Nosocomial pneumonia. Diagnosis and prevention

Silver-coated endotracheal tubes for prevention of ventilator-associated pneumonia in critically ill patients

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the most common nosocomial infections in intubated and mechanically ventilated patients. Endotracheal tubes (ETTs) appear to be an independent risk factor for VAP. Silver-coated ETTs slowly release silver cations. It is these silver ions that appear to have a strong antimicrobial effect. Because of this antimicrobial effect of silver, silver-coated ETTs could be an effective intervention to prevent VAP in people who require mechanical ventilation for 24 hours or longer.

OBJECTIVES

Our primary objective was to investigate whether silver-coated ETTs are effective in reducing the risk of VAP and hospital mortality in comparison with standard non-coated ETTs in people who require mechanical ventilation for 24 hours or longer. Our secondary objective was to ascertain whether silver-coated ETTs are effective in reducing the following clinical outcomes: device-related adverse events, duration of intubation, length of hospital and intensive care unit (ICU) stay, costs, and time to VAP onset.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014 Issue 10, MEDLINE, EMBASE, EBSCO CINAHL, and reference lists of trials. We contacted corresponding authors for additional information and unpublished studies. We did not impose any restrictions on the basis of date of publication or language. The date of the last search was October 2014.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) and quasi-randomized trials that evaluated the effects of silver-coated ETTs or a combination of silver with any antimicrobial-coated ETTs with standard non-coated ETTs or with other antimicrobial-coated ETTs in critically ill people who required mechanical ventilation for 24 hours or longer. We also included studies that evaluated the cost-effectiveness of silver-coated ETTs or a combination of silver with any antimicrobial-coated ETTs.

DATA COLLECTION AND ANALYSIS

Two review authors (GT, HV) independently extracted the data and summarized study details from all included studies using the specially designed data extraction form. We used standard methodological procedures expected by The Cochrane Collaboration. We performed meta-analysis for outcomes when possible.

MAIN RESULTS

We found three eligible randomized controlled trials, with a total of 2081 participants. One of the three included studies did not mention the amount of participants and presented no outcome data. The 'Risk of bias' assessment indicated that there was a high risk of detection bias owing to lack of blinding of outcomes assessors, but we assessed all other domains to be at low risk of bias. Trial design and conduct were generally adequate, with the most common areas of weakness in blinding. The majority of participants were included in centres across North America. The mean age of participants ranged from 61 to 64 years, and the mean duration of intubation was between 3.2 and 7.7 days. One trial comparing silver-coated ETTs versus non-coated ETTs showed a statistically significant decrease in VAP in favour of the silver-coated ETT (1 RCT, 1509 participants; 4.8% versus 7.5%, risk ratio (RR) 0.64, 95% confidence interval (CI) 0.43 to 0.96; number needed to treat for an additional beneficial outcome (NNTB) = 37; low-quality evidence). The risk of VAP within 10 days of intubation was significantly lower with the silver-coated ETTs compared with non-coated ETTs (1 RCT, 1509 participants; 3.5% versus 6.7%, RR 0.51, 95% CI 0.31 to 0.82; NNTB = 32; low-quality evidence). Silver-coated ETT was associated with delayed time to VAP occurrence compared with non-coated ETT (1 RCT, 1509 participants; hazard ratio 0.55, 95% CI 0.37 to 0.84). The confidence intervals for the results of the following outcomes did not exclude potentially important differences with either treatment. There were no statistically significant differences between groups in hospital mortality (1 RCT, 1509 participants; 30.4% versus 26.6%, RR 1.09, 95% CI 0.93 to 1.29; low-quality evidence); device-related adverse events (2 RCTs, 2081 participants; RR 0.65, 95% CI 0.37 to 1.16; low-quality evidence); duration of intubation; and length of hospital and ICU stay. We found no clinical studies evaluating the cost-effectiveness of silver-coated ETTs.

AUTHORS' CONCLUSIONS

This review provides limited evidence that silver-coated ETT reduces the risk of VAP, especially during the first 10 days of mechanical ventilation.

Ventilator-Associated Pneumonia at a Tertiary-Care Center in a Developing Country: Incidence, Microbiology, and Susceptibility Patterns of Isolated Microorganisms

Objective:

Ventilator-associated pneumonia (VAP) complicates the course of up to 24% of intubated patients. Data from the Middle East are scarce. The objective of this study was to evaluate the incidence, microbiology, and antimicrobial susceptibility patterns of isolated microorganisms in VAP in a developing country.

Design:

Prospective observational cohort study.

Setting:

The American University of Beirut Medical Center, a tertiary-care center that serves as a major referral center for Lebanon and neighboring countries.

Patients:

All patients admitted to the intensive care and respiratory care units from March to September 2001, and who had been receiving mechanical ventilation for at least 48 hours, were included in the study. Results of samples submitted for culture were recorded and antimicrobial susceptibility testing of isolated pathogens was performed.

Results:

Seventy patients were entered into the study. The incidence of VAP was 47%. Gram-negative bacilli accounted for 83% of all isolates. The most commonly identified organism was Acinetobacter anitratus, followed by Pseudomonas aeruginosa. Fifty percent of all gram-negative bacterial isolates were classified as antibiotic resistant. Compared with patients without VAP, patients with VAP remained intubated for a longer period and stayed in the intensive care unit longer. VAP was not associated with an increased mortality rate.

Conclusion:

Compared with other studies, the results from this referral center in Lebanon indicate a higher incidence of VAP and a high prevalence of resistant organisms. These data are relevant because they direct the choice of empiric antibiotic therapy for VAP.

Randomized, controlled trial on tracheal colonization of ventilated infants: can gravity prevent ventilator-associated pneumonia?

OBJECTIVE

The goal was to test the hypothesis that intubated infants positioned on their sides would be less likely to contract bacterial colonization in their tracheae, compared with those positioned supine.

METHODS

We conducted a prospective, randomized, controlled trial with 60 intubated infants; 30 infants were positioned supine (supine group), and 30 infants were maintained in the lateral position (lateral group). Tracheal aspirates were cultured and bacterial colony counts were recorded after 48 hours and after 5 days of mechanical ventilation.

