KEY POINTS
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While physicians have treated pneumonia for centuries, each stage of the clinical decision-making process still poses challenges, from determining the most appropriate care setting for a patient with suspected pneumonia to planning follow-up after antibiotic completion. Over the years, doctors have witnessed the advent of new medical and respiratory therapies, as well as the development of antibiotic resistance in the treatment of this common infection.
Patients hospitalized with pneumonia are divided into 2 categories: those with community-acquired pneumonia (CAP), and those who develop hospital-acquired or ventilator-associated pneumonia while already hospitalized.
Each patient population faces unique exposures to organisms, and therefore recommended diagnostic tests, empiric treatment regimens, and goals for infection prevention vary.
This article reviews guidelines from the Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) 1 and interprets recent studies to address questions that arise specifically in the inpatient treatment of CAP.
Risk stratification of community-acquired pneumonia
The IDSA/ATS 2019 1 guidelines emphasize the importance of first determining what level of patient care is needed: Is outpatient treatment appropriate or does the patient need to be admitted to the hospital, or even the intensive care unit?
Appropriate classification can prevent stress on the patient and the health care system associated with underestimation or overestimation of disease severity.
Patients at high risk of death whose acuity is not fully appreciated face inadequate support, while those admitted despite low risk of death may be unnecessarily subjected to the risks of the hospital environment, such as infections from multidrug-resistant organisms. associated with medical care.
Risk calculators are routinely used to help clinicians evaluate their patients in daily practice, although they have not been specifically validated to predict the need for admission.
CURB-65 is a simple calculator based on 5 risk factors. Patients receive 1 point each for confusion , elevated blood urea nitrogen ( BUN), increased respiratory rate , low blood pressure, and age greater than or equal to 65 years; the higher the total score, the greater the risk of 30-day mortality.
According to the IDSA/ATS, patients with scores of 0 or 1 can be treated as outpatients, those with scores of 2 should be admitted to the hospital, and those with scores of 3, 4, or 5 need care in the intensive care unit. . ( Editor’s note: You can find an online version of this calculator by clicking here )
A shortened version of this calculator, CRB-65, allows for outpatient risk stratification without laboratory work. 1
The Pneumonia Severity Index incorporates 20 risk factors to place patients into 5 classes correlated with mortality risk 5.
The authors suggest outpatient management for those in classes I or II and inpatient management for those in risk classes IV and V. Patients in class III can be safely treated in an outpatient setting with appropriate support or in an inpatient observation unit. ( N. del E.: clicking here you will have a Spanish version of this tool)
While CURB-65 may be better in busy clinical settings as it is a shorter risk stratification scale for CAP, the 2019 IDSA/ATS guidelines prefer the Pneumonia Severity Index as it has been studied and validated more. widely. 1
The IDSA/ATS guidelines list a separate set of major and minor criteria to define “severe pneumonia” to determine which patients with suspected CAP deserve intensive care. 1 At least 1 of the major criteria or at least 3 of the minor criteria are required for the diagnosis of severe pneumonia (see table below).
A retrospective review of more than 1,800 patients found that 45% of patients who had "low risk" CAP according to the Pneumonia Severity Index were admitted. 7 Patients with cognitive impairment, coronary artery disease, diabetes mellitus, lung disease, multilobar radiographic opacities, home oxygen therapy, corticosteroid use, or antibiotic use before presentation had higher odds of hospitalization.
The authors emphasize that clinical judgment must be applied to the results of any of these calculators to appropriately classify patients with pneumonia.
Diagnosis of community acquired pneumonia
After submitting a patient with suspected CAP to the safest level of care, various radiographic and laboratory methods can be used to verify the diagnosis and identify the organism most likely responsible for the ongoing infection.
Chest radiographs with demonstrable infiltrates are required to diagnose CAP and distinguish it from upper respiratory tract infection. 1
Different organisms can be associated with characteristic infiltration patterns, often manifesting within 12 hours after the onset of symptoms:
Non-segmental or lobar focal pneumonia (Fig. 1)
Typical bacterial pneumonias caused by organisms such as Streptococcus pneumoniae tend to manifest with airspace opacity in 1 segment or lobe, although the use of antibiotics can alter their pathophysiology to create a patchy, multilobular pattern of opacity.
Multifocal bronchopneumonia or lobar pneumonia
Bronchopneumonias, similarly characterized by an irregular pattern, are most commonly caused by Staphylococcus aureus , Haemophilus influenzae , and fungi. 8
Focal or diffuse "interstitial" pneumonia (fig. 2)
Atypical bacterial organisms, including Legionella pneumophila , Mycoplasma pneumoniae , and Chlamydophila pneumoniae, frequently involve the lung bases in a bilateral, diffuse reticulonodular pattern, but may begin as isolated lobar opacities on chest radiography. 9 Viral organisms are also associated with diffuse and bilateral lung involvement.
Early radiographic identification of pulmonary complications , such as pleural effusions or cavitating lesions, may provide further clues to the causative organism and allow timely intervention. 9
How accurate is chest x-ray?
