Appropriate use of indwelling urethra catheters in hospitalized patients: results of a multicentre prevalence study.

BACKGROUND: Although indwelling urethra catheterization is a medical intervention with well-defined risks, studies show that approximately 14-38% of the indwelling urethra catheters (IUCs) are placed without a specific medical indication. In this paper we describe the prevalence of IUCs, including their inappropriate use in the Netherlands. We also determine factors associated with inappropriate use of IUCs in hospitalized patients. METHODS: In 28 Dutch hospitals, prevalence surveys were performed biannually in 2009 and 2010 within the PREZIES-network. All patients admitted to a participating hospital and who had an IUC in place at the day of the survey were included. Pre-determined criteria were used to categorize the indication for catheterization as appropriate or inappropriate. RESULTS: A total of 14,252 patients was included and 3020 (21.2%) of them had an IUC (range hospitals 13.4-27.3). Initial catheter placement was inappropriate in 5.2% of patients and 7.5% patients had an inappropriate indication at the day of the survey. In multivariate analyses inappropriate catheter use at the time of placement was associated with female sex, older age, admission on a non-intensive care ward, and not having had surgery. Inappropriate catheter use at the time of survey showed comparable associated factors. CONCLUSIONS: Although lower than in many other countries, inappropriate use of IUC is present in Dutch hospitals. To reduce the inappropriate use of IUCs, recommended components of care (bundle for UTI), including daily revision and registration of the indication for catheterization, should be introduced for all patients with an IUC. Additionally, an education and awareness campaign about appropriate indications for IUC should be available.

An evidence-based recommendation on bed head elevation for mechanically ventilated patients.

INTRODUCTION: A semi-upright position in ventilated patients is recommended to prevent ventilator-associated pneumonia (VAP) and is one of the components in the Ventilator Bundle of the Institute for Health Care Improvement. This recommendation, however, is not an evidence-based one. METHODS: A systematic review on the benefits and disadvantages of semi-upright position in ventilated patients was done according to PRISMA guidelines. Then a European expert panel developed a recommendation based on the results of the systematic review and considerations beyond the scientific evidence in a three-round electronic Delphi procedure. RESULTS: Three trials (337 patients) were included in the review. The results showed that it was uncertain whether a 45° bed head elevation was effective or harmful with regard to the occurrence of clinically suspected VAP, microbiologically confirmed VAP, decubitus and mortality, and that it was unknown whether 45° elevation for 24 hours a day increased the risk for thromboembolism or hemodynamic instability. A group of 22 experts recommended elevating the head of the bed of mechanically ventilated patients to a 20 to 45° position and preferably to a ≥ 30° position as long as it does not pose risks or conflicts with other nursing tasks, medical interventions or patients' wishes. CONCLUSIONS: Although the review failed to prove clinical benefits of bed head elevation, experts prefer this position in ventilated patients. They made clear that the position of a ventilated patient in bed depended on many determinants. Therefore, given the scientific uncertainty about the benefits and harms of a semi-upright position, this position could only be recommended as the preferred position with the necessary restrictions.

Urethral catheters: can we reduce use?

BACKGROUND: Indwelling urinary catheters are the main cause of healthcare-associated urinary tract infections. It can be expected that reduction of the use of urinary catheters will lead to decreased numbers of urinary tract infection. METHODS: The efficacy of an intervention programme to improve adherence to recommendations to reduce the use of urethral catheters was studied in a before-after comparison in ten Dutch hospitals. The programme detected barriers and facilitators and each individual facility was supported with developing their own intervention strategy. Outcome was evaluated by the prevalence of catheters, alternatives such as diapers, numbers of urinary tract infections, the percentage of correct indications and the duration of catheterization. The costs of the implementation as well as the catheterization were evaluated. RESULTS: Of a population of 16,495 hospitalized patients 3335 patients of whom 2943 were evaluable for the study, had a urethral catheter. The prevalence of urethral catheters decreased insignificantly in neurology (OR 0.93; 95% CI 0.77 - 1.13) and internal medicine wards (OR 0.97; 95% CI 0.83 - 1.13), decreased significantly in surgical wards (OR 0.84; 95% CI 0.75 - 0.96), but increased significantly in intensive care (IC) and coronary care (CC) units (OR 1.48; 95% CI 1.01 - 2.17). The use of alternatives was limited and remained so after the intervention. Duration of catheterization decreased insignificantly in IC/CC units (ratio after/before 0.95; 95% CI 0.78 - 1.16) and neurology (ratio 0.97; 95% CI 0.80 - 1.18) and significantly in internal medicine (ratio 0.81; 95% CI 0.69 - 0.96) and surgery wards (ratio 0.80; 95% CI 0.71 - 0.90). The percentage of correct indications on the day of inclusion increased from 50 to 67% (p < 0.0001). The prevalence of urinary tract infections in catheterized patients did not change. The mean cost saved per 100 patients was € 537. CONCLUSION: Targeted implementation of recommendations from an existing guideline can lead to better adherence and cost savings. Especially, hospitals which use a lot of urethral catheters or where catheterization is prolonged, can expect important improvements.

