Soft Palate Laceration

DoveLewis Surgeon Coby Richter, DVM, DACVS, reveiws a referral case of a dog with a soft palate laceration caused by a stick.

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Case

A two-year-old Labrador retriever mix neutered male dog presented as a referral for suspected stick-related trauma. The day prior to presentation, the dog had been playing fetch with tree branches and the caretaker observed blood on one of the sticks. No obvious wounds were found by the owners, but they noticed that the dog was lethargic and not interested in eating or drinking that night. He was brought to the primary care veterinarian where thoracic radiographs showed pneumomediastinum. The dog was referred to DoveLewis for surgical consultation.

Upon arrival, the dog was quiet, alert and responsive and reluctant to allow oral examination. No nasal discharge was seen nor hemorrhagic saliva, no malodor from his mouth noted. He had a normal TPR and was estimated at 5% dehydration. No subcutaneous emphysema was palpable and he was eupneic. Palpation of the laryngeal region of the neck revealed non-fluctuant soft tissue swelling primarily on the right side which was painful. No cough was elicited. Auscultation of his chest and trachea revealed normal bronchovesicular noises with minimal upper airway noise. An extended data base revealed mild elevation in lactate at 2.4 mmol/L (range 0.5 – 2.0 mmol/L) and chloride at 117 mmol/L (range 109-112 mmol/L).

 

Initial Findings

The owners were offered computed tomography under anesthesia with surgical repair to follow as indicated for suspected pharyngeal penetrating injury. Endoscopy to evaluate esophageal integrity was also recommended. The owners elected anesthetized examination and repair with endoscopy if indicated but declined the CT scan. A cephalic intravenous catheter was placed and the dog was given methadone (0.32 mg/kg IV) and started on crystalloid replacement fluids for three hours prior to anesthesia to address dehydration. Premedication of hydromorphone (0.04 mg/kg), midazolam (0.2 mg/kg IV) and ketamine (2.2 mg/kg IV) followed by propofol to effect allowed a smooth induction. At induction he was started on ampicillin sulbactam at 30mg/kg IV and a fentanyl CRI. Intubation was uncomplicated and the endotracheal tube was secured to the lower jaw to allow safe access to the soft palate, pharynx, larynx and esophagus. The dog was maintained in sternal recumbency with his upper jaw suspended using a sling just caudal to the upper canines.

A full thickness 4 cm soft palate laceration (right of midline) extending from the caudal border of the hard palate to 1 cm rostral to the caudal border of the soft palate was found with significant adhered woody debris and non-viable tissue (Images 1 and 2). A matching full thickness laceration of the roof of the pharynx was found that extended caudally dorsal to the esophagus (Image 3). This was the presumed source of the pneumomediastinum seen by the referring veterinarian on thoracic radiographs and the origin of subcutaneous emphysema that developed subsequently. The esophagus showed no mucosal damage in the rostral 1/3 and had normal tone of the upper esophageal sphincter. Small fragments of woody debris were found within the pharyngeal roof laceration. Neither laceration was actively hemorrhaging.

 

Image 1: Soft palate laceration prior to debridement without and with probe.

 

Image 2: Soft palate laceration prior to debridement without and with probe.

 

Image 3: A is the right tonsil, B is the endotracheal tube, C is a spay hook used as a probe holding the soft palate defect open, the solid black arrow points to the opening of the pharyngeal puncture wound.

 

The larynx appeared normal and was packed with a moist laparotomy sponge to protect the airway during lavage and repair. Warm saline was used to flush the pharyngeal laceration pocket, the soft tissue defect and the nasopharynx until no further debris was recovered. A deep culture was collected from the pharyngeal laceration and the pocket left open to heal by second intention (clients declined submission of culture). Non-viable tissue was sharply debrided from the soft palate injury, preserving the rim of tissue caudally. The soft palate defect was closed with absorbable suture beginning with the dorsal mucosa/submucosa (floor of the nasopharynx) with 3-0 absorbable monofilament in an interrupted pattern with knots ventral, followed by figure of 8 mattress sutures in the muscles (palatinus and levator veli palatine) and finally 4-0 rapidly absorbable monofilament in an interrupted cruciate pattern to close the ventral mucosa/submucosa (knots ventral). All layers were closed with minimal tension despite significant debridement (Image 4).

