ET intubation was achieved successfully using a laryngoscope with a polyvinylchloride ET tube( size 4.5 mm) with a stylet inserted in the lumen. The stylet was removed and the ET tube secured in place. The pilot cuff was inflated until no air leakage was heard when a manual breath was administered at a peak pressure of 20 cmH 2
O.
Anaesthesia was maintained with sevoflurane( SevoFlo, Zoetis) at an end-tidal percentage of 2 % vaporised in 100 % oxygen delivered via a circle breathing system. Rebreathing systems are more economical in terms of oxygen and volatile anaesthetic agent consumption. Additionally, they keep the circulating air warm and moist, helping to prevent hypothermia and drying of the airways. The oxygen fresh gas flow( FGF) was set at 4.0 l / min initially, to ensure a quick delivery of anaesthetic gas, and gradually decreased to 1.0 l / min.
The patient was connected to a multiparameter monitor including electrocardiography( ECG), capnography, spirometry, pulse oximetry and oscillometric blood pressure. All parameters were recorded every 5 minutes. Intravenous fluid therapy with Hartmann ' s solution( Aqupharm 11, Animalcare Ltd) was provided at a rate of 5 ml / kg / hour. Eye lubrication was applied. Thoracic radiographs revealed no signs of aspiration pneumonia.
In the theatre room, the patient was positioned in sternal recumbency with the head elevated, connected to the multiparameter monitor as described earlier, and the body temperature was monitored rectally. The sevoflurane concentration was maintained within an end-tidal range of 2 – 2.3 %, while the FGF was set at 2.0 l / min and gradually reduced after 10 minutes to 1.0 l / min, then after a further 10 minutes it was reduced to 0.5 l / min. This stepwise reduction primed the breathing system with oxygen and sevoflurane, ensuring adequate anaesthetic gas delivery before transitioning to low-flow anaesthesia.
Hypercapnia( end-tidal CO 2
60 mmHg) was noticed on capnography, and mechanical ventilation was initiated. The patient subequently became moderately hypotensive, with a mean arterial pressure( MAP) of 55 mmHg, and received a 5 ml / kg bolus of crystalloid fluids over 10 minutes, which improved the MAP to 65 mmHg.
The patient underwent soft palate resection and laryngeal saccules excision. Before proceeding with removal of the ET tube for debulking of the laryngeal fold mass, a bolus of 0.5 μg / kg dexmedetomidine was administered, followed by an increase in the CRI rate to 1 μg / kg / hour, and the sevoflurane was discontinued.
Flow-by oxygen was provided at 3.0 l / min and intermittent boluses of propofol( 40 mg total) were administered to maintain an adequate depth of anaesthesia. The dog ' s oxygen saturation( SpO 2
), respiratory rate and pattern, heart rate, MAP and facial reflexes were closely monitored.
The surgical procedure for the mass excision lasted 10 minutes. In the first 5 minutes the SpO 2 was maintained above 97 %, and afterwards decreased gradually, reaching 90 % before ET intubation was performed with a size 5.0 mm ET tube. Anaesthesia was maintained with sevoflurane for the bilateral wedge rhinoplasty, and intermittent positive-pressure ventilation( IPPV) was restarted. Dexamethasone 0.1 mg / kg( Colvasone Veterinary, Norbrook) was administered IV to reduce postoperative swelling, and acepromazine 0.005 mg / kg( Acecare, Animalcare Ltd) was given IV to provide anxiolytic effects during the recovery period. An emergency ET intubation kit was prepared.
The sevoflurane was discontinued and the patient was gradually weaned off mechanical ventilation. Oxygen supplementation was provided until the patient was able to maintain SpO 2 above 97 % on room air, and the dexmedetomidine CRI was maintained at a rate of 1 μg / kg / hour. The patient ' s SpO 2 was monitored continuously using a pulse oximeter. On the first attempt to remove the ET tube, 30 minutes after discontinuing the sevoflurane, the patient started bleeding from the surgical site and developed dyspnoea. Anaesthesia was induced with propofol( 2 mg / kg) and the patient ' s trachea was re-intubated with a size 4.5 mm ET tube. She was maintained under anaesthesia via a circle breathing system delivering 100 % oxygen with end-tidal sevoflurane at 1.6 %.
On oral examination it was noticed that the haemorrhage had ceased; the oral cavity was suctioned and no regurgitated contents were noticed. A second attempt was made to remove the ET tube 20 minutes later, but the patient showed signs of respiratory distress, dyspnoea and oxygen desaturation. Anaesthesia was induced again with 2 mg / kg propofol, and her trachea was re-intubated with a size 4.5 mm ET tube. Owing to the patient ' s inability to control and maintain an open upper airway, the anaesthesia and surgery teams decided to perform a temporary tracheostomy. The tracheostomy tube was removed 3 days later after intensive nursing care and close monitoring, and the patient made a full recovery.
Nursing considerations
BOAS is a progressive respiratory condition caused by an abnormal skull conformation in brachycephalic animals, leading to structural airway changes and restricted breathing. Dogs significantly affected by BOAS have an elongated soft palate, hypoplastic trachea, stenotic nares and aberrant nasal turbinates. Some affected dogs may develop everted laryngeal saccules and laryngeal collapse associated with increased negative intraglottic luminal pressure during inspiration [ 1 ]. These animals are also predisposed to conditions such as gastrooesophageal reflux( GOR) and regurgitation, aspiration pneumonia, hiatal hernia, corneal ulceration and stressinduced hyperthermia [ 2 ].
26 Veterinary Nursing Journal