PNEUMONIA

 

Etiology/S&S/Diagnosis/Treatment:

 

  1. TYPICAL
     
    1. Strep. Pneumonia:
      Frequent cause of CAP (Community Acquired Pneumonia). Especially common in     COPD, asplenism, SC. Pt c/o fever, chills, cough. On CXR -– typically a lobar appearance. PCN G IV or IM, Ampicillin or Amoxicillin, Erythromycin, PCN V po x 10-14 d. are all accepted  treatment modalities. Also effective are many  other synthetic penicillins, 2d  and 3d generation cephalosporins (Cefotaxime, Ceftriaxone), and the new macrolides.  Some strains are now  resistant to PCN. The resistance to commonly  prescribed antibiotics is as follows:  TMP/SMX = 18% resistance to S. Pneumonia, Macrolides = 10% resistance to S. Pneumonia Quinolones = 0.2 % resistance to S. Pneumonia
       
    2. Staph. aureus:
      Affects pt with DM, IVDA or recent viral URI. On CXR - patchy appearance. Pt is treated with       b -lactamase resistant PCN (nafcillin) or, if risk of MRSA, Vancomycin. High risk of forming abscess and empyema.
       
    3. H. Flu:
      COPDers are very susceptible. CXR - patchy infiltrate. Generally responds to ampicillin  or amoxicillin, but given  resistant strains,  2nd or 3d generation cephalosporin  are commonly used. TMP/SMX is an alternative, as are azithromycin  or clarithromycin.
       
    4. Moraxella catarrhalis:
      Common in COPDers  or/and geriatric population. Treated with Erythromycin, TMP/SMX,  or amoxicillin-clavulanate (Augmentin).
       
    5. Klebsiella:
      COPDers, ETOH, nursing home pts are the common targets.  Jelly-red sputum is characteristic. Treated  with aminoglycoside + 3d  generation cephalosporin.
       
    6. P. aureginosa:
      Pt with CF, neutropenic pts and nosocomial  pts are susceptible. Aminoglycoside + anti-pseudomonal  PCN (e.g., Timentin).

       
  2. ATYPICAL
     
    1. Mycoplasma:
      Common cause of  CAP. Also called "walking pneumonia" .  Pt looks better  than the CXR.  Pt c/o myalgias, dry cough. On exam bullous myringitis, pericarditis, hepatitis may be found. CXR typically shows bilateral interstitial infiltrate.  If  the antibodies (complement fixation) in acute or convalescent phase are high, it is diagnostic. The cold agglutinins are not specific for dx. Treated with Erythromycin x 10 - 14 d, or  the  newer macrolides.

             Chlamydia (psittaci, trachomatis, TWAR):
      Presents like other atypical pneumonias (dry, prolonged and chronic cough,  URI). Many pts may present with S & S of pharyngitis, tracheobronchitis, and "new onset asthma". Chlamydia represents 5-15% of CAP. CXR looks like any  atypical  pneumonia. Only serological studies can confirm the dx. Treated with Erythromycin  or the newer macrolides.

      Viral (influenza, RSV, Coxackie, Varicella):
      Some occur as epidemics, some occur predominantly in children. Yet, sporadic cases can occur. Pt c/o cough, SOB, myalgias, malaise, URI, +/- GI symptoms. On labs - WBC with lymphocytic predominance.CXR looks like any  other atypical pneumonia. Fourfold  viral titer increase from acute to convalescent stage is diagnostic. Treatment is supportive. In cases of influenza A - Amantadine within 48 hours. In case of RSV - Ribavirin. In case of  Herpes  and Varicella - Acyclovir. New medications and guidelines are put on the market  frequently and it is advisable  to  check updated publications.  

