Chapter 16: Bacterial Pneumonia - · PDF filePathophysiology § Infections of ... §...

Lecture Notes

Chapter 16: Bacterial Pneumonia

Objectives §  Explain the epidemiology §  Identify the common causes §  Explain the pathological changes in the lung §  Identify clinical features §  Explain the treatment and prognosis

Introductory Remarks §  The term refers to inflammation of the lung

parenchyma and is most often caused by infection

§ Caused by a variety of infectious agents, including bacteria, viruses, and fungi.

§ Continues to be a common medical problem despite advent of antibiotics

§ Returning as a serious problem due to emergence of antibiotic-resistant organisms

Introductory Remarks § Most cases are contracted outside the hospital

and referred to as community-acquired pneumonia

§  The hospitalized pneumonia patient is referred to as having nosocomial pneumonia

§ Represents the sixth leading cause of death §  Serious medical problem among hospitalized

and elderly patients whose immune systems are inadequate.

Etiology § Distal airways are generally protected by

mechanical and chemical systems but may be sabotaged by factors such as: smoking, alcohol abuse, chronic lung disease, neuromuscular disease, intubation, or acute viral upper respiratory tract infection

Etiology § Community-acquired is usually treated on an

outpatient basis with few problems § Nosocomial is often difficult to treat and more

life-threatening

Etiology

Pathophysiology §  Infections of the lung parenchyma provoke a

reaction that causes an outpouring of fluid, inflammatory proteins, and white blood cells

§  Interstitial and alveolar spaces become flooded with edema and exudative material

Pathophysiology §  Some bacterial organisms can cause abscesses and

permanently damage lung tissue (Necrotizing Pneumonia)

§  Acute inflammation and consolidation can lead to â in ventilation and gas exchange and ultimately V/Q mismatching and shunting.

§  Lung consolidation associated with pneumonia â lung complianceàápt’s WOB.

§  Lung volumes are typically â during acute stages of pneumonia, but usually return to normal

Clinical Features: History and Physical Examination

§  Typically patient complains of an abrupt onset of fever, cough, and sputum production; dyspnea and chest pain common

§  Appears acutely ill with tachycardia and tachypnea §  Severe cases may reveal cyanosis and use of

accessory muscles §  Lobar pneumonia may demonstrate unilateral reduction

in chest expansion §  á tactile fremitus and â resonance to percussion over

consolidated region §  Coarse crackles or bronchial breath sounds §  Pleural friction rub if pleural inflammation

Clinical Features: Laboratory Findings and Chest Radiographs §  In most cases, laboratory findings will reveal

leukocytosis §  The chest radiograph is considered the gold standard

for confirming the diagnosis §  The CXR provides information about the extent of lung

involvement and often show areas of increased density with air bronchograms, involvement of the entire lobe (lobar pneumonia), patchy segmental distribution (bronchopneumonia), areas of radiolucency caused by lung destruction (necrotizing pneumonia), or interstitial infiltrates (viral pneumonia)

Clinical Features: ABGs and Sputum Analysis §  ABG analysis is usually not needed, however when

significant may reveal hypoxemia and respiratory alkalosis

§  Microbiological evaluation of sputum is done to identify pathogens responsible for respiratory infection and is best performed before antibiotics are administered

§  A Gram stain and culture are helpful when a good specimen is obtained

§  If positive, the Gram stain allows more specific antibiotic therapy to be started while the culture may help in identifying the specific pathogen and the sensitivity testing identifies effective antibiotics

Treatment §  Some patients may be treated as outpatients

but severe cases should be managed in the hospital

§  Severe cases generally require supportive care in addition to antibiotic therapy

§  Supportive care includes fluid and nutritional therapy, oxygen, aerosol therapy, cooling measures and deep venous thrombi prophylaxis if the patient is bedbound

§ Mechanical ventilation is uncommon

Treatment §  Attending physicians can predict most likely

offending organism, therefore initial antibiotic therapy is necessarily determined empirically

§  An appropriate antibiotic should be started as soon as possible

§ Gram-positive, elongated diplococci are generally treated with oral ampicillin or penicillin

§ High doses of amoxicillin or cephalosporins are commonly used for pneumococcal pneumonia

Treatment and Prognosis §  Gram-negative coccobaccilli is most likely H. influenza

and suggests ampicillin or a second-generation cephalosporin should be used

§  Antibiotics are given for 5 to 7 days for uncomplicated pneumonia and for 10 days in severe cases

§  Hospital admission is based not only on the severity of the infection but also the presence of certain risk factors

§  Advanced age, coexisting illness, high fever, or leukopenia place the patient at greater risk

Treatment and Prognosis §  The patient admitted for pneumonia is at risk for

acquiring a nosocomial infection §  Careful handwashing and use of sterile technique during

airway care is crucial §  Gram-negative organisms are often relatively resistant

to therapy §  Prognosis for community-acquired pneumonia on an

outpatient basis is excellent with mortality rates about 1% to 3%

§  Mortality climbs to about 12% for those admitted and as high as 40% for patients admitted to the ICU

Concluding Remarks §  Pneumonia refers to inflammation of the lung

parenchyma §  It can occur outside the hospital (community-acquired)

or in the hospitalized patient (nosocomial) §  It results in ventilation-perfusion mismatching or

shunting §  The CXR is considered the gold standard for confirming

the diagnosis §  Antibiotic therapy is the treatment of choice §  The prognosis is excellent for community-acquired with

mortality climbing for the hospitalized and the patient admitted to the ICU