Optimal use of antibiotics for intubation-associated pneumonia

Ventilator-Associated Pneumonia: A Review

Ventilator-associated pneumonia is the most frequent intensive care unit (ICU)-related infection in patients requiring mechanical ventilation. In contrast to other ICU-related infections, which have a low mortality rate, the mortality rate for ventilator-associated pneumonia ranges from 20% to 50%. These clinically significant infections prolong duration of mechanical ventilation and ICU length of stay, underscoring the financial burden these infections impose on the health care system. The causes of ventilator-associated pneumonia are varied and differ across different patient populations and different types of ICUs. This varied presentation underscores the need for the intensivist treating the patient with ventilator-associated pneumonia to have a clear knowledge of the ambient microbiologic flora in their ICU. Prevention of this disease process is of paramount importance and requires a multifaceted approach. Once a diagnosis of ventilator-associated pneumonia is suspected, early broad-spectrum antibiotic administration decreases morbidity and mortality and should be based on knowledge of the sensitivities of common infecting organisms in the ICU. De-escalation of therapy, once final culture results are available, is necessary to minimize development of resistant pathogens. Duration of therapy should be based on the patient’s clinical response, and every effort should be made to minimize duration of therapy, thus further minimizing the risk of resistance.

Selecting against antibiotic-resistant pathogens: optimal treatments in the presence of commensal bacteria

Using optimal control theory as the basic theoretical tool, we investigate the efficacy of different antibiotic treatment protocols in the most exacting of circumstances, described as follows. Viewing a continuous culture device as a proxy for a much more complex host organism, we first inoculate the device with a single bacterial species and deem this the 'commensal' bacterium of our host. We then force the commensal to compete for a single carbon source with a rapidly evolving and fitter 'pathogenic bacterium', the latter so-named because we wish to use a bacteriostatic antibiotic to drive the pathogen toward low population densities. Constructing a mathematical model to mimic the biology, we do so in such a way that the commensal would be eventually excluded by the pathogen if no antibiotic treatment were given to the host or if the antibiotic were over-deployed. Indeed, in our model, all fixed-dose antibiotic treatment regimens will lead to the eventual loss of the commensal from the host proxy. Despite the obvious gravity of the situation for the commensal bacterium, we show by example that it is possible to design drug deployment protocols that support the commensal and reduce the pathogen load. This may be achieved by appropriately fluctuating the concentration of drug in the environment; a result that is to be anticipated from the theory optimal control where bang-bang solutions may be interpreted as intermittent periods of either maximal and minimal drug deployment. While such 'antibiotic pulsing' is near-optimal for a wide range of treatment objectives, we also use this model to evaluate the efficacy of different antibiotic usage strategies to show that dynamically changing antimicrobial therapies may be effective in clearing a bacterial infection even when every 'static monotherapy' fails.

Etiology of Ventilator-Associated Pneumonia

This review focuses on the top ten causes of ventilator-associated pneumonia (VAP), updating an earlier study. These pathogens have specific risk factors, different patterns of clinical resolution, and a wide range of attributable mortality. The discussion herein analyzes these aspects, placing particular emphasis on risk factors, attributable mortality, resistance, and the implications for management.

Advances in the management of pneumonia in the intensive care unit: review of current thinking

Interventions to prevent pneumonia in the intensive care unit should combine multiple measures targeting the invasive devices, microorganisms and protection of the patient. Microbiological investigation is useful for evaluating the quality of the respiratory sample, and permits early modification of the regimen in light of the microbiological findings. Once pneumonia develops, the appropriateness of the initial antibiotic regimen is a vital determinant of outcome. Three questions should be formulated: (1) is the patient at risk of acquiring methicillin-resistant Staphylococcus aureus, (2) is Acinetobacter baumannii a problem in the institution, and (3) is the patient at risk of acquiring Pseudomonas aeruginosa? Antibiotic therapy should be started immediately and must circumvent any pathogen resistance mechanisms developed after previous antibiotic exposure. Therefore, antibiotic choice should be institution-specific and patient-oriented.

Judicious Use of Antimicrobials in the Critical Care Setting

This article reviews the judicious use of antibiotics in an intensive care setting. Risk factors for both infection and antimicrobial resistance are discussed. Various methods hospitals can apply to promote the optimal use of antibiotics also are reviewed. These methods include empiric therapy, antibiotic cycling, treatment guidelines and protocols, and antibiotic susceptibility monitoring.

Hospital-acquired pneumonia: etiologic considerations

The development of pneumonia requires the pathogen to reach the alveoli and the host defenses to be overwhelmed, either by microorganism virulence or by inoculums size. The endogenous sources of microorganisms are nasal carriers, sinusitis, mouth, oropharynx, gastric, or tracheal colonization, and hematogenous spread. The exogenous sources of microorganisms are biofilm of the tracheal tube, ventilator circuits, nebulizers, and humidifiers. Health care workers may also play a role in this setting. Different microorganisms can be found depending on the onset time of pneumonia and on the local pattern variation encountered between different institutions and countries. Healthy patients may be chronically colonized. A very important, unresolved issue is the definition of early and late-onset pneumonia; it still remains uncertain from the literature whether the given threshold refers to the number of days in hospital or to the number of days following intubation. Noninvasive ventilation is demonstrating that the term "ventilator-associated pneumonia" is perhaps inaccurate and should be referred to as "intubation-associated pneumonia."

