Signalment and History
Tigger is a 6-month-old male neutered Domestic Short Hair cat who was presented for repair of a fractured left femur. (Fig. 1) Tigger had been hit by a car a few days before presentation.
Physical Examination
On physical examination, the left rear leg was moderately swollen and crepitus was evident at the midshaft femur. The cat was also mildly dyspneic with tachypnea and mildly labored breathing. Thoracic auscultation was within normal limits.
Diagnostic Evaluation
Thoracic radiographs showed pneumomediastinum and avulsion of the thoracic trachea with air-filled mediastinum seen bridging the gap. (Fig. 2) A mid-shaft oblique femoral fracture was also found. Tigger was transferred to the ICU for continuous monitoring and oxygen therapy if necessary.
Anesthesia and Surgery
Tigger was sedated and an intravenous catheter was placed. The right side of his thorax was clipped and an initial cleansing of the surgical site was performed. Anesthesia was induced with propofol and an endotracheal carefully placed. The size of the endotracheal tube was smaller than indicated to avoid further injury to the trachea. Intermittent positive pressure ventilation (IPPV) was avoided to prevent disruption of the tenuous mediastinal connection between the ends of the ruptured trachea.
The right lateral thorax was prepared for aseptic surgery. A right lateral thoracotomy was performed at the 4thintercostal space. A Buford rib retractor was placed and the cranial thorax was explored. Dissection of the trachea confirmed a complete avulsion of the trachea midway between the thoracic inlet and the carina. The mediastinum was serving as the only connection between the 2 ends of the ruptured trachea.
The mediastinum was carefully dissected and the proximal trachea exposed. The endotracheal tube was found within the tracheal lumen, grabbed with thumb forceps, and pulled farther out. The tube was then inserted into the distal tracheal segment. IPPV was then begun and maintained for the duration of the anesthetic episode. The ends of the ruptured trachea were healthy; no debridement was necessary. The tracheal anastomosis was performed with 4-0 PDS in a simple interrupted pattern. The sutures were placed by grabbing 1-2 tracheal rings on each side of the anastomosis and were full-thickness bites from outside to inside, exiting the tracheal lumen. (Fig. 3) All sutures were pre-placed to allow accurate placement and then tied. (Fig. 4)
Before closing the thorax, the endotracheal tube was gently pulled back and forth within the trachea to confirm that no sutures had penetrated the tube. A thoracic drain tube was placed and the thoracotomy closed routinely. The fractured femur was then repaired. Tigger recovered uneventfully from anesthesia.
Postoperative Care
Tigger was returned to the ICU and given intravenous fluids and analgesics for pain. He did well overnight with stable vital signs and eupneic breathing. One day postoperatively Tigger was doing well with no dyspnea, normal vital signs, and a good appetite. Minimal amounts of air or fluid had been recovered through the thoracic drain tube so it was removed. Tigger continued to do well and was discharged from the hospital on the 2nd day postoperatively with continued analgesic therapy and instructions to keep him indoors and restrict activity.
Tigger returned for a recheck examination 1 month postoperatively. The referring veterinarian had removed skin sutures 2 weeks after surgery and the thoracic and leg incisions were well healed. On physical examination, Tigger was bright and alert with pink mucous membranes and normal auscultation of the heart and lungs. He was weight bearing on the left rear leg. Repeat thoracic radiographs were normal with only a slight indentation of the tracheal lumen at the site of repair. (Fig. 5) Radiographs of the left femur showed normal progression of healing at the fracture site. Tigger was discharged with instructions to continue rest and return in 4 weeks for repeat radiographs of the left femur to assess continued healing.
Discussion
Tracheal avulsion in cats is rare but has been reported. (1). It is likely the result of blunt trauma that causes the head and neck to be hyperextended which stretches the trachea leads to rupture. The site of rupture is usually the thoracic trachea midway between the thoracic inlet and the carina. The airway lumen is maintained by the mediastinum resulting in a so-called “pseudo airway”, allowing the cats to continue ventilating. In one study some cats presented up to 3 weeks after the traumatic episode. (1)
Cats with tracheal avulsion present for variable signs of dyspnea. Cats with delayed diagnosis may have trachea stenosis as fibrosis occurs at each end of the ruptured segments. Removal of the stenotic tracheal rings may be necessary to facilitate an adequate lumen at the anastomosis. (2)
The anesthetic protocol for these cats is designed around providing adequate oxygen flow and ventilation without causing iatrogenic disruption of the pseudo trachea. After induction, endotracheal intubation on Tigger was performed carefully without attempting to bridge the gap with the tube which could cause more injury. IPPV was avoided until the endotracheal tube was manipulated by the surgeon to provide a secure pathway for the delivery of oxygen. Immediately after thoracotomy, the first objective was to quickly pull the endotracheal tube from the proximal tracheal segment and place it in the distal segment to allow ventilation with oxygen and anesthetic gas. The trachea could then be carefully repaired.
Based upon our experience with Tigger and a review of the reported cases, the prognosis for cats with tracheal avulsion is good after a successful repair. Most cats show adequate healing of the airway and can go on to live a normal life.
References
1. R N White, C A Burton. Surgical management of intrathoracic tracheal avulsion in cats: long-term results in 9 consecutive cases. Vet Surg, Sep-Oct 2000;29(5):430-5
2. Fingland RB. Obstructive upper airway disorders. In: Saunders Manual of Small Animal Practice, 3d edition, Birchard SJ, Sherding RG, eds., Elsevier, 2006, pg. 1663-1664.