The usefulness of chest radiographs in the diagnosis of CAP is subject to interobserver variability, with some studies citing 65% accuracy in the diagnosis of viral pneumonia, 67% in the diagnosis of bacterial pneumonia, and no statistical reliability for Differentiate bacterial from non-bacterial pneumonia.
Microbiology
A thorough social history should be collected from each patient with suspected CAP to detect possible occupational, travel, or endemic exposures. This will guide microbiological testing and empiric antibiotic treatment.
For example, patients presenting during influenza season or with known exposures to poultry in areas of previous influenza outbreaks should be tested for influenza A and B with a nasopharyngeal swab.
Isolation of a specific organism in outpatients with CAP may not be necessary but is recommended to guide reduction of empiric antibiotic regimens. 1 Before treatment, Gram stain and culture should be performed in patients capable of adequately expectorating a good quality sample or by endotracheal aspiration in intubated patients.
Patients who meet criteria for severe pneumonia as defined by the IDSA/ATS guidelines deserve blood and sputum cultures , as well as urinary antigen testing for L pneumophila and S. pneumoniae . 1
Procalcitonin test
Procalcitonin testing may help differentiate viral from bacterial pathogens in patients admitted for CAP, avoiding the use of unnecessary antibiotics and allowing rapid reduction of empiric therapy more effectively than clinical judgment alone. 13
Although any infectious pneumonia can precipitate elevations of this serum biomarker, typical bacteria tend to produce higher levels of procalcitonin than atypical bacteria or viruses. 14
Cytokines , associated with bacterial infections, increase procalcitonin release, while interferons , associated with viral infections, inhibit procalcitonin release. However, this biomarker is not perfect and will not be elevated in up to 23% of typical bacterial infections. 14
For this reason, the authors state that procalcitonin should not replace clinical judgment in guiding the decision to initiate antimicrobial therapy for patients with suspected CAP, but can be used in conjunction with clinical judgment to reduce therapy.
In patients whose medical histories suggest alternative causes of respiratory distress or improvement with concomitantly administered therapies such as diuresis, a negative procalcitonin may help guide discontinuation of antibiotics.
On the other hand, in patients with Influenza proven by PCR, elevated procalcitonin may suggest continuation of antibiotics to treat bacterial superinfection.
Management of CAP
Antibiotic therapy
The selection of antibiotics before identifying a causal pathogen should be made based on the risk factors and the degree of the patient’s disease.
Doxycycline can be used as an alternative to macrolide or respiratory fluoroquinolone to cover atypical organisms such as Chlamydia pneumoniae, Legionella pneumophila , and Mycoplasma pneumoniae in patients with prolonged QTc. In patients allergic to penicillin, aztreonam should be used in combination with an aminoglycoside and a respiratory fluoroquinolone.
Patients who may have been exposed to influenza or who have a history of injection drug use or structural lung disease or who have a lung abscess, cavitary infiltrates, or endobronchial obstruction also deserve coverage for acquired methicillin-resistant S. aureus (MRSA). in the community with vancomycin or linezolid.
If an organism is identified by culture, PCR, or serology, the empiric antibiotic regimen should be tailored to this organism.
Nasal MRSA screening can be reliably used to guide empiric and targeted antimicrobial regimens; Patients started on vancomycin or linezolid based on the above risk factors can be safely tapered based on a negative nasal swab. fifteen
Pneumococcal urinary antigen has equally reliable negative predictive value and can also be used to reduce empiric antimicrobial therapy. 16
In the event that microbiologic evaluation does not identify a causative organism, the patient’s individual risk factors listed above should be considered in tapering therapy to a final regimen with coverage for MRSA, Pseudomonas aeruginosa , or atypical pathogens, as indicated. indicate.
Pseudomonas pneumonia has been associated with a higher risk of mortality and relapse than pneumonia caused by other pathogens.
IDSA/ATS guidelines recommend against using corticosteroids for treatment except in patients with refractory septic shock.
Subsequent management
Patients who are hemodynamically stable , can safely ingest medications, and have a normal gastrointestinal tract can be discharged on oral therapy without waiting to observe clinical response.
Antibiotics should be administered for at least 5 days , although longer periods may be necessary in immunocompromised patients or those with pulmonary or extrapulmonary complications. 1
An infectious disease consultation may be beneficial if long-term intravenous antibiotic therapy is anticipated or if the patient progressively deteriorates on guideline-based antimicrobial therapy.
Consultation with pulmonology may be necessary for bronchoscopy to obtain deep respiratory specimens, especially if the patient is clinically worsening and the causative pathogen remains unidentified.
The authors acknowledge that the yield of bronchoscopy and bronchoalveolar lavage specimens is reduced with increased duration of antibiotic therapy, but believe that in the setting of clinical worsening despite antibiotics, bronchoalveolar lavage may help to successfully identify multidrug-resistant or atypical pathogens that may not be covered by the current antibiotic regimen.
Consultation with pulmonology is also indicated for patients with complications of pneumonia, such as empyema, requiring procedural intervention.
Authors’ conclusions
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