The Effect of Nebulized Colistin on the Incidence of Gram Negative Bacterial Ventilator Associated Pneumonia in Intensive Care Unit Patients.

INTRODUCTION Pneumonia in the intensive care unit (ICU) constitutes the most frequent infection and is most often associated with the application of the mechanical ventilation. VAP (Ventilator - Associated Pneumonia) is defined as the nosocomial pneumonia in a patient on mechanical ventilatory support (by endotracheal tube or tracheostomy) for more than 48 hours. The risk for such complication is proportionally increased with the duration of hospitalization. The symptoms include the appearance of pulmonary infiltrate, fever, leukocytosis and purulent tracheobronchial secretions although this symptomatology is not always present. VAP is usually caused by nosocomial species and especially by gram negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae.

VAP is frequently complicated with the entry of bacteria in the circulation of blood resulting in bacteremia and sepsis. In this respect, this disorder is associated with substantial morbidity and devastating costs of hospitalization. Notably, the cost of one episode of VAP is estimated in 57000 $ per occurrence.

Inhaled antibiotics achieve high (both peak and trough) concentrations in respiratory secretions. Endobronchial antibiotics have been given initially in cystic fibrosis patients for the prevention of Pseudomonas aeruginosa pneumonia. More recently, some studies reported on the use of endobronchial antibiotics in non-cystic fibrosis patients for VAP treatment. There are only a few, relatively small, one-centre studies about the prevention of VAP; in those studies Colistin was given by instillation or nebulization and decreased the incidence of Gram-negative pneumonia.

AIM To study prospectively the effect of nebulized colistin on the incidence of Ventilator Associated Pneumonia due to gram negative bacteria in the ICU.

STUDY DESIGN Parallel two group blinded randomized controlled clinical trial. The trial medication will be commenced within 12 hours of randomization. The treatment group will receive nebulized colistin (500000 international units of colistimethate sodium, three times a day) for 10 days.