Using flexible methods to determine risk factors for ventilator-associated pneumonia in the Netherlands.

Seven hospitals participated in the Dutch national surveillance for ventilator-associated pneumonia (VAP) and its risk factors. We analysed time-independent and time-dependent risk factors for VAP using the standard Cox regression and the flexible Weighted Cumulative Effects method (WCE) that evaluates both current and past exposures. The prospective surveillance of intensive care patients aged ≥16 years and ventilated ≥48 hours resulted in the inclusion of 940 primary ventilation periods, comprising 7872 ventilation days. The average VAP incidence density was 10.3/1000 ventilation days. Independent risk factors were age (16-40 years at increased risk: HR 2.42 95% confidence interval 1.07-5.50), COPD (HR 0.19 [0.04-0.78]), current sedation score (higher scores at increased risk), current selective oropharyngeal decontamination (HR 0.19 [0.04-0.91]), jet nebulizer (WCE, decreased risk), intravenous antibiotics for selective decontamination of the digestive tract (ivSDD, WCE, decreased risk), and intravenous antibiotics not for SDD (WCE, decreased risk). The protective effect of ivSDD was afforded for 24 days with a delay of 3 days. For some time-dependent variables, the WCE model was preferable over standard Cox proportional hazard regression. The WCE method can furthermore increase insight into the active time frame and possible delay herein of a time-dependent risk factor.

Associations between surgical site infection risk and hospital operation volume and surgeon operation volume among hospitals in the Dutch nosocomial infection surveillance network.

OBJECTIVE: To examine the association between hospital operation volume and surgeon operation volume and the risk of surgical site infection (SSI). DESIGN: Prospective, multicenter cohort study based on surveillance data. METHODS: Data were obtained from the Dutch surveillance network for nosocomial infections (Preventie Ziekenhuisinfecties door Surveillance [PREZIES]) on 9 different types of orthopedic surgery, general surgery, and gynecology procedures performed during 1996-2003. Multilevel logistic regression analysis was performed to assess the independent effect of hospital volume and surgeon volume on SSI risk. RESULTS: Hospital volume was not significantly associated with SSI risk for any of the selected procedures. Low surgeon volume was associated with an increased risk for an infection for 7 of 9 types of procedures, although this effect was statistically significant only for knee arthroplasty. For 4 procedures, the odds of exceeding the 75th percentile for duration of surgery were greater when the surgeon volume was low than when the surgeon volume was moderate or high. CONCLUSIONS: Patients operated on by surgeons with a low operation volume seem to have a higher risk of developing an SSI with some procedures, particularly knee arthroplasty. The higher SSI risk for surgeons with a low operation volume is possibly partly mediated by the longer duration of surgery, a well-known risk factor for development of SSI.

Incidence and risk factors of device-associated infections and associated mortality at the intensive care in the Dutch surveillance system.

OBJECTIVE: To examine the incidence of and risk factors for device-associated infections and associated mortality. DESIGN AND SETTING: Prospective surveillance-based study in ICUs of 19 hospitals in The Netherlands. PATIENTS: The study included 2,644 patients without infection at admission during 1997-2000, staying in the ICU for at least 48 h. MEASUREMENTS AND RESULTS: The occurrence of ventilator-associated pneumonia (VAP), central venous catheter (CVC) related bloodstream infection (CR-BSI), urinary catheter-associated urinary tract infection (CA-UTI) and risk factors was monitored. Of the ventilated patients 19% developed pneumonia (25/1,000 ventilator days); of those with a central line 3% developed CR-BSI (4/1,000 CVC days,) and of catheterized patients 8% developed CA-UTI (9/1,000 catheter days). Longer device use increased the risk for all infections, especially for CR-BSI. Independent risk factors were sex, immunity, acute/elective admission, selective decontamination of the digestive tract, and systemic antibiotics at admission, dependent upon the infection type. Crude mortality significantly differed in patients with and without CR-BSI (31% vs. 20%) and CA-UTI (27% vs. 17%) but not for VAP (26% vs. 23%). Acquiring a device-associated infection was not an independent risk factor for mortality. Being in need of ventilation or a central line, and the duration of this, contributed significantly to mortality, after adjusting for other risk factors. CONCLUSIONS: Device use was the major risk factor for acquiring VAP, CR-BSI and CA-UTI. Acquiring a device-associated infection was not an independent risk factor for mortality, but device use in itself was.