Pneumonia in the intensive care unit

OBJECTIVE

To update the state-of-the-art on pneumonia in adult patients in the intensive care unit (ICU), with special emphasis on new developments in management.

METHODS

We searched MEDLINE, using the following keywords: hospital-acquired pneumonia, ventilator-associated pneumonia and healthcare-associated pneumonia, diagnosis, therapy, prevention.

RESULTS

Interventions to prevent pneumonia in the ICU should combine multiple measures targeting the invasive devices, microorganisms, and protection of the patient. Once pneumonia develops, the appropriateness of the initial antibiotic regimen is a vital determinant of outcome. Three questions should be formulated: a) Is the patient at risk of methicillin-resistant Staphylococcus aureus?; b) Is Acinetobacter baumannii a problem in the institution?; and c) is the patient at risk of Pseudomonas aeruginosa? Antibiotic therapy should be started immediately and must circumvent pathogen-resistance mechanisms developed after previous antibiotic exposure. Therefore, antibiotic choice should be institution specific and patient oriented. Microbiologic investigation is useful on evaluating the quality of the respiratory sample and permits early modification of the regimen in light of the microbiologic findings.

CONCLUSION

A decision tree outlining an approach to the evaluation and management of ventilator-associated pneumonia is provided.

Therapy of ventilator-associated pneumonia. A patient-based approach based on the ten rules of "The Tarragona Strategy"

Therapy of ventilator-associated pneumonia should be a patient-based approach focusing on some key features are listed here: early initial therapy should be based on broad-spectrum antibiotics. Empirical treatment may be targeted after direct staining and should be modified according to good-quality quantitative microbiological findings, but should never be withdrawn in presence of negative direct staining or delayed until microbiological results are available. Courses of therapy should be given at high doses according to pharmacodynamic and tissue penetration properties. Prolonging antibiotic treatment does not prevent recurrences. Methicillin-sensitive Staphylococcus aureus should be expected in comatose patients. Methicillin-resistant Staphylococcus aureus should not be expected in patients without previous antibiotic coverage. Pseudomonas aeruginosa should be covered with combination therapy. Antifungal therapy, even when Candida spp is isolated in significant concentrations, is not recommended for intubated nonneutropenic patients. Vancomycin, given at the standard doses and route of administration for the treatment of VAP caused by Gram-positive pathogens, is associated with poor outcomes. The choice of initial antibiotic should be based on the patient's previous antibiotic exposure and comorbidities, and local antibiotic susceptibility patterns, which should be updated regularly.

Antibiotic prescription practices, consumption and bacterial resistance in a cross section of Swedish intensive care units

BACKGROUND

The purpose of this work was to study usage of antibiotics, its possible determinants, and patterns of bacterial resistance in Swedish intensive care units (ICUs).

METHODS

Prospectively collected data on species and antibiotic resistance of clinical isolates and antibiotic consumption specific to each ICU in 1999 were analyzed together with answers to a questionnaire. Antibiotic usage was measured as defined daily doses per 1000 occupied bed days (DDD1000).

RESULTS

Data were obtained for 38 ICUs providing services to a population of approximately 6 million. The median antibiotic consumption was 1257 DDD1000 (range 584-2415) and correlated with the length of stay but not with the illness severity score or the ICU category. Antibiotic consumption was higher in the ICUs lacking bedside devices for hand disinfection (2193 vs. 1214 DDD1000, p=0.05). In the ICUs with a specialist in infectious diseases responsible for antibiotic treatment the consumption pattern was different only for use of glycopeptides (58% lower usage than in other ICUs: 26 vs. 11 DDD1000,P=0.02). Only 21% of the ICUs had a written guideline on the use of antibiotics, 57% received information on antibiotic usage at least every 3 months and 22% received aggregated resistance data annually. Clinically significant antimicrobial resistance was found among Enterbacter spp. to cephalosporins and among Enterococcus spp. to ampicillin.

CONCLUSIONS

Availability of hand disinfection equipment at each bed and a specialist in infectious diseases responsible for antibiotic treatment were factors that correlated with lower antibiotic consumption in Swedish ICUs, whereas patient-related factors were not associated with antibiotic usage.

Ventilator-associated pneumonia

Ventilator-associated pneumonia is the most serious infectious complication in critically ill patients, associated with increased length of intensive care unit treatment and high mortality rates. Investigations focused on outcome variables have improved the database to estimate diagnostic and therapeutic management strategies. This knowledge has diminished the importance of the discussion on how to diagnose the pneumonia. This review summarizes recent data on epidemiology and mortality, risk factors and prevention, diagnosis, microbiology and antimicrobial treatment of ventilator-associated pneumonia.