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.

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.