General Medical Officer (GMO) Manual: Pneumonia

General Medical Officer (GMO) Manual: Clinical Section

Pneumonia

Department of the Navy
Bureau of Medicine and Surgery
Peer Review Status: Internally Peer Reviewed

(1) Introduction

Pneumonia is the 5th most common cause of death and is a common infectious disease of lung parenchyma. Pneumonia is loosely divided into community acquired and nosocomial groups. Pneumonia that develops either during the hospital stay or within 4 to 6 weeks after discharge from the hospital, in the nursing home or in long-term care facilities, is considered nosocomial pneumonia. Pneumonia that develops in other settings is called community acquired pneumonia. Community acquired pneumonia is further divided into acute bacterial pneumonia and atypical pneumonia.

(2) Etiology

The common causes of community acquired pneumonia are Pneumococcus, Hemophilus influenzae, Legionella (bacterial), Mycoplasma, and Chlamydia. Other uncommon causes of community acquired pneumonia are Group A Streptococcus, Staph aureus, gram-negative rods, Moraxella catarrhalis (smokers), and anaerobes (aspiration). Other rare causes of pneumonia based on endemic areas are Coccidiomycosis, histoplasmosis, Blastomycosis, and Rickettsia. Finally consider Pneumocystis carinii pneumonia (PCP) and tuberculosis (TB) in immunosuppressed patients.

(3) Clues from the history and physical exam

With pleuritic type chest pain, suspect a pleural effusion; rigors are more common with pneumococcal lung infection. Check the respiratory rate and observe the patient closely if above 25. Check tilts to assess whether the patient is dehydrated. Check the oxygen saturation. Hemoptysis (blood tinged sputum) is rare with Mycoplasma pneumonia but is often seen with bacterial, TB, and fungal type lung infections. Severe coughing spells and wheezing in a non-asthmatic is suggestive of chlamydia. Associated headache and GI symptoms suggest Legionella.

(4) Diagnosis

After gathering the history and performing the physical exam, request a CBC, chemistry studies, CXR, and sputum smear. Always check a pulse oximetry. If a pulse oximetry is not available, place the patient on oxygen. Initiate IV hydration.

A WBC of < 3,000/mm3 or > 25,000 is an ominous sign. A respiratory rate >30, a diastolic blood pressure < 60 mmHg, and a BUN > 20 are other poor prognostic signs. If you suspect tuberculosis based upon clinical and/or radiographic features, ISOLATE the patient immediately. Do not hesitate when in doubt.

Perform a sputum gram stain. If the gram stain demonstrates gram positive organisms suggestive of Pneumococcus or Streptococci, begin a third generation cephalosporin such as Ceftriaxone or Cefuroxime. If either antibiotic is not available, penicillin may be given at a dosage schedule of 2 million units every 4 hours (IV). If a sputum sample is not available or the gram stain is not helpful, begin empiric therapy with Ceftriaxone (or Cefuroxime) and Azithromycin. If the gram stain demonstrates gram-negative cocco-bacillary forms, begin Ceftriaxone, Cefuroxime or Septra.

(5) Radiographic Red Flags

(a) Volume loss – This implies endobronchial obstruction (i.e. foreign body, anatomical abnormalities, or tumor). The patient needs bronchoscopy and isolation.

(b) Pleural effusion – Look at the costophrenic angle. If this is obliterated, request lateral decubitus x-ray views. If the fluid layers out to more than 10mm, a thoracentesis should be performed to determine the cause. If clinical deterioration occurs, tap the fluid even if it is <10mm.

(c) Adenopathy - Hilar and mediastinal adenopathy signify an atypical pneumonia. Suspicion for organisms such as tuberculosis or fungi should be high. Isolate the patient and do an aggressive workup for diagnosis.

(d) Cavitation – The most common community acquired pneumonias rarely cavitate except Staph aureus pneumonia. When cavitation is seen, isolate the patient. Suspect tuberculosis, aspiration pneumonia, and a fungal infection.

(e) Multilobar involvement – When more than two lobes are involved, this signifies high mortality in pneumonia.

