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Lower Respiratory Tract Infections:PneumoniaPharm.D Balsam Alhasan
PNEUMONIA
• Pneumonia is the most common infectious cause of
death in the United States. It occurs in persons of all
ages, although the clinical manifestations are most
severe in the very young, the elderly, and the chronically
ill.
PATHOPHYSIOLOGY
• Microorganisms gain access to the lower respiratory tract by
three routes: they may be inhaled as aerosolized particles;
they may enter the lung via the bloodstream from an
extrapulmonary site of infection; or aspiration of
oropharyngeal contents may occur.
PATHOPHYSIOLOGY
• Lung infections with viruses suppress the bacterial clearing
activity of the lung by impairing alveolar macrophage function
and mucociliary clearance, thus setting the stage for
secondary bacterial pneumonia.
• The vast majority of pneumonia cases acquired in the
community by otherwise healthy adults are due to S.
pneumoniae (pneumococcus) (up to 75% of all acute bacterial
pneumonias in the United States).
PATHOPHYSIOLOGY
• Other common bacterial causes include M. pneumoniae ,
Legionella , and C. pneumoniae , which are referred to as
“atypical” pathogens.
• Community-acquired pneumonias caused by Staphylococcus
aureus and gram-negative rods are observed primarily in the
elderly, especially those residing in nursing homes, and in
association with alcoholism and other debilitating conditions.
PATHOPHYSIOLOGY
• Gram-negative aerobic bacilli and S. aureus are also the
leading causative agents in hospital-acquired pneumonia.
• Anaerobic bacteria are the most common etiologic agents in
pneumonia that follows the gross aspiration of gastric or
oropharyngeal contents.
PATHOPHYSIOLOGY
• In the pediatric age group, most pneumonias are due to
viruses, especially respiratory syncytial virus, parainfluenza,
and adenovirus. Pneumococcus is the most common bacterial
cause, followed by Group A Streptococcus and S. aureus.
CLINICAL PRESENTATION
Gram-Positive and Gram-Negative Bacterial Pneumonia
• Infection with Legionella pneumophila is characterized by
multisystem involvement, including rapidly progressive
pneumonia. It has a gradual onset, with prominent
constitutional symptoms such as malaise, lethargy, weakness,
and anorexia occurring early in the course of the illness. A dry,
nonproductive cough is initially present that over several days
becomes productive of mucoid or purulent sputum.
• Fevers exceed 40°C (104°F) and are typically unremitting and
associated with a relative bradycardia. Pleuritic chest pain and
progressive dyspnea may be seen, and fine rales are found on
lung examination, progressing to signs of frank consolidation
later in the course of the illness.
Gram-Positive and Gram-Negative Bacterial Pneumonia
• Extrapulmonary manifestations remain evident throughout the course
of the illness and include diarrhea, nausea, vomiting, myalgias, and
arthralgias.
• Substantial changes in a patient’s mental status, often out of
proportion to the degree of fever, are seen in approximately one-fourth
of patients. Obtundation, hallucinations, grand mal seizures, and focal
neurologic findings have also been associated with this illness.
Gram-Positive and Gram-Negative Bacterial Pneumonia
• Laboratory findings include leukocytosis with predominance of
mature and immature granulocytes in 50% to 75% of patients.
Because L. pneumophila stains poorly with commonly used
stains, routine microscopic examination of sputum is of little
diagnostic value. Fluorescent antibody testing can be
performed to diagnose Legionnaires’ disease.
Gram-Positive and Gram-Negative Bacterial Pneumonia
Anaerobic Pneumonia
• The course of anaerobic pneumonia is typically indolent with
cough, lowgrade fever, and weight loss, although an acute
presentation may occur. Putrid sputum, when present, is
highly suggestive of the diagnosis. Chest radiographs reveal
infiltrates typically located in dependent lung segments, and
lung abscesses develop in 20% of patients 1 to 2 weeks into
the course of the illness.
Mycoplasma pneumoniae
• M. pneumoniae pneumonia presents with a gradual onset of
fever, headache, and malaise, with the appearance 3 to 5 days
after the onset of illness of a persistent, hacking cough that
initially is nonproductive. Sore throat, ear pain, and rhinorrhea
are often present. Lung findings are generally limited to rales
and rhonchi; findings of consolidation are rarely present.
Mycoplasma pneumoniae
• Nonpulmonary manifestations are extremely common and
include nausea, vomiting, diarrhea, myalgias, arthralgias,
polyarticular arthritis, skin rashes, myocarditis and pericarditis,
hemolytic anemia, meningoencephalitis, cranial neuropathies,
and Guillain-Barré syndrome. Systemic symptoms generally
clear in 1 to 2 weeks, whereas respiratory symptoms may
persist up to 4 weeks.
