Pneumonia

Pneumonia is an infection of the gas exchange segments of the lung parenchyma. It can cause a profound inflammatory response leading to airspace accumulation of purulent debris. Pneumonia costs are $8 billion annually, accounts for nearly one-tenth of all hospital admissions, and remains a leading cause of mortality in the United States.

Etiology and Risk Factors

  • There are numerous risk factors as discussed in (Table 3D.1).
  • The pathogens involved vary depending upon the host (see Table 3D.2).

    Table Risk factors for pneumonia
    Risk Factor Comments
    Aspiration/absent gag reflex Stroke, intubation, seizure, altered mental status, sedative use
    Mucociliary clearance disorders Smoking, alcohol, COPD, cystic fibrosis, chronic bronchitis, viral infections
    Alteration of normal oral flora Acute illness and antibiotic use
    Immunocompromise AIDS*, diabetes, transplant, steroid use, asplenia,
    sickle cell disease, uremia, neoplasia, chemotherapy,
    extremes of age, complement deficiency
    Hematogeonous Indwelling catheters, intrathoracic devices
    Geography/environment American southwest (Valley Fever), Ohio/
    Mississippi Valleys (histoplasmosis, blastomycosis),
    Southeast Asia (tuberculosis), pigeon droppings
    (psittacosis), bovine sources (Q fever), buildings
    with contaminated water supply
    Community dwelling Dormitory, prison, barracks, nursing home

    AIDS: acquired immune deficiency syndrome

    Diagnosis

  • Pneumonia is sometimes divided into two categories depending upon the causative agent and presentation (see Table 3D.3). Note that considerable overlap exists between the two categories and differentiation in the ED may be difficult.
  • Patients typically complain of dyspnea, cough, and fever. Depending upon the etiology, they may also have night sweats, weight loss, myalgias, and localized extra pulmonary symptoms. History should focus on acuity symptom onset, presence of associated symptoms, recent travel history, immunization history, and comorbidities. In certain populations such as the elderly, pneumonia can present with nonspecific symptoms such as weakness and fatigue.
  • Physical exam findings depend upon the etiology and the extent of lung involvement.
    Pulmonary exam often reveals rales and decreased or bronchial breath sounds. Although sometimes difficult to assess in the ED, patients can also have dullness to percussion, tactile fremitus, and ego phony. Associated findings include tachypnea, tachycardia, diaphoresis, AMS, and increased work of breathing. Note that the pulmonary examination sometimes does not correlate with CXR findings.
  • Laboratory Studies
  • Sputum—Because of the low sensitivity of the sputum Gram stains, the clinical utility in the ED is controversial. This test is most helpful if a single predominant organism is identified and requires an adequate specimen (>25 WBCs and < 10 epithelial cells

    Table Common pathogens in pneumonia
    Population Causative Pathogen
    Community acquired Streptococcus pneumoniae, Mycoplasma pneumoniae,
    viruses, Chlamydia pneumoniae, Haemophilus influenzae,
    Legionella, Staphylococcus aureus
    Nosocomial (>likely
    to be resistant to
    antibacterial therapy)
    Gram-negative bacilli, Staphylococcus aureus, anaerobes,
    and Streptococcus pneumoniae (less frequent)

    Table Typical and atypical pneumonias
    Category Pathogens Presentation
    Typical
    (usually bacterial)
    Streptococcus pneumoniae
    Haemophilus influenzae
    Staphylococcus aureus
    Klebsiella pneumoniae
    Anaerobes
    Psuedomonas aeruginosa
    Acute onset
    Shaking chills and high fever
    Cough with purulent sputum
    Dyspnea
    Pleuritic chest pain
    Atypical Mycoplasma pneumoniae
    Viruses
    Legionella
    Chlamydia pneumoniae
    Mycobacterium tuberculosis
    Pneumocystis carinii
    Gradual onset
    Low grade fever
    Scant sputum
    Mild respiratory complaints
    Extrapulmonary complaints
    Mycoplasma: myalgias, headache,
    sore throat, rash
    Viral: upper respiratory symptoms
    Legionella: AMS, gastrointestinal
    symptoms

    per high power field) as well as experienced laboratory personnel. Sputum cultures are helpful for critically ill or immunocompromised patients but are rarely of use to the EP and should not be routinely ordered. An acid fast (AFB) stain is indicated patients with risk factors or presentation consistent with tuberculosis (TB).

