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 they are with viral pneumonia. Most types of bacterial pneumonia can be cured within one to two weeks of appropriate medication. 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.
Natural History
- Pneumococcal pneumonia is the most common clinical presentation of pneumococcal disease amongst adults, although pneumonia without bacteremia or empyema is not considered to be “invasive” disease. [1]
- The incubation period of pneumococcal pneumonia is short, about 1 to 3 days. [1]
- Symptoms generally include an abrupt onset of fever and chills or rigors. [1]
- Typically there is a single rigor; repeated shaking chills are uncommon. [1]
- Other common symptoms include: pleuritic chest pain, cough productive of mucopurulent, rusty sputum, dyspnea, tachypnea, hypoxia, tachycardia, malaise, and weakness. Nausea, vomiting, and headaches occur less frequently.[1]
- Transmission of Streptococcus pneumoniae occurs as a result of direct person-to-person contact via respiratory droplets and by autoinoculation in persons carrying the bacteria in their upper respiratory tract. [1]
- The pneumococcal serotypes most often responsible for causing infection are those that are most frequently found in carriers.[1]
Complications
Pleural Effusion and Empyema
- Community-acquired pneumonia may be complicated by parapneumonic pleural effusions. Thoracentesis and pleural fluid analysis should be performed.
- Empyema may occur if there is local formation of pus in the pleural cavity; this requires drainage in addition to antibiotic therapy.
Abscess
- Intraparenchymal abscesses (with or without loculation) may be seen in aspiration pneumonia. They are often primarily anaerobic or polymicrobial.
Sepsis and Septic Shock
- Sepsis most often occurs with bacterial pneumonia, with Streptococcus pneumoniae as the most common etiology.
Respiratory Failure
- Patients at the opposite ends of the age spectrum are at a high risk of respiratory failure.
- Non-invasive maneuvers, such as a bilevel positive airway pressure (BI-PAP) machine, may be used for respiratory support. Otherwise, intubation with mechanical ventilation may be required.
- Pneumonia may be complicated by acute respiratory distress syndrome (ARDS), which results from a combination of infection and inflammatory response.
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 out of every twenty people with pneumococcal pneumonia will die.[2] In cases where 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-resistant Staphylococcus aureus (MRSA) pneumonia while on a ventilator will die.[3] In regions of the world without advanced health care systems, pneumonia is even deadlier. Limited access to clinics and hospitals, x-rays, antibiotic choices, and inability to treat underlying conditions will inevitably lead to higher rates of death from pneumonia.
- Individuals who are treated for CAP outside of the hospital have a mortality rate of less than 1%.
- Fever typically responds in the first two days of therapy and other symptoms resolve in the first week.
- The CXR, however, may remain abnormal for at least a month, even when CAP has been successfully treated.
- Amongst 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 radiologic imaging (such as a computed tomography scan) or a procedure such as a bronchoscopy or lung biopsy.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "CDC Pneumococcal Disease Clinical Features".
- ↑ 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