NEUMONIA NOSOCOMIAL

NEUMONIA NOSOCOMIALMg. Bernardo C. DAMASO MATA

NEUMONIA NOSOCOMIALNosocomial Pneumonia,Hospital-Acquired Pneumonia,Ventilator-Associated Pneumonia, andHealth CareAssociated PneumoniaNeumonia intrahospitalariaNEUMONIA NOSOCOMIALEssentials of diagnosisHospital-acquired pneumonia (HAP) occurs >48 hours after admission to the hospital or other health care facility and excludes any infection present at the time of admission.Health careassociated pneumonia (HCAP) occurs in community members whose extensive contact with healthcare has changed their risk for virulent and drug resistant organisms.At least two of the following: fever, leukocytosis, purulent sputum.New or progressive parenchymal opacity on chest radiograph.Especially common in patients requiring intensive care or mechanical ventilation.NEUMONIA NOSOCOMIALHospitalized patients carry different flora with different resistance patterns than healthy patients in the community, and their health status may place them at higher risk for more severe infection. The diagnostic approach and antibiotic treatment of patients with hospital-acquired pneumonia (HAP) is, therefore, different from patients with CAP.NEUMONIA NOSOCOMIALSimilarly, management of patients in whom pneumonia develops following endotracheal intubation and mechanical ventilation (ventilator-associated pneumonia or VAP) should address issues specific to this group of patients.NEUMONIA NOSOCOMIAL

NEUMONIA NOSOCOMIALSome community members have extensive contact with the healthcare system and carry flora that more closely resemble hospitalized patients than healthy community residents. When pneumonia develops in these persons, the infection is referred to as health careassociated pneumonia (HCAP). Initial management and antibiotic therapy should be targeted to the common flora and specific risk factors for severe disease.NEUMONIA NOSOCOMIALConsidered together, these nosocomial pneumonias (HAP/VAP/HCAP) represent an important cause of morbidity and mortality despite widespread use of preventive measures, advances in diagnostic testing, and potent new antimicrobial agents. HAP is the second most common cause of infection among hospital inpatients and is the leading cause of death due to infection with mortality rates ranging from 20% to 50%. NEUMONIA NOSOCOMIALWhile a minority of cases occurs in ICU patients, the highest-risk patients are those in ICUs or who are being mechanically ventilated; these patients also experience higher morbidity and mortality from HAP. As management of more chronic illnesses shifts to the outpatient setting, more cases of HCAP are caused by unusual organisms, and there is a high frequency of drug resistance.Definitive identification of the infectious cause of a lower respiratory infection is rarely available on presentation, thus, rather than pathogen-directed antibiotic treatment, the choice of empiric therapy is informed by epidemiologic and patient data.NEUMONIA NOSOCOMIALNEUMONIA NOSOCOMIAL

Definition & PathogenesisHAP develops more than 48 hours after admission to the hospital and VAP develops in a mechanically ventilated patient more than 48 hours after endotracheal intubation.HCAP is defined as pneumonia that occurs in a nonhospitalized patient with extensive healthcare contact, and the risk factors for HCAP are outlined in Table 912.NEUMONIA NOSOCOMIALNEUMONIA NOSOCOMIAL

Definition & PathogenesisThree factors distinguish nosocomial pneumonia from CAP: (1) different infectious causes; (2) different antibiotic susceptibility patterns, specifically, a higher incidence of drug resistance; and (3) the patients underlying health status that puts them at risk for more severe infections.NEUMONIA NOSOCOMIALDefinition & PathogenesisSince access to the lower respiratory tract occurs primarily through microaspiration, nosocomial pneumonia starts with a change in upper respiratory tract flora. Colonization of the pharynx and possibly the stomach with bacteria is the most important step in the pathogenesis of nosocomial pneumonia. NEUMONIA NOSOCOMIALDefinition & PathogenesisPharyngeal colonization is promoted by exogenous factors (eg, instrumentation of the upper airway with nasogastric and endotracheal tubes; contamination by dirty hands, equipment, and contaminated aerosols; and treatment with broad-spectrum antibiotics that promote the emergence of drug-resistant organisms) and patient factors (eg, malnutrition, advanced age, altered consciousness, swallowing disorders, and underlying pulmonary and systemic diseases). NEUMONIA NOSOCOMIALDefinition & PathogenesisWithin 48 hours of admission, 75% of seriously ill hospitalized patients have their upper airway colonized with organisms from the hospital environment.NEUMONIA NOSOCOMIALDefinition & PathogenesisImpaired cellular and mechanical defense mechanisms in the lungs of hospitalized patients raise the risk of infection after aspiration has occurred. Tracheal intubation increases the risk of lower respiratory infection by mechanical obstruction of the trachea, impairment of mucociliary clearance, trauma to the mucociliary escalator system, and interference with coughing. Tight adherence of bacteria such as Pseudomonas to the tracheal epithelium and the biofilm that lines the endotracheal tube makes clearance of these organisms from the lower airway difficult.NEUMONIA NOSOCOMIALDefinition & PathogenesisThe role of the stomach in the pathogenesis of HCAP remains controversial. Observational studies have suggested that elevation of gastric pH due to antacids, H2-receptor antagonists, proton pump inhibitors (PPIs), or enteral feeding is associated with gastric microbial overgrowth, tracheobronchial colonization, and HAP/VAP.NEUMONIA NOSOCOMIALDefinition & PathogenesisSucralfate, a cytoprotective agent that does not alter gastric pH, is associated with a trend toward a lower incidence of VAP. The Infectious Disease Society of America recommends that acid suppressive medications (H2-receptor antagonists and PPIs) only be given to patients at high risk for stress gastritis.NEUMONIA NOSOCOMIALDefinition & PathogenesisThe microbiology of the nosocomial pneumonias differs from CAP but is substantially the same among HAP, VAP, and HCAP (Table 913). The most common organisms responsible for HAP include:S aureus (both methicillinsensitive S aureus and MRSA), P aeruginosa, gram-negative rods including non-extended spectrum b-lactamase (ESBL) producing and ESBL-producing (Enterobacter species, K pneumoniae, and Escherichia coli). NEUMONIA NOSOCOMIALNEUMONIA NOSOCOMIAL