Adhering to a national surgical care bundle reduces the risk of surgical site infections.

BACKGROUND: In 2008, a bundle of care to prevent Surgical Site Infections (SSIs) was introduced in the Netherlands. The bundle consisted of four elements: antibiotic prophylaxis according to local guidelines, no hair removal, normothermia and 'hygiene discipline' in the operating room (i.e. number of door movements). Dutch hospitals were advised to implement the bundle and to measure the outcome. This study's goal was to assess how effective the bundle was in reducing SSI risk. METHODS: Hospitals assessed whether their staff complied with each of the bundle elements and voluntary reported compliance data to the national SSI surveillance network (PREZIES). From PREZIES data, we selected data from 2009 to 2014 relating to 13 types of surgical procedures. We excluded surgeries with missing (non)compliance data, and calculated for each remaining surgery with reported (non)compliance data the level of compliance with the bundle (that is, being compliant with 0, 1, 2, 3, or 4 of the elements). Subsequently, we used this level of compliance to assess the effect of bundle compliance on the SSI risk, using multilevel logistic regression techniques. RESULTS: 217 489 surgeries were included, of which 62 486 surgeries (29%) had complete bundle reporting. Within this group, the SSI risk was significantly lower for surgeries with complete bundle compliance compared to surgeries with lower compliance levels. Odds ratios ranged from 0.63 to 0.86 (risk reduction of 14% to 37%), while a 13% risk reduction was demonstrated for each point increase in compliance-level. Sensitivity analysis indicated that due to analysing reported bundles only, we probably underestimated the total effect of implementing the bundle. CONCLUSIONS: This study demonstrated that adhering to a surgical care bundle significantly reduced the risk of SSIs. Reporting of and compliance with the bundle compliance can, however, still be improved. Therefore an even greater effect might be achieved.

Impact of postdischarge surveillance on surgical site infection rates for several surgical procedures: results from the nosocomial surveillance network in The Netherlands.

OBJECTIVE: To compare the number of surgical site infections (SSIs) registered after hospital discharge with respect to various surgical procedures and to identify the procedures for which postdischarge surveillance (PDS) is most important. DESIGN: Prospective SSI surveillance with voluntary PDS. Recommended methods for PDS in the Dutch national nosocomial surveillance network are addition of a special registration card to the outpatient medical record, on which the surgeon notes clinical symptoms and whether a patient developed an SSI according to the definitions; an alternative method is examination of the outpatient medical record. SETTING: Hospitals participating in the Dutch national nosocomial surveillance network between 1996 and 2004. RESULTS: We collected data on 131,798 surgical procedures performed in 64 of the 98 Dutch hospitals. PDS was performed according to one of the recommended methods for 31,134 operations (24%) and according to another active method for 32,589 operations (25%), and passive PDS was performed for 68,075 operations (52%). Relatively more SSIs were recorded after discharge for cases in which PDS was performed according to a recommended method (43%), compared with cases in which another active PDS method was used (30%) and cases in which passive PDS was used (25%). The highest rate of SSI after discharge was found for appendectomy (79% of operations), followed by knee prosthesis surgery (64%), mastectomy (61%), femoropopliteal or femorotibial bypass (53%), and abdominal hysterectomy (53%). CONCLUSIONS: For certain surgical procedures, most SSIs develop after discharge. SSI rates will be underestimated if no PDS is performed. We believe we have found a feasible and sensitive method for PDS that, if patients routinely return to the hospital for a postdischarge follow-up visit, might be suitable for use internationally.

Improved risk adjustment for comparison of surgical site infection rates.

