Pneumonia

by Mary J. O.

Case Presentation

A 74-year-old male with a history of hypertension and diabetes presented to the emergency department with a cough productive of rust-colored sputum. His complaints started approximately three days earlier and progressively worsened. The patient reported difficulty in breathing, shaking chills, and fever up to 39ºC. He had no sick contacts. On examination, the physician noticed an elderly gentleman in mild respiratory distress. His vital signs were: BP: 110/70 mmHg, HR: 102 bpm, RR 20 bpm, T 38.4ºC and SpO2 91% on room air. Auscultation revealed rales at the right lung base.

Introduction

Pneumonia is an acute respiratory infection of the lung parenchyma, particularly the alveoli. The healthy alveoli fill with air when a person breathes; however, in pneumonia, the fluid or pus in the alveoli makes breathing painful and inhibits air exchange. Despite modern research and the development of a variety of antimicrobial agents, pneumonia remains a leading cause of death worldwide, especially in the very young and the elderly.

The most common causes of pneumonia are bacteria and viruses, but fungi, protozoans, and parasites can also cause infection. These organisms, typically found in the nasopharynx, can infect the lungs by inhalation. Additionally, airborne droplets (such as from a cough or sneeze) or blood-borne infections (such as from mother to baby during delivery) may spread the disease.

For an overview of pneumonia, watch the video below:

Classification

Community-acquired pneumonia (CAP) occurs in patients with no recent hospitalization or exposure to the healthcare system. The most common bacterial cause of CAP is Streptococcus pneumoniae. Its incidence is declining due to vaccination. Other common bacteria are Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus. These so-called “typical” pneumonia agents generally present with primarily respiratory symptoms and a lobar consolidation on chest radiograph. Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella sp. are among the common atypical causes of bacterial pneumonia. They may present with a subacute onset, more generalized, non-respiratory symptoms and respond to different antibiotics than the typical organisms. The radiographs may not show an infiltration.

Common viral causes of pneumonia include influenza, respiratory syncytial virus (RSV), parainfluenza, coronaviruses, adenoviruses, and rhinoviruses. Recently, a number of new viral pathogens have emerged, including coronaviruses that causes severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS-CoV).

Hospital-acquired pneumonia (HAP) refers to pneumonia newly-contracted at least 48-72 hours after hospitalization. It is the second most common type of nosocomial infection (after urinary tract infections), and a common cause of death in the intensive care unit. Ventilator-associated pneumonia (VAP) is pneumonia that occurs 48 hours or more after a patient receives mechanical ventilation through an endotracheal tube or tracheostomy. Intubation allows oral and gastric secretions and microorganisms to enter the lower respiratory tract. Multidrug-resistant (MDR) organisms usually cause VAP.

Healthcare-associated pneumonia (HCAP) is a particular subset of nosocomial pneumonia in which patients come from the community but have frequent interactions with the healthcare system. It includes patients who were hospitalized within the last 90 days, reside in a long-term care facility such as a nursing home, receive hemodialysis or wound care, have contact with a family member with MDR pathogens, or are on chemotherapy or intravenous antibiotics. Like HAP and VAP, patients with HCAP are at risk for multidrug-resistant pathogens.

Critical Bedside Actions and General Approach

Initial evaluation should focus on ensuring adequate ventilation and oxygenation. Hypoxic patients should receive supplemental oxygen. Endotracheal intubation may be required in patients with severe respiratory distress. Early and aggressive fluid resuscitation is necessary for patients who are hemodynamically unstable or who are presenting with sepsis. Empiric antibiotic therapy should be started once the diagnosis of pneumonia is established, even before the definite identification of a microbial cause.

