Notes on Surgery of the Trachea in Small Animals

Tracheal Surgery in Small Animals

Tracheal Anatomy

  • Location: Part of the lower respiratory tract.

  • Extent: Extends from the cricoid cartilage to the carina.

  • Portions: Consists of extrathoracic and intrathoracic sections.

  • Structure:- Composed of incomplete cartilage rings, approximately 35 in number.

    • Cartilage is hyaline.

    • Annular ligaments connect the rings, allowing for shape and length accommodation.

    • Trachealis muscle provides dorsal connection.

  • Cross-Sectional Anatomy:- Mucosa: Contains goblet cells.

    • Submucosa: Features tubuloalveolar mucus glands.

Surgical Approaches to the Trachea

  • Ventral Midline Cervical Approach:- Indication: Primarily for the cranial cervical trachea.

    • Muscles Incised: Sternohyoideus and sternothyroideus muscles.

    • Important Structures to Note: Recurrent laryngeal nerve, vagosympathetic trunks, right and left common carotid arteries, thyroid glands, and esophagus.

  • Median Sternotomy:- Indication: Used for approaches to the caudal cervical and cranial thoracic trachea.

  • Intercostal Thoracotomy:- Right 3rd Intercostal Space (ICS): For the cranial thoracic trachea.

    • Right 4th ICS: For the tracheal bifurcation.

Surgical Tracheal Diseases (DAMNIT Mnemonic)

  • D - Degenerative, Developmental: E.g., Tracheal collapse.

  • A - Anatomical/Anomalous, Acquired, Allergic, Auto-Immune: E.g., Esophagotracheal or esophagobronchial fistula.

  • M - Metabolic, Mechanical: E.g., Foreign bodies.

  • N - Neoplastic, Nutritional: E.g., Osteosarcoma, osteochondroma, chondrosarcoma, leiomyoma, rhabdomyosarcoma, Adenocarcinoma (AdCa), Lymphosarcoma (LSA), Fibrosarcoma (FSA), Squamous Cell Carcinoma (SCC).

  • I - Infectious, Inflammatory, Idiopathic, Iatrogenic:- E.g., Spirocerca lupi/Onchocerca sp., Cuterebra.

    • E.g., Tracheal rupture secondary to Endotracheal (ET) tube trauma.

  • T - Trauma, Toxin:- Tears/Ruptures (internal vs. external).

    • Hematomas.

Tracheal Collapse

  • Medical Management: This is the initial approach. (Refer to Internal Medicine Notes for details).

  • Surgical Treatment Indication: ONLY considered when medical management fails.

External Prosthetic Tracheal Rings

  • Indication: Exclusively for cervical trachea collapse.

  • Material: Polypropylene.

  • Surgical Approach: Ventral midline cervical approach.

  • Technique: Rings are secured to the cartilaginous rings. Placement must begin and end in an area of normal trachea to ensure stability and proper support.

  • Outcomes: Generally good, with immediate improvement in clinical signs.

Complications of External Prosthesis

  • Laryngeal Paralysis:- Reported in 11% to 30% of surgical cases.

    • May result from direct damage during surgery or continuous trauma from the implants.

  • Tracheal Necrosis:- A life-threatening complication secondary to damage to the trachea's segmental blood supply.

    • Clinical signs include coughing and subcutaneous emphysema.

  • Pneumothorax:- Can occur due to the diffusion of air through the mediastinum during surgery.

    • Also possible from accidental penetration of the thoracic cavity near the caudal cervical trachea.

Intraluminal Stent

  • Type: Self-expanding nitinol stents.

  • Deployment: Constrained on a delivery system for precise placement.

  • Sizing: Diameter and length are determined based on diagnostic imaging, often utilizing an esophageal measurement probe.

  • Placement: Performed fluoroscopically or endoscopically.

  • Function: Provides circumferential support to the trachea without impacting surrounding vessels or nerves.

Advantages of Intraluminal Stenting

  • Minimally invasive.

  • Shortened anesthesia time.

  • Can be used in both cervical and thoracic trachea.

  • Results in immediate improvement in clinical signs.

Disadvantages of Intraluminal Stenting

  • Requires specialized equipment (fluoroscopy or endoscopy).

  • Significantly expensive (dollars).

  • Shorter life-span compared to external tracheal rings.

  • Moderate to high complication rate.

Complications of Stenting

  1. Stent Fracture: Can be life-threatening if fractured pieces migrate.

  2. Stent Migration: Primarily due to incorrect sizing.

  3. Tracheitis: Documented in approximately 60% of patients.

  4. Collapse Beyond Stented Region: Collapse can occur in adjacent areas, such as the mainstem bronchi.

  5. Tracheal Obstruction Secondary to Granulation Tissue Formation: May respond to treatment with corticosteroids and colchicine.

  6. Tracheal Rupture.

  • Note: Nitinol (self-expanding intraluminal stents) are generally the most accepted option due to very low rates of stent migration.