Definition & PathogenesisVAP patients may be infected with:Acinetobacter species and Stenotrophomonas maltophilia. HCAP patients may have common organisms:S pneumoniae, H influenzae that are more likely to be drug resistant, or flora that resembles HAP. Anaerobic organisms (bacteroides, anaerobic streptococci, fusobacterium) may also cause pneumonia in the hospitalized patient; when isolated, they are commonly part of a polymicrobial flora. Mycobacteria, fungi, chlamydiae, viruses, rickettsiae, and protozoal organisms are uncommon causes of nosocomial pneumonias.NEUMONIA NOSOCOMIAL

NEUMONIA NOSOCOMIAL

NEUMONIA NOSOCOMIALClinical FindingsA. Symptoms and SignsThe symptoms and signs associated with nosocomial pneumonias are nonspecific; however, two or more clinical findings (fever, leukocytosis, purulent sputum) in the setting of a new or progressive pulmonary opacity on chest radiograph are approximately 70% sensitive and 75% specific for the diagnosis of VAP in one study. Other findings include those listed above for CAP.NEUMONIA NOSOCOMIALClinical FindingsA. Symptoms and SignsThe differential diagnosis of new lower respiratory tract symptoms and signs in hospitalized patients includes congestive heart failure, atelectasis, aspiration, ARDS, pulmonary thromboembolism, pulmonary hemorrhage, and drug reactions.NEUMONIA NOSOCOMIALB. Laboratory FindingsDiagnostic evaluation for suspected nosocomial pneumonia includes blood cultures from two different sites. Blood cultures can identify the pathogen in up to 20% of all patients with nosocomial pneumonias; positivity is associated with increased risk of complications and other sites of infection. Blood counts and clinical chemistry tests do not establish a specific diagnosis of HCAP; however, they help define the severity of illness and identify complications.NEUMONIA NOSOCOMIALB. Laboratory FindingsThe assessment of oxygenation by an arterial blood gas or pulse oximetry determination helps define the severity of illness and determines the need assisted ventilation. Thoracentesis for pleural fluid analysis should be considered in patients with be considered in patients with pleural effusions.Examination of sputum is attended by the same disadvantages as in CAP. Gram stains and cultures of neither sensitive nor specific in the diagnosis of nosocomial pneumonias. The identification of a bacterial organism by culture of sputum does not prove that the organism is a lower respiratory tract pathogen. However, it can be used to help identify bacterial antibiotic sensitivity patterns and as a guide to adjusting empiric therapy.

NEUMONIA NOSOCOMIALC. ImagingRadiographic findings in HAP/VAP are nonspecific and often confounded by other processes that led initially to hospitalization or ICU admission. NEUMONIA NOSOCOMIALD. Special ExaminationsEndotracheal aspiration using a sterile suction catheter and fiberoptic bronchoscopy with bronchoalveolar lavage or a protected specimen brush can be used to obtain lower respiratory tract secretions for analysis, most commonly in patients with VAP. Endotracheal aspiration cultures have significant negative predictive value but limited positive predictive value in the diagnosis of specific infectious causes of HAP/VAP. NEUMONIA NOSOCOMIALD. Special ExaminationsAn invasive diagnostic approach using quantitative culture of bronchoalveolar lavage samples or protected specimen brush samples in patients in whom VAP is suspected leads to significantly less antibiotic use, earlier attenuation of organ dysfunction, and fewer deaths at 14 days.Measurement of procalcitonin levels holds promise as a noninvasive strategy to distinguish bacterial pneumonia from noninfectious causes of fever with pulmonary infiltrates in hospitalized patients.NEUMONIA NOSOCOMIALTreatmentTreatment of the nosocomial pneumonias, like treatment of CAP, is usually empiric (Table 914). Because of the high mortality rate, therapy should be started as soon as pneumonia is suspected. There is no consensus on the best regimens because this patient population is heterogeneous and local flora and resistance patterns must be taken into account.NEUMONIA NOSOCOMIALTreatmentAfter results of sputum, blood, and pleural fluid cultures are available, it may be possible to de-escalate initially broad therapy. Duration of antibiotic therapy should be individualized based on the pathogen, severity of illness, response to therapy, and comorbid conditions. Data from a large trial assessing treatment outcomes in VAP suggest that 8 days of antibiotics is as effective as 15 days, except in cases caused by P aeruginosa.NEUMONIA NOSOCOMIALNEUMONIA NOSOCOMIAL

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