Differential Diagnosis

  • Asthma
  • Bronchitis
  • Chronic obstructive pulmonary disease (COPD)
  • Lung cancer
  • Pulmonary edema
  • Pulmonary embolism
  • Upper respiratory tract infections

Clinical Presentation

The classic symptoms of pneumonia are fever/chills, cough (often productive of purulent sputum), pleuritic chest pain, and shortness of breath. Elderly patients may present with nonspecific symptoms, such as general malaise, anorexia, and confusion. On physical examination, tachycardia and tachypnea are usually present. Patients may be hypoxic and hypotensive. Auscultation of the chest may reveal coarse rales or bronchial breath sounds. There may also be dullness to percussion and increased tactile fremitus. No single clinical finding is reliable in establishing a diagnosis of pneumonia.

For examples of lung sounds, please see the following video:

Emergency/Diagnostic Tests and Interpretation

  • Pulse oximetry to screen for hypoxia. Hypoxia is an indication for admission.
  • Chest x-ray (CXR): generally the most important study to determine the presence of pneumonia, although it cannot establish the causative agent. The absence of findings on CXR should not preclude the use of antibiotics in patients thought to have pneumonia based on clinical presentation.

40 yo Female with respiratory distress

377.1 - pneumonia1

  • Computed tomography (CT) of the chest: more sensitive than CXR, but often not necessary.
  • Point-of-care ultrasound is becoming more widely used for the rapid diagnosis of pneumonia. It can be more sensitive than CXR, though findings of consolidation on ultrasound are not specific for pneumonia. The accuracy of ultrasound is operator-dependent.

The ultrasound below shows consolidation and pleural effusion related to pneumonia.

  • A complete blood count (CBC) may show the presence of leukocytosis, but this often does not affect overall management.
  • An elevated lactate level may indicate the need for more aggressive fluid resuscitation.
  • If congestive heart failure is in the differential diagnosis, B-type natriuretic peptide (BNP) may help distinguish between CHF and pneumonia.
  • The utility of routine blood cultures has been questioned due to the low yield, but they should be drawn before the initiation of antibiotics in patients who will be admitted, particularly in severely ill patients. Cultures are positive in 20-25% of pneumonia caused by S. pneumoniae, but the percentage is even lower in pneumonia due to other causes. Positive blood cultures may help determine local antibiotic resistance patterns.
  • Sputum Gram stain and culture can help identify a bacterial pathogen, but like blood cultures, the usefulness in the emergency department setting is very limited. With an adequate specimen, sputum studies are positive in more than 80% of cases of S. pneumoniae, but that percentage is much less for other pathogens.
  • Urine antigen tests are available for Legionella pneumophila serotype 1 (74% sensitivity) and pneumococcus.
  • Rapid diagnostic tests are available for many viruses, including RSV and influenza.

Treatment Options

Once pneumonia has been diagnosed, antimicrobial therapy should be started as soon as possible, as early initiation leads to better outcomes. Antimicrobial therapy should be tailored to the most likely causative organisms in order to avoid drug toxicity, decrease the rate of resistance to broad-spectrum antibiotics, and reduce cost. The empiric treatment of CAP has been made more difficult by the emergence of drug-resistant Streptococcus pneumoniae (DRSP).

Risk factors for resistant S. pneumoniae include age > 65 years; recent treatment or repeated therapy with beta-lactams, macrolides, or fluoroquinolones; and medical comorbidities, including immunosuppression.

The following recommendations are adapted from: the EMRA Antibiotic Guide; Musher et al., NEJM; and World Health Organization (WHO) guidelines.

Outpatient therapy (adults):

  • Amoxicillin/clavulanate, with the addition of azithromycin or doxycycline if atypical organisms are suspected
  • Levofloxacin or moxifloxacin monotherapy may be used instead
  • If influenza is suspected, treat early with oseltamivir

Inpatient therapy (adults):

  • Ceftriaxone or cefotaxime, with the addition of azithromycin or doxycycline
  • Levofloxacin or moxifloxacin may be used instead
  • If influenza is suspected, treat early with oseltamivir
  • If MRSA is suspected, vancomycin or linezolid should be added
  • If the patient is allergic to penicillin, use aztreonam and levofloxacin instead
  • If Pseudomonas is likely, use double coverage until susceptibilities are back – levofloxacin or gentamicin, with the addition of an anti-pseudomonal beta-lactam: cefepime, piperacillin/tazobactam, or aztreonam

