Small Animal Bronchoscopy and Operating Procedures

The preferred bronchoscope is a fiberoptic endoscope with a diameter of 3.5–6.0 mm and a working length of at least 55 cm. This is a typical size for human bronchoscopes, and a 5 mm diameter endoscope is suitable for most dog sizes.

Cats require narrower bronchoscopes for endoscopy. A 55 cm working length endoscope may be too short to fully examine the lobar bronchi of large dogs.

Longer veterinary endoscopes are available to address this issue, but gastroscopes/duodenoscopes can also be used. Although such endoscopes can be up to 8 mm in diameter, airway obstruction is relative due to the larger size of dogs.

A limitation of using endoscopes longer than 55 cm with a diameter <6 mm or narrower sizes is that images are often less clear due to fewer light-transmitting optical fibers. A recent advancement addressing this is the development of video bronchoscopes.

Figure 1: Connecting the endotracheal tube to the breathing circuit using an elbow port.

Inhalational anesthesia is recommended; however, intubation should only be performed if the endoscope can easily pass through the endotracheal tube, allowing simultaneous movement of air and the endoscope. An elbow port connector can be used to provide continuous gas anesthesia while the endoscope passes through the endotracheal tube.

If the endoscope cannot pass through the endotracheal tube, intravenous anesthesia must be used. To reduce the risk of hypoxemia, additional oxygen can be delivered alongside the bronchoscope via a urinary catheter or other type of flexible thin catheter. A flow rate of 1–3 liters per minute can be safely used.

Pre-oxygenation is highly beneficial, especially if oxygenation is impaired. This can be provided via nasal oxygen catheter or face mask.

The patient should be placed in a prone position with the head elevated and neck extended (Figure B.42). However, some clinicians prefer lateral recumbency as it facilitates easier manipulation, insertion, and maneuvering of the endoscope.

A mouth gag is essential to keep the mouth open and prevent the endoscope from being bitten due to the gag reflex triggered by endoscope contact with the pharynx.

Figure 2: Prone position of the animal for bronchoscopy. Intubation must be removed, and the endoscope inserted directly into the trachea unless using a very narrow-diameter endoscope.

Extra caution is required when the endoscope is placed in the airway without oxygen delivery, as severe hypoxemia may occur. Therefore, pulse oximetry must be closely monitored. Additionally, the endoscope may interfere with ventilation, leading to hypercapnia, pulmonary hyperventilation, trauma, and bronchospasm.

Cats require extra care during bronchoscopy as their airways are particularly prone to bronchospasm.

The procedure should be completed as quickly as possible to minimize trauma.

Due to cats' susceptibility to laryngospasm, lidocaine should be sprayed on the larynx before intubation. Clinicians should wait 30–60 seconds for the lidocaine to anesthetize the larynx, then insert the tube gently; intubation should only be performed when the larynx is open, using a twisting motion.

If using a commercial topical lidocaine spray, clinicians should be aware of the dose delivered per pump, as repeated use may cause toxicity. A dose of 1 mg/kg of 2% lidocaine is appropriate for cats (i.e., approximately 0.2 ml for a 4 kg cat).

To reduce the risk of bronchospasm, terbutaline (0.015 mg/kg subcutaneously or intramuscularly) can be administered approximately 30 minutes before bronchoscopy. Onset of action is 15–30 minutes, which can usually be observed by an increase in heart rate.

Terbutaline should also be available for administration if bronchospasm occurs during the procedure. If this fails to stabilize the animal, short-acting corticosteroids (e.g., dexamethasone sodium phosphate 0.1 mg/kg intravenously once) should be considered.

Suction equipment (or a 10–20 ml syringe connected to a sterile urinary catheter) should be available to clear any secretions from the oropharynx. If possible, cats should remain prone during the procedure. If a cat resists oropharyngeal suctioning, re-induction of anesthesia may be necessary to effectively clear the upper airway.

Figure 3: Prone position of the animal for bronchoscopy. Intubation must be removed, and the endoscope inserted directly into the trachea unless using a very narrow-diameter endoscope.

Figure 4: Lung Anatomy

Adequate ventilation must be ensured during foreign body retrieval.Foreign body retrieval can be very challenging. Surgeons should be prepared to stop the procedure and plan for surgery if the operation takes too long.There is a risk of airway injury or rupture and pneumothorax. Therefore, thoracentesis or thoracostomy tube placement equipment should be available.