Aerosolized Antibiotics in the Treatment of Ventilator Associated Pneumonia

The purpose of this study is to determine if administering inhaled antibiotics directly into the lungs in conjunction with intravenous (IV) antibiotics leads to better outcomes and decreased recurrence of ventilator associated pneumonia (VAP) when compared to IV antibiotics alone.

Ventilator associated pneumonia (VAP) remains a serious problem in critically ill patients with an incidence of 8-28% and mortality ranging from 24-57%. A landmark study comparing eight days versus fifteen days of antibiotic therapy reported a pulmonary infection recurrence rate of 26-29%. Costs associated with VAP can reach up to $40,000 per occurrence.

Aerosolized antibiotics have been used to treat ailments such as cystic fibrosis and bronchiectasis. Previous research indicates that aerosolized antibiotics attain a 200 fold greater concentration in the lung than in the blood, and that sputum trough levels remain 20 fold greater than that of acceptable serum antibiotic troughs. Additionally, aerosolized antibiotics are considered safe (without increased risk of bacterial resistance) with better treatment success when compared to controls (OR 2.75, 95% CI 1.06-7.17), although no mortality benefit has been identified. Some studies have shown reduced systemic toxicity when using aerosolized antibiotics while others have shown no difference. Aerosolized tobramycin prevents pseudomonas infections in patients with Cystic Fibrosis. Furthermore aerosolized antibiotics improve pulmonary function in these patients, including Forced Expiratory Volume in 1 second (FEV1), and decrease the need for hospitalization. Lung transplant patients and patients with Human Immunodeficiency Virus (HIV) also benefit from aerosolized fungal prophylaxis and treatment. The benefit has been less clear in patients with non-Cystic Fibrosis bronchiectasis, and although some studies show benefits to aerosolized antibiotics in preventing and treating nosocomial pneumonias, no large prospective randomized trials have been performed to confirm the benefit or to change practice recommendations.

Antimicrobials must reach the site of infection, bind the target site, and remain bound for a sufficient time period to disrupt the life cycle of the cells. Only 21% of an administered antibiotic dose actually ends up in the lung parenchyma. Multiple studies have shown that the ideal particle size for inhalation is between 1 and 5 microns. Particles that are too small get exhaled, and particles that are too large do not reach the alveoli. Non-humidified nebulization is better for drug administration than humidified air. Isotonicity of the drug, pH, and the presence of preservatives in the solution also need to be evaluated for optimal drug delivery and function. The ideal method of administration of aerosolized antibiotics also remains to be determined.

Inhaled tobramycin has been used in several studies over the past thirty years, mostly in patients with Cystic Fibrosis. It has been shown to be effective in decreasing sputum colony counts of Pseudomonas Aeruginosa. Inhaled gentamycin has also been shown to delay acquisition of Pseudomonas in children with Cystic Fibrosis, as well as decreasing disease progression. Chest tightness and persistent cough are the side effects mentioned within these studies. This suggests that inhalation is a safe method for the administration of tobramycin.

It has been shown that in Community-Acquired Pneumonia (CAP) the alveolar macrophages initiate a pro-inflammatory cascade. Failure to control excessive inflammation, leads to an exaggerated systemic response resulting in organ damage. Local and systemic levels of these pro-inflammatory mediators have been shown to correlate with the severity of disease. The investigators speculate that a similar response exists in patients with VAP.

The investigators propose a prospective, randomized trial designed to assess the value of aerosolized antibiotics in the treatment of ventilator associated pneumonia and to evaluate the impact of co-existing, non-bacterial pathogens and cytokines on the ability to clear pneumonia in culture-proven cases of VAP. Eligible patients will be randomized at the time of bronchoalveolar lavage or combicath to receive either adjuvant aerosolized antibiotics plus routine IV antibiotics or aerosolized placebo plus routine IV antibiotics. Individual clinical indicators will be recorded and used to monitor the effect of aerosolized antibiotics \[temperature, leukocyte count, chest radiograph appearance, ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2 ratio), mechanical ventilation status, and vital signs\].

Eligibility Criteria:
Inclusion Criteria:

1. Clinical Pulmonary Infection Score (CPIS) greater than or equal to 6
2. Intubated greater than or equal to 48 hours
3. Screened for possible eligibility
4. Bronchoscopy and bronchoalveolar lavage (BAL) or combicath performed
5. Started on empiric intravenous (IV) and inhaled antibiotics after BAL for suspected ventilator associated pneumonia (VAP)
6. \> 104 Colony Forming Units (CFU) on BAL

Exclusion Criteria:

1. \<18 years of age
2. Pregnant
3. Human Immunodeficiency Virus (HIV) or on chronic immunosuppressants
4. Absolute Neutrophil Count \<1,000
5. Allergy to vancomycin or tobramycin
6. Anaphylaxis to penicillin
7. Cystic Fibrosis
8. Previous enrollment
9. Creatinine \>2 mg/dl or doubled within the previous 72 hours