Lower Respiratory Tract InfectionsPneumonia

Definitions :


Pneumonia : is the inflammation of the lung parenchyma (i.e. the alveoli rather than the bronchi), of infective origin and characterized by consolidation.
Consolidation is a pathological process in which the alveoli are filled with a mixture of inflammatory exudates b, bacteria, and WBCs. Consolidation appear on chest radiography as an opaque area in the normally clear lung field(1).
Traditionally, pneumonia is categorized as community-acquired pneumonia (CAP), hospital-acquired(Nosocomial) pneumonia , or Aspiration pneumonia(1,2).

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.The vast majority of pneumonia cases acquired in the community by otherwise healthy adults are due to S. pneumoniae (pneumococcus) or Mycoplasma. pneumoniae Other common bacterial causes include Legionella and C. pneumoniae. Community-acquired pneumonias caused by Staphylococcus aureus and gram-negative rods are observed primarily in the elderly, and in association with alcoholism and other debilitating conditions.
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.
In the pediatric age group, most pneumonias are due to viruses. Pneumococcus is the most common bacterial cause.

Clinical Presentation:

Although the clinical presentation of pneumonia varies according to pathogen, common symptoms of bacterial pneumonia include a productive cough, fever, chills, rigor and dyspnea. Signs of bacterial pneumonia include tachycardia, elevated white blood cell counts, localized lung consolidation and the presence of an infiltrate on chest radiography. Particular pathogens such as pneumococcus and staphylococcus may cause hemoptysis, or rust-colored sputum.
However, only a sputum culture can accurately identify the microorganism causing the pneumonia

Diagnosis


Diagnosis of pneumonia is based on :
1-Signs and Symptoms. 2-Physical Examination. 3-Chest Radiograph.
4-Laboratory Examination (e.g. elevated white blood cell counts (Leukocytosis)).
Desired Outcome


Eradication of the organism and complete clinical cure are the primary

Treatment


1-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.

2-The supportive care of the patient with pneumonia includes the use of humidified oxygen for hypoxemia, fluid resuscitation (by intravenous route if necessary), administration of bronchodilators when bronchospasm is present, optimal nutritional support, fever control ,and chest physiotherapy with postural drainage if there is evidence of retained secretions. Important therapeutic adjuncts include adequate hydration (by intravenous route if necessary),

3-The treatment of bacterial pneumonia initially involves the empiric use of a relatively broad-spectrum antibiotic (or antibiotics) effective against probable pathogens .
Once the results of appropriate cultures are known ,therapy should be narrowed to cover specific pathogens. Appropriate empiric choices for the treatment of bacterial pneumonias relative to a patient's underlying disease are shown in TABLE 1 for adults and Table 2 for




Daily Antibiotic dose
Antibiotic Class
Antibiotic

Pediatric (mg/kg/day)
Adult (total dose/day)
Macrolide
Clarithromycin
15
0.5-1 g
Erythromycin
30-50
1-2 g
Azalide
Azithromycin
10 mg/kg x 1 day, then 5 mg/kg/day x 4 days
500 mg day 1, then 250 mg/day x 4 days
TetracyclineA
Tetracycline HCL
25-50
1-2 g
Oxytetracycline
15-25
0.25-0.3 g
Penicillin
Ampicillin
100-200
2-6 g
Amoxicillin/amoxicillin-clavulanateB
40-90
0.75-1 g
Piperacillin-tazobactam
200-300
12 g
Ampicillin-sulbactam
100-200
4-8 g
Extended-spectrum cephalosporins
Ceftriaxone
50-75
1-2 g

Ceftazidime
150
2-6 g
Cefepime
100-150
2-4 g
Fluoroquinolones
GatifloxacinC
10-20
0.4 g

Levofloxacin
10-15
0.5-0.75 g
Ciprofloxacin
20-30
0.5-1.5 g
Aminoglycosides
Gentamicin
7.5
3-6 mg/kg
Tobramycin
7.5
3-6 mg/kg
Note: Doses may be increased for more severe disease and may require modification in patients with organ dysfunction. A-Tetracyclines are rarely used in pediatric patients, particularly in those younger than 8 yr of age because of tetracycline-induced permanent tooth discoloration. B-Higher dose amoxicillin, amoxicillin-clavulanate (e.g., 90 mg/kg/day) is used for penicillin-resistant S. pneumoniae. C-Fluoroquinolones are avoided in pediatric patients because of the potential for cartilage damage; however, their use in pediatrics is emerging. Doses shown are extrapolated from adults and will require further study.

References:

1- Walker R, Edwards C, editors. Clinical Pharmacy and Therapeutics, 2nd ed. Edinburgh: Churchill Livingstone, 1999.
2-Cooper, Daniel H.; Krainik, Andrew J.; Lubner, Sam J.; Reno, Hilary E. L. Washington Manual of Medical Therapeutics, The, 32nd Edition. Copyright 2007 . Published by Lippincott Williams & Wil
3. DiPiro JT, Talbert RL, Yee GC, et al., eds. Pharmacotherapy: A Pathophysiologic Approach, 5th ed. New York: McGraw-Hill; 2005.
4- G. Paul Sesin, Sarah Caron. Community-Acquired Pneumonia.A Practical Overview for Pharmacists. Us pharmacist. Vol. No: 28:01 Posted: 1/15/03