Hospital-Acquired Pneumonia

Hospital-Acquired Pneumonia.

Carl Stuart

Stuart Medical Series 

Introduction.

Evidence-based practice requires that clinical management protocols should be informed by the most current evidence as adduced from research and studies. These research and studies are normally guided by PICO statements. The PICO statement enables the investigator or researcher to identify a problem that requires a better intervention than the one currently used. As PICO-guided studies do compare two or more medical interventions in terms of their prognosis and clinical outcome, such studies have been used to provide evidence to support the change in intervention strategies in various pathologies.

PICO Statement.

The PICO statement for this study is stated below as:

In patients suffering from hospital acquired pneumonia, how does therapy with broad-spectrum antibiotics compare with combination therapy in effecting an improvement in lung function tests?

PICO Question.

Based on the above statement, it can be seen that the parameters of the PICO question are:

Population of Interest: Patients suffering from hospital acquired pneumonia.

Intervention of Interest:  Broad-spectrum antibiotics.

Comparison Intervention of Interest: Combination therapy.

Outcome of Interest:  Improvement of the lung function tests.

Hence, it can be inferred that the PICO statement can also be used as the structured PICO question.

Structured PICO Question.

In patients suffering from hospital acquired pneumonia, how does therapy with broad-spectrum antibiotics compare with combination therapy in effecting an improvement in lung function tests?

Hospital-Acquired Pneumonia

The broad area of interest in this study is hospital acquired pneumonia, and thus it is imperative to provide a background knowledge of hospital acquired pneumonia.

            Hospital-Acquired Pneumonia (often abbreviated as HAP) is a designation used to describe the types of pneumonia that a patient contracts in a hospital setting within 48-72 hours post-admission. Studies have shown that HAP is mainly caused by bacterial infections.The main implicated bacteria are gram negative bacilli (about 52% of the cases) and MRSA (Methicillin Resistant Staphylococcus Aureus) (about 19% of all cases). In the ICU, the main infectious agents are Pseudomonas auroginosa, Staphylococcus aureus, Enteroacter species, Klebsiella pneumonia and Haemophilus influenza. A minority of cases of HAP are caused by viral infection with the main infectious agents being cytomegalovirus in immunecompetent patient, and respiratory syncytial and influenza viruses in immunecompromised patients.

HAP is a cause of significant mortality in the intensive care unit and the high-dependency units. As such, effective management protocols must be instituted once the patient has been diagnosed with HAP, as this reduces the associated length of hospital stay, alleviates the symptoms associated with the condition and it also assures the management team of an excellent prognosis of the infection. Research has shown that there are two types of HAP: VAP (Ventilator-associated pneumonia) and HCAP (Healthcare-Acquired pneumonia).

1.      Ventilator-associated pneumonia

VAP occurs in patients whose respiration is being supported by mechanical ventilators. As such, definitive categorization of the causative agents is made after a positive culture is obtained post-intubation.

2.      Healthcare-Acquired pneumonia

HCAP occurs in non-hospitalized patients but its etiology, prevention strategies, natural history, and management plans are similar to HAP. It main affects people confined in extended care facilities and nursing homes.

Clinical Aspects of HAP.

            The main sign and symptoms of HAP is a progressive infiltrate in chest radiographs alongside one or more of the following findings: purulent sputum, fever and leukocytosis of over 10,000 cells/μl. The pulmonary infiltrates and the accumulation of the sputum within the lungs do lead to respiratory insufficiency, and as such pneumonia does impair lung function as measured by spirometry.

The main parameters measured by spirometry in pneumonia patients are following pulmonary volumes and pulmonary capacities. The pulmonary volumes are tidal volume, residual volume, inspiratory reserve volume and expiratory reserve volume; and the pulmonary capacities are the functional residual volume, inspiratory capacity, vital capacity and the total lung volumes. Improvement in these parameters does indicate that HAP is resolving.

Treatment of HAP.

The treatment of HAP includes the use of either Broad-spectrum antibiotics or combination therapy. HCAP patients are likely to be managed with broad-spectrum antibiotics. However, use of broad-spectrum antibiotics for managing VAP has been ineffective as most nosocomial infections are resistant to the most commonly used broad-spectrum antibiotic, ceftriaxone. However, studies done by expert panel have shown that combination therapy is more efficacious as compared to broad-spectrum antibiotics in the management of HAP. The most commonly used combination therapy is fluoroquinolone (such as moxifloxacin), amoxiclav (amoxicillin combined with clavulanic acid) and a macrolide, and parenteral fluoroquinolones, a macrolide plus a third generation cephasporin. Some protocols require that the management team should conduct a microbiological study (mainly culture and sensitivity) of the specimen before administering any drugs. According to the guidelines published by the IDSA (Infectious Diseases Society of America) and ATS (American Thoracic Society), the following combination of drugs is recommended for HAP patients confined in ICU:

1.      Cephalosporin: Cefepime; OR piperacillin–tazobactam; OR Monobactam: Meropenem, Imipenem; PLUS

2.      Fluoroquinolone: levofloxacin, ciprofloxacin; OR Aminoglycosides: gentamicin, tobramycin or amikacin; PLUS

3.      Vancomycin or linezolid.

Evidence-based resources

After providing the background information about the problem under study (that is, the disease afflicting the patient), it is necessary to identify and locate evidence-based resources and articles that can be used to answer the PICO Question. In this case, the resources can be categorized into three broad categories:

1.      General information resources: They do provide detailed information pertaining to the problem under study. Most of these resources are books or clinical manuals. In this case, the relevant books include Merck Manual of Diagnosis and Therapy, Current Diagnosis and Treatment, and Harrison's Principles of Internal Medicine. Also some online sources such as UpToDate can be used.

2.      Filtered resources: These are literature created by subject specialist and clinical experts who have studied the problem under study extensively (in this case, HAP). These resources utilize clinical evidence to recommend the most appropriate management plans for diseases.These resources include Cochrane Database of Systematic Reviews, Systematic Review or Meta-Analysis, Clinical Practice Guidelines, Critically Appraised Research Studies and Individual Research Studies.

3.      Unfiltered resources: these resources are utilized if one cannot locate unfiltered resources. These resources allow the researcher to place limits for that may pertain to the search, for example age, language and year of publication. The most common resources are Medline and CINAHL.