HCAP, HAP, or VAP (adults) [choose one from each category below]:

  • Beta-lactams: cefepime, ceftazidime, piperacillin/tazobactam, aztreonam
  • Levofloxacin, or azithromycin plus gentamicin
  • MRSA coverage: vancomycin or linezolid

Outpatient therapy (pediatrics):

  • Amoxicillin (preferred in low-resource settings) or amoxicillin/clavulanate
  • If atypical pneumonia suspected, azithromycin

Inpatient therapy (pediatrics):

  • Ampicillin
  • Ceftriaxone or cefotaxime
  • If MRSA is suspected, add clindamycin or vancomycin
  • If atypical organisms suspected, azithromycin

Special Considerations

  • Specific Organisms and Associations
    • S. pneumoniae is the single most commonly identified organism in both adults and children with CAP. It is classically associated with rust-colored sputum and lobar consolidation.
    • H. influenzae is a common pathogen in patients with chronic obstructive pulmonary disease (COPD), diabetes, malignancy, alcoholism, and malnutrition.
    • M. catarrhalis is another common pathogen in patients with COPD, although it more often causes COPD exacerbations than pneumonia.
    • Klebsiella pneumoniae rarely causes CAP in a healthy host but can cause severe pneumonia in patients with chronic illnesses, such as alcoholism or diabetes. The sputum produced is often mixed with blood, giving it the color of red currant jelly.
    • S. aureus can cause severe, necrotizing pneumonia with cavitary lesions. It can often occur after an infection with influenza. Intravenous drug users can also get hematogenous spread.
    • C. pneumoniae is a relatively common cause of CAP, causing subacute systemic symptoms, such as fever, malaise, myalgias, and non-productive cough.
    • M. pneumoniae is a common cause of CAP, particularly in younger patients. It can be associated with rashes, sore throat, and ear pain. The classic finding associated with this pathogen is bullous myringitis, though it is actually not common and is nonspecific.
    • The Legionella genus is comprised of over 50 species of intracellular organisms that live in aquatic environments and cause infection when inhaled. There have been no documented cases of person-to-person transmission. Elderly patients are at risk of severe pneumonia, often with gastrointestinal symptoms such as abdominal pain and diarrhea. Hyponatremia is often present as well.
    • Anaerobic infections can result from the aspiration of oropharyngeal contents. These infections are often polymicrobial. Risk factors are patients with decreased level of consciousness or severe periodontal disease.
    • Fungi are a rare cause of pulmonary infections. Histoplasma capsulatum lives in soil that contains large amounts of bird or bat droppings and causes disease when spores are inhaled. It is found most commonly in the central and eastern United States, near the Ohio and Mississippi River valleys. H. capsulatum can also be found in Central and South America, Asia, Africa and Australia. Coccidiodes immitis is found in the southwestern United States and Central and South America.
    • Other rare causes of pneumonia are: tularemia (caused by the bacterium Francisella tularensis) is spread by contact with infected mammals, especially rabbits. Psittacosis (caused by Chlamydia psittaci) can be spread to humans from infected birds. Sheep, cattle, and goats are the natural reservoir of Q fever (caused by Coxiella burnetii).
  • Pediatric Patients
    • Pneumonia is the leading cause of death of children worldwide, killing more than malaria, measles, and AIDS combined. In neonates, organisms that colonize the maternal vaginal canal, such as Group B Streptococcus (GBS), Listeria monocytogenes, and Escherichia coli may cause pneumonia. Viruses are a common cause of pneumonia in infants and young children. RSV and parainfluenza infections most often occur in the wintertime. Symptomatic treatment is recommended for cases of viral pneumonia. In school-age children, M. pneumoniae and C. pneumoniae infections are more common. Pediatric patients often do not present with the classic signs of pneumonia, such as a productive cough. Often, the only signs are tachypnea and increased work of breathing.
  • Geriatric Patients
    • Elderly patients are more susceptible to pneumonia than younger patients and have a higher rate of morbidity and mortality. Even after recovery from pneumonia, they have a higher rate of mortality in one year. They often do not present with the classic signs and symptoms of pneumonia, such as fever, cough, sputum production, or leukocytosis. Frequently, the only sign of pneumonia may be confusion or malaise. The most common cause of community-acquired pneumonia in the elderly remains S. pneumoniae. However, geriatric patients are more likely to have resistant types of this organism.
  • Pregnant Patients
    • Pneumonia is the most frequent cause of non-obstetric infection in the pregnant patient. The pregnant woman is predisposed to infection due to an alteration in immune status, making her more susceptible to infection. In the postpartum period, pneumonia can occur from aspiration as a complication of obstetric anesthesia. Additionally, there is an increased risk of aspiration due to increased intragastric pressure from the gravid uterus and relaxation of the gastroesophageal sphincter due to progesterone.
    • Evaluation and treatment are more complicated because there are two patients to care for simultaneously. Chest radiography should be performed with the protection of the fetus. Appropriate antimicrobial therapy should be selected to avoid teratogenicity. Fetal complications are common as fever and hypoxemia are harmful to development. Preterm labor is a known complication of pneumonia, and tocolytic therapy may be required. Testing for Group B Streptococcus before delivery and intrapartum administration of antibiotics can prevent the transmission of the bacteria to the neonate.
  • Immunocompromised Patients
    • Pneumocystis jirovecii (formerly P. carinii) is a fungal agent that does not cause infection in healthy people but is an important cause of opportunistic infection in immunocompromised hosts. It remains the most common AIDS-defining illness in individuals with human immunodeficiency virus (HIV). The classic symptoms are fever, nonproductive cough, fatigue, shortness of breath especially with exertion, bilateral interstitial infiltrates, and hypoxia. Trimethoprim/sulfamethoxazole (TMP/SMX), also known as cotrimoxazole, is the drug of choice for PCP, although alternatives (such as pentamidine, dapsone, and atovaquone) are often needed due to allergic reactions, adverse effects, or treatment failure. Adjunctive therapy with corticosteroids has been shown to improve survival, especially in patients who are hypoxic.
    • Another pathogen to consider in immunocompromised patients is Mycobacterium tuberculosis. Cytomegalovirus (CMV) and varicella zoster are rare causes of viral pneumonia.