RESULTS

After 2 days, the numbers of positive tracheal cultures in the supine group (67%) and in the lateral group (47%) showed no statistical difference. After 5 days of mechanical ventilation, tracheal cultures differed significantly between groups. Cultures were positive for 26 infants (87%) in the supine group and 9 infants (30%) in the lateral group. Compared with the lateral group, more infants in the supine group experienced increased colony counts or had new organisms in their tracheal aspirates over time (21 vs 8 infants). The most common organisms isolated from tracheal aspirates in both groups were Gram-negative rods.

CONCLUSIONS

Respiratory contamination is very common among ventilated infants. Therefore, judicious use of mechanical ventilation cannot be overemphasized. Gravitational force can ameliorate the onset of respiratory colonization. The mechanism and clinical applicability of such observations need to be explored further.

Pseudomonas aeruginosa induces localized immunosuppression during pneumonia

Hospital-acquired bacterial pneumonia is a common and serious complication of modern medical care. Many aspects of such infections remain unclear, including the mechanisms by which invading pathogens resist clearance by the innate immune response and the tendency of the infections to be polymicrobial. Here, we used a mouse model of infection to show that Pseudomonas aeruginosa, a leading cause of hospital-acquired pneumonia, interferes with the ability of recruited phagocytic cells to eradicate bacteria from the lung. Early in infection, phagocytic cells, predominantly neutrophils, are recruited to the lungs but are incapacitated when they enter the airways by the P. aeruginosa toxin ExoU. The resulting paucity of functioning phagocytes allows P. aeruginosa to persist within the lungs and results in local immunosuppression that facilitates superinfection with less-pathogenic bacteria. Together, our results provide explanations for previous reports linking ExoU-secreting P. aeruginosa with more severe pulmonary infections and for the tendency of hospital-acquired pneumonia to be polymicrobial.

Effectiveness of an Educational Program to Reduce Ventilator-Associated Pneumonia in a Tertiary Care Center in Thailand: A 4-Year Study

BACKGROUND

Ventilator-associated pneumonia (VAP) is considered to be an important cause of infection-related death and morbidity in intensive care units (ICUs). We sought to determine the long-term effect of an educational program to prevent VAP in a medical ICU (MICU).

METHODS

A 4-year controlled, prospective, quasi-experimental study was conducted in an MICU, surgical ICU (SICU), and coronary care unit (CCU) for 1 year before the intervention (period 1), 1 year after the intervention (period 2), and 2 follow-up years (period 3). The SICU and CCU served as control ICUs. The educational program involved respiratory therapists and nurses and included a self-study module with preintervention and postintervention assessments, lectures, fact sheets, and posters.

RESULTS

Before the intervention, there were 45 episodes of VAP (20.6 cases per 1000 ventilator-days) in the MICU, 11 (5.4 cases per 1000 ventilator-days) in the SICU, and 9 (4.4 cases per 1000 ventilator-days) in the CCU. After the intervention, the rate of VAP in the MICU decreased by 59% (to 8.5 cases per 1000 ventilator-days; P=.001) and remained stable in the SICU (5.6 cases per 1000 ventilator-days; P=.22) and CCU (4.8 cases per 1000 ventilator-days; P=.48). The rate of VAP in the MICU continued to decrease in period 3 (to 4.2 cases per 1000 ventilator-days; P=.07), and rates in the SICU and CCU remained unchanged. Compared with period 1, the mean duration of hospital stay in the MICU was reduced by 8.5 days in period 2 (P<.001) and by 8.9 days in period 3 (P<.001). The monthly hospital antibiotic costs of VAP treatment and the hospitalization cost for each patient in the MICU in periods 2 and 3 were also reduced by 45%-50% (P<.001) and 37%-45% (P<.001), respectively.

CONCLUSIONS

A focused education intervention resulted in sustained reductions in the incidence of VAP, duration of hospital stay, cost of antibiotic therapy, and cost of hospitalization.

Contaminated oral intubation equipment associated with an outbreak of carbapenem-resistant pseudomonas in an intensive care unit

Twenty intensive care patients were diagnosed as infected or colonized by Pseudomonas aeruginosa within a one-month period; a rate three to four times higher than the typical background frequency of this infection in the intensive care unit (ICU). Patients with positive respiratory specimens were mechanically ventilated, which included re-used disinfected bite blocks during intubation. Fourteen specimens from 20 positive patients originated in the respiratory tract. Seven clonal variants were isolated and identified as originating from the same strain by pulsed-field analysis. These isolates were also matched to the strain detected on the re-used bite blocks, which had been disinfected with 140ppm sodium hydrochloride. Notably, Staphylococcus aureus was also detected on bite blocks sterilized with ethylene dioxide, indicating incomplete disinfection. In immunocompromised patients, re-use of bite blocks during intubation must be prohibited. Single-use kits or intubation without the use of bite blocks is recommended.

Ventilator-associated pneumonia: monotherapy is optimal if chosen wisely

Traditionally, ventilator-associated pneumonia (VAP) has been treated either with double drug therapy or with monotherapy. Double drug therapy has been used to increase spectrum, for possible synergy, and to decrease the emergence of resistance. VAP therapy should be directed primarily against Pseudomonas aeruginosa, which also provides aerobic Gram-negative coverage, the usual pathogens in VAP. The potent anti-P. aeruginosa antibiotics available today have sufficient activity that double drug coverage is unnecessary. Double drug therapy does not decrease resistance if a 'high resistance potential' antibiotic is used in the combination. The study by Damas and colleagues in this issue of Critical Care supports monotherapy for VAP. Optimal therapy for VAP involves selecting a potent anti-P. aeruginosa antibiotic with a 'low resistance potential' that minimizes drug-drug interactions, minimizes resistance, and is cost effective. Monotherapy of VAP should be the standard of care.