 

Image 4: Repaired laceration.

 

Recovery

Recovery from anesthesia was smooth. The dog was started on a non-steroidal anti-inflammatory (meloxicam 0.1 mg/kg) and antinausea medication (maropitant 1mg/kg) and he was continued on ampicillin sulbactam while in hospital. He was discharged 14 hours later on a 2-week course of amoxicillin clavulanate as well as one week of oral meloxicam and gabapentin for pain and inflammation. Feeding instructions included 10 days of hand feeding canned food formed into meatballs followed by 1 week of canned food then transition to normal diet. Chew toys and other oral treats were discouraged for 4 weeks. The dog was seen for a recheck oral examination 14 days following repair at which time the soft palate was intact and no evidence of abscess formation. Subcutaneous emphysema which had developed the evening after surgical repair resolved over 4-5 days at home according to the owners. They reported no difficulties in feeding or drinking. A follow up phone call with the clients one year after injury confirmed an uncomplicated recovery.

 

Discussion

Soft palate lacerations are common in dogs with oral stick penetrating injuries. A sedated oral exam is usually necessary to accurately diagnose and create a treatment plan. In this dog, oral examination in the awake patient revealed only “abrasions” to the oropharynx. With suspected trauma to the pharyngeal region, preparation for full anesthesia including rapid intubation and available blunt suction (such as a Yankauer tip) should be made prior to beginning sedation. Plain radiographs are often unrewarding in establishing the severity of damage or in identifying organic material (e.g. sticks) but are still useful for diagnosing pathology such as pneumomediastinum. The CT scan was recommended to better evaluate for remaining foreign material and to evaluate for any other cause of the pneumomediastinum. In the described injury, the caudal margin of the soft palate was preserved which simplified repair and retained vascular supply, but often soft palate lacerations result in a caudal cleft. The most common complication of soft palate repair in dogs and cats is dehiscence of the repair with resulting cleft or stoma. Other complications include abscess formation, oronasal fistula, cutaneous draining tracts related to retained foreign material and nasal discharge.

 

Tips

Keys to successful repair include early and appropriate debridement, tension-free, multilayer closure and gentle tissue handling to preserve viability. The principle blood supply to the soft palate is from the minor palatine arteries although there can be anastomosis with the major palatine arteries which primarily serve the hard palate. Using a small, tapered needle and monofilament absorbable suture, as well as placing stay sutures to manipulate the palate will reduce risk of further damaging vascular supply. Electrocautery should be avoided if possible, using pressure with gauze or cotton tipped applicator when necessary for hemostasis. As much as possible, sutures should be interrupted and knots should be buried in the dorsal and deep layers. Start the repair at the caudal margin and work rostrally to improve alignment of tissues. Flush regularly during closure with warm saline to improve visibility and reduce contamination.

The caudal pharynx should be packed with moist lap sponge to prevent flush from accumulating around the endotracheal tube. In smaller patients, gauze squares can be tied together and used to preserve working space but still protect the airway. A single, temporary interrupted suture in the widest part of the closure can help identify tension prior to closure. If tissue damage and necrosis require debridement causing tension across the proposed closure, a partial thickness releasing incision can be made on the nasopharyngeal side and/or the oropharyngeal side lateral and parallel to the defect. A tonsillectomy (unilateral) is another means of gaining a tension free closure for soft palate defects that are off midline. Large defects or injuries in which there is significant damage to vascular structures serving the soft and hard palate may require staged repairs and/or oral, pharyngeal, nasal or skin flaps to achieve tension free closure.

 

Conclusion

Surgical repair of acute traumatic soft palate lacerations has better prognosis with fewer complications than repair of congenital soft palate defects or chronic fistulas. Post-operative care is generally soft food for 2 weeks, pain medication and anti-inflammatory medication and prevention of other foreign material entering the mouth during healing (toys, treats etc.). Antibiotics are determined on a case by case basis and were used in this dog due to the pharyngeal puncture and pocket dorsal to the esophagus. Esophagostomy or gastrostomy tube feeding is not usually necessary for soft palate repairs.

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