Ear, nose and throat (ENT) diseases are relatively common in veterinary patients. A thorough understanding of the disease process will increase the welfare of the patient as well as help avoid potentially life-threatening complications. To high-light some general considerations of ENT disease, this presentation will focus on two ENT surgical procedures: total ear canal ablation (TECA) and lateral bulla osteotomy (LBO) and brachycephalic airway obstruction surgery (BAOS).
Total Ear Canal Ablation And Lateral Bulla Osteotomy
Introduction
A TECA/LBO is the removal of all parts of the external ear canal to the level of the external acoustic auditory meatus (TECA), followed by access into the tympanic bulla (LBO) for debridement of the middle ear.
Indications
There are two main indications:
As an end-stage, or salvage, procedure for dogs and cats with irreversible ear canal disease, typically due to chronic otitis externa. Chronic infection and inflammation lead to an increasingly poorly aerated ear canal due to narrowing of the canal lumen, further worsening the original cause of the otitis externa. When the ear disease becomes refractory to medical management, or the animal is in constant pain with the disease, then a TECA/LBO can be performed. It should be emphasised that all medical routes should be exhausted prior to surgery being recommended. Furthermore, ear canal disease may also be due to other causes, such as congenital stenosis (most commonly seen in the Shar-Pei), trauma and also neoplasia (benign and malignant).
As treatment for middle ear disease. In the dog, middle ear infection is most likely to be secondary to chronic otitis externa, due to extension of infection through or across the tympanic membrane. Primary infection or neoplasia of the middle ear is also possible both in the cat and dog. Benign polyps of the middle ear occur very commonly in the cat and more rarely in the dog, although in the cat these are more commonly treated by ventral bulla osteotomy without total ear canal ablation.
Preoperative Assessment
General history and physical examination.
A thorough dermatological examination is worthwhile in cases of otitis externa, as treatment of underlying skin disease is imperative for medical management of otitis externa.
Preoperative blood tests are indicated for animals with history or physical examination findings suggestive of underlying (e.g., hyperadrenocorticism, hypothyroidism) or concurrent (e.g., renal) disease.
Imaging:
Plain radiographs of the skull may be helpful, although changes in the middle ear cannot always be detected radiographically, and may be non-specific. Useful views are dorsoventral skull, open-mouth rostrocaudal and oblique views of the bullae.
More advanced imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI) are increasingly used.
Ultrasonography can be used in the cat and some small dogs: however, interpretation of this view is a fairly specialised affair.
Perioperative Care
Analgesia. An opiate (pure agonist such as methadone) and a non-steroidal anti-inflammatory drug (NSAID) should be administered immediately pre-operatively to gain the benefit of pre-emptive analgesia, assuming there are no contraindications. Other techniques, such as a ketamine or lidocaine infusion, or local nerve block, are required in some individuals.
An intravenous line is required as perioperative fluid therapy is beneficial: surgery can be prolonged and there is the possibility of significant blood loss in some cases.
The site is contaminated and so perioperative antibiotics are required. A broad-spectrum bactericidal drug (such as a cephalosporin) should be used; it must be administered intravenously about 30 minutes before the first incision. Preoperative antibiotics, to clear infection prior to surgery, are not normally necessary.
An adequate area, involving the whole pinna and area ventral to the ear canal opening, should be prepared. Some gentle cleaning down the canal is desirable, but it is impossible to clean this area completely. Vigorous flushing of the ear canal should be avoided, as many of these patients will have a ruptured tympanic membrane, and vestibular signs may be induced.
The patient's head should be rested on a sandbag to stabilise it, and the front legs should be tied caudally.
A standard surgical kit is required, along with some more specialised equipment (two large Gelpi retractors, one medium Gelpi, diathermy, suction with a Frasier suction tip, Rongeurs for the bulla osteotomy, Volkmann spoon to debride in the middle ear).
Samples may need to be taken for bacteriology (material from the middle ear can be sent to the laboratory) and/or histopathology.
After the surgery is performed, the surgical site should be lavaged with a large volume of sterile isotonic solution (such as saline or Hartmann's solution).
Some clinicians place a Penrose drain before closure.
The dead space should be carefully closed down with synthetic absorbable suture material, and monofilament non-absorbable skin sutures should be placed.
The procedure can be repeated on the other side under the same anaesthetic, although this may make the anaesthetic longer than is desirable. It is usually recommended to repeat the procedure on the other side 2-4 weeks after the first surgery.
Postoperative Care
Some clinicians favour a head bandage to put pressure on the surgical wound.
An Elizabethan collar is sometimes required to prevent patient self-trauma.
Opioid medication should be continued for at least 24-48 hours, and NSAID medication should be prescribed for at least 5-7 days.
Intravenous fluid therapy can be discontinued when the animal is fully awake, but should be continued if haemorrhage is severe.
Antibiotics should be prescribed for 5-7 days as the surgery is classified as contaminated. The course should be of the same antibiotic as administered intravenously. Some clinicians favour a longer course (e.g., 4 weeks) but this is not necessary in most cases.
The wound should be cleaned, as often it will discharge some serosanguinous fluid.
General nursing to make the animal feel better.
Lead walks only for 2 weeks to prevent the wound being damaged.