Ventilator-associated pneumonia: diagnosis, treatment, and prevention

While critically ill patients experience a life-threatening illness, they commonly contract ventilator-associated pneumonia. This nosocomial infection increases morbidity and likely mortality as well as the cost of health care. This article reviews the literature with regard to diagnosis, treatment, and prevention. It provides conclusions that can be implemented in practice as well as an algorithm for the bedside clinician and also focuses on the controversies with regard to diagnostic tools and approaches, treatment plans, and prevention strategies.

Enfoque clínico del paciente con neumonía asociada a ventilación mecánica

Ventilator-associated pneumonia (VAP) is the most frequent infection in the intensive care unit. The importance of this entity lies not only in its high incidence but also in the significant mortality it produces. Therefore, a new episode of VAP should be clinically suspected when new or persistent radiological opacity, purulent respiratory secretions and other signs of sepsis (fever and leukocytosis) are present. In these patients, at the very least, tracheal aspirate samples with quantitative culture and direct staining should be immediately obtained, followed by prompt initiation of empirical broad-spectrum antibiotic therapy. The choice of initial antibiotic therapy should be patient-based, taking into account the risk factors associated especially with VAP caused by Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus, because of the high associated mortality. To evaluate resolution of VAP, we analyze various clinical variables (based mainly on resolution of fever and hypoxemia) and microbiologic information. Once the microorganism responsible for VAP has been isolated, antibiotic therapy can be adapted, based on de-escalation, to reduce the emergence of resistant bacteria. Recent studies suggest that shorter antibiotic regimens reduce the emergence of antibiotic-resistant pathogens, cost and adverse events.

Nosocomial infections in a Dutch neonatal intensive care unit: surveillance study with definitions for infection specifically adapted for neonates

The incidence of nosocomial infection in neonatal intensive care units (NICUs) is high compared with other wards. However, no definitions for hospital-acquired infection are available for NICUs. The aim of this study was to measure the incidence of such infections and to identify risk factors in the NICU of the VU University Medical Center, which serves as a level III regional NICU. For this purpose, a prospective surveillance was performed in 1998-2000. We designed definitions by adjusting the current definitions of the Centers for Disease Control and Prevention (CDC) for children <1 year of age. Birth weight was stratified into four categories and other baseline risk factors were dichotomized. Analysis of risk factors was performed by Cox regression with time-dependent variables. The relationship between the Clinical Risk Index for Babies (CRIB) and nosocomial infection was investigated. Furthermore, for a random sample of cases, we determined whether bloodstream infection and pneumonia would also have been identified with the CDC definitions. Seven hundred and forty-two neonates were included in the study. One hundred and ninety-one neonates developed 264 infections. Bloodstream infection (N=138, 14.9/1000 patient-days) and pneumonia (N=69, 7.5/1000 patient-days) were the most common infections. Of bloodstream infections, 59% were caused by coagulase-negative staphylococci; in 21% of neonates, blood cultures remained negative. In 25% of pneumonias, Enterobacteriaceae were the causative micro-organisms; 26% of cultures remained negative. Compared with the Nosocomial Infections Surveillance System (NNIS) of the CDC, our device utilization ratios and device-associated nosocomial infection rates were high. The main risk factors for bloodstream infection were birth weight [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.45-2.17] and parenteral feeding with hospital-pharmacy-produced, all-in-one mixture 'Minimix' (HR 3.69, 95%CI 2.03-6.69); administration of intravenous antibiotics (HR 0.39, 95%CI 0.26-0.56) was a protective risk factor. The main risk factors for pneumonia were low birth weight (HR 1.37, 95%CI 1.01-1.85) and mechanical ventilation (HR 9.69, 95%CI 4.60-20.4); intravenous antibiotics were protective (HR 0.37, 95%CI 0.21-0.64). In a subcohort of 232 very-low-birthweight neonates, the CRIB was not predictive for infection. With the CDC criteria, only 75% (21/28) of bloodstream infections and 87.5% of pneumonias (21/24) would have been identified. In conclusion, our local nosocomial infection rates are high compared with those of NICUs participating in the NNIS. This can be partially explained by: (1) the use of our definitions for nosocomial infection, which are more suitable for this patient category; and (2) the high device utilization ratios.

Treatment and control of severe infections caused by multiresistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections. Severe infections, such as pneumonia or bacteraemia, are associated with high mortality rates and are often difficult to treat, as the repertoire of useful anti-pseudomonal agents is limited (some beta-lactams, fluoroquinolones and aminoglycosides, and the polymyxins as last-resort drugs); moreover, P. aeruginosa exhibits remarkable ability to acquire resistance to these agents. Acquired resistance arises by mutation or acquisition of exogenous resistance determinants and can be mediated by several mechanisms (degrading enzymes, reduced permeability, active efflux and target modification). Overall, resistance rates are on the increase, and may be different in different settings, so that surveillance of P. aeruginosa susceptibility is essential for the definition of empirical regimens. Multidrug resistance is frequent, and clinical isolates resistant to virtually all anti-pseudomonal agents are increasingly being reported. Monotherapy is usually recommended for uncomplicated urinary tract infections, while combination therapy is normally recommended for severe infections, such as bacteraemia and pneumonia, although, at least in some cases, the advantage of combination therapy remains a matter of debate. Antimicrobial use is a risk factor for P. aeruginosa resistance, especially with some agents (fluoroquinolones and carbapenems), and interventions based on antimicrobial rotation and restriction of certain agents can be useful to control the spread of resistance. Similar measures, together with the prudent use of antibiotics and compliance with infection control measures, are essential to preserve the efficacy of the currently available anti-pseudomonal agents, in view of the dearth, in the near future, of new options against multidrug-resistant P. aeruginosa strains.

The attributable cost and length of hospital stay because of nosocomial pneumonia in intensive care units in 3 hospitals in Argentina: a prospective, matched analysis

BACKGROUND

No information is available on the financial impact of nosocomial pneumonia in Argentina. To calculate the cost of nosocomial pneumonia in intensive care units, a 5-year, matched cohort study was undertaken at 3 hospitals in Argentina.

SETTING

Six adult intensive care units (ICU).

