Severity of illness scoring systems to adjust nosocomial infection rates: a review and commentary

Pediatric Risk of Mortality and Hospital Infection

We studied the association of Pediatric Risk of Mortality scores with nosocomial infections among 341 critically ill patients admitted to a pediatric intensive care unit between June 1998 and December 2000. Through stepwise logistic regression analysis, the best predictors for nosocomial infections were device utilization ratio, antimicrobial therapy, and length of stay.

Usefulness of Severity-of-Illness Scores Based on Admission Data Only in Nosocomial Infection Surveillance Systems

Background.

Surveillance of nosocomial infection (NI) and the use of reference data for comparison is recommended to improve the quality of patient care. In addition to standardization according to device use, another stratification of reference data according to patients' severity-of-illness scores is often required for benchmarking in intensive care units (ICUs).

Objective.

To determine whether severity-of-illness scores on admission to the ICU are sufficient data for predicting the development of NI.

Methods.

This study was performed in an interdisciplinary ICU at a teaching hospital. Two scores were studied: the Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system and the Therapeutic Intervention Scoring System (TISS). The patient's clinical condition was evaluated on admission and reevaluated daily during the period before the development of NI. In addition, we recorded the number of intubations for every patient-day, the age and sex of the patients, and their history of operations. The Fisher exact test and the stepwise multiple logistic regression model were applied to identify significant predictors of NI.

Results.

During a 12-month period, 270 patients with ICU stays of more than 24 hours were included in the study. Sixty-nine NIs were identified (incidence, 25.6 cases per 100 patients [95% confidence interval, 19.9-32.3]). A mean APACHE II score and a mean TISS score above the median for these scores, duration of ventilation above the median in the period before the development of NI, and patient age were significantly associated with the development of NI; the score data on admission provided a clearly poorer prediction.

Conclusion.

The APACHE II and TISS scores on admission are not useful predictors for NI in ICUs.

Effect of Nurse Staffing and Antimicrobial-Impregnated Central Venous Catheters on the Risk for Bloodstream Infections in Intensive Care Units

Background:

Defining risk factors for central venous catheter (CVC)-associated bloodstream infections (BSIs) is critical to establishing prevention measures, especially for factors such as nurse staffing and antimicrobial-impregnated CVCs.

Methods:

We prospectively monitored CVCs, nurse staffing, and patient-related variables for CVC-associated BSIs among adults admitted to eight ICUs during 2 years.

Results:

A total of 240 CVC-associated BSIs (2.8%) were identified among 4,535 patients, representing 8,593 CVCs. Antimicrobial-impregnated CVCs reduced the risk for CVC-associated BSI only among patients whose CVC was used to administer total parenteral nutrition (TPN, 2.6 CVC-associated BSIs per 1,000 CVC-days vs no TPN, 7.5 CVC-associated BSIs per 1,000 CVC-days;P= .006). Among patients not receiving TPN, there was an increase in the risk of CVC-associated BSI in patients cared for by “float” nurses for more than 60% of the duration of the CVC. In multivariable analysis, risk factors for CVC-associated BSIs were the use of TPN in non-antimicrobial-impregnated CVCs (P= .0001), patient cared for by a float nurse for more than 60% of CVC-days (P= .0019), no antibiotics administered to the patient within 48 hours of insertion (P= .0001), and patient unarousable for 70% or more of the duration of the CVC (P= .0001). Peripherally inserted central catheters (PICCs) were associated with a lower risk for CVC-associated BSI (P= .0001).

Conclusions:

Antimicrobial-impregnated CVCs reduced the risk of CVC-associated BSI by 66% in patients receiving TPN. Limiting the use of float nurses for ICU patients with CVCs and the use of PICCs may also reduce the risk of CVC-associated BSI.

Assessing the impact of an educational intervention on ventilator-associated pneumonia in a pediatric critical care unit

BACKGROUND

Ongoing educational programs targeting health care professionals have shown positive outcomes by reducing the morbidity and mortality associated with health care-associated infections (HAIs). We undertook this study to measure the impact of such a program in a pediatric critical care unit of a developing country.

METHODS

This prospective study was conducted in 2 time periods of 6 months each, with an educational intervention for resident doctors and nurses in between. The rates of ventilator-associated pneumonia (VAP) during the preintervention and postintervention periods were estimated by active surveillance.

RESULTS

The incidence density of VAP was reduced by 28% (20.2 vs 14.6 per 1,000 ventilator-days; P = .21, Z test) despite a significant increase in the ventilator utilization ratio during the postintervention period (0.64 vs 0.88; P < .0001, Pearson's χ² test). There was a statistically significant reduction in mortality among patients who received mechanical ventilation for ≥48 hours in the postintervention period (49.3% vs 31.4%; P = .029, Pearson's χ² test).

CONCLUSIONS

Educational programs have a positive impact on reducing the morbidity and mortality associated with HAIs. Incidence rates based on device-days should be compared by keeping the variations in device utilization ratio in mind.

Association between APACHE II score and nosocomial infections in intensive care unit patients: A multicenter cohort study

OBJECTIVE

To examine whether nosocomial infection risk increases with APACHE II score, which is an index of severity-of-illness, in intensive care unit (ICU) patients.

METHODS

Using the Japanese Nosocomial Infection Surveillance database, 8,587 patients admitted to 34 participating ICUs between July 2000 and May 2002, aged 16 years or older, who had stayed in the ICU for 2 days or longer, had not transferred to another ICU, and had not been infected within 2 days after ICU admission, were followed until ICU discharge, Day 14 after ICU admission, or the development of nosocomial infection. Adjusted odds ratios with their 95% confidence intervals for nosocomial infections were calculated using logistic regression models, which incorporated sex, age, operation, ventilator; central venous catheter, and APACHE II score (0-5, 6-10, 11-15, 16-20, 21-25, 26-30, and 31+).