Sutures should be removed 12-14 days postoperatively.
Complications
Wound dehiscence or infection. If this occurs, the wound is generally managed as an open wound.
Haemorrhage--can occur intraoperatively, most worryingly from the retroglenoid vein; fatal bleeding has been reported.
Recurrence of middle ear infection--nearly always due to inadequate debridement of the secretory lining of the tympanic bulla. Clinical signs may not develop for many months after surgery, and would include swelling over the area, head tilt, pain on opening the mouth or vestibular signs.
Vestibular signs--due to damage during surgery to the vestibular apparatus.
Facial nerve paralysis--may be permanent if the facial nerve has been transected during surgery, more commonly temporary due to neuropraxia and resolves after 4-6 weeks.
Brachycephalic Airway Obstruction Syndrome Surgery
Introduction
BAOS is a disease seen commonly in brachycephalic breeds and leads to respiratory difficulty for the animal. The following changes are typically seen:
Stenotic nares
Compact turbinate bones in the nasal cavity
Overlong and thickened soft palate
Hypoplastic trachea
These primary anatomical changes will cause an increased respiratory effort, as the animal attempts to force through enough air, especially during hot weather or when exercising. The increased effort causes an increased negative pressure within the airway, leading to secondary changes:
Eversion and sometimes enlargement of the tonsils
Eversion of the laryngeal saccules
Laryngeal collapse
Surgery is aimed at reducing intra-airway pressure:
Widening the nares. Some animals are very young when they present, and this is the most appropriate procedure in immature animals.
Shortening the soft palate (staphylectomy)
Removing the tonsils (tonsillectomy)
Some surgeons remove the laryngeal saccules
Indications for Surgery
This is for any animal that has exercise intolerance or syncope associated with upper respiratory tract obstruction.
Preoperative Assessment
History and general physical examination:
The animal's body condition should be assessed, as excessive fat around the pharynx will worsen the condition.
Coughing is not a common feature of BAOS and so should increase the suspicion of a concurrent disease.
Oesophageal disease (especially in the Bulldog) can mimic the signs of BAOS and so a thorough history is very important.
Blood tests are indicated if there is evidence of concurrent disease in the history or physical examination.
Imaging:
Radiographs of the chest: to rule out lower airway disease.
Positive contrast oesophagography: if any oesophageal disease is suspected.
A lateral radiograph of the head and neck: to assess soft palate length and to screen for hypoplastic trachea.
Laryngoscopy--the gold standard to diagnose the condition.
Tracheobronchoscopy--if lower airway disease is suspected, and possibly to confirm a hypoplastic trachea.
Perioperative Care
Analgesia--see previous section for TECA/ LBO analgesia.
The premedication is usually lighter for these animals, and rapidly metabolised induction and maintenance agents should be used. This is because a rapid recovery from anaesthesia is vital--the more rapidly the animal can recover from anaesthesia, the quicker it will recover control of its airway.
Once the diagnosis of BAOS has been made by laryngoscopy, the airway should be secured with an endotracheal tube.
Positioning of the animal for surgery is critical to make the surgery easier:
The maxilla should be suspended by tape or bandage from above, with the tape just caudal to the incisors.
Sandbags under the neck should be avoided as this makes judging the palate length more difficult.
A gag should be used.
The endotracheal tube should be tied to the lower jaw, with the tongue held underneath on the midline.
No clipping or aseptic preparation is required for the pharyngeal surgery. The high number of bacteria in the oropharynx means that intravenous antibiotics should be administered, as described in the previous section. The hair around the nares can be clipped and the area aseptically prepared as normal.
A standard surgical kit is required. Good theatre lights are important, and need to be directed into the caudal oropharynx.
Healing of tissues of the oropharynx is quick, so rapidly absorbed synthetic suture materials should be used.
Postoperative Care
The animal should only be recovered from anaesthesia when the surgeon is absolutely sure there is no ongoing haemorrhage into the airway. This is critical to a safe recovery.
The endotracheal tube should be maintained as long as possible until the animal is fully awake.
The animal's head should be elevated on a sandbag during recovery.
Some surgeons use corticosteroids to reduce postoperative swelling. Obviously NSAIDs should not be used if that is the case.
Some institutions keep intravenous anaesthetic agents and an endotracheal tube near the animal for 24 hours after surgery in case the airway occludes.
A 5-7-day course of antibiotics is required, although infection is rarely a problem as the pharyngeal mucosa heals very quickly.
Postoperative analgesia is similar to that for TECA/LBO.
Feeding can be started after the animal is fully awake, and should be tinned consistency only for 4 weeks.
An Elizabethan collar is sometimes required to prevent self-trauma of the nasal sutures.
Gentle exercise only for 2-3 weeks.
Complications
Upper respiratory tract obstruction. This may be due to swelling or, more commonly, haemorrhage and should be a rare complication if the surgery is performed adequately.
Swallowing disorders due to excessive soft palate resection, or sometimes due to postoperative swelling.
Ongoing clinical signs--there are three potential causes:
Inadequate surgery
Concurrent airway disease that may or may not respond with more time (e.g., laryngeal collapse or hypoplasic trachea)
Misdiagnosis (oesophageal or lower airway disease)