METHODS

Three hundred seven patients with nosocomial pneumonia (exposed) and 307 patients without nosocomial pneumonia (unexposed) were matched for hospital, ICU type, year admitted to study, length of stay more than 7 days, sex, age, antibiotic use, and average severity of illness score (ASIS). The patient's length of stay (LOS) in the ICU was obtained prospectively in daily rounds, the cost of a day was provided by the hospital's finance department, and the cost of antibiotics prescribed for nosocomial pneumonia was provided by the hospital's pharmacy department.

RESULTS

The mean extra LOS for 307 cases (compared with controls) was 8.95 days, the mean extra antibiotic defined daily doses (DDD) was 15, the mean extra antibiotic cost was $996, the mean extra total cost was $2255, and the extra mortality was 30.3%.

CONCLUSIONS

Nosocomial pneumonia results in significant patient morbidity and consumes considerable resources. In the present study, patients with nosocomial pneumonia had significant prolongation of hospitalization, cost, and a high extra mortality. The present study illustrates the potential cost savings of introducing interventions to reduce nosocomial pneumonia. To our knowledge, this is the first study evaluating this issue in Argentina.

Pneumonia in patients who require prolonged mechanical ventilation

Nosocomial pneumonia is the most important infectious disease in patients who require prolonged mechanical ventilation. Understanding of the etiology helps to prevent ventilator-associated pneumonia (VAP). VAP can develop in four ways: by aspiration, inhalation, hematogenous spread and by contiguous spread. The two most common are aspiration from the oropharyngeal region and inhalation, usually from manipulation of tubing or infected equipment. VAP is prevented by hand-washing, keeping the head of the bed at 45 and, in some cases, by treating the surface bacteria which usually cause VAP. Sputum can be used for the diagnosis of VAP in most of these patients instead of invasive bronchoscopy. However, if the patients are critically ill, then bronchoscopy is used. Treatment in these patients depends on the bacteria. Pseudomonas is treated by two drugs (beta-lactam plus a quinolone or aminoglycoside), Acinetobacteria by ampicillin/sulbactam or carbapenam, extended-spectrum beta-lactam-producing bacteria by carbapenums, and Staphylococcus by vancomycin or linezolid.

Antiseptic impregnated endotracheal tubes for the prevention of bacterial colonization

The effect of endotracheal tubes (ETTs) impregnated with chlorhexidine (CHX) and silver carbonate (antiseptic ETTs) against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacter aerogenes [organisms associated with ventilator-associated pneumonia (VAP)], was evaluated in a laboratory airway model. Antiseptic ETTs and control ETTs (unimpregnated) were inserted in culture tubes half-filled with agar media (airway model) previously contaminated at the surface with 10(8) cfu/mL of the selected test organism. After five days of incubation, bacterial colony counts on all ETT segments were determined. Swabs of proximal and distal ends of the agar tract in antiseptic and control models were subcultured. The initial and residual CHX levels, (five days post-implantation in the model) were determined. Cultures of antiseptic ETTs revealed colonization by the tested pathogens ranging from 1-100 cfu/tube, compared with approximately 10(6) cfu/tube for the control ETTs (P < 0.001). Subcultures from proximal and distal ends of the agar tract showed minimal or no growth in the antiseptic ETTs compared with the control ETTs (P < 0.001). The amount of CHX retained in the antiseptic ETTs after five days of implantation was an average of 45% of the initial level. Antiseptic ETTs prevented bacterial colonization in the airway model and also retained significant amounts of the antiseptic. These results indicate that the effectiveness of antiseptic-impregnated ETTs in preventing the growth of bacterial pathogens associated with VAP may vary with different organisms.

Ventilator-associated pneumonia in extremely preterm neonates in a neonatal intensive care unit: characteristics, risk factors, and outcomes

OBJECTIVE

To determine the rates, characteristics, risk factors, and outcomes of ventilator-associated pneumonia (VAP) in extremely preterm neonates in a neonatal intensive care unit (NICU).

METHODS

A prospective cohort study was conducted at the St Louis Children's Hospital on all patients who had birth weight <or=2000 g and were admitted to the NICU for >or=48 hours from October 2000 to July 2001. Extremely preterm neonates were defined as neonates with estimated gestational age (EGA) <28 weeks. The primary outcome was the development of VAP. Secondary outcomes were death and NICU length of stay (LOS). Multiple logistic regression was performed to determine independent predictors for VAP and mortality.

RESULTS

A total of 229 patients were enrolled. Sixty-seven (29%) had EGA <28 weeks. Nineteen episodes of VAP occurred in 19 (28.3%) of 67 mechanically ventilated patients. VAP rates were 6.5 per 1000 ventilator days for patients with EGA <28 weeks and 4 per 1000 ventilator days for EGA >or=28 weeks. By multivariate analysis, bloodstream infection before VAP (adjusted odds ratio: 3.5; 95% confidence interval [CI]: 1.2-10.8) was an independent risk factor for VAP after adjustment for the duration of endotracheal intubation. Ventilator-associated pneumonia (adjusted odds ratio: 3.4; 95% CI: 1.2-12.3) was an independent predictor of mortality. A strong association between VAP and mortality was observed in neonates who stayed in the NICU >30 days (relative risk: 8.0; 95% CI: 1.9-35.0). Patients with VAP also had prolonged NICU LOS (median: 138 vs 82 days).

CONCLUSIONS

VAP occurred at high rates in extremely preterm neonates and was associated with increased mortality. Additional studies are needed to develop interventions to prevent VAP in NICU patients.

A 7-year study of severe hospital-acquired pneumonia requiring ICU admission

OBJECTIVE

To examine the characteristics, prognostic factors, and outcome of patients with severe hospital-acquired pneumonia admitted to the ICU.

DESIGN AND SETTING

Prospective observational clinical study in two medical-surgical ICUs with 16 and 20 beds

PATIENTS AND PARTICIPANTS

During a 7-year period all hospitalized patients requiring admission to either ICU for hospital-acquired pneumonia were followed up.