(f) Progression of pneumonia while on antibiotics – Suspect TB, fungal, PCP, or Legionella as the etiology.

RED FLAGS require aggressive diagnostic, therapeutic management, and early transfer or MEDEVAC.

(6) Antibiotic therapy

The following description outlines empiric therapy for outpatient CAP:

(a) Erythromycin 500mg , one PO, every 6 hours, or

(b) Azithromycin 250mg, two PO initially, followed by one PO every day for the remaining 4 more days, or

(d) Doxycycline 100mg, one PO BID.

In patients with comorbidities such as smoking, alcoholism or those older than 60, consider coverage for H. influenzae with the addition of a second generation cephalosporin:

(a) Cefuroxime (Ceftin) 500mg, one PO BID, or

(b) Cefpodoxime (Vantin) 200mg, one PO BID, or

(d) Septra DS, one PO BID.

If the patient requires hospitalization, use the same antibiotic agents; a macrolide with a second or third generation cephalosporin such as Ceftriaxone (Rocephin 2 gm IV QD), or Cefuroxime 1.5 gm IV, every 8 hours.

(7) Specific Therapy

(a) Empiric
Erythromycin; 500mg every 6 hours (with or without Cefuroxime TID or Septra twice a day). Add H. Influenza coverage for smokers and for patients older than 40. Strongly consider Doxycycline for wheezing pneumonias (as Chlamydia pneumonias frequently are).

(b) Pneumococcus
Penicillin G IV 600,000-1.2 million units every 4 hours. If there are high rates of Penicillin resistance in the area or if the organism’s susceptibility (MIC) to PCN is >0.1 micrograms/ml, IV Rocephin with Vancomycin (1 gm IV Q 12 hours) should be used. The newer quinilones such as levofloxacin or trovofloxacin have good activity against PCN resistant pneumococcus and can be used. Ciprofloxacin should not be used.

(c) H. influenzae
Cefuroxime (Ceftin 500 mg) orally or IV. Intravenous Ceftriaxone or Septra DS one tab PO BID (if the organism is sensitive) or Augmentin, orally or IV 500 mg TID should be considered.

(d) Chlamydia pneumoniae
Tetracycline 500 PO QID or Doxycycline 100 BID PO or IV. Macrolides or fluroquinolones can also be used.

(e) Moraxella catarrhalis
Usually causes acute bronchitis but is covered by macrolides such as Erythromycin, Azithromycin, or Clarithromycin. Tetracycline, Septra, or Augmentin can also be used.

(f) Staph aureus
Oxacillin or Nafcillin 2 gm IV every 6 hours or Vancomycin 1 gram every 12 hours IV (for penicillin allergic patients).

(g) Legionella pneumophila:
Erythromycin 1 gm IV every 6 hours with or Azithromycin 500 mg IV QD with or without Rifampin 600mg PO BID.

(h) Suspected Tuberculosis
Rifampin 600mg PO QD, INH 300mg PO QD, PZA 25mg/kg/day PO, Ethambutol 25mg/kg/day PO. Assess the liver enzymes before and during therapy.

(i) Pneumocystis carinii pneumonia (PCP)
Septra DS 2 PO QID, or Clindamycin (Cleocin) 600 mg PO QID plus Primaquine 26.3 mg PO QD, or Dapsone 100 mg PO QD plus Trimethoprim 20 mg/kg PO daily, divided into a QID dosage schedule.

(8) Aspiration pneumonia

This can occur after dental work or drinking alcohol. Clues can include bad smelling or tasting sputum, night sweats, and mild anemia. Treatment choices include Timentin IV, Unisyn IV, Augmentin PO or Clindamycin PO.

(9) Re-evaluation

Once therapy is started, daily clinical reevaluation is necessary to ensure a good response to therapy. The chest x-ray findings may lag behind the clinical response but should be obtained in 2-3 weeks to ensure complete resolution of the infiltrate.

Reviewed by CAPT Angeline A. Lazararus, MC, USN, Pulmonary Specialty Leader, Department of Internal Medicine, National Naval Medical Center, Bethesda, MD (1999).