Pneumonia medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Most cases of pneumonia can be treated without hospitalization. Typically, oral antibiotics, rest, fluids, and home care are sufficient for complete resolution. However, people with pneumonia who are having trouble breathing, people with other medical problems, and the elderly may need more advanced treatment. If the symptoms get worse, the pneumonia does not improve with home treatment, or complications occur, the person will often have to be hospitalized.

Medical Therapy

Antibiotics are used to treat bacterial pneumonia. In contrast, antibiotics are not useful for viral pneumonia, although they sometimes are used to treat or prevent bacterial infections that can occur in lungs damaged by a viral pneumonia. The antibiotic choice depends on the nature of the pneumonia, the most common microorganisms causing pneumonia in the local geographic area, and the immune status and underlying health of the individual. Treatment for pneumonia should ideally be based on the causative microorganism and its known antibiotic sensitivity. However, a specific cause for pneumonia is identified in only 50% of people, even after extensive evaluation. Because treatment should generally not be delayed in any person with a serious pneumonia,empiric treatment is usually started well before laboratory reports are available. In the United Kingdom, amoxicillin is the antibiotic selected for most patients with community-acquired pneumonia, sometimes with added clarithromycin; patients allergic to penicillins are given erythromycin instead of amoxicillin. In North America, where the "atypical" forms of community-acquired pneumonia are becoming more common,azithromycin, clarithromycin, and the fluoroquinolones have displaced amoxicillin as first-line treatment. The duration of treatment has traditionally been seven to ten days, but there is increasing evidence that shorter courses (as short as three days) are sufficient.^[1]^[2]^[3]

Antibiotics for hospital-acquired pneumonia include vancomycin, third- and fourth-generation cephalosporins, carbapenems, fluoroquinolones, and aminoglycosides. These antibiotics are usually given intravenously. Multiple antibiotics may be administered in combination in an attempt to treat all of the possible causative microorganisms. Antibiotic choices vary from hospital to hospital because of regional differences in the most likely microorganisms, and because of differences in the microorganisms' abilities to resist various antibiotic treatments.

People who have difficulty breathing due to pneumonia may require extra oxygen. Extremely sick individuals may require intensive care treatment, often including intubation and artificial ventilation.

Viral pneumonia caused by influenza A may be treated with rimantadine or amantadine, while viral pneumonia caused by influenza A or B may be treated with oseltamivir or zanamivir. These treatments are beneficial only if they are started within 48 hours of the onset of symptoms. Many strains of H5N1 influenza A, also known as avian influenza or "bird flu," have shown resistance to rimantadine and amantadine. There are no known effective treatments for viral pneumonias caused by the SARS coronavirus, adenovirus, hantavirus, or parainfluenza virus.

CAP is treated by administering an antibiotic which is effective in killing the offending microorganism as well as managing any complications of the infection.
If the causative microorganism is identified, different antibiotics are tested in the laboratory in order to identify which medication will be most effective.
Often, however, no microorganism is ever identified.
Also, since laboratory testing can take several days, there is some delay until an organism is identified.
In both cases, a person's risk factors for different organisms must be remembered when choosing the initial antibiotics (called empiric therapy).
Additional consideration must be given to the setting in which the individual will be treated.
Most people will be fully treated after taking oral pills while other people need to be hospitalized for intravenous antibiotics and, possibly, intensive care.
In general, all therapies in older children and adults will include treatment for atypical bacteria. Typically this is a macrolide antibiotic such as azithromycin or clarithromycin although a fluoroquinolone such as levofloxacin can substitute.
The treatment of pneumonia involves three critical decisions: firstly whether the patient truly has pneumonia, secondly what is the severity of the pneumonia, and lastly whether hospitalization is required for adequate management.

The decision to hospitalize

Some people with CAP require hospitalization and more intensive care than the majority. Clinical prediction rules, such as the pneumonia severity index and CURB-65 have been developed to help guide the decision^[2]. Factors which increase the need for hospitalization include:
- Age > 65 yrs, in most cases, men over 70 and women over 80 should be managed as inpatients when diagnosed with CAP
- Confusion
- Underlying chronic illnesses;
- Evidence of infection outside the lung.
- Vitals:
  - Respiratory rate > 30 breaths/minute;
  - SBP < 90 mmHg;
  - Heart rate > 125/min;
  - Temperature < 35 or >40°C;
- Laboratory results which increase the need for hospitalization include:
  - Arterial oxygen tension < 60 mm Hg,
  - Carbon dioxide > 50 mmHg,
  - pH < 7.35 on room air;
  - Hematocrit < 30%;
  - Creatinine > 1.2 mg/dl or
  - Blood urea nitrogen > 20 mg/ dl;
  - White blood cell count < 4 × 10^9/L or > 30 × 10^9/L; and
  - Absolute neutrophil count < 1 x 10^9/L.
  - X-ray findings which increase the need for hospitalization include involvement of more than one lobe of the lung, presence of a cavity, and the presence of a pleural effusion.

Newborn infants

Most newborn infants with CAP are hospitalized and given intravenous ampicillin and gentamicin for at least ten days. This treats the common bacteria Streptococcus agalactiae, Listeria monocytogenes, and Escherichia coli. If herpes simplex virus is the cause, intravenous acyclovir is administered for 21 days.