MEASUREMENTS AND RESULTS

We diagnosed 96 episodes of severe hospital-acquired pneumonia, and in 67 cases a causal diagnosis was made. Most episodes were late-onset pneumonia. Gram-negative micro-organisms were isolated in 51% of episodes diagnosed, and Pseudomonas aeruginosa was the most frequent pathogen isolated (24%). Clearly significant variations happened between hospitals, particularly affecting the incidence of Aspergillus spp. and Legionella pneumophila. Forty-nine patients developed septic shock (51%). Fifty-one patients died (53%). Aspergillosis and pneumonia due to P. aeruginosa were associated with the highest mortality. Septic shock (OR: 14.27) and chronic obstructive pulmonary disease (OR: 6.11) were independently associated with a poor prognosis.

CONCLUSIONS

Patients with severe hospital-acquired pneumonia admitted to the ICU present high mortality. The presence of septic shock and chronic obstructive pulmonary disease in conjunction with specific microorganisms are associated with a poor prognosis. Local epidemiological data combined with a patient-based approach may allow a more accurate therapy decision making.

Variability in antibiotic prescribing patterns and outcomes in patients with clinically suspected ventilator-associated pneumonia

STUDY OBJECTIVES

To describe the variation in clinical practice strategies for the treatment of suspected ventilator-associated pneumonia (VAP) in a population of critically ill patients, and to determine whether initial empiric treatment with certain antibiotics, monotherapy vs combination antibiotic therapy, or appropriate vs inappropriate antibiotic therapy is associated with survival, length of hospital stay, or days free of antibiotics.

DESIGN

Prospective, observational cohort study.

SETTING

Medical-surgical ICUs of two university-affiliated tertiary medical centers.

PATIENTS

Between May 1, 1998, and August 1, 2000, we screened 7,030 ICU patients and identified 156 patients with clinically suspected VAP. Patients were followed up until death or discharge from the hospital.

RESULTS

The mean age was 62 years, mean APACHE (acute physiology and chronic health evaluation) II score was 14, and mortality was 34%. Combination antibiotic therapy was used in 53% of patients. Piperacillin-tazobactam, fluoroquinolones, vancomycin, cephalosporins, and aminoglycosides were the most commonly employed antibiotics. Initial empiric antibiotics were deemed appropriate in 92% of patients. The predominant organisms isolated from respiratory secretions included Pseudomonas aeruginosa and Staphylococcus aureus. Patients had lower in-hospital mortality rates if their initial treatment regimen included an antipseudomonal penicillin plus beta-lactamase inhibitor (hazard ratio [HR], 0.41; 95% confidence interval [CI], 0.21 to 0.80; p = 0.009). There was also a strong trend toward reduced mortality rates in patients treated with aminoglycosides (HR, 0.43; 95% CI, 0.16 to 1.11; p = 0.08). Specific antibiotic therapy was not associated with length of hospital stay or days free of antibiotics. Outcomes were similar for patients treated with monotherapy vs combination therapy, and for patients who received initial appropriate vs inappropriate therapy.

CONCLUSIONS

Patients with clinically suspected VAP who receive initial empiric therapy with antipseudomonal penicillins plus beta-lactamase inhibitors, and possibly aminoglycosides, have lower in-hospital mortality rates when compared with those who are not treated with these antibiotics. These agents should be considered for the initial empiric therapy of VAP.

Occurrence of ventilator-associated pneumonia in mechanically ventilated pediatric intensive care patients during stress ulcer prophylaxis with sucralfate, ranitidine, and omeprazole

PURPOSE

The purpose of the study was to evaluate the effects of sucralfate, ranitidine, and omeprazole use on incidence of ventilatory-associated pneumonia (VAP) and mortality in ventilated pediatric critical care patients.

MATERIALS AND METHODS

This prospective study was conducted at the pediatric intensive care unit (PICU) between August 2000 and February 2002. A total of 160 patients who needed mechanical ventilation were randomized into 4 groups according to the computer-generated random number table: group (S), (n = 38) received sucralfate suspension 60 mg/kg/d in 4 doses via the nasogastric tube that was flushed with 10 mL of sterile water; group (R), (n = 42) received ranitidine 2 mg/kg/d intravenously in 4 doses; group (O), (n = 38) received omeprazole 1 mg/kg/d intravenously in 2 doses; and group (P), (n = 42) did not receive any medication for stress ulcer prophylaxis. Treatment was begun within 6 hours of PICU admission.

RESULTS

Seventy patients (44%) developed VAP. VAP rate was 42% (16 of 38) in the sucralfate group, 48% (20 of 42) in the ranitidine group, 45% (17 of 38) in the omeprazole group, and 41% (17 of 42) in the nontreated group. Overall mortality rate was 22% (35 of 160); it was 21% (8 of 38) in the sucralfate group, 23% (10 of 42) in the ranitidine group, 21% (8 of 38) in the omeprazole group, and 21% (9 of 42) in the nontreated group. Our results did not show any difference in the incidence of VAP and mortality in mechanically ventilated PICU patients treated with ranitidine, omeprazole, or sucralfate, or nontreated subjects (P =.963, confidence interval [CI] = 0.958-0.968; P =.988, CI = 0.985-0.991, respectively). Nine patients (5.6%) had macroscopic bleeding. There was no statistically significant difference in macroscopic bleeding between groups.

CONCLUSIONS

Our results did not show any difference in the incidence of VAP, macroscopic stress ulcer bleeding, and mortality in the mechanically ventilated PICU patients treated with ranitidine, omeprazole, or sucralfate, or nontreated subjects. None of the treatment regimens increased VAP compared with the nontreated group. Because there is insufficient data about stress ulcer prophylaxis and VAP in the pediatric age group, more studies with larger numbers of patients are needed.

