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All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Anesthesia and intubation
- Sedate the animals (three-month-old New Zealand white rabbits (male or female), weighing ~2.5 kg each) by intramuscular (IM) injection of ketamine (25 mg/kg, 50 mg/mL, 0.5 mL/kg) + xylazin (3 mg/kg, 20 mg/mL, 0.15 mL/kg). Wait ~20 min for the animals to sleep
deeply (complete muscular atony).
NOTE: This premedication will allow a simple, fast and painless intubation process. Deep analgesia and anesthesia is induced as described in step 1.1.8.
- Place an intravenous (IV) cannula into the marginal vein from the ear and keep it closed until intubation is completed.
NOTE: This IV line will serve to perfuse fentanyl and propofol for deep analgesia and anesthesia, respectively (see step 1.8).
- Maintain anesthesia by supplying 5% sevoflurane in pure oxygen until intubation is performed.
NOTE: This step is necessary only if the animal shows signs of awakening (eye movements, muscular contractions).
- Anesthetize the trachea locally by spraying 10% lidocaine. Place the rabbit in prone position and maintain its head in vertical extension.
- Slide the first endotracheal tube of small diameter (2.5 mm) into the rabbit trachea until airflow can be heard in the tube. This will open the larynx and facilitate the insertion of the definitive tube.
- Insert a guide (intubation catheter) in the tube to fix the position of the tube into the trachea. Remove the small diameter tube and slide the definitive endotracheal tube (4.9 mm) on the guide.
- Remove the guide and inflate the balloon at the end of the endotracheal tube to seal and block the device into the trachea. The tube will stay in place but it may be secured by using a lace tied around the forehead. Immediately ventilate (7 mL/kg, frequency of 40/min) the animal with 3% sevoflurane in pure oxygen.
- Continuously perfuse (ear vein) fentanyl (0.01 mg/mL, 2–4 mL/h) to induce analgesia, 2–4 mg/kg of (2%) propofol (20 mg/mL, 4–8 mL/h) to induce anesthesia, and 4 mL/kg/h of Ringer's acetate to maintain iso-volumetric conditions.
- Place a rectal temperature probe. Also monitor heart function, temperature and oxygen saturation during the entire process.
- Control the depth of anesthesia by monitoring autonomous breathing; if the animal shows signs of autonomous breathing, dispense a small bolus of propofol and fentanyl.