RESULTS

There were 683 patients with nosocomial infections. Adjusted odds ratios for nosocomial infections gradually increased with APACHE II score. Women and elective operation showed significantly low odds ratios, while urgent operation, ventilator, and central venous catheter showed significantly high odds ratios. Age had no significant effect on the development of nosocomial infection.

CONCLUSIONS

Nosocomial infection risk increases with APACHE II score. APACHE II score may be a good predictor of nosocomial infections in ICU patients.

Interhospital differences and case-mix in a nationwide prevalence survey

A prevalence survey is a time-saving and useful tool for obtaining an overview of healthcare-associated infection (HCAI) either in a single hospital or nationally. Direct comparison of prevalence rates is difficult. We evaluated the impact of case-mix adjustment on hospital-specific prevalences. All five tertiary care, all 15 secondary care and 10 (25% of 40) other acute care hospitals took part in the first national prevalence survey in Finland in 2005. US Centers for Disease Control and Prevention criteria served to define HCAI. The information collected included demographic characteristics, severity of the underlying disease, use of catheters and a respirator, and previous surgery. Patients with HCAI related to another hospital were excluded. Case-mix-adjusted HCAI prevalences were calculated by using a multivariate logistic regression model for HCAI risk and an indirect standardisation method. Altogether, 587 (7.2%) of 8118 adult patients had at least one infection; hospital-specific prevalences ranged between 1.9% and 12.6%. Risk factors for HCAI that were previously known or identified by univariate analysis (age, male gender, intensive care, high Charlson comorbidity and McCabe indices, respirator, central venous or urinary catheters, and surgery during stay) were included in the multivariate analysis for standardisation. Case-mix-adjusted prevalences varied between 2.6% and 17.0%, and ranked the hospitals differently from the observed rates. In 11 (38%) hospitals, the observed prevalence rank was lower than predicted by the case-mix-adjusted figure. Case-mix should be taken into consideration in the interhospital comparison of prevalence rates.

Risk factors for healthcare-associated infection in pediatric intensive care units: a systematic review

A systematic review of observational studies on risk factors for healthcare-associated infection in pediatric Intensive Care Units (ICU) was carried out. Studies indexed in MEDLINE, LILACS, Cochrane, BDENF, CAPES databases published in English, French, Spanish or Portuguese between 1987 and 2006 were included and cross references added. Key words for search were 'cross infection' and 'Pediatric Intensive Care Units' with others sub-terms included. 11 studies were selected from 419 originally found: four studies had healthcare-associated infection as the main outcome without a specific site; three articles identified factors associated with lower respiratory tract infection (pneumonia or tracheitis); three articles were concerned with laboratory-confirmed bloodstream infection; and a single retrospective study analyzed urinary tract infection. The production of evidence on risk factors Paediatric ICU has not kept up the same pace of that on adult - there are few studies with adequate design and statistical analysis. The methodological diversity of the studies did not allow for a summarized measurement of risk factors.

Risk factors for healthcare-associated infection in a pediatric intensive care unit

OBJECTIVE

Identify risk factors for first-onset healthcare-associated infection (HAI) in a pediatric intensive care unit (PICU).

DESIGN

Prospective cohort study.

SETTING

Medical-surgical PICU in a hospital for patients in the public healthcare system.

PATIENTS

From January 2005 to June 2006, daily surveillance was carried out on 870 patients ages 0 to 18 yrs during their stay in the PICU through to 48 hrs after discharge (5773 patient-days).

MEASUREMENTS AND MAIN RESULTS

In 256 admissions, there were 363 episodes of HAI, with a cumulative incidence of 41.7% and a density of 62.9 of 1000 patient-days. Intrinsic and extrinsic factors were investigated and measured until occurrence of first-onset HAI (diagnosed according to Nosocomial Infection Surveillance System criteria) or until discharge or death. In the multivariate logistic regression analysis, risk factors for first-onset HAI in the PICU (controlled for length of stay) were as follows: age under 2 years (odds ratio [OR]), 1.80; 95% confidence interval [CI]), 1.30-2.49); days on ventilator duration (OR, 1.16; 95% CI, 1.08-1.25); transfused blood products (OR, 1.49; 95% CI, 1.08-2.06), glucocorticoids (OR, 1.45; 95% CI, 1.04-2.02) and H2 blockers (OR, 1.47; 95% CI, 1.05-2.06).

CONCLUSIONS

Efforts toward a reduction in the exposure to extrinsic risk factors should be made, as each of these factors separately explains 30% of the risk of HAI. Interventions directed at processes related to the use of a ventilator and limitations on its duration of use should be a priority in HAI control strategies, as each day of ventilator use increases the risk of HAI.

Nurse working conditions and patient safety outcomes

BACKGROUND

System approaches, such as improving working conditions, have been advocated to improve patient safety. However, the independent effect of many working condition variables on patient outcomes is unknown.

OBJECTIVE

To examine effects of a comprehensive set of working conditions on elderly patient safety outcomes in intensive care units.

DESIGN

Observational study, with patient outcome data collected using the National Nosocomial Infection Surveillance system protocols and Medicare files. Several measures of health status and fixed setting characteristics were used to capture distinct dimensions of patient severity of illness and risk for disease. Working condition variables included organizational climate measured by nurse survey; objective measures of staffing, overtime, and wages (derived from payroll data); and hospital profitability and magnet accreditation.

SETTING AND PATIENTS

The sample comprised 15,846 patients in 51 adult intensive care units in 31 hospitals depending on the outcome analyzed; 1095 nurses were surveyed.

MAIN OUTCOME MEASURES

Central line associated bloodstream infections (CLBSI), ventilator-associated pneumonia, catheter-associated urinary tract infections, 30-day mortality, and decubiti.