Tracheal Trauma
Types of Trauma

  • Internal Trauma:- Rupture or necrosis, often secondary to an ET tube.

    • More common in cats.

    • Can occur during dental procedures.

    • May also result from foreign bodies.

  • External Trauma:- Caused by blunt or penetrating injuries.

    • Examples include bite wounds, lacerations, puncture wounds, avulsion, transection, or loss of tissue.

Clinical Signs of Tracheal Trauma

  • Mild to severe subcutaneous emphysema: Indicative of a tracheal tear, typically observed within minutes to hours after trauma, depending on the tear size.

  • Anorexia.

  • Lethargy.

  • Stridor.

  • Coughing.

  • Dyspnea.

Management of Tracheal Trauma

  • Medical Management for Minor Tears/Ruptures:- Many minor tears respond to conservative medical management.

    • Cage rest.

    • Oxygen supplementation.

    • Sedatives.

    • Thoracocentesis or thoracostomy tube placement for pneumothorax.

    • Consider a temporary tracheostomy if dyspnea persists or worsens.

  • Indications for Surgical Intervention:- Dyspnea persists or worsens with medical management.

    • Pneumothorax persists for more than 2-3 days.

    • Severe tracheal damage is visible.

  • Surgical Options:- Primary Closure: Simple continuous pattern used for direct repair of tears.

    • Tracheal Resection and Anastomosis: For more extensive damage.

    • Post-Operative Monitoring: Long-term monitoring is crucial for scarring and tracheal narrowing.

Tracheal Resection and Anastomosis

  • Indications: Irreparable trauma, tracheal stenosis, and tracheal tumors.

  • Technique: Split-cartilage technique is preferred.- Benefit: Results in the least amount of post-operative stenosis.

    • Challenge: Can be difficult to perform in small dogs and cats.

    • Steps:1. Place stay sutures cranial and caudal to the resection sites.

      1. Split the tracheal cartilages with a No. 11 blade.

      2. Transect the trachealis muscle with Metzenbaum scissors.

      3. Appose the trachealis muscle using three or four interrupted sutures.

      4. Approximate the split cartilages.

Extent of Resection and Tension Relief

  • Allowed Resection: Up to 25% to 50% of the trachea can be resected in adult dogs, and 20% to 25% in puppies.

  • Tension: Tension becomes obvious after resecting 3-4 rings.

  • Tension-Relieving Sutures: Place three or four tension-relieving sutures around cartilages adjacent to the anastomosis site to reduce strain.

Complications of Tracheal Resection and Anastomosis

  • Subcutaneous (SQ) emphysema.

  • Pneumomediastinum and pneumothorax.

  • Infection.

  • Stricture (narrowing).

  • Poor apposition of mucosa.

  • Tension at the surgical site.

  • Inflammation.

Tracheostomies

  • Types: Temporary and Permanent.

Permanent Tracheostomy

  • Indications (Salvage Procedure):- Untreatable upper airway obstruction (e.g., palliation for nonresectable laryngeal neoplasia, Stage III laryngeal collapse).

    • Failure of other upper airway treatments (e.g., failed treatment of laryngeal paralysis or laryngeal collapse).

  • Surgical Considerations:- Creation of a stoma (an opening) into the trachea.

    • The stoma will decrease by 40-50% in size in most animals, so it is crucial to make it large initially.

    • Accurate apposition of the skin and tracheal mucosa is essential to reduce inflammation and the extent of stenosis.

Prognosis and Long-term Care for Permanent Tracheostomy

  • Prognosis:- Dogs: Good if the underlying disease is benign. However, owners must be diligent with care, and symptomatic treatment for tracheitis may be required. While 80% complications are reported, 5/15 cases demonstrated a good quality of life. Individual case reports indicate survival for 4.5 - 5 years.

    • Cats: Prognosis is generally guarded to poor.

    • Complications impacting prognosis: Mucus plugs are very common and can lead to acute death. Soft tracheal cartilage may predispose the trachea to collapse; consider placement of external rings adjacent to the tracheostomy site.

    • Median survival times have been reported as 20.5 and 42 days in specific study cohorts.

  • Long-term Care:- Excessive secretions are common for several weeks post-operatively until squamous metaplasia of the mucosa is complete.

    • Maintenance of the opening:- Clipping hair around the stoma as needed.

      • No swimming is permitted.

      • Protection from foreign bodies (e.g., plant material) is crucial.

      • Use a harness instead of a collar to avoid pressure on the stoma.

Tracheal Foreign Bodies

  • Presentation: Variable clinical presentations depending on the foreign body's location and nature.

  • Removal Techniques (for foreign bodies at the entrance of the trachea):- Tracheobronchoscopy.

    • Fluoroscopy combined with a guided balloon catheter.

    • Vacuum applications.

A Case of Freely Moving Foreign Body Inside Trachea

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