Characterization of an Animal Model of Ventilator-Acquired Pneumonia: Animal PreparationWith the pig in the supine position, intravascular catheters were inserted into the jugular vein and femoral artery under surgical conditions. A 7.5F Swan-Ganz catheter (Baxter Healthcare Corporation; Santa Ana, CA) was placed into the pulmonary artery via the external jugular vein through a right cervical cutdown and a 3F polyethylene catheter (Plastimed; St. Leu la Foret, France) was percutaneously inserted into the right or left femoral artery. These catheters were used for monitoring of hemodynamic and oxygenation parameters and for blood sampling. Finally, urinary drainage was obtained by vesical insertion of a 8F suprapubic catheter (Vesicoset; Angiomed; Karlsruhe, Germany) through surgical midline minipelvitomy. After this initial preparation, the animals were turned to the prone position with the snout positioned approximately 30° downwards from the neck axis to allow continuous drainage of oropharyngeal secretions onto an absorbent pad. Prone position was used since in pigs, as in sheep or cows, MV in the supine position results in lung atelectasis with severe ventilation/perfusion mismatch after a few hours.
Experimental Design
Three series of experiments were conducted. In the first series, we sought to discover whether pigs undergoing prolonged MV would develop VAP. Accordingly, once prepared as described above, a first group of 23 animals (control group) was subjected to MV under general anesthesia for a duration of 4 days in detail canadianfamilypharmacy. Ventilation parameters were adjusted to maintain arterial PaCO2 between 35 and 45 mm Hg and arterial oxygen saturation > 90% throughout the study period. Endotracheal suctioning was performed every 4 h for removal of secretions in excess. Parenteral feeding, fluids, and electrolytes were provided through continuous infusion of Ringer’s lactate (125 mL/h) and 10% glucose (40 mL/h). Additional vascular volume was administered as needed with a fluid gelatin (Plasmion; Rhone Poulenc Rohrer; Antony, France) to maintain cardiac output at 60 to 80% of the baseline level. Since the occurrence of VAP in the control group was a nearly constant feature, in a second series of experiments, we sought to discover whether antibiotics administered prophylacti-cally could prevent the occurrence of pneumonia in this model. Accordingly, a second group of nine animals (ATB group) were studied with the same protocol except that ceftriaxone (Rocephin; Roche Laboratories), 1 g (IV), was administered 15 min before intubation and then 1 g twice daily until day 4. Ceftriaxone was chosen since we knew from the previous experiments that this antibiotic was effective on most of the organisms causing pneumonia in ventilated pigletts.