Mycoplasma pneumoniae
• Radiographic findings include patchy or interstitial infiltrates,
which are most commonly seen in the lower lobes.
• Sputum Gram stain may reveal mononuclear or
polymorphonuclear leukocytes, with no predominant
organism. Although M. pneumoniae can be cultured from
respiratory secretions using specialized medium, 2 to 3 weeks
may be necessary for culture identification.
Viral Pneumonia
• The clinical pictures produced by respiratory viruses are
sufficiently variable and overlap to such a degree that an
etiologic diagnosis cannot confidently be made on clinical
grounds alone. Serologic tests for virusspecific antibodies are
often used in the diagnosis of viral infections.
Viral Pneumonia
• The diagnostic fourfold rise in titer between acute and
convalescent phase sera may require 2 to 3 weeks to develop;
however, same-day diagnosis of viral infections is now possible
through the use of indirect immunofluorescence tests on
exfoliated cells from the respiratory tract.
• Radiographic findings are nonspecific and include bronchial
wall thickening and perihilar and diffuse interstitial infiltrates.
Nosocomial Pneumonia
• The strongest predisposing factor for nosocomial pneumonia is
mechanical ventilation. Risk is increased by prior antibiotic use,
use of H2-receptor antagonists, and severe illness.
• The diagnosis of nosocomial pneumonia is usually established
by presence of a new infiltrate on chest radiograph, fever,
worsening respiratory status, and the appearance of thick,
neutrophil-laden respiratory secretions.
DESIRED OUTCOME
• Eradication of the offending organism and complete
clinical cure are the primary objectives. Associated
morbidity should be minimized (e.g., renal, pulmonary,
or hepatic dysfunction).
TREATMENT
• The first priority on assessing the patient with pneumonia is to
evaluate the adequacy of respiratory function and to
determine whether there are signs of systemic illness,
specifically dehydration or sepsis with resulting circulatory
collapse.
TREATMENT
• The supportive care of the patient with pneumonia includes
the use of humidified oxygen for hypoxemia, fluid
resuscitation, administration of bronchodilators when
bronchospasm is present, and chest physiotherapy with
postural drainage if there is evidence of retained secretions.
TREATMENT
• Important therapeutic adjuncts include adequate hydration (by IV route
if necessary), optimal nutritional support, and fever control.
• The treatment of bacterial pneumonia initially involves the empiric use
of a relatively broad-spectrum antibiotic (or antibiotics) effective against
probable pathogens after appropriate cultures and specimens for
laboratory evaluation have been obtained. Therapy should be narrowed
to cover specific pathogens once the results of cultures are known.
TREATMENT
• Appropriate empiric choices for the treatment of bacterial
pneumonias relative to a patient’s underlying disease are
shown in Table 43-6 for adults and Table 43-7 for children.
Dosages for antibiotics to treat pneumonia are provided in
Table 43-8.
TREATMENT
• Antibiotic concentrations in respiratory secretions in excess of the
pathogen minimum inhibitory concentration (MIC) are necessary
for successful treatment of pulmonary infections.
• For treatment of bacterial pneumonia with concentration-
independent antimicrobials (e.g., β-lactams and carbapenems), a
plasma drug concentration exceeding the pathogen MIC for more
than 50% of the dosing interval correlates with bacteriologic cure.
TREATMENT
• For concentration-dependent antimicrobials (e.g.,
aminoglycosides and fluoroquinolones) a peak drug
concentration to pathogen MIC ratio >8 to 10 or a ratio of
pathogen MIC to antibiotic area under the curve >25 to 40 for
gram-positive pathogens and >100 for gram-negative
pathogens correlates with bacteriologic cure.
TREATMENT
• Drugs recommended for empiric treatment of community-
acquired pneumonia are presented in Table 43-9.
• The benefit of antibiotic aerosols or direct endotracheal
instillation has not been consistently demonstrated.
Evaluation Of Therapeutic Outcomes• With community-acquired pneumonia, time for resolution of cough,
sputum production, and presence of constitutional symptoms (e.g.,
malaise, nausea or vomiting, lethargy) should be assessed. Progress
should be noted in the first 2 days, with complete resolution in 5 to 7
days.
• With nosocomial pneumonia, the above parameters should be
assessed along with white blood cell counts, chest radiograph, and
blood gas determinations.
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