Disposition Decisions

A number of clinical prediction rules and guidelines have been developed to determine whether patients with CAP should be admitted or can be safely treated as an outpatient. As with all clinical prediction rules, these scores should be used as a guideline and should not override the judgment of the physician.

Pneumonia Severity Index (PSI)

The PSI is the most widely studied clinical prediction rule for pneumonia. It stratifies patients into five classes for risk of death (Risk Class I to V) from all causes within 30 days of presentation based on medical history, physical examination, and laboratory/radiologic findings. All-cause mortality ranges from 0.1% for Risk Class I to 27.0-29.2% for Class V. As points are assigned by age, it may underestimate severe pneumonia in otherwise young, healthy patients and may overestimate severity in older patients (any patient over 50 years of age is automatically classified into Risk Class II).

Click on the link to access a calculator for PSI.

CURB-65 severity score

The PSI score uses twenty variables and may be cumbersome to use in the emergency department. The CURB-65 score only requires five variables and is easier to compute.

  • Confusion
  • Urea > 7 mmol/L (in the United States, blood urea nitrogen > 19 mg/dL)
  • Respiratory rate ≥ 30 breaths/minute
  • Blood pressure (systolic < 90 mmHg or diastolic ≤ 60 mmHg)
  • Age ≥ 65 years

One point is given for each variable and patients can be stratified according to increasing risk of mortality, ranging from 0.7% mortality for a score of 0 to 57% mortality for a score of 5. Consider an ICU admission for patients with a score of 4 or 5.

Compared to the CURB-65 score, the PSI identified a greater number of patients as low-risk (68% vs. 61%). The low-risk patients according to the PSI had a slightly lower 30-day mortality (1.4%) compared to the CURB-65 (1.7%). The clinical relevance of the slightly improved accuracy of the PSI is unknown.