RESULTS

Units with higher staffing had lower incidence of CLBSI, ventilator-associated pneumonia, 30-day mortality, and decubiti (P <or= 0.05). Increased overtime was associated with higher rates of catheter-associated urinary tract infections and decubiti, but slightly lower rates of CLBSI (P <or= 0.05). The effects of organizational climate and profitability were not consistent.

CONCLUSIONS

Nurse working conditions were associated with all outcomes measured. Improving working conditions will most likely promote patient safety. Future researchers and policymakers should consider a broad set of working condition variables.

Comparison of the National Surgical Site Infection surveillance data between The Netherlands and Germany: PREZIES versus KISS

As there has been increasing interest in comparing surgical site infection (SSI) rates between countries, we compared the SSI surveillance data for The Netherlands ('PREZIES') and Germany ('KISS'). Both surveillance systems have comparable protocols with many similar risk factors, including SSI definitions developed by the Centers for Disease Control and Prevention and optional postdischarge surveillance. Nine surgical procedure categories from several specialities were included, the reporting of which were similar, with respect to content and with enough data for proper comparison. Differences for the SSI data were found between PREZIES and KISS for duration of surgery, wound contamination class, American Society of Anesthesiologists physical status classification and the postoperative duration of hospitalization. A significantly higher superficial SSI rate was found for seven surgical procedures according to PREZIES and a higher deep SSI rate for five procedures. When considering only deep SSI during hospitalization, the differences in SSI rates were much smaller. Differences in intensity of postdischarge surveillance led to 34% of SSI being detected after discharge for PREZIES and 21% for KISS. In conclusion, even though similar infection surveillance protocols are used in The Netherlands and Germany, differences occurred in the implementation. Comparisons between countries are most reliable if only deep SSIs during hospitalization are taken into account, since these SSI are not affected by postdischarge surveillance and the diagnostic sensitivity for deep SSI is probably more alike between countries than for superficial SSI.

Surgical site infection in patients submitted to digestive surgery: risk prediction and the NNIS risk index

BACKGROUND

Some problems have been reported with the power of the National Nosocomial Infection Surveillance (NNIS) risk index to predict the risk of surgical site infections (SSI) for specific procedures.

OBJECTIVES

To develop an alternative risk prediction index for SSI and to compare the performance with the NNIS index.

METHODS

A prospective cohort study was carried out with all (609) patients submitted to digestive tract surgery in 2 general teaching hospitals in the city of São Paulo, Brazil, from August 2001 through March 2002.

RESULTS

The final incidence rate of SSI was 24.5%; 149 cases of SSI were identified: 33 (22.1%) during hospitalization and 116 (77.9%) after discharge. Logistic multivariate analysis was used for construction of the model. Obesity, surgery risk, adjusted duration, and video laparoscopic surgery were statistically significant (P < .05) for all previous procedures. The performance of the NNIS model in this study showed a low predictive capacity for the occurrence of SSI as determined by the receiver operating characteristic (ROC) curve (0.627; 95% CI: 0.575-0.678) compared with the alternative model developed with this population (0.732; 95% CI: 0.685-0.779).

CONCLUSION

The presence of obesity, adjusted duration, and surgery risk significantly increased the risk for SSI. The NNIS risk index was not significant for SSI in the sample studied, and laparoscopic access was associated with a significant reduction in the risk for SSI. Although the NNIS index is a well-known and simple index, other models depicting variables related to SSI with a better sensitivity and specificity can be developed. Additional studies are required to confirm our results.

Predicting Nosocomial Bloodstream Infections Using Surrogate Markers of Injury Severity

BACKGROUND

Injury severity indices are numerical scores that are utilized to predict nosocomial bloodstream infections (BSI) in critically ill patients. However, surrogate markers of injury severity (SMIS) may be more clinically meaningful than these commonly used numerical injury severity indices with respect to the control and prevention of nosocomial BSI.

OBJECTIVE

The purpose of this study was to demonstrate the clinical and research implications of using the SMIS in predicting nosocomial BSI.

METHOD

A prospective nonexperimental cohort study was conducted on 361 critically ill trauma patients. Three logistic regression models were examined for their clinical relevance and statistical parsimony. The first model included the Injury Severity Score (ISS) and 5 other independent predictors, and excluded the SMIS. The second model included all study variables. The third model excluded the ISS.

RESULTS

The analysis suggested that number of blood units transfused, number of central venous catheters inserted, and use of chest tube(s) were the SMIS. The ISS was found to be an independent predictor of nosocomial BSI only when the SMIS were not included in the model. The model that included the SMIS and excluded the ISS explained the highest variance in nosocomial BSI and had the best negative predictive value (93%).

DISCUSSION

Clinicians can use knowledge of SMIS to develop interventions that minimize the risk of nosocomial BSI. Hence, the SMIS can serve not only as a prediction tool but also as a way to enhance control and prevention strategies for BSI.

Nosocomial infective endocarditis in critically ill patients: a report of three cases and review of the literature

Nosocomial infective endocarditis (NIE) is a relatively uncommon but nevertheless a serious complication affecting critically ill hospitalized patients who are frequently exposed to life-saving invasive procedures. We report three cases of NIE in a tertiary-care hospital encountered during a period of two years. The first case developed in a 50% burn-injured patient; the second in a liver transplant recipient; and the third in a renal transplant recipient. All patients met indications for cardiac surgical intervention, however, the patient who had received a liver transplant (case 2) was considered a poor candidate and unfit for surgery; she subsequently died. The other two patients underwent open-heart surgery. The burns patient (case 1) survived; conversely, the renal transplant recipient (case 3) died postoperatively. We have reviewed the literature concerning NIE in critically ill patients and describe the epidemiology, microbiology and clinical features of this uncommon infection and comment on its diagnosis and management.

Infection in prolonged pediatric critical illness: A prospective four-year study based on knowledge of the carrier state

OBJECTIVE

This study was performed to determine the rate, timing, and incidence density of infections occurring in a subgroup of patients requiring a prolonged stay in a regional pediatric intensive care unit.

