index was positively correlated with an increasing SSI rate for all 7 procedures; the strongest correlation was found for appendectomy, cesarean section, and colon surgery, and the poorest correlation was found for CABG surgery. We believe that risk stratification with the NNIS risk index is appropriate for comparison of data for most procedures and superior to use of no risk adjustment. However, for some procedures, particularly CABG, further studies of alternative risk indexes are needed to better stratify patients.

Hospital Outbreak of Norwalk-Like Virus

An outbreak of gastroenteritis caused by Norwalk-like virus occurred in two areas of the hospital: area 1, consisting of three adjacent and interconnected wards, with mostly elderly patients; and area 22, an acute ward in a separate building with elderly patients. In area 1, 40 patients and 20 staff were affected; in area 2, 18 patients and 14 staff were affected. Infection control measures were instituted in consultation with the government health authority. These measures did not appear to affect the course of the outbreak, but may have prevented spreads to the other wards.

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 Nosocomial Infection Surveillance System-based surveillance for SSI following CABG surgery.