Children

Treatment of CAP in children depends on both the age of the child and the severity of his/her illness. Children less than five do not typically receive treatment to cover atypical bacteria. If a child does not need to be hospitalized, amoxicillin for seven days is a common treatment. However, with increasing prevalence of DRSP, other agents such as cefpodoxime will most likely become more popular in the future.^[3] Hospitalized children should receive intravenous ampicillin, ceftriaxone, or cefotaxime.

Adults

In 2001, the American Thoracic Society, drawing on work by the British and Canadian Thoracic Societies, established guidelines for the management of adults with CAP which divided individuals with CAP into four categories based upon common organisms encountered.^[4]

Healthy outpatients without risk factors

This group, the largest, is composed of otherwise healthy patients without risk factors for DRSP, enteric Gram negative bacteria, Pseudomonas, or other less common causes of CAP. The primary microoganisms in this group are viruses, atypical bacteria, penicillin sensitive Streptococcus pneumoniae, and Hemophilus influenzae. Recommended management is with a macrolide antibiotic such as azithromycin or clarithromycin for seven^[4] to ten days.

Outpatients with underlying illness and/or risk factors

This group does not require hospitalization; its members either have underlying health problems (such as emphysema or congestive heart failure) or is at risk for DRSP and/or enteric Gram negative bacteria. Treatment is with a fluoroquinolone active against Streptococcus pneumoniae such as levofloxacin or a beta-lactam antibiotic such as cefpodoxime, cefuroxime, amoxicillin, or amoxicillin/clavulanate plus a macrolide antibiotic such as azithromycin or clarithromycin for seven to ten days.

Hospitalized individuals not at risk for Pseudomonas

This group requires hospitalization and administration of intravenous antibiotics. Treatment is with either an intravenous fluoroquinolone active against Streptococcus pneumoniae such as levofloxacin or beta-lactam antibiotic such as cefotaxime, ceftriaxone, ampicillin/sulbactam, or high-dose ampicillin plus an intravenous macrolide antibiotic such as azithromycin or clarithromycin for seven to ten days.

Individuals requiring intensive care at risk for Pseudomonas

Individuals being treated in an intensive care unit with risk factors for infection with Pseudomonas aeruginosa require specific antibiotics targeting this difficult to eradicate bacteria. One possible regimen is an intravenous antipseudomonal beta-lactam such as cefepime, imipenem, meropenem, or piperacillin/tazobactam plus an intravenous antipseudomonal fluoroquinolone such as levofloxacin. Another recommended regimen is an intravenous antipseudomonal beta-lactam such as cefepime, imipenem, meropenem, or piperacillin/ tazobactam plus an intravenous aminoglycoside such as gentamicin or tobramycin plus either an intravenous macrolide such azithromycin or an intravenous nonpseudomonal fluoroquinolone such as ciprofloxacin.

Treatment

In cases of viral pneumonia where influenza A or B are thought to be causative agents, patients who are seen within 48 hours of symptom onset may benefit from treatment with oseltamivir or zanamivir. Respiratory syncytial virus|RSV may be treated with ribavirin. Herpes simplex virus and varicella-zoster virus infections are usually treated with aciclovir, whilst ganciclovir is used to treat cytomegalovirus. There is no known efficacious treatment for pneumonia caused by SARS coronavirus, adenovirus, hantavirus, or parainfluenza virus; treatment is largely supportive.

Infectious Diseases Society of America/American Thoracic Society consensus recommendation on empiric antibiotics for community-acquired pneumonia in adults. ^[5] (DONOT EDIT)

“

A major goal of therapy is eradication of the infecting organism, with resultant resolution of clinical disease. As such, antimicrobials are a mainstay of treatment. Appropriate drug selection is dependent on the causative pathogen and its antibiotic susceptibility. Recommendations are generally for a class of antibiotics rather than a specific drug, unless outcome data clearly favor one drug. Because overall efficacy remains good for many classes of agents, the more potent drugs are given preference because of their benefit in decreasing the risk of selection for antibiotic resistance. Other factors for consideration of specific antimicrobials include pharmacokinetics/pharmacodynamics, compliance, safety, and cost.

Previously healthy and no risk factors for drug-resistant Streptococcus pneumoniae (DRSP) infection:

1. A macrolide (azithromycin, clarithromycin, or erythromycin) (Strong recommendation; level I evidence) 2. Doxycycline (Weak recommendation; level III evidence)

Presence of comorbidities, such as chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancies; asplenia; immunosuppressing conditions or use of immunosuppressing drugs; use of antimicrobials within the previous 3 months (in which case an alternative from a different class should be selected); or other risks for DRSP infection:

1. A respiratory fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin [750 mg]) (Strong recommendation; level I evidence) 2. A beta-lactam plus a macrolide (Strong recommendation; level I evidence) (High-dose amoxicillin [e.g., 1 g 3 times daily] or amoxicillin-clavulanate [2 g 2 times daily] is preferred; alternatives include ceftriaxone, cefpodoxime, and cefuroxime [500 mg 2 times daily]; doxycycline (level II evidence) is an alternative to the macrolide.)

High rate of infections

3. In regions with a high rate (125%) of infection with high-level (MIC > 16 mg/mL) macrolide-resistant Streptococcus pneumoniae, consider use of alternative agents listed above in (2) for patients without comorbidities (moderate recommendation; level III evidence)

Inpatients, non-ICU treatment

A respiratory fluoroquinolone (strong recommendation; level I

evidence)

A b-lactam plus a macrolide (strong recommendation; level I