DESIGN

Prospective, observational cohort study over 4 yrs.

SETTING

This epidemiologic descriptive study was performed in a university hospital 20-bed pediatric intensive care unit.

PATIENTS

Critically ill children requiring > or = 4 days of intensive care.

INTERVENTIONS

The microbial carrier state of the children was monitored by surveillance cultures of throat and rectum, obtained on admission and twice weekly afterward.

MEASUREMENTS AND MAIN RESULTS

Data are presented on a total of 1,241 children, accounting for 1,443 admissions to the unit, corresponding to 18,203 patient days. The median pediatric index of mortality was 0.063 (interquartile range, 0.025-0.131), and the mortality rate in this subset of children was 9.6%. Five hundred twenty children had infections, an overall infection rate of 41.9% (520 of 1,241); 14.5% (180 of 1,241) of the children developed viral and 33.0% (410 of 1,241) developed bacterial/yeast infections. The incidence of bloodstream infection was 20.1 and lower airway infection 9.1 episodes per 1,000 patient days. We found that 13.3% of the children were infected with a bacterial/yeast microorganism acquired on the pediatric intensive care unit; 4.0% (50 of 1,241) of children developed infections due to resistant microorganisms. There were a total of 803 bacterial/yeast infectious episodes, of which 59.8% (480) were due to microorganisms imported in the patients' admission flora. These primary endogenous infections predominantly occurred within the first week of pediatric intensive care unit stay. The other 38.9% (312) were caused by microorganisms acquired on the pediatric intensive care unit. A total of 38 viral infections (24.5%) were acquired during pediatric intensive care unit stay.

CONCLUSIONS

Two thirds of all infections diagnosed in children with prolonged illness on pediatric intensive care unit were due to microorganisms present in the patients' admission flora.

Active surveillance reduces the incidence of vancomycin-resistant enterococcal bacteremia

The impact of active surveillance of patients at risk for infection with vancomycin-resistant enterococci (VRE) was examined, and VRE bacteremia rates and the degree of VRE clonality in 2 similar neighboring hospitals were compared. Hospital A did not routinely screen patients for VRE rectal colonization; hospital B actively screened high-risk patients. Retrospective observations were made over the course of 6 years, beginning when initial VRE bloodstream isolates were recovered at each institution. The rate of VRE bacteremia was 2.1-fold higher at hospital A, and the majority of hospital A isolates were clonally related: 4 clones were responsible for infection in >75% of patients with VRE bacteremia, and isolates from 30% of patients were from the most common clone. The 4 most common clones at hospital B were responsible for infection in 37% of patients, and isolates from 14.5% of patients were from the most common clone. Lower VRE bacteremia rates and a more polyclonal population, representing less horizontal transmission, may result from routine screening of patients who are at risk for VRE and prompt contact isolation of colonized individuals.

Five years working with the German nosocomial infection surveillance system (Krankenhaus Infektions Surveillance System)

A national surveillance system for nosocomial infections, Krankenhaus Infektions Surveillance System (KISS), was established in Germany as a joint effort by the National Reference Center for Hospital Epidemiology (currently called the National Reference Center for the Surveillance of Nosocomial Infections) and the Robert Koch Institute. To begin with a well-accepted and proven method, surveillance protocols were developed on the basis of the National Nosocomial Infections Surveillance system. Hospitals from all parts of Germany took part voluntarily. There were 4 surveillance components: intensive care departments (227), patients undergoing operation (231 departments), neonatal intensive care departments (23 hospitals), and patients undergoing bone marrow and peripheral blood stem cell transplants (10 hospitals). Five years after the introduction of KISS many hospitals have introduced continuous surveillance activities whereby the various definitions and methods have attained wide acceptance. This has lead to much better understanding and cooperation between clinicians and infection control personnel in preventing nosocomial infections. KISS is considered the national reference database, but continuous evaluation and development of KISS are necessary to react adequately.

Effects of rapid detection of bloodstream infections on length of hospitalization and hospital charges

Current automated continuous-monitoring blood culture systems afford more rapid detection of bacteremia and fungemia than is possible with non-instrument-based manual methods. Use of these systems has not been studied objectively with respect to impact on patient outcomes, including hospital charges and length of hospitalization. We conducted a prospective, two-center study in which the time from the obtainment of the initial positive blood culture until the Gram stain was called was evaluated for 917 cases of bloodstream infection. Factors showing univariate associations with a shorter time to notification included higher body temperature and respiratory rate and higher percentage of immature neutrophils. Multiple linear regression models determined that the primary predictors of both increased microbiology laboratory and total hospital charges for patients with bloodstream infection were nonmicrobiologic and included length of stay and host factors such as the admitting service and underlying illness score. Significant microbiologic predictors of increased charges included the number of blood cultures obtained, nosocomial acquisition, and polymicrobial bloodstream infections. Accelerated failure time regression analysis demonstrated that microbiologic factors, including time until notification, organism group, and nosocomial acquisition, were independently associated with length of hospitalization after bacteremia, as were the factors of admitting service, gender, and age. Our data suggest that an increased time to notification of bloodstream infection is independently associated with increased length of stay. We conclude that the time to notification is an obvious target for efforts to shorten length of stay. The newest generation of automated continuous-monitoring blood culture systems, which shorten the time required to obtain a positive result, should impact length of hospitalization.

The use of economic modeling to determine the hospital costs associated with nosocomial infections

Hospital-associated infection is well recognized as a patient safety concern requiring preventive interventions. However, hospitals are closely monitoring expenditures and need accurate estimates of potential cost savings from such prevention programs. We used a retrospective cohort design and economic modeling to determine the excess cost from the hospital perspective for hospital-associated infection in a random sample of adult medical patients. Study patients were classified as being not infected (n=139), having suspected infection (n=8), or having confirmed infection (n=17). Severity of illness and intensive unit care use were both independently associated with increased cost. After controlling for these confounding effects, we found an excess cost of $6767 for suspected infection and $15,275 for confirmed hospital-acquired infection. The economic model explained 56% of the total variability in cost among patients. Hospitals can use these data when evaluating potential cost savings from effective infection-control measures.