To calculate a CURB-65 score, click on the link.

SMART-COP

The SMART-COP rule is a clinical rule that predicts which patients with community-acquired pneumonia may need intensive care, such as mechanical ventilation or inotropic support. A SMART-COP score of ≥ 3 points identified 92% of patients who required intensive care measures. While this score was superior to CURB-65 for predicting whether a patient would need intensive respiratory or vasopressor support, like the PSI, the sensitivity of SMART-COP is reduced in younger patients and was noted in one study to stratify 15% of young adults incorrectly.

To see the SMART-COP tool, follow the link.

Ultimately, the decision to admit a patient depends on the physician’s judgment, but all the factors listed in the above scoring systems should be considered.

References and Further Reading

  • American Thoracic Society Documents. Guidelines for the Management of Adults with Hospital-acquired, Ventilator-associated, and Healthcare-associated Pneumonia. Am J Respir Crit Care Med 2005; 171(4):388-416.
  • Aujesky D, Auble TE, YE DM, et al. Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia. Am J Med 2005; 118:384.
  • Blaivas M. Lung Ultrasound in Evaluation of Pneumonia. J Ultrasound Med 2012;31:823–826.
  • Chalmers JD, Singanayagam A, Hill AT. Predicting the need for mechanical ventilation and/or inotropic support for young adults admitted to the hospital with community-acquired pneumonia. Clin Infect Dis 2008 Dec 15; 47(12):1571-4.
  • Charles PG, Wolfe R, Whitby M, et al. SMART-COP: a tool for predicting the needs for intensive respiratory or vasopressor support in community-acquired pneumonia. Clin Infect Dis 2008 Aug 1; 47(3):375-84.
  • File, TM. Antibiotic studies for the treatment of community-acquired pneumonia in adults. In: UpToDate, Bartlett JG (Ed), UpToDate, Waltham, MA. (Accessed on August 18, 2015.)
  • Fine MJ, Hough LJ, Medsger AR, et al. The hospital admission decision for patients with community-acquired pneumonia. Results from the Pneumonia Patient Outcomes Research Team cohort study. Arch Intern Med 1997; 157:36.
  • Koenig SM, Truwit JD. Ventilator-Associated Pneumonia: Diagnosis, Treatment, and Prevention. Clin Microbiol Rev 2006 Oct; 19(4):637–657.
  • Levine BJ, ed. 2013 EMRA Antibiotic Guide. 15th ed. Texas: Emergency Medicine Residents’ Association; 2012.
  • Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003 Mary; 58(5):377-82.
  • Lung Sounds – Rales, Rhonchi, Wheezes. TheLungSounds [uploaded May 21, 2012]. Available from: http://www.youtube.com/watch?v=gOB0nM0PRTc. Accessed November 30, 2015.
  • Musher DM, Thorner AR. Community-Acquired Pneumonia. N Engl J Med 2014; 371:1619-1629.
  • Patel S. CURB-65 Severity Score. Available from: http://www.mdcalc.com/curb-65-severity-score-community-acquired-pneumonia. Accessed November 30, 2015.
  • Patel S. PSI/PORT Score: Pneumonia Severity Index for CAP. Available from: http://www.mdcalc.com/psi-port-score-pneumonia-severity-index-adult-cap. Accessed November 30, 2015.
  • Pneumonia in the Pregnant Patient: A Synopsis. Medscape General Medicine. 1999;1(3) Available from: http://www.medscape.com/viewarticle/717402_1. Accessed November 30, 2015.
  • SMART-COP tool for assessing the severity of community-acquired pneumonia (CAP) in adults. Therapeutic Guidelines Ltd. [July 2010]. Available from: http://lifeinthefastlane.com/wp-content/uploads/2010/07/etg-smartcop.pdf. Accessed November 30, 2015.
  • What is pneumonia? Khan Academy [uploaded June 6, 2014]. Available from: http://www.youtube.com/watch?v=dzJNabJAPaE. Accessed November 30, 2015.

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