       
  3. PCP
     
    1. Pneumocystis carinii - Acutely ill Occurs in HIV pt with low CD count < 200/mm3, or other immunocompromised patients, and in pts who are treated with steroids and immunocompromised. No risk of acquiring  PCP by person-to-person spread. Pt generally c/o dyspnea, cough (generally not productive), hiccups and fever.  CXR shows ¥butterfly  wing¥ appearance. Presence of normal CXR (10%) doesn't r/o PCP pneumonia.  Pts  often have ( LDH  (> 450 IU). ABG should be performed not for documenting A-a gradient, which can be normal, but to see the pO2.   If the latter is < 75 mmHg, steroids are instituted as part of treatment. The absolute dx is done on the floor by way of fiberoptic broncoscopy, biopsy and  lavage. Culture or examination of induced sputum by indirect immunofuorescence are also  floor diagnostic  tests. In the ER pt is treated with TMP/SMX as 15-20mg/kg/day (TMP component) divided q6 - q8 hrs IV  or Pentamidine 4 mg/kg qd TMP 20 mg/kg/day administered in 4 divided doses and given PO q6 -q8 hrs.  If the pO2 is < 70 mmHg on RA or A-a gradient is >30, 40mg Prednisone bid is started in ER.
       
    2. Pneumocystis carinii - Not acutely ill TMP/SMX 2 DS tabs po q8h (total of 15-20mg/kg/day basesd on TMP) po x 21 days
                                            or
      Dapson 100 mg po qd + TMP 5 mg/kg po q8h x 21 days

       
    3. Pneumocystis carinii - prophylaxis TMP/SMX DS 1 tab po qd

        
  4. ASPIRATION  PNEUMONIA
     
    1. Not to be confused with aspiration pneumonitis, which presents hours after aspiration, with SOB and fever secondary to chemical reaction. Aspiration Pneumonia  occurs days after the episode. Presents with fever, SOB, tachypnea.  CXR typically shows infiltrate in inferior part  of  RUL. Ticarcillin clavulanate (Timentin®) 3.1 g q4-6 hrs is a good choice for treatment. Clindamycin  600 mg  IV q6 hr is an alternative to cover  anaerobes. Intubation and  PEEP are instituted if  there is no adequate oxygenation.
       
  5. NOSOCOMIAL  PNEUMONIA
     
    1. Affects hospitalized and nursing home patients.  Often due to aspiration.  CXR shows infiltrate in inferior  part of  RUL.  Broad coverage for G (+), G (-) and coverage for anaerobic oral flora with Ticarcillin  clavulanate (Timentin) + Gentamicin is indicated.  Consider Legionella  if  S & S are suggestive.
       
  6. LEGIONELLA
    1. Water born sources. Pt presents with GI symptoms,  ­LFTs, bradycardia, cough ( non-   productive). Pt may   also have AMS. Hyponatremia  may be present. CXR - bilateral infiltrates.  Sputum tested  with DFA (Direct  Fluorescent  AB) and  rise in serum titers from acute to convalescent phase are used for diagnosis. Treated with Erythromycin IV or newer macrolides.
       
  7. TB
    1. Pts present with cough, fever, night sweats, weight loss. CXR most commonly will be abnormal (shows infiltrate, cavitation, pl. effusion or miliary pattern). In ER one can  only  suspect TB and put pt in isolation. Following are some medications that pts are started on:

      • INH 5 - 10 mg/kg up to 300 mg PO / qd (adverse effects: neuritis, hepatitis, sz)
      • Ethambutol  20 mg/kg PO / qd (causes optic neuritis)
      • Rifampin 600 mg PO / qd (can cause  hepatitis)
      • PZA  1-2 gm PO / qd (causes hepatitis). 

        At least two medication regimen is used  to avoid drug resistance.









       
  8. FUNGAL
     
    1. Seen in immunocompromised host. Common pathogens  are Cryptococcus, Histoplasmosis, Coccidioidomycosis, Aspargillosis. CXR classically shows fungoid  mass. Treatment is generally Amphotericin. Doses may vary according to etiology.

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