[Surveillance of nosocomial infections in intensive care units. Current data and interpretations]

The German nosocomial infections surveillance system KISS was established in 1996 using a surveillance protocol based on the National Nosocomial Infections Surveillance (NNIS) System. Meanwhile data from a total of 274 intensive care units (ICU) are available, among them 134 interdisciplinary, 71 surgical, 55 medical, 9 neurosurgical and 5 paediatric ICUs. The data comprise about 6,966 surveillance months with more than 500,000 intensive care patients and more than 1.8 million patient days. A total of 6,888 cases of pneumonia and 2,357 cases of central venous catheter (CVC) associated primary bloodstream infections (BSI) were recorded. Ventilator associated pneumonia rates and CVC associated primary BSI rates are presented, stratified according to the type of the ICU and affiliation to a university, a teaching hospital or another type of hospital. The most frequent pathogens associated with ventilator associated pneumonia were S. aureus (24.1%), followed by P. aeruginosa (16.8%) and Klebsiella spp. (12.1%). In the case of CVC associated primary BSI coagulase negative staphylococci dominated (30.9%) followed by S. aureus (15.4%) and Enterococci spp. (11.6%). A remarkable increase of Methicillin Resistant Staphylococcus aureus (MRSA) infections was observed during the period from 1997 to 2002. 19.2% of S. aureus associated pneumonia cases and 25.5% of S. aureus associated primary BSI were due to MRSA. KISS data are useful benchmarks for internal quality management, however a careful interpretation is necessary to stimulate infection control efforts.

Use of the injury severity score to predict nosocomial bloodstream infections among critically ill trauma patients

Nosocomial bloodstream infections (NBSI) are associated with increased hospital length of stay (LOS), mortality, and costs. At this writing, no available reports describe the association between injury severity and NBSI among critically ill adult trauma patients. This study aimed to examine the use of the Injury Severity Score (ISS) as a predictor of NBSI among critically ill adult trauma patients. A case-control design was used to compare the mean ISS of 190 critically ill trauma patients equally divided between those with positive test results for NBSI and those with negative results. The mean hospital LOS (34.8 days versus 16.5 days) and the mean intensive care unit LOS (28.1 days versus 13 days) were significantly higher among the patients with NBSI than among the control subjects without such infection (P <.001 and P <.001, respectively). The mean LOS until the diagnosis of NBSI was significantly lower than the total LOS of the control subjects (odds ratio [OR], 0.959; 95% confidence interval [CI], 0.93-0.99). The ISS score and age were found to be independent predictors of NBSI. The findings provide a means for using the ISS score as a predictor of NBSI in the critically ill adult trauma population.

Trauma severity scoring systems as predictors of nosocomial infection

OBJECTIVES

To describe the patterns of nosocomial infections in patients with traumatic injuries and to compare the associations between injury severity, derived from various severity scoring systems, and subsequent nosocomial infections.

DESIGN

Prospective observational study.

SETTING

A 750-bed university hospital serving as a medical school and referral center for the southern part of Thailand.

PARTICIPANTS

All trauma patients admitted to the hospital for more than 3 days during 1996 to 1999 were eligible for this study.

METHODS

The severity of injuries was measured in terms of injury severity score (ISS), revised trauma score (RTS), new injury severity score (NISS), and trauma injury severity score (TRISS). Infections acquired during hospitalization were categorized using Centers for Disease Control and Prevention criteria. The association between severity of injury and nosocomial infection was examined with Poisson regression models.

RESULTS

There were 222 nosocomial infections identified among 146 patients, yielding an infection rate of 0.8 infections per 100 patient-days. Surgical-site infection was the most common site-specific infection, accounting for 31.1% of all infections. The incidence of intravenous catheter-related bloodstream infection was 1.6 infections per 100 catheter-days. The bladder catheter-related urinary tract infection rate was 2.8 infections per 100 catheter-days. The rate of ventilator-associated pneumonia was 3.2 infections per 100 ventilator-days. The incidence of infection correlated well with injury severity. The infection incidence rate ratios for one severity category increment of ISS, NISS, RTS, and TRISS were 1.65 (95% confidence interval [CI95], 1.42 to 1.92), 1.79 (CI95, 1.55 to 2.05), 1.64 (CI95 1.43 to 1.88), and 1.32 (CI95, 1.14 to 1.52), respectively.

CONCLUSIONS

Surgical-site infection was the most common site-specific nosocomial infection. The NISS might be the most appropriate severity scoring system for adjustment of infection rates in trauma patients.

Infection control in the ICU

Nosocomial infections (NIs) now concern 5 to 15% of hospitalized patients and can lead to complications in 25 to 33% of those patients admitted to ICUs. The most common causes are pneumonia related to mechanical ventilation, intra-abdominal infections following trauma or surgery, and bacteremia derived from intravascular devices. This overview is targeted at ICU physicians to convince them that the principles of infection control in the ICU are based on simple concepts and that the application of preventive strategies should not be viewed as an administrative or constraining control of their activity but, rather, as basic measures that are easy to implement at the bedside. A detailed knowledge of the epidemiology, based on adequate surveillance methodologies, is necessary to understand the pathophysiology and the rationale of preventive strategies that have been demonstrated to be effective. The principles of general preventive measures such as the implementation of standard and isolation precautions, and the control of antibiotic use are reviewed. Specific practical measures, targeted at the practical prevention and control of ventilator-associated pneumonia, sinusitis, and bloodstream, urinary tract, and surgical site infections are detailed. Recent data strongly confirm that these strategies may only be effective over prolonged periods if they can be integrated into the behavior of all staff members who are involved in patient care. Accordingly, infection control measures are to be viewed as a priority and have to be integrated fully into the continuous process of improvement of the quality of care.