Early tracheostomy does not improve outcome in burn patients

Early tracheostomy (ET) has been claimed to reduce ventilator support or intensive care unit or hospital length of stay in intensive care unit patients. This study was performed to assess the potential benefits of ET in burn patients. From October 1996 to July 2001, we evaluated all intubated and acutely burned adults using a formula to predict the probability of prolonged ventilator dependence. We randomized each patient with a probability of prolonged ventilator dependence more than 0.5 to ET, performed on the next operative day, or to conventional therapy (CON), which consisted of continued endotracheal intubation as needed, with tracheostomy (TRACH) performed on postburn day (PBD) 14 if necessary. During this period, 44 patients were randomized, 23 to CON and 21 to ET. Groups did not differ in age, total burn size, or inhalation injury, although ET patients had larger full-thickness burns. ET patients underwent TRACH at a mean of PBD 4 vs PBD 14.8 for CON patients (P <.01). ET patients had a significant improvement in PaO2 /FiO2 ratios within 24 hours following TRACH (139 +/- 15 vs 190 +/- 12; P <.01). There were no differences in ventilator support, length of stay, incidence of pneumonia, or survival. However, six CON patients (26%) were successfully extubated by PBD 14 compared with one ET patient (P <.01). Although tracheostomy offers some advantages in terms of patient comfort and security, routine performance of ET in burn patients does not improve outcomes, nor does it result in earlier extubation. This may be partly caused by the comfort and convenience of tracheostomy.

An outbreak of multidrug-resistant Pseudomonas aeruginosa associated with increased risk of patient death in an intensive care unit

OBJECTIVE

To investigate an outbreak of multidrug-resistant Pseudomonas aeruginosa in an intensive care unit (ICU).

DESIGN

Epidemiologic investigation, environmental assessment, and ambidirectional cohort study.

SETTING

A secondary-care university hospital with a 10-bed ICU.

PATIENTS

All patients admitted to the ICU receiving ventilator treatment from December 1, 1999, to September 1, 2000.

RESULTS

An outbreak in an ICU with multidrug-resistant isolates of P aeruginosa belonging to one amplified fragment-length polymorphism (AFLP)-defined genetic cluster was identified, characterized, and cleared. Molecular typing of bacterial isolates with AFLP made it possible to identify the outbreak and make rational decisions during the outbreak period. The outbreak included 19 patients during the study period. Infection with bacterial isolates belonging to the AFLP cluster was associated with reduced survival (odds ratio, 5.26; 95% confidence interval, 1.14 to 24.26). Enhanced barrier and hygiene precautions, cohorting of patients, and altered antibiotic policy were not sufficient to eliminate the outbreak. At the end of the study period (in July), there was a change in the outbreak pattern from long (December to June) to short (July) incubation times before colonization and from primarily tracheal colonization (December to June) to primarily gastric or enteral July) colonization. In this period, the bacterium was also isolated from water taps.

CONCLUSION

Complete elimination of the outbreak was achieved after weekly pasteurization of the water taps of the ICU and use of sterile water as a solvent in the gastric tubes.

Iseganan HCl: a novel antimicrobial agent

Iseganan HCl is an antimicrobial peptide under development for the prevention of oral mucositis, a severe consequence of some chemotherapy and radiation therapy regimens. Several attributes of iseganan make it an optimal candidate for study in this clinical situation where both local and systemic host defenses may be impaired. These include broad spectrum and rapid bactericidal activity, a lack of observed resistance and cross-resistance and stability in biological fluids. Clinical trials of patients receiving stomatotoxic chemotherapy followed by a haematopoietic stem cell transplant show iseganan reduces the occurrence of oral mucositis and ameliorates sequelae such as mouth pain, throat pain and difficulty swallowing. Iseganan is well-tolerated, which is partly attributable to a lack of systemic absorption following topical oral administration. Other promising areas of investigation include topical oral application for the prevention of ventilator-associated pneumonia and nebulisation for treatment of chronic lung infection in patients with cystic fibrosis. Future studies will expand on the role of iseganan as a novel antimicrobial.

Aerobic Gram-negative Bacillary Pneumonia

Gram-negative bacilli (GNB) are a common cause of severe hospital-acquired pneumonia. Due to changes in the health care environment and selective antimicrobial pressure, these bacteria also are becoming a more common cause of pneumonia in venues outside of the traditional hospital setting and are increasingly resistant to antimicrobial agents. Risk factors for acquisition of GNB allow the clinician to efficiently identify patients who are likely to have pneumonia due to these pathogens. Available diagnostic techniques have a limited capacity to accurately detect GNB pulmonary infection. Yet, a pathogen specific diagnosis and knowledge of local resistance patterns are quintessential elements in formulating an effective treatment plan. This article reviews the epidemiologic characteristics, pathogenesis, and current management issues of GNB pneumonia.

Posing clinical questions: framing the question for scientific inquiry

Much of nursing practice is (and always has been) based on information generated through inquiry. Finding the best answers quickly and effectively for the questions that arise in the clinical setting facilitates care, increases nursing efficiency, and improves patient outcome and satisfaction. Posing clinical questions also can help nurses identify and fill in gaps in knowledge, keep up with advances in clinical practice, and strengthen interactions with their peers, team members, and patients and their families. Formulating clinical questions that lead to sound, evidence-based answers to resolve clinical problems or direct patient-care decisions takes time and practice. The information in this article will assist nurses to develop the skill of framing clinical questions efficiently and effectively.

Pneumonia in the elderly

Pneumonia is one of the commonest infections in elderly patients. The pathogens responsible for pneumonias in the elderly are the same as in younger adults. Because of associated cardiopulmonary disease and/or impaired host defenses, pneumonia in elderly patients is associated with increased mortality and morbidity compared to younger patients. The clinical importance of pneumonias in the elderly relates to age-dependent and pathologic changes in the immune system as well as the lungs. Pneumonias in the elderly may be classified, for clinical purposes, according to their location of acquisition, i.e. community-acquired pneumonias, nursing home-acquired pneumonias, or hospital-acquired pneumonias. The clinical presentation of pneumonias in the elderly may be difficult, due to pre-existing cardiopulmonary disease that mimics pneumonia. This review discusses the diagnostic and therapeutic approaches to elderly patients with pneumonia.