OBJECTIVE: To develop prognostic models for improved risk adjustment in surgical site infection surveillance for 5 surgical procedures and to compare these models with the National Nosocomial Infection Surveillance system (NNIS) risk index. DESIGN: In a multicenter cohort study, prospective assessment of surgical site infection and risk factors was performed from 1996 to 2000. In addition, risk factors abstracted from patient files, available in a national medical register, were used. The c-index was used to measure the ability of procedure-specific logistic regression models to predict surgical site infection and to compare these models with models based on the NNIS risk index. A c-index of 0.5 indicates no predictive power, and 1.0 indicates perfect predictive power. SETTING: Sixty-two acute care hospitals in the Dutch national surveillance network for nosocomial infections. PARTICIPANTS: Patients who underwent 1 of 5 procedures for which the predictive ability of the NNIS risk index was moderate: reconstruction of the aorta (n=875), femoropopliteal or femorotibial bypass (n=641), colectomy (n=1,142), primary total hip prosthesis (n=13,770), and cesarean section (n=2,962). RESULTS: The predictive power of the new model versus the NNIS index was 0.75 versus 0.62 for reconstruction of the aorta (P<.01), 0.78 versus 0.58 for femoropopliteal or femorotibial bypass (P<.001), 0.69 versus 0.62 for colectomy (P<.001), 0.64 versus 0.56 for primary total hip prosthesis arthroplasty (P<.001), and 0.70 versus 0.54 for cesarean section (P<.001). CONCLUSION: Data available from hospital information systems can be used to develop models that are better at predicting the risk of surgical site infection than the NNIS risk index. Additional data collection may be indicated for certain procedures--for example, total hip prosthesis arthroplasty.

Effect of optimized antibiotic prophylaxis on the incidence of surgical site infection.

OBJECTIVE: To compare the rate of surgical site infection (SSI) before and after an intervention period in which an optimized policy for antibiotic prophylaxis was implemented. To demonstrate that a more prudent, restrictive policy would not have a detrimental effect on patient outcomes. DESIGN: Before-after trial with prospective SSI surveillance in the Dutch nosocomial surveillance network (Preventie Ziekenhuisinfecties door Surveillance [PREZIES]), using the criteria of the Centers for Disease Control, including postdischarge surveillance for up to 1 year. METHODS: During a preintervention period and a postintervention period (both 6-13 months), 12 Dutch hospitals collected data on antimicrobial prophylaxis and SSI rates. The study was limited to commonly performed surgical procedures in 4 specialties: vascular, intestinal, gynecological and orthopedic surgery. Selected risk factors for analysis were sex, age, American Society of Anesthesiologists classification, wound contamination class, duration of surgery, length of hospital stay before surgery, and urgency of surgery (elective or acute). RESULTS: A total of 3,621 procedures were included in the study, of which 1,668 were performed before the intervention and 1,953 after. The overall SSI rate decreased from 5.4% to 4.5% (P=.22). Among the procedures included in the study, the largest proportion (55%) were total hip arthroplasty, and the smallest proportion (2%) were replacement of the head of the femur. SSI rates varied from 0% for vaginal hysterectomy to 21.1% for femoropopliteal or femorotibial bypass surgery. Crude and adjusted odds ratios showed that there were no significant changes in procedure-specific SSI rates after the intervention (P>.1). CONCLUSIONS: An optimized and restrictive antibiotic prophylaxis policy had no detrimental effect on the outcome of clean and clean contaminated surgery, as measured by SSI rate.

Internal and External Validation of a Computer-Assisted Surveillance System for Hospital-Acquired Infections in a 754-Bed General Hospital in the Netherlands.

OBJECTIVE To evaluate a computer-assisted point-prevalence survey (CAPPS) for hospital-acquired infections (HAIs). DESIGN Validation cohort. SETTING A 754-bed teaching hospital in the Netherlands. METHODS For the internal validation of a CAPPS for HAIs, 2,526 patients were included. All patient records were retrospectively reviewed in depth by 2 infection control practitioners (ICPs) to determine which patients had suffered an HAI. Preventie van Ziekenhuisinfecties door Surveillance (PREZIES) criteria were used. Following this internal validation, 13 consecutive CAPPS were performed in a prospective study from January to March 2013 to determine weekly, monthly, and quarterly HAI point prevalence. Finally, a CAPPS was externally validated by PREZIES (Rijksinstituut voor Volksgezondheid en Milieu [RIVM], Bilthoven, Netherlands). In all evaluations, discrepancies were resolved by consensus. RESULTS In our series of CAPPS, 83% of the patients were automatically excluded from detailed review by the ICP. The sensitivity of the method was 91%. The time spent per hospital-wide CAPPS was ~3 hours. External validation showed a negative predictive value of 99.1% for CAPPS. CONCLUSIONS CAPPS proved to be a sensitive, accurate, and efficient method to determine serial weekly point-prevalence HAI rates in our hospital. Infect Control Hosp Epidemiol 2016;1-6.