[Annual incidence and risk factors for nosocomial bacterial infections in an acute care geriatric unit]

PURPOSE

Elderly inpatients are particularly exposed to the risk of nosocomial infections, thus the study of their risk factors and consequences is of interest.

METHODS

Among 1,565 subjects referred to a short-term geriatric unit, patients hospitalised for a year for an acute event and unable to move themselves were followed up for the occurrence of nosocomial infections.

RESULTS

Among these 402 immobilised patients (age: 86.3 +/- 7.6 years), 102 nosocomial infections occurred in 91 patients (22.6%), whereas the estimation of the incidence in the total hospitalised population (1,565 subjects, age: 85.1 +/- 6.2 years) was 9.4% (95% confidence interval [CI] 8.3-11.2). Forty-seven point seven percent of nosocomial infections were urinary tract nosocomial infections, 27.5% were lower respiratory nosocomial infections, 9.2% were cutaneous nosocomial infections, 7.3% were septicaemia and 8.2% were of unknown origin. The relative risk (RR) of NI linked to functional dependency for mobility was 5.5 (95% CI: 3.93-7.7, P < 0.001). Other risk factors were: for all nosocomial infections: cancer diagnosis (RR 1.1, 95% CI: 1.1-1.2, P = 0.01); and respectively for urinary tract NI: bladder indwelling (RR 4.8, 95% CI: 2.9-7.7, P < 0.001), pulmonary NI: swallowing disorders (RR 5.4, 95% CI: 2.8-10.5, P < 0.001); and septicaemia: venous catheter (RR 5.4, 95% CI: 1.3-23.3, P = 0.002). NI were associated with an increased length of stay (22.1 +/- 11.7 days in infected patients vs 16.3 +/- 9.5 days in immobilised non-infected subjects, P < 0.001). The mean length of stay for the 1,565 subjects was 10.3 +/- 7.6 days. Death was attributed to nosocomial infections in 13 subjects. In conclusion, functional dependency for mobility, bladder indwelling, venous catheter, swallowing disorders and diagnosis of cancer were risk factors for nosocomial infections in hospitalised elderly subjects in an acutecare setting.

The role of the infection control professional in the intensive care unit

By design, multiple invasive procedures are performed in the intensive care unit (ICU). Although great care is taken to control morbidity and forestall mortality, this invasive environment places ICU patients and staff at immense risk of nosocomial (hospital-acquired) infection. The role of the infection control professional (ICP) within the ICU involves data collection, dissemination of data with feedback, expertise in the investigation of outbreaks, product evaluation proficiency, and fluid consultation aptitude. This article provides an inside view of how specialty infection control staff and ICU staff can optimize infection control to decrease the incidence of nosocomial infections. A description of what the ICP does not do in the ICU is also given, providing a clear guideline for how these two disciplines can best provide a safe intensive care experience.

Methodological principles of case-control studies that analyzed risk factors for antibiotic resistance: a systematic review

Case-control studies that analyze the risk factors for antibiotic-resistant organisms have varied epidemiological methodologies, which may lead to biased estimates of antibiotic risk factors. A systematic review of case-control studies that analyzed risk factors for antibiotic-resistant organisms addressed 3 methodological principles: method of control group selection, adjustment for time at risk, and adjustment for comorbid illness. A total of 406 abstracts were reviewed. Thirty-seven studies met the inclusion and exclusion criteria and were reviewed and evaluated for the 3 methodological principles. Thirteen (35%) of 37 studies chose the preferred control group. Eleven adjusted for time at risk. Twenty-seven adjusted for comorbid illness. Future studies need to consider more closely the optimization of control group selection, adjusting for confounding caused by time at risk, and adjusting for confounding caused by comorbid illness.

New technology for detecting multidrug-resistant pathogens in the clinical microbiology laboratory

Northwestern Memorial Hospital instituted in-house molecular typing to rapidly assess microbial clonality and integrated this typing into an infection control program. We compared data on nosocomial infections collected during 24 months before and 60 months after implementing the new program. During the intervention period, infections per 1,000 patient-days fell 13% (p=0.002) and the percentage of hospitalized patients with nosocomial infections decreased 23% (p=0.000006). In our hospital, the percentage of patients with nosocomial infections is 43% below the U.S. rate. Our typing laboratory costs approximately $400,000 per year, a savings of $5.00 for each dollar spent.

Risk assessment and standardized nosocomial infection rate in critically ill children

OBJECTIVES

To develop and validate a pediatric nosocomial infection risk (PNIR) assessment model, and to compare the daily trends in risk factors between patients with nosocomial infection (cases) and without nosocomial infection (controls) in the pediatric intensive care unit (ICU).

DESIGN

Prospective cohort.

SETTING

A 16-bed pediatric ICU in an urban, university-affiliated, multidisciplinary, regional referral center.

PATIENTS

Patients available for study included consecutive admissions to the unit between May 1, 1992, and April 30, 1993, and between May 9, 1995, and December 11, 1995. Patients from both data collection periods were pooled and randomly divided into training (70%) and validation (30%) samples.

MEASUREMENTS AND MAIN RESULTS

In the logistic regression analysis using admission day data, three factors were shown to remain as independent risk factors. Invasive device use, parenteral nutrition, and the interaction between severity of illness-modified Pediatric Risk of Mortality III-24 score and postoperative care were associated with 2, 6, and 1.5 times the risk of developing nosocomial infection, respectively. This PNIR model performed well in both the training and validation samples as indicated by the goodness-of-fit test, which evaluated standardized nosocomial infection rates (observed vs. predicted nosocomial infection rates). The internal validity of the PNIR model was good. In trend analysis, severity of illness and invasive device use appear to have similar trend patterns, during the first week of pediatric ICU stay. There was no difference in any of these risk factors between cases and controls after 7 days of pediatric ICU stay.

