Antibiotic prophylaxis and the risk of surgical site infections following total hip arthroplasty: timely administration is the most important factor.

BACKGROUND: Surgical site infections (SSIs) following total hip arthroplasty can lead to prolonged hospitalization, increased morbidity and mortality, and high costs. This article analyzes the effect of various parameters of surgical antibiotic prophylaxis on the risk of SSI following total hip arthroplasty. METHODS: Data about SSI and potential prophylaxis-, patient-, and procedure-related risk factors were prospectively collected for 1922 patients who underwent elective total hip arthroplasty in 11 hospitals that participated in the Dutch intervention project, Surgical Prophylaxis and Surveillance. Multivariate logistic regression analysis was performed to correct for random variation among hospitals. RESULTS: SSIs (superficial and deep) occurred in 50 patients (2.6%). The highest odds ratios for SSI were found in patients who received prophylaxis after incision (2.8, 95% confidence interval [CI], 0.9-8.6; P=.07), had an American Society of Anesthesiology score that was >2 (2.8, 95% CI, 0.8-9.2; P=.09), and experienced a duration of surgery that was >75th percentile (2.5; 95% CI, 1.1-5.8; P=.04). Prolonged prophylaxis after the end of surgery and the use of antibiotic-impregnated cement did not contribute to fewer SSIs in this study. CONCLUSIONS: This study suggests that intervention programs in search of amendable factors to prevent SSI should focus on timely administration of antibiotic prophylaxis.

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.

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.

Reduced risk of surgical site infections through surveillance in a network.

OBJECTIVE: To estimate the effect of multicentre surveillance for nosocomial infections on patients' risk of surgical site infection (SSI). DESIGN: Prospective multi-centre cohort study, from January 1996 to December 2000. SETTING: Acute care hospitals in The Netherlands. STUDY PARTICIPANTS: All 50 hospitals performing surveillance for one of seven selected procedures in the Dutch surveillance network for nosocomial infections PREZIES were invited. Thirty-seven hospitals participated (74%) and provided information on 21 920 operations, after which 885 (4%) SSI occurred. INTERVENTIONS: The surveillance comprised the following: Development of surveillance methodology by multidisciplinary team; use of a standardized registration protocol and software; regular training of data collectors; anonymous inter-hospital comparison of infection rates and feedback of results; appointment of one contact person per hospital, responsible for data collection; and dissemination of results to other health care professionals. Regular discussion of both successful and failing prevention strategies that had been instituted based on the surveillance results. OUTCOME MEASURE: Risk of SSI. RESULTS: The risk of infection was reduced for patients who had an operation during the fourth surveillance year (RR = 0.69; 95% confidence interval (CI) = 0.52-0.89) and decreased further for patients operated on during the fifth surveillance year (RR = 0.43; CI = 0.24-0.76) as compared with patients who underwent surgery within one year of the start of surveillance in their hospital. No significant risk reduction was observed for patients operated on during the second and third surveillance years. CONCLUSION: Surveillance, supported by participation in a surveillance network, reduced the risk of SSI in surgical patients registered in the Dutch surveillance network PREZIES. Our results suggest that infection control teams need to be perseverant and that surveillance programmes should be given time before evaluation.

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.

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.

False-positive mycobacterium tuberculosis cultures in 44 laboratories in The Netherlands (1993 to 2000): incidence, risk factors, and consequences.

False-positive Mycobacterium tuberculosis cultures are a benchmark for the quality of laboratory processes and patient care. We studied the incidence of false-positive cultures, risk factors, and consequences for patients during the period from 1993 to 2000 in 44 peripheral laboratories in The Netherlands. The national reference laboratory tested 8,889 M. tuberculosis isolates submitted by these laboratories. By definition, a culture was false positive (i) if the DNA fingerprint of the isolate was identical to that of an isolate from another patient processed within 7 days in the same laboratory, (ii) if the isolate was taken from a patient without clinical signs of tuberculosis, and/or (iii) if the false-positive test result was confirmed by the peripheral laboratory and/or the public health tuberculosis officer. We identified 213 false-positive cultures (2.4%). The overall incidence of false-positive cultures decreased over the years, from 3.9% in 1993 to 1.1% in 2000. Laboratories with false-positive cultures more often processed less than 3,000 samples per year (P < 0.05). Among 110 patients for whom a false-positive culture was identified from 1995 to 1999, we found that for 36% of the patients an official tuberculosis notification had been provided to the appropriate public health services, 31% of the patients were treated, 14% of the patients were hospitalized, and a contact investigation had been initiated for 16% of the patients. The application of DNA fingerprinting to identify false-positive M. tuberculosis cultures and the provision of feedback to peripheral laboratories are useful instruments to improve the quality of laboratory processes and the quality of medical care.

An outbreak of diarrhea in a neonatal medium care unit caused by a novel strain of rotavirus: investigation using both epidemiologic and microbiological methods.

OBJECTIVE: In December 1999, an outbreak of diarrhea was reported in a general hospital neonatal medium care unit (NMCU) caused by a novel strain of rotavirus with genotype P[6], G9. An investigation was conducted to determine risk factors for illness among neonates. DESIGN: Rotavirus diagnosis was by latex agglutination and typing by reverse transcriptase polymerase chain reaction. A case-control study was performed using data collected from medical records on exposures in a 3-day period before illness (cases) or a random 3-day period (controls). Environmental swabs were tested for rotavirus. Antenatal blood samples from mothers and blood samples provided by hospital staff were analyzed for rotavirus antibodies. RESULTS: Fifty-six cases of rotaviral illness were confirmed by latex agglutination. Forty-seven of these were among 118 neonates exposed to the NMCU (attack rate, 40%). There was a 4-week period with no clinical cases in the course of the outbreak. Increased frequency (> or = 15 times in 3 days) of ungloved nasogastric feeding was a significant risk factor (adjusted odds ratio, 8.79), controlling for birth weight and gestational age. Environmental sampling showed persistence of the virus on ward surfaces despite cleaning. None of 24 NMCU staff members had high levels of antibodies against P[6], G9. Three (8%) of 38 mothers had high antibody levels; 2 had infants who became ill. The outbreak ended with a 7-day ward closure, disinfection, and introduction of gloved nasogastric feeding. CONCLUSIONS: Case-control studies can be successful in identiffying risk factors for nosocomial outbreaks of diarrhea. High levels of rotavirus antibodies in mothers may not protect infants. The environment may be the most important reservoir of rotavirus during outbreaks.