Hospital-related determinants for surgical-site infection following hip arthroplasty.

OBJECTIVE: To determine hospital-related risk factors for surgical-site infection (SSI) following hip arthroplasty. DESIGN: Prospective, multicenter cohort study based on surveillance data and data collected through a structured telephone interview. With the use of multilevel logistic regression, the independent effect of hospital-related characteristics on SSI was assessed. SETTING: Thirty-six acute care hospitals in the Dutch surveillance network for nosocomial infections (PREZIES), from 1996 to 2000. PATIENTS: Thirteen thousand six hundred eighty patients who underwent total or partial hip arthroplasty. RESULTS: A high annual volume of operations was associated with a reduced risk of SSI (risk-adjusted risk ratio [RR] per 50 extra operations, 0.85; 95% confidence interval [CI95], 0.74-0.97). With each extra full-time-equivalent infection control staff member per 250 beds available for prevention of SSI, the risk for SSI was decreased (RR, 0.48; CI95, 0.16-1.44), although the decrease was not statistically significant. Hospital size, teaching status, university affiliation, and number of surgeons and their years of experience showed no important association with the risk of SSI. CONCLUSION: Undergoing surgery in a hospital with a low volume of operations increases a patient's risk of SSI.

[Healthcare-associated infections on readmission: 1 in 3 is linked to previous hospital admission]. / Zorggerelateerde infecties bij heropname: 1 op de 3 ziekenhuisinfecties is gerelateerd aan eerdere opname.

OBJECTIVE: To gain insight into the prevalence of healthcare-associated (HAI) infections in hospital patients in the Netherlands, and their link with previous hospital admission. DESIGN: Cross-sectional study. METHOD: This prevalence study was carried out in 36 hospitals at 42 locations in the Netherlands in March 2014. All inpatients at the time of the study were evaluated for the presence of an HAI, according to the standard protocol and in accordance with internationally determined definitions. It was subsequently determined whether the HAI had been acquired during the current admission or was linked to a previous recent admission. Readmission had to have taken place within a predetermined time period. RESULTS: A total of 9,420 patients were evaluated for the presence of an HAI; 470 (5.0%) HAI were reported, of which almost 36% was linked to a previous admission. Two-thirds of the HAI were post-operative surgical-site infections. Almost 88% of the patients with HAI were treated with antibiotics, versus 32% of the patients without HAI. CONCLUSION: Registration of HAI on admission to hospital provides insight into the frequency of HAI that become apparent after discharge. There is no insight into the treatment frequency of HAI by general practitioners. An inventory of the treatment frequency of HAI in primary care is advised, to evaluate infection-prevention policy in hospitals and to optimise primary care.

Promoting quality through surveillance of surgical site infections: five prevention success stories.

BACKGROUND: Public reports of successful quality improvement efforts are useful, but seldom available. We present 5 successful efforts to prevent surgical site infections (SSIs) with the use of prospectively collected surveillance data. METHODS: Before-and-after intervention studies were conducted in 5 acute care public hospitals in the national surveillance network for SSI in The Netherlands from 1992 to 2000. Patients undergoing surgery for total hip prosthesis (3 hospitals), knee prosthesis (2 hospitals), prosthesis of the femur head (1 hospital), or appendectomy (1 hospital) were included. Included were 1066 patients before intervention, and 1269 patients after intervention. Multidisciplinary evaluation of infection control policy led to subsequent changes of infection control measures, mainly involving the discipline of staff and organization of perioperative infection prevention procedures. RESULTS: All 5 hospitals drastically reduced their SSI rates to the national average or below. Absolute declines ranged from 2.1% to 13.9%, but not all reductions were statistically significantly different from 0%. CONCLUSION: Surveillance results provide a basis for improvement of infection prevention.

Surveillance and epidemiology of surgical site infections after cardiothoracic surgery in The Netherlands, 2002-2007.

