Pneumonia

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Epidemiology 5 Pathology 6 History 7 Clinical-manifestations 8 Laboratory 9 Diagnostic-procedures 10 Radiology 11 Complications 12 Management 13 More General Terms 14 Additional Terms 15 References

More Specific Terms

• aspiration pneumonia
• community-acquired pneumonia (CAP)
• eosinophilic pneumonia
• nosocomial pneumonia (hospital-acquired pneumonia)
• Pneumocystis pneumonia (PCP)
• pulmonary infiltrate in immunocompromised host
• Staphylococcal pneumonia
• ventilator-associated pneumonia
• viral pneumonia

Introduction

• Infection of the pulmonary parenchyma.

Etiology

• bacterial

• community-acquired: Streptococcus pneumoniae (90% of identified isolates in adults)
• nosocomial (60% gram-negative bacilli)
• Mycobacterium tuberculosis
• other

• viral
• fungal
• parasites: Pneumocystis carinii ( AIDS)
• rickettsiae

• see etiology of pneumonia
• also see characteristics of etiologic agents of pneumonia

Epidemiology

• compromised hosts are particularly vulnerable
• pneumonia accounts for 10% of admissions to hospital wards & is still a common cause of death

Pathology

• the most common mechanism for acquiring pneumonia is aspiration of organisms from the oropharynx

• aerobic gram-positive cocci & anaerobes most common
• 50% of adults aspirate during sleep
• aspiration increases with:

• impaired consciousness
• neurologic disorders
• or endotracheal tubes

• less common mechanisms

• inhalation of infected particles
• hematogenous or contiguous spread from another infected site
• open trauma to chest

• alterations in host defenses contribute to the pathophysiology of pneumonia

• abnormal mucociliary function
• decreased IgA allowing adherence of bacteria to airways
• compromised cellular immunity
• compromised humoral immunity

• severity of pneumococcal pneumonia associated with bacterial load

History

• onset, duration, systemic symptoms, fever, weight loss, other medical conditions, recent antibiotic use, travel history, exposure to animals, tuberculosis history, sick contacts, alcohol/other drug use, HIV risk factors, occupational history

Clinical-manifestations

• fever
• tachycardia
• postural changes
• tachypnea may be only sign in elderly [15]
• rales
• egophony
• inspiratory chest expansion lag on affected side
• splinting
• increased fremitus
• dullness to percussion
• bronchial breath sounds
• bronchophony

Laboratory

• Sputum

• gram stain

• > 5 epithelial cells per low power field suggests oral- pharyngeal rather than pulmonary secretions
• > 25 neutrophils per low power field suggests lower respiratory tract infection
• can lead to diagnosis in 15-45% of cases [13,14]

• culture

• no anaerobic cultures because of contamination from pharyngeal anaerobes
• cultures can be misleading

• fluorescent antibody studies

• Legionella pneumophila

• Complete blood count

• leukocyte count

• may be low or normal in the elderly or immunocompromised
• a leukocyte count < 10,000/ mm3 is common in Mycoplasma pneumonia

• blood cultures

• for all hospitalized patients with pneumonia
• 20-30% of patients with bacterial pneumonia have positive blood cultures

• arterial blood gas
• chemistry profile

• electrolytes
• liver function tests
• renal function tests
• glucose

• serologic studies

• coccidioidomycosis titers
• Mycoplasma titers
• HIV testing

Diagnostic-procedures

• invasive procedures may be indicated in treatment failures or suspected non- bacterial origin of severe disease
• transtracheal aspiration
• transthoracic needle aspiration ( thoracentesis)
• bronchial brushings
• bronchoalveolar lavage or endotracheal aspiration
• transbronchial biopsy
• open lung biopsy
• induced sputum or Lukens trap

Radiology

• chest radiograph

• lobar

• Streptococcus pneumonia
• Haemophilus influenza

• interstitial

• Mycoplasma pneumonia
• viral pneumonia

• bilateral

• aspiration

• cavitary

• Mycobacterium tuberculosis
• Klebsiella pneumonia
• Staphylococcus aureus
• Pseudomonas aeruginosa

• radiographic resolution lags behind clinical improvement
• follow-up chest X-rays 8 weeks after onset

• to show resolution & absence of underlying lung cancer
• may not be necessary in younger patients [19]

Complications

• pleural ( parapneumonic) effusion - thoracentesis
• empyema - requires chest tube drainage
• abscess formation ( empyema)
• pericarditis ( purulent)
• adult respiratory distress syndrome ( ARDS)
• sepsis with DIC
• multi-organ failure
  

• Also see poor prognostic factors & criteria for severe pneumonia
  

• disease interaction(s) of pneumonia with dementia

Management

• 
  

• supportive measures

• hydration
• oxygen
• noninvasive positive pressure ventilation may reduce need for endotracheal intubation

• empiric antimicrobial therapy

• community-acquired pneumonia in adults [12] (see community-acquired pneumonia)
• nosocomial pneumonia

• etiology: most frequently:

• gram negative organisms
• Staphylococcus
• Legionella

• empiric therapy:

• ceftriaxone or cefotaxime plus an aminoglycoside
• mezlocillin or ceftazidime plus an aminoglycoside if Pseudomonas is likely ( ICU setting or immunocompromised host)
• fluoroquinolone plus an aminoglycoside or aztreonam if Pseudomonas is suspected

• levofloxacin
• trovafloxacin

• aspiration pneumonia

• community-acquired: anaerobes & gram-positive cocci
• nosocomial: gram-negative organisms & S. aureus
• empiric therapy:

• fluoroquinolone plus clindamycin or metronidazole - trovafloxacin may be used alone
• penicillin/beta-lactamase inhibitor

• pneumonia in adults with cystic fibrosis
• switching to oral therapy

• patient is afebrile and stable
• patients with bacteremia & other medical problems may need longer IV antibiotic therapy
  

• * Some fluoroquinolones are not recommended for empiric antimicrobial activity in pneumonia because of unreliable activity against Streptococcus pneumoniae. Fluoroquinolones with enhanced activity against Streptococcus pneumonia include:

• levofloxacin
• sparfloxacin
• trovafloxacin
• grepafloxacin
• moxifloxacin
• gatifloxacin
• gemifloxacin
  

• Antimicrobial therapy for pneumonia caused by specific organisms (select or see specific organism)
  
• Response to therapy

• most patients will show clinical improvement within 48-72 hours
• fever & leukocytosis generally resolves by day 4
• chest X-ray often lags behind clinical improvement
• follow-up chest X-ray to show resolution (8-12 weeks after onset) [17]
• weeks to months may be necessary for complete resolution of symptoms [7]
  

• Duration of therapy: ( bacterial pneumonia)

• 2 to 3 weeks [6]
• 8 days equivalent to 15 days for ventilator-associated pneumonia [11]
  

• Also see treatment failure

More General Terms

• lung disease
• pulmonary infection

Additional Terms

• characteristics of etiologic agents of pneumonia
• etiology of pneumonia
• poor prognostic factors & criteria for severe pneumonia
• pulmonary infiltrate in immunocompromised host
• risk factors for hospital-acquired pneumonia
• treatment failure, pneumonia

References

1. Manual of Medical Therapeutics, 28th edition, Ewald & McKenzie (eds) Little, Brown & Co, 1995, pg 299-302
2. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 421
3. Contributions from Linda Kuribayashi MD, Dept of Medicine, UCSF Fresno
4. Bartlett JG et al Community-acquired pneumonia in adults: guidelines for management. The Infectious Diseases Society of America. Clinical Infectious Diseases 26:811-38, 1998 PMID: [1]
5. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 796-99
6. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
7. Journal Watch 21(3):22, 2001 Marrie TJ et al Predictors of symptom resolution in patients with community-acquired pneumonia. Clin Infect Dis 31:1362, 2000 PMID: [2]
8. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1146
9. Bartlett JG et al Community-acquired pneumonia in adults: guidelines for management. The Infectious Diseases Society of America. Clin Infect Dis 26:811, 1998 PMID: [3]
10. Geriatrics Review Syllabus, American Geriatrics Society, 5th edition, 2002-2004
11. Journal Watch 24(2):10, 2004 Chastre J et al Comparison of 8 vs 15 days of antibiotic therapy for ventilator-associated pneumonia in adults: a randomized trial. JAMA 290:2588, 2003 PMID: [4]
12. Selected Treatment Issues in the Updated Guidelines for Community-Acquired Pneumonia in Immunocompetent Adults and Bacterial Sinusitis Prescriber's Letter 11(2):12 2004 Detail-Document#: [5] (subscription needed) [6]
13. Journal Watch 24(20):151, 2004 Garcia-Vazquez E, Marcos MA, Mensa J, de Roux A, Puig J, Font C, Francisco G, Torres A. Assessment of the usefulness of sputum culture for diagnosis of community-acquired pneumonia using the PORT predictive scoring system. Arch Intern Med. 2004 Sep 13;164(16):1807-11. PMID: [7]
14. Musher DM, Montoya R, Wanahita A. Diagnostic value of microscopic examination of gram-stained sputum and sputum cultures in patients with bacteremic pneumococcal pneumonia. Clin Infect Dis. 2004 Jul 15;39(2):165-9. Epub 2004 Jul 01. PMID: [8]
15. Internal Medicine World Report 2006; 21(2)
16. The Canadian Critical Care Trials Group. A randomized trial of diagnostic techniques for ventilator-associated pneumonia. N Engl J Med 2006, 355:2619 PMID: [9]
17. Bruns AH, Oosterheert JJ, Prokop M, Lammers JW, Hak E, Hoepelman AI. Patterns of resolution of chest radiograph abnormalities in adults hospitalized with severe community-acquired pneumonia. Clin Infect Dis. 2007 Oct 15;45(8):983-91. Epub 2007 Sep 12. PMID: [10]
18. Rello J et al. Severity of pneumococcal pneumonia associated with genomic bacterial load. Chest 2009 Sep; 136:832. PMID: [11]
19. Tang KL et al. Incidence, correlates, and chest radiographic yield of new lung cancer diagnosis in 3398 patients with pneumonia. Arch Intern Med 2011 Jul 11; 171:1193 PMID: &dopt=Abstract
20. Pneumonia: NIH Institute and Center Resources [12]

pneumonia (PNA)