Ventilator-associated pneumonias in a cardiothoracic surgery centre postoperative intensive care unit

Cases of ventilator-associated pneumonia (VAP) were investigated in a cardiothoracic surgery postoperative intensive care unit between 1 January 1999 and 31 December 1999. A total of 1716 patients who had undergone cardiothoracic operations and admitted to the intensive care unit (ICU) were included in the study. Patient- and laboratory-based prospective surveillance of VAP was done along with other hospital-acquired infections. During the study period a total of 26 585 patient-days with 2708 ventilator-days were recorded. Forty-six cases of VAP occurred in 36 of 1716 patients who had undergone cardiothoracic operations (2.09%, 1.3 episodes of pneumonia per patient). The ventilator utilization rate at our institution was 0.10. There were 16.4 VAPs per 1000 ventilation days. Thirty-eight percent of VAP were caused by Gram-negative enteric rods, 34% by Pseudomonas aeruginosa, and 17% by Staphylococcus aureus. VAP was polymicrobial in 9% of cases. No causative micro-organism was identified in 2% of cases. The same bacteria were isolated in both blood and endotracheal aspirate cultures in 10 of 46 pneumonia cases (22%). The crude mortality rate of VAP was calculated as 30%

Are quantitative cultures useful in the diagnosis of hospital-acquired pneumonia?

Noninvasive and invasive tests have been developed and studied for their utility in diagnosing and guiding the treatment of hospital-acquired pneumonia, a condition with an inherently high mortality. Early empiric antibiotic treatment has been shown to reduce mortality, so delaying this treatment until test results are available is not justifiable. Furthermore, tailoring therapy based on results of either noninvasive or invasive tests has not been clearly shown to affect morbidity and mortality. This may be related to quantitative limitations of these tests or possibly to a high false-negative rate in patients who receive early antibiotic treatment and may therefore have suppressed bacterial counts. Results of these tests, however, do influence treatment. It is therefore hoped that they may ultimately provide a rational basis for making therapeutic decisions. In the future, outcomes research should be a part of large-scale clinical trials, and noninvasive and invasive tests should be incorporated into the design in an attempt to provide a better understanding of the value of such tests.

Hospital-acquired pneumonia: risk factors, microbiology, and treatment

Pneumonia complicates hospitalization in 0.5 to 2.0% of patients and is associated with considerable morbidity and mortality. Risk factors for hospital-acquired pneumonia (HAP) include mechanical ventilation for > 48 h, residence in an ICU, duration of ICU or hospital stay, severity of underlying illness, and presence of comorbidities. Pseudomonas aeruginosa, Staphylococcus aureus, and Enterobacter are the most common causes of HAP. Nearly half of HAP cases are polymicrobial. In patients receiving mechanical ventilation, P aeruginosa, Acinetobacter, methicillin-resistant S aureus, and other antibiotic-resistant bacteria assume increasing importance. Optimal therapy for HAP should take into account severity of illness, demographics, specific pathogens involved, and risk factors for antimicrobial resistance. When P aeruginosa is implicated, monotherapy, even with broad-spectrum antibiotics, is associated with rapid evolution of resistance and a high rate of clinical failures. For pseudomonal HAP, we advise combination therapy with an antipseudomonal beta-lactam plus an aminoglycoside or a fluoroquinolone (eg, ciprofloxacin).

Ventilator-associated pneumonia or not? Contemporary diagnosis

Ventilator-associated pneumonia (VAP) is pneumonia in patients who have been on mechanical ventilation for > or =48 hours. VAP is most accurately diagnosed by quantitative culture and microscopy examination of lower respiratory tract secretions, which are best obtained by bronchoscopically directed techniques such as the protected specimen brush and bronchoalveolar lavage. These techniques have acceptable repeatability, and interpretation of results is unaffected by antibiotics administered concurrently for infection at extrapulmonary sites as long as antimicrobial therapy has not been changed for <72 hours before bronchoscopy.

Nosocomial pneumonia. Diagnostic and therapeutic considerations

Many patients with presumed nosocomial pneumonia probably have infiltrates on the chest radiograph, fever, and leukocytosis resulting from noninfectious causes. Because of the high mortality and morbidity associated with nosocomial pneumonias, however, most clinicians treat such patients with a 2-week empiric trial of antibiotics. Before therapy is initiated, the clinician should rule out other causes of pulmonary infiltrates, fever, and leukocytosis that mimic a nosocomial pneumonia (e.g., pre-existing interstitial lung disease, primary or metastatic lung carcinomas, pulmonary emboli, pulmonary drug reactions, pulmonary hemorrhage, collagen vascular disease affecting the lungs, or congestive heart failure). If these disorders can be eliminated from diagnostic consideration, a 2-week trial of empiric monotherapy is indicated. The clinician should treat cases of presumed nosocomial pneumonia as if P. aeruginosa were the pathogen. Although P. aeruginosa is not the most common cause of nosocomial pneumonia, it is the most virulent pulmonary pathogen associated with nosocomial pneumonia. Coverage directed against P. aeruginosa is effective against all other aerobic gram-negative bacillary pathogens causing hospital-acquired pneumonia. The clinician should select an antibiotic for empiric monotherapy that is highly effective against P. aeruginosa, has a good side-effect profile, has a low resistance potential, and is relatively inexpensive in terms of its cost to the institution. The preferred agents for empiric monotherapy for nosocomial pneumonia are cefepime, meropenem, and piperacillin. Single organisms are responsible for nosocomial pneumonia, not multiple pathogens. S. aureus rarely, if ever, causes nosocomial pneumonia but is mentioned frequently in studies based on cultures of respiratory tract secretions. S. aureus, unless accompanied by a necrotizing pneumonia with rapid cavitation within 72 hours, in the sputum indicates colonization rather than infection and should not be addressed therapeutically. Antibiotics associated with a high resistance potential should not be used as monotherapy or included in combination therapy regimens (i.e., ceftazidime, ciprofloxacin, imipenem, or gentamicin). Combination therapy is more expensive than monotherapy and is indicated only when P. aeruginosa is extremely likely, based on its characteristic clinical presentation, or is proved by tissue biopsy. Therapy should not be based on respiratory secretion cultures regardless of technique. Optimal combination regimens include cefepime or meropenem plus levofloxacin or piperacillin or aztreonam or amikacin. Nosocomial pneumonias usually are treated for 14 days. Lack of radiographic or clinical response to appropriate empiric nosocomial pneumonia monotherapy after 14 days suggests an alternate diagnosis. In these patients, a tissue biopsy specimen should be obtained to determine the cause of the persistence of pulmonary infiltrates unresponsive to appropriate antimicrobial therapy.