  • Serum
  • There are no specific laboratories for pneumonia although CBC, electrolytes, and renal function studies are often ordered. These tests should be obtained routinely in patients who are critically ill or if significant comorbid disease is present. Note that presence of an elevated WBC does not identify a bacterial source. Nor does a normal WBC rule it out.
  • Serum antibody titers are available for Legionella, Mycoplasma pneumoniae, and viruses among others but are of little use in the ED.
  • CXR
  • Ordered in nearly all patients with suspected pneumonia although studies debate the utility of this study in otherwise healthy people being treated empirically as an outpatient.
  • Certain radiographic patterns have been described depending upon the etiology (see Table 3D.4). These patterns sometimes vary and do not provide an accurate means of diagnosis.
  • Note that radiographic findings often lag behind clinical symptoms. Patients with early disease and immunosuppression may not have classic findings.
  • Differential diagnosis includes COPD, bronchitis, asthma, allergic reaction, and PE among others.

    Treatment

  • Stabilization of cardiopulmonary status is the first priority. Depending on the disease severity, patients may have respiratory compromise and/or circulatory collapse that mandate immediate intervention.
  • Early antibiotic treatment decreases morbidity and mortality. Empiric therapy should be started as soon as possible after appropriate resuscitative measures. Many patients are treated as outpatients, although certain groups are at risk for poor outcome and should be considered for hospital admission (see Table 3D.5). Admitted patients should

    Table Radiographic presentation of pneumonia
    Radiographic Pattern Pathogens
    Lobar Streptococcus pneumoniae
    Klebsiella pneumoniae (classically RUL, bulging fissure)
    Patchy Atypical agents
    Haemophilus influenzae
    Staphylococcus aureus
    Fungi
    Viruses
    Interstitial Mycoplasma pneumoniae
    Viruses
    Pneumocystis carinii
    Abscess Tuberculosis and other fungi
    Staphylococcus aureus
    Effusion Streptococcus pneumoniae
    Staphylococcus aureus
    Mycoplasma pneumoniae
    Viruses
    Tuberculosis
    Apical Tuberculosis
    Klebsiella pneumoniae

    receive IV antibiotics and outpatients appropriate oral therapy as indicated for their age, comorbid conditions, and suspected pathogen (see Table 3D.6).

  • All discharged patients should follow-up with their primary care physician.
Suggested Reading
  1. Feldman CF. Pneumonia in the elderly. Clin Chest Med 1999; 20(3):563.
  2. Dean NC. Use of prognostic scoring and outcome assessment tools in the admission decision forcommunity-acquired pneumonia. Clin Chest Med 1999; 20(3):521.
  3. American Thoracic Society: Guidelines for the initial management of adults with community acquired pneumonia: Diagnosis, assessment of severity, and initial microbial therapy. Am Rev Respir Dis 1999; 148:1418.

    Table High risk patients
    Risk Factor Comment
    Abnormal vital signs Tachypnea (>30/min)
    Hypotension (< 70 mm Hg systolic)
    O saturation < 95% on room air
    Extremes of age <6 mos or >60 yr
    Comorbid conditions or disease Pregnancy
    Congestive heart failure
    Renal or hepatic insufficiency
    Immunosuppression: HIV, asplenia, diabetes, alcohol/drug abuse
    Recent hospital admission
    Patients who fail initial therapy
    Risk of aspiration Stroke, AMS, alcohol abuse
    Pathogen Suspected tuberculosis
    Gram-negative bacilli on sputum examination
    Inability to care for self as outpatient

    Antimicrobial guidelines for pneumonia
    Group Treatment Alternatives
    Outpatient therapy Erythromycin Levofloxacin
    Adults 18-65 yr Clarithromycin Second generation
    cephalosporin
    No comorbid disease Azithromycin (5 days) Doxycycline
    Amoxicillin/clavulanate
    Outpatient therapy Bactrim
    Adult >65 Doxycycline
    Alcohol/tobacco use Azithromycin (5 days)
    Levofloxacin
    Inpatient therapyª Ceftriaxone or cefotaxime + macrolide
    General ward Cefuroxime + macrolide
    Levofloxacin
    Inpatient therapy Azithromycin + ampicillin/sulbactam
    Suspected aspiration Levofloxacin + clindamycin
    Second or third generation cephalosporin + clindamycin
    Inpatient therapy Ticarcillin/clavulanate + aminoglycoside
    Ventilated/ICU Piperacillin/tazobactam + aminoglycoside
    Ceftazidime + aminoglycoside
    Imipenem

    * All regimens are for 7-14 days unless otherwise noted
    ª All medications for inpatient therapy via IV route

  4. Emergency Medicine Reports: Community-acquired pneumonia (CAP) in the geriatric patient: Evaluation, risk-stratification, and antimicrobial treatment guidelines for inpatient and outpatient management 2000; 21(20).
  5. The Sanford Guide to Antimicrobial Therapy, 31st edition. 2001.
       
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