New approaches for treating pneumonia

A revised classification system for pneumonia has been developed


Pneumonia is listed among the top 10 most common causes of death in the United States. It is listed as the seventh leading cause of death in adults > 65 years of age6.

The annual incidence is as high as 4 million cases, resulting in 500, 000 to 1 million hospitalizations per year1,2.

Because of the increased complexity of pathogens and the environment in which the patient was exposed to them, a revised classification system for pneumonia has been developed.

This was done to help with decisions regarding empirical antibiotic strategies and determine which patients may require hospitalization for treatment.

These categories are: community acquired pneumonia (CAP), healthcare-associated pneumonia (HCAP), hospital acquired pneumonia (HAP) and ventilator associated pneumonia (VAP).

Most CAP cases are mild, often do not require hospitalization and mortality is low. When the severity of the patient's condition dictates hospitalization, mortality can be as high as 15 percent. CAP has a much lower incidence of multidrug-resistant pathogens than HCAP, HAP, or VAP3.

CAP
Acute pulmonary infection, patient has not been hospitalized or resided in a long-term care facility for 14 or more days prior to presentation.

HCAP

  • Patient hospitalized for two or more days in the past 90 days
  • Long-term care resident
  • Receiving home IV antibiotic therapy
  • Dialysis patient
  • Receiving chronic wound care
  • Receiving chemotherapy
  • Immunocompromised patient

HAP
New pulmonary infection occurring 48 hours or more after hospital admission

VAP
New pulmonary infection occurring 48 hours or more after endotracheal intubation

Pathophysiology
Pneumonia results from the body's response to microbial pathogens at the alveolar level. These pathogens normally reside in the oral and nasal mucosa and become problematic when they are aspirated into the lower airways. This often occurs during sleep, (small-volume aspiration) or in patients with decreased level of consciousness.

Pathogens can also be inhaled as droplets or occasionally they are spread by contiguous extension from other infected areas.

Mechanisms that bypass or impede the upper airway's natural defenses such as endotracheal tubes or nasogastric tubes also place patients at increased risk of infection.

Once pathogens reach the alveolar level, the body normally responds with resident macrophages that are extremely efficient at killing and removing these invaders.

When their capacity is exceeded, clinical pneumonia develops. Pneumonia is a result of the host's inflammatory response, rather than the proliferation of microorganisms.

As this response continues to mount inflammation progresses, secretions increase along with alveolar capillary leak similar to that of acute respiratory distress syndrome, but in pneumonia initially this is localized.

Management
Management of pneumonia is dependent on several risk factors; the patient's age, comorbidities, possible exposure to drug resistant organisms, and failing current treatment for what initially presented as mild pneumonia all lead to increased risk of a poor outcome.

A patient that meets CAP criteria that is less than 65 years old that appears to otherwise be in good health can successfully be treated as an outpatient.

Initial severity scoring and appropriate triage of patients at risk of poor outcome is critical. Organisms causing pneumonia vary hospital-to-hospital and even ICU-to-ICU in the same hospital.

The physician rarely knows the causative pathogens at the onset. Initial therapy should be broad enough to cover the most likely pathogens knowing that if the early treatment fails and a second course of treatment is required mortality rates increase7.

There are several tools available to help assign scores to quantify the risk -- PSI/PORT (pneumonia severity index), CURB-65, SMART-COP, etc. These can be helpful but all have their shortcomings and should not be used as a stand-alone tool. Use them to help quantify risk and help standardize patient disposition8.

Blood cultures should be drawn prior to starting antibiotics. When antibiotics are started, initial therapy needs to be broad. This can be tailored more specifically once results from blood and possibly sputum cultures are returned. Combination antibiotic therapy should be started to increase the likelihood of successful treatment.

There is no drug regimen that fits all. Consulting with the local infectious disease physician for ill appearing patients can be very helpful. This may be someone in your hospital, or your region depending on facility size.

Take-home points
HCAP, HAP, VAP or severe CAP are all associated with a more serious disease, higher mortality, greater length of stay, and increased cost when compared to mild CAP3. This equals high-risk patients.

In high-risk patients, combination antibiotic therapy should be promptly started once the diagnosis of pneumonia has been established. Early initiation of appropriate combination antibiotic therapy is associated with improved outcome.

In addition to antimicrobial therapy, adequate hydration, oxygen therapy as indicated and mechanical ventilation when needed is essential for support and successful resolution of the disease.

Patients that are not responding well to treatment by day two or three should be reevaluated for possible treatment alterations.

References:

  1. Halm EA, Teirstein AS: Management of community acquired pneumonia. N Engl J Med 347: 2039, 2002.
     
  2. Clinical Classifications for Health Policy Research: Hospital Inpatient Statistics, 1996. Rockville, MD, Agency for Health Care Policy and Research. HCPR publication no. 99-0034; 1999.
     
  3. Kollef et al. Epidemiology and outcomes of health-care-associated pneumonia: results from a large US database of culture-positive pneumonia. Chest (2005) vol. 128 (6) pp. 3854-62
     
  4. Hiramatsu and Niederman. Health-care-associated pneumonia: a new therapeutic paradigm. Chest (2005) vol. 128 (6) pp. 3784-7
     
  5. Emerman C.L., Anderson E., Cline D.M. (2012). Chapter 68. Community-Acquired Pneumonia, Aspiration Pneumonia, and Noninfectious Pulmonary Infiltrates. In J.E. Tintinalli, G.D. Kelen, J.S. Stapczynski (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e. Retrieved January 24, 2012.
     
  6. Murphy et al. Deaths: Preliminary Data for 2010. Natl Vital Stat Rep (2012) vol. 60 (4) pp. 1-69
     
  7. Woodhead et al. Community-acquired pneumonia on the intensive care unit: secondary analysis of 17,869 cases in the ICNARC Case Mix Programme Database. Critical care (London, England) (2006) vol. 10 Suppl 2 pp. S1
     
  8. Jo et al. The effects of incorporating a pneumonia severity index into the admission protocol for community-acquired pneumonia. J Emerg Med (2012) vol. 42 (2) pp. 133-8
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