OBJECTIVE: Surgical site infections after cardiothoracic surgery substantially increase the risk for illness, mortality, and costs. Surveillance of surgical site infections might assist in the prevention of these infections. This study describes the Dutch surveillance methods and results of data collected between 2002 and 2007. METHODS: Three cardiothoracic procedures were included: coronary artery bypass graft procedures, valve surgery, and a combination of coronary artery bypass graft procedures with concomitant valve surgery. The surgical site infections were divided into sternal and harvest-site infections. Postdischarge surveillance of surgical site infections was mandatory for sternal wounds and elective for harvest-site wounds, with a follow-up period of 42 postoperative days. Multivariate logistic regression was used for risk factor analysis of coronary artery bypass grafts, with adjustment for random variation among hospitals. RESULTS: Eight of the 16 Dutch cardiothoracic centers participated and collected data on 4066 procedures and 183 surgical site infections, revealing a surgical site infection rate of 2.4% for sternal wounds and 3.2% for harvest sites. Sixty-one percent of all surgical site infections were recorded after discharge. For sternal surgical site infections after coronary artery bypass graft procedures, the significant risk factors were rethoracotomy, diabetes, preoperative length of stay, and obesity; for harvest-site infections, the most relevant risk factor was a long time on extracorporeal circulation. Adjusted surgical site infection rates regarding coronary artery bypass graft procedures varied between hospitals from 0.0% to 9.7%. CONCLUSIONS: Large differences were found in surgical site infection rates between Dutch hospitals, which indicate room for improvement. The follow-up of patients after hospital discharge reduces underestimation of surgical site infection rates.

Trends in the incidence of surgical site infection in the Netherlands.

OBJECTIVE: To evaluate the time trend in the surgical site infection (SSI) rate in relation to the duration of surveillance in The Netherlands. SETTING: Forty-two hospitals that participated in the the Dutch national nosocomial surveillance network, which is known as PREZIES (Preventie van Ziekenhuisinfecties door Surveillance), and that registered at least 1 of the following 5 frequently performed surgical procedures for at least 3 years during the period from 1996 through 2006: mastectomy, colectomy, replacement of the head of the femur, total hip arthroplasty, or knee arthroplasty. METHODS: Analyses were performed for each surgical procedure. The surveillance time to operation was stratified in consecutive 1-year periods, with the first year as reference. Multivariate logistic regression analysis was performed using a random coefficient model to adjust for random variation among hospitals. All models were adjusted for method of postdischarge surveillance. RESULTS: The number of procedures varied from 3,031 for colectomy to 31,407 for total hip arthroplasty, and the SSI rate varied from 1.6% for knee arthroplasty to 12.2% for colectomy. For total hip arthroplasty, the SSI rate decreased significantly by 6% per year of surveillance (odds ratio [OR], 0.94 [95% confidence interval {CI}, 0.90-0.98]), indicating a 60% decrease after 10 years. Nonsignificant but substantial decreasing trends in the rate of SSI were found for replacement of the head of the femur (OR, 0.94 [95% CI, 0.88-1.00]) and for colectomy (OR, 0.92 [95% CI, 0.83-1.02]). CONCLUSIONS: Even though most decreasing trends in the SSI rate were not statistically significant, they were encouraging. To use limited resources as efficiently as possible, we would suggest switching the surveillance to another surgical procedure when the SSI rate for that particular procedure has decreased below the target rate.

Quality improvement of surgical prophylaxis in Dutch hospitals: evaluation of a multi-site intervention by time series analysis.

OBJECTIVES: Misuse of antibiotics in surgical prophylaxis is still quite common. The objectives of this study were to reduce the quantity and improve the quality of surgical prophylaxis and to reduce costs. METHODS: Prospective multi-site study of elective procedures in 13 Dutch hospitals. The quality of prophylaxis was audited before and after an intervention consisting of performance feedback and implementation of national clinical practice guidelines. Process outcome parameters were antibiotic choice, duration, timing, antibiotic volume and costs. Segmented regression analysis was used to estimate the effect size of the intervention. Patient outcome was documented by the incidence of surgical site infections (SSI). RESULTS: Before the intervention, 1763 procedures were recorded and 2050 thereafter. Antimicrobial use decreased from 121 to 79 DDD (defined daily doses)/100 procedures and costs reduced by 25% per procedure. After the intervention, antibiotic choice was inappropriate in only 37.5% of the cases instead of in 93.5% expected cases had the intervention not occurred. Prolonged prophylaxis was observed in 31.4% instead of 46.8% expected cases and inappropriate timing in 39.4% instead of the expected 51.8%. Time series analysis showed that all improvements were statistically significant (P < 0.01) and that they could be fully attributed to the intervention. The overall SSI rates before and after intervention were 5.4% (95% CI: 4.3-6.5) and 4.6% (95% CI: 3.6-5.4), respectively. CONCLUSIONS: The intervention led to improved quality of surgical prophylaxis and to reduced antibiotic use and costs without impairment of patient outcome.