Experience with Pneumonia in Acutely Burned Patients Requiring Ventilator Support

Acutely burned patients requiring ventilatory support who developed pneumonia while in the hospital were retrospectively reviewed. The Centers for Disease Control and Prevention (CDC) clinical criteria for pneumonia are based on clinical findings, radiographic findings, and culture data. During an 18-month period, 784 burn patients were admitted. Of these, 145 (18.5%) were placed on ventilators for at least 1 day. Fifty-three (36.6%) patients on ventilators developed acute pneumonia based on CDC criteria. Identification of causative organisms was based on positive cultures from blood or endotracheal aspiration within 3 days of the diagnosis of pneumonia. Thirty-nine patients were diagnosed as having inhalation injury. Forty-seven patients were placed on ventilatdrs before or on the day of admission. Ages ranged from 2 to 82 years (mean, 39). Burn size ranged from 2 to 85 per cent (mean, 29.7%) of total body surface area. The total number of ventilator days was 1310 for the 53 patients, with a mean of 27.7 days. Ten patients had positive blood cultures during the period in which pneumonia was present. Thirty-one different organisms were recovered from blood or tracheal aspirates. The most commonly recovered organism was Pseudomonas aeruginosa. In 30 incidences, polymicrobial cultures were encountered. Initiation of appropriate antimicrobial therapy was begun on the basis of clinical impression and current burn unit experience and revised on the basis of the culture data. Of the 53 patients, 13 (25.5%) died, all while still on ventilators. The other 40 patients survived. Thirty-four were weaned off their ventilators, and 6 were transferred while still on ventilator support.

Stenotrophomonas maltophilia infection and colonization in the intensive care units of two community hospitals: A study of 143 patients

STUDY OBJECTIVE

To study the epidemiology of Stenotrophomonas maltophilia infections in the intensive care units (ICUs) of community general hospitals.

DESIGN

Retrospective chart review of 143 patients with cultures positive for S. maltophilia over a 2-year period.

SETTING

Intensive care units of 2 community general hospitals.

RESULTS

Patients with S. maltophilia infection or colonization were elderly (mean age 62.4 years), intubated for a mean of 11.8 days, and had a mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score of 16.6. A tracheostomy was present in 22.4%, and underlying chronic respiratory disease and malignancy were found in 25.9% and 15.4%, respectively. Only 2 patients (1.4%) were neutropenic. Most isolates (89.5%) were from the respiratory tract and were part of a polymicrobial culture in 52. 5% of patients. Only a slightly higher APACHE II score (mean = 18.0, SD 7.8 vs mean = 15.6, SD 6.2, P = 0.052) differentiated patients with infection from those with colonization. All but 2 patients were exposed to antibiotics before their positive culture. Crude mortality rate was 41.3% overall and was significantly higher in those with an APACHE II score of 15 or more (48.8% vs 30.5%, P = 0. 028).

CONCLUSION

S. maltophilia is emerging as an important cause of nosocomial infection, especially pneumonia, in ICUs of community general hospitals. Patients tend to be elderly, intubated for a mean of about 12 days, have high APACHE II scores, and frequently have a tracheostomy or underlying chronic respiratory disease. In contrast to earlier reports, neutropenia and underlying malignancy are uncommon in our ICU population. We found prior antibiotic exposure was almost universal and similar to previous reports, but use of imipenem was much less common in our community hospital patients. Patients with a high APACHE II score should be considered infected rather than colonized, but differentiation of infection from colonization remains problematic. Isolation of S. maltophilia from a patient carries a crude mortality rate of 41.3%, and patients with an APACHE II score of 15 or more have a significantly higher mortality rate than those with lesser scores, approaching 50%. Trimethoprim-sulfamethoxazole (TMP-SMX) remains the drug of choice for infections caused by S. maltophilia.

Epidemiology of ventilator-acquired pneumonia based on protected bronchoscopic sampling

We performed a prospective observational cohort study of the epidemiology and etiology of nosocomial pneumonia in 358 medical ICU patients in two university-affiliated hospitals. Protected bronchoscopic techniques (protected specimen brush and bronchoalveolar lavage) were used for diagnosis to minimize misclassification. Risk factors for ventilator-associated pneumonia were identified using multiple logistic regression analysis. Twenty-eight cases of pneumonia occurred in 358 patients for a cumulative incidence of 7.8% and incidence rates of 12.5 cases per 1, 000 patient days and 20.5 cases per 1,000 ventilator days. Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Hemophilus species made up 65% of isolates from the lower respiratory tract, whereas only 12.5% of isolates were enteric gram-negative bacilli. Daily surveillance cultures of the nares, oropharynx, trachea, and stomach demonstrated that tracheal colonization preceded ventilator-associated pneumonia in 93.5%, whereas gastric colonization preceded tracheal colonization for only four of 31 (13%) eventual pathogens. By multiple logistic regression, independent risk factors for ventilator- associated pneumonia were admission serum albumin <= 2.2 g/dl (odds ratio [OR] 5.9; 95% confidence interval [CI] 2.0-17.6; p = 0.0013), maximum positive end-expiratory pressure >= 7.5 cm H2O (OR, 4.6; 95% CI, 1.4 to 15.1; p = 0.012), absence of antibiotic therapy (OR, 6.7; 95% CI, 1.8 to 25.3; p = 0.0054), colonization of the upper respiratory tract by respiratory gram-negative bacilli (OR, 3.4; 95% CI, 1.1 to 10.1; p = 0.028), pack-years of smoking (OR, 2.3 for 50 pack-years; 95% CI, 1. 2 to 4.2; p = 0.012), and duration of mechanical ventilation (OR, 3. 4 for 14 d; 95% CI, 1.5 to 7.8; p = 0.0044). Several of these risk factors for ventilator-associated pneumonia appear amenable to intervention.