CONCLUSIONS

The PNIR assessment model incorporates intrinsic factors, such as patient severity of illness, and extrinsic factors contributing to the development of nosocomial infection in this high-risk population. The methodology using intrinsic and extrinsic factors to adjust for nosocomial infections should be taken into consideration when evaluating interhospital comparison of nosocomial infection rates, quality assessment, intervention strategies, and use of treatment modalities.

Nosocomial infections in medical intensive care units in the United States. National Nosocomial Infections Surveillance System

OBJECTIVE

To describe the epidemiology of nosocomial infections in medical intensive care units (ICUs) in the United States.

DESIGN

Analysis of ICU surveillance data collected through the National Nosocomial Infections Surveillance (NNIS) System between 1992 and 1997.

SETTING

Medical ICUs in the United States.

PATIENTS

A total of 181,993 patients.

MEASUREMENTS AND MAIN RESULTS

Nosocomial infections were analyzed by infection site and pathogen distribution. Urinary tract infections were most frequent (31%), followed by pneumonia (27%) and primary bloodstream infections (19%). Eighty-seven percent of primary bloodstream infections were associated with central lines, 86% of nosocomial pneumonia was associated with mechanical ventilation, and 95% of urinary tract infections were associated with urinary catheters. Coagulase-negative staphylococci (36%) were the most common bloodstream infection isolates, followed by enterococci (16%) and Staphylococcus aureus (13%). Twelve percent of bloodstream isolates were fungi. The most frequent isolates from pneumonia were Gram-negative aerobic organisms (64%). Pseudomonas aeruginosa (21%) was the most frequently isolated of these. S. aureus (20%) was isolated with similar frequency. Candida albicans was the most common single pathogen isolated from urine and made up just over half of the fungal isolates. Fungal urinary infections were associated with asymptomatic funguria rather than symptomatic urinary tract infections (p < .0001). Certain pathogens were associated with device use: coagulase-negative staphylococci with central lines, P. aeruginosa and Acinetobacter species with ventilators, and fungal infections with urinary catheters. Patient nosocomial infection rates for the major sites correlated strongly with device use. Device exposure was controlled for by calculating device-associated infection rates for bloodstream infections, pneumonia, and urinary tract infections by dividing the number of device-associated infections by the number of days of device use. There was no association between these device-associated infection rates and number of hospital beds, number of ICU beds, or length of stay. There is a considerable variation within the distribution of each of these infection rates.

CONCLUSIONS

The distribution of sites of infection in medical ICUs differed from that previously reported in NNIS ICU surveillance studies, largely as a result of anticipated low rates of surgical site infections. Primary bloodstream infections, pneumonia, and urinary tract infections associated with invasive devices made up the great majority of nosocomial infections. Coagulase-negative staphylococci were more frequently associated with primary bloodstream infections than reported from NNIS ICUs of all types in the 1980s, and enterococci were a more frequent isolate from bloodstream infections than S. aureus. Fungal urinary tract infections, often asymptomatic and associated with catheter use, were considerably more frequent than previously reported. Invasive device-associated infections were associated with specific pathogens. Although device-associated site-specific infection rates are currently our most useful rates for performing comparisons between ICUs, the considerable variation in these rates between ICUs indicates the need for further risk adjustment.

APACHE II and ISS scores as predictors of nosocomial infections in trauma patients

BACKGROUND

Nosocomial infections affect more than 2 million patients annually in the United States at a cost of $4.5 billion. The aim of this study is to identify the role of the APACHE II score and the Injury Severity Scale (ISS) as independent predictors of nosocomial infections in trauma patients admitted to the intensive care unit (ICU).

METHODS

A retrospective chart review of 113 trauma patients admitted to the ICU was conducted by an infectious disease physician. Demographic data and incidence of nosocomial infections were recorded. Multivariate logistic regression analysis was used to determine variables that are predictive of the occurrence of nosocomial infections.

RESULTS

Presence or absence of intubation, ICU length of stay, APACHE II score, and ISS were related to the presence of infections; however, only the ICU length of stay was an independent predictor of a nosocomial infection, with an odds ratio of 1.81. By linear regression, 17% of the variance in the ICU duration of stay was a result of the APACHE II score in patients with a score >/=5.

CONCLUSION

APACHE II score and ISS score were not good predictors of the incidence of nosocomial infections in trauma patients admitted to the ICU, but the APACHE II score has a modest correlation with the duration of stay in the ICU. A stratified cohort study could identify the subset of patients for which the APACHE II score predicts a prolonged stay in the ICU, thus an increased risk of infection.

The prevalence of colonization with vancomycin-resistant Enterococcus at a Veterans' Affairs institution

OBJECTIVE

To study vancomycin-resistant Enterococcus (VRE) prevalence, risk factors, and clustering among hospital inpatients.

DESIGN

Rectal-swab prevalence culture survey conducted from February 5 to March 22, 1996.

SETTING

The Veterans' Affairs Medical Center, Atlanta, Georgia.

PATIENTS

Hospital (medical and surgical) inpatients.

RESULTS

The overall VRE prevalence was 29% (42/147 patients). The VRE prevalence was 52% (38/73 patients) among patients who had received at least one of six specific antimicrobials during the preceding 120 days, compared with only 5% (4/74) among those who had not received the antimicrobials (relative risk, 9.6; P<.001). The longer the period (up to 120 days) during which antimicrobial use was studied, the more closely VRE status was predicted. Among 67 hospital patients in 28 multibed rooms, clustering of VRE among current roommates was not found.

CONCLUSIONS

At this hospital with relatively high VRE prevalence, VRE colonization was related to antibiotic use but not to roommate VRE status. In hospitals with a similar VRE epidemiology, obtaining cultures from roommates of VRE-positive patients may not be as efficient a strategy for identifying VRE-colonized patients as obtaining screening cultures from patients who have received antimicrobials.

