Community-acquired pneumonia natural history, complications and prognosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Chetan Lokhande, M.B.B.S [2]
Overview
Complications including sepsis, respiratory failure, pleural effusion, and empyema may occur despite appropriate antibiotic treatment. Complications are associated with bacterial pneumonia more frequently than viral pneumonia.
Complications
Pleural Effusion and Empyema
- Pleural effusion may be complicated with community-acquired pneumonia. Thoracentesis and pleural fluid analysis should be performed.
- Empyema may occur if there is local formation of pus in the pleural cavity which requires drainage in addition to antibiotic therapy.
Abscess
- Abscess with or without loculation, typically seen in aspiration pneumonia, is often caused by anaerobic bacteria and polymicrobial.
- Antibiotics usually suffice to treat abscesses. Drainage may be considered for non-responders.
Sepsis and Septic Shock
- Sepsis most often occurs with bacterial pneumonia, with Streptococcus pneumoniae as the most common etiology.
- Individuals with sepsis require hospitalization in an intensive care unit. They often require medications and intravenous fluids to keep their blood pressure from going too low. Sepsis can cause liver, kidney, and heart damage among other organ dysfunctions.
Respiratory Failure
- Non-invasive maneuvers such as a bilevel positive airway pressure machine may be used for respiratory support.
- Otherwise, intubation with mechanical ventilation may be required.
- Pneumonia may complicate acute respiratory distress syndrome (ARDS), which results from a combination of infection and inflammatory response. The lungs quickly fill with fluid and become very stiff. This stiffness, combined with severe difficulties extracting oxygen due to the alveolar fluid, creates a need for mechanical ventilation.
Prognosis and Mortality
With treatment, most types of bacterial pneumonia can be cured within one to two weeks. Viral pneumonia may last longer, and mycoplasmal pneumonia may take four to six weeks to resolve completely. The eventual outcome of an episode of pneumonia depends on how ill the person is when he or she is first diagnosed.
In the United States, about one of every twenty people with pneumococcal pneumonia will die[1] In cases where the pneumonia progresses to blood poisoning (bacteremia), one of every five will die. The death rate (or mortality) also depends on the underlying cause of the pneumonia. Pneumonia caused by Mycoplasma, for instance, is associated with little mortality. However, about half of the people who develop methicillin-resistantStaphylococcus aureus (MRSA) pneumonia while on a ventilator will die.[2] In regions of the world without advanced health care systems, pneumonia is even deadlier. Limited access to clinics and hospitals, limited access to x-rays, limited antibiotic choices, and inability to treat underlying conditions inevitably leads to higher rates of death from pneumonia.
- Individuals who are treated for CAP outside of the hospital have a mortality rate less than 1%.
- Fever typically responds in the first two days of therapy and other symptoms resolve in the first week.
- The x-ray, however, may remain abnormal for at least a month, even when CAP has been successfully treated.
- Among individuals who require hospitalization, the mortality rate averages 12% overall, but it is as much as 40% in people who have bloodstream infections or require intensive care.[3]
- When CAP does not respond as expected, there are several possible causes.
- A complication of CAP may have occurred or a previously unknown health problem may be playing a role.
- Additional causes include inappropriate antibiotics for the causative organism (such as drug resistant Streptococcus pneumoniae, a previously unsuspected microorganism (such as tuberculosis), or a condition which mimics CAP (such as Wegener's granulomatosis).
- Additional testing may be performed and may include additional radiologic imaging (such as a computed tomography scan) or a procedure such as a bronchoscopy or lung biopsy.
Clinical Prediction Rules
Clinical prediction rules have been developed to more objectively prognosticate outcomes in pneumonia. These rules can be helpful in deciding whether or not to hospitalize the person.
References
- ↑ http://www.kidshealth.org/parent/infections/bacterial_viral/pneumonia.html
- ↑ Combes A, Luyt CE, Fagon JY, Wollf M, Trouillet JL, Gibert C, Chastre J; PNEUMA Trial Group. Impact of methicillin resistance on outcome of Staphylococcus aureus ventilator-associated pneumonia. Am J Respir Crit Care Med. 2004 Oct 1;170(7):786-92. PMID 15242840
- ↑ Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, Coley CM, Marrie TJ, Kapoor WN. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997 Jan 23;336(4):243–250. PMID 8995086
- ↑ Lim WS, van der Eerden MM, Laing R; et al. (2003). "Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study". Thorax. 58 (5): 377–82. PMID 12728155.