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