Development of the Sternal Wound Infection Prediction Scale

OBJECTIVE

To develop an instrument to reliably predict the occurrence of sternal wound infection (SWI).

DESIGN

Instrument development with retrospective chart review.

SETTING

Southwestern university-affiliated medical center.

PATIENTS

One hundred eighty-five adults who underwent cardiac surgery. SWI developed in 94 patients, and 91 remained infection free. In phase 1, there were 82 subjects: SWI developed in 41, and 41 remained infection free. In phase 2, there were 103 subjects: SWI developed in 53, and 50 remained infection free.

OUTCOME MEASURE

Development of a postoperative SWI.

INTERVENTION

The Sternal Wound Infection Prediction Scale (SWIPS) was developed in 2 phases. Phase 1 consisted of designing the SWIPS with use of 19 risk factors most often identified with SWI and revising this scale (SWIPS-R) with use of 21 risk factors. Eighty-two patient records were reviewed. After determining the mean cutscores in phase 1, phase 2 provided cross-validation results with use of 103 additional patient records.

RESULTS

The SWIPS produced 62.1% correct predictions of infection and noninfection; whereas the SWIPS-R produced 72.8% correct predictions. Phase 2 cross-validation results for the 21 risk factors demonstrated that 62.1% and 72.8% of the patients were correctly diagnosed using the SWIPS and SWIPS-R, respectively. A multivariate logistic regression was also performed on the risk factors to predict infection/noninfection groups for all 185 patients. A reduced logistic regression model included 9 of the risk factors and correctly classified 76.2% of the subjects.

CONCLUSIONS

The SWIPS-R, with 21 risk factors, and the logistic regression model, with 12 risk factors, provided excellent classification rates of infection/noninfection. However, more data need to be collected to further strengthen reliability.

Comparing Nosocomial Infection Rates Among Surgical Intensive-Care Units: The Importance of Separating Cardiothoracic and General Surgery Intensive-Care Units

Among surgical intensive-care units (ICUs), we assessed differences in risk-adjusted nosocomial infection rates between cardiothoracic (CT) and general surgery ICUs, using National Nosocomial Infection Surveillance data from 1987 to 1995. Device-associated rates and average length of stay were significantly lower in CT ICUs. Comparisons of risk-adjusted nosocomial infection rates among CT ICUs should be made separately from rates from general surgery ICUs.

Requirements for infrastructure and essential activities of infection control and epidemiology in hospitals: A consensus panel report. Society for Healthcare Epidemiology of America

The scientific basis for claims of efficacy of nosocomial infection surveillance and control programs was established by the Study on the Efficacy of Nosocomial Infection Control project. Subsequent analyses have demonstrated nosocomial infection prevention and control programs to be not only clinically effective but also cost-effective. Although governmental and professional organizations have developed a wide variety of useful recommendations and guidelines for infection control, and apart from general guidance provided by the Joint Commission on Accreditation of Healthcare Organizations, there are surprisingly few recommendations on infrastructure and essential activities for infection control and epidemiology programs. In April 1996, the Society for Healthcare Epidemiology of America established a consensus panel to develop recommendations for optimal infrastructure and essential activities of infection control and epidemiology programs in hospitals. The following report represents the consensus panel's best assessment of needs for a healthy and effective hospital-based infection control and epidemiology program. The recommendations fall into eight categories: managing critical data and information; setting and recommending policies and procedures; compliance with regulations, guidelines, and accreditation requirements; employee health; direct intervention to prevent transmission of infectious diseases; education and training of healthcare workers; personnel resources; and nonpersonnel resources. The consensus panel used an evidence-based approach and categorized recommendations according to modifications of the scheme developed by the Clinical Affairs Committee of the Infectious Diseases Society of America and the Centers for Disease Control and Prevention's Hospital Infection Control Practices Advisory Committee.

Hospital-acquired infections in the United States. The importance of interhospital comparisons

To use infection rates as a basis for measuring quality of care, the rates must be meaningful for interhospital comparison. A crude, overall nosocomial infection rate of a hospital provides no means of adjustment for patients' intrinsic or extrinsic risks. Before interhospital comparison, rates should be adjusted for nosocomial infection risk factors. Interhospital comparison of rates requires that a hospital participate in a multicenter surveillance system or aggregated national database. This article outlines a series of questions for hospital administrations to pose before entering such an endeavor.

Improving hospital-acquired infection rates: the CDC experience

BACKGROUND

The National Nosocomial Infections Surveillance (NNIS) System, begun in 1970 by the Centers for Disease Control to collect data on hospital-acquired infections, is one of the oldest continuously operating clinical performance indicator systems in the United States. Growth of the system, from 19 to 230 hospitals, has been accompanied by developments such as the evolution from hospitalwide to targeted surveillance, improved data processing and telecommunications for data collection and reporting, and risk adjustment.

ELEMENTS OF A SUCCESSFUL SYSTEM

The NNIS System provides specific, standardized methods for data collection and uses device-associated, device-day rates to risk adjust the data and make it meaningful for interhospital comparison. The system has been used as a tool for improving quality of care through prevention of nosocomial infections. For example, an 800-bed teaching hospital's rate of ventilator-associated nosocomial pneumonia in the surgical intensive care unit-49.5 infections per 1,000 ventilator days-was in excess of the 90th percentile. Improvements in care, including changing tubing and cascades every 48 hours and Ambu bags every 24 hours, as well as increased clinical evaluation of patients, was followed 12 months later by a decrease to 25.8 infections, well below the 90th percentile.

INFORMATION DISSEMINATION

Since 1992, staff from NNIS hospitals have met in a biennial conference to learn about advances in nosocomial infection surveillance and to share information with one another on infection control and quality improvement programs.

CONCLUSIONS

The NNIS experience can be used as a source of guidance for assessing the effectiveness and utility of other indicator systems.