Epinephrine Nebulization in the Postanesthetic Care of a Canine Patient With Brachycephalic Obstructive Airway Syndrome

The prevalence of brachycephalic obstructive airway syndrome (BOAS) has risen in recent years due to the increasing popularity of brachycephalic breeds. Notably, in 2022, the French bulldog claimed the top spot as the most popular dog breed in America, overtaking the Labrador retriever, which held the position for 31 consecutive years.¹

BOAS is defined by an animal having some or all of the following abnormalities: elongated soft palate, hypoplastic trachea, stenotic nares, everted laryngeal saccules, macroglossia, enlarged tonsils, and redundant nasal turbinates.² Dogs diagnosed with BOAS often exhibit increased respiratory noise and effort, with clinical signs that can progressively worsen, sometimes leading to acute respiratory distress requiring emergency surgical intervention.

Surgery has become the standard of care for most patients with BOAS because it can significantly improve the quality of life for affected dogs by offering long-term relief. However, complications may still occur. These complications are primarily related to postoperative inflammation and edema of the pharynx, larynx, and surrounding soft tissues caused by surgical manipulation.

Signalment, Presentation, and History

This report details the case of a 1-year-old female French bulldog referred to a specialty veterinary hospital for the management of BOAS. The owner noted that the dog had difficulty sleeping and often propped her mouth open on a toy for comfort. Additionally, the dog had a history of chronic urinary tract infections treated with various antibiotics, as well as a syncopal episode that occurred after a brief walk around the neighborhood.

Upon arrival, the patient was in stable condition, with the following vital signs:

• Mentation: Bright, alert, and responsive
• Heart rate (HR): 130 beats per minute (bpm) with a regular rhythm; no murmur auscultated; strong, synchronous femoral pulses
• Respiratory rate (RR): 30 breaths/min with stertorous breathing at rest with referred upper airway noises
• Temperature: 38.2 °C (100.8 °F)
• Mucous membrane: Pink, moist
• Body weight: 12.6 kg (27.8 lb)
• Body condition score: 6/9
• Physical examination revealed no abnormalities except for the presence of stridor and increased respiratory effort.

After the consultation, the owner chose to proceed with preoperative diagnostics, including thoracic radiography, hematologic screening, and a functional airway examination. Based on the findings, the plan was to perform a bilateral laryngeal sacculectomy, along with a standard staphylectomy and bilateral wedge resection if necessary.

Treatment and Outcome

The patient was administered gabapentin (16 mg/kg PO). After 60 minutes, a 20-gauge IV catheter was placed in the left cephalic vein and ondansetron (0.5 mg/kg IV), pantoprazole (1 mg/kg IV), cisapride (0.5 mg/kg IV over 30 minutes), and maropitant (1 mg/kg IV) were administered.

Blood was then collected for a complete hematologic panel, which yielded unremarkable results. Similarly, 3-view thoracic radiographs were also unremarkable, with genetic anatomical changes related to BOAS.

Following radiography, the patient was transported to the anesthesia preparation area, and the owner provided consent to proceed with surgery. The patient was positioned in sternal recumbency and administered butorphanol at a dose of 0.4 mg/kg IV. Shortly thereafter, the patient was preinstrumented to monitor electrocardiogram, pulse oximetry, and blood pressure (BP) during the functional and structural airway examination. Flow-by oxygen was provided via a loose-fitting face mask at a rate of 2 L/min for 5 minutes. Once the surgical team arrived, a safety induction checklist was completed, and propofol was administered in 1 mg/kg increments, titrated to effect, to facilitate the airway exam and reduce the risk of apnea associated with propofol boluses. Doxapram was available for respiratory stimulation but was not required.

The airway examination confirmed that corrective surgery was necessary. To facilitate intubation, lidocaine (2 mg/kg IV) and an additional dose of propofol (1 mg/kg IV) were administered, and a 5.5 mm endotracheal tube (ETT) was successfully placed and confirmed via capnography. The patient was then connected to an adult rebreathing universal F-circuit with a 2-L reservoir bag, and 100% oxygen was delivered at a flow rate of 1 L/min (80 mL/kg/min). To maintain general anesthesia, a propofol constant-rate infusion (CRI) at 150 µg/kg/min and dexmedetomidine CRI at 1 µg/kg/hr were initiated.

First vitals after induction included:

• Peripheral oxygen saturation (Spo₂): 100% (reference range, > 95%)
• HR: 80 bpm
• Oscillometric noninvasive BP: 140/50 (75) mm Hg (hypotension defined as mean arterial pressure < 60 mm Hg)
• Sinus rhythm: Normal
• End-tidal carbon dioxide: 53 mm Hg (reference range, 35 to 45 mm Hg)
• RR: 10 breaths/min
• Rectal temperature: 38.3 °C (100.9 °F)

IV fluid therapy was initiated with lactated Ringer’s solution at a rate of 5 mL/kg/hr. Before surgery, the patient’s esophagus and stomach were suctioned with minimal return. An arterial line was placed in the right dorsal pedal artery to obtain more accurate invasive BP readings; the first was 100/65 (75) mm Hg.

A lidocaine splash block was applied to the palate, and the patient’s anesthetic depth was deemed appropriate, indicated by the absence of a palpebral reflex, minimal jaw tone, and ventromedial eye positioning. With these parameters confirmed, the first surgical incision was made. Ten minutes into the surgery, the patient showed signs of a light plane of anesthesia, as evidenced by an increased RR, HR, central eye positioning, and a significant palpebral reflex. In response, the propofol CRI was increased from 150 to 200 µg/kg/min, and a 1 mg/kg bolus of propofol was administered. Additionally, the patient received 1 mg/kg IV ketamine to deepen anesthesia depth and 0.02 mg/kg IV buprenorphine for analgesia.

After medication alteration, the patient was placed on intermittent positive-pressure ventilation due to hypoventilation:

• HR: 100 bpm
• RR: 12 breaths/min
• Tidal volume: 250 mL
• Peak inspiratory pressure: 15 cm H₂O
• BP: Remained consistent, with a mean arterial pressure of 70 to 80 mm Hg
• Rectal temperature: 38 °C (100.4 °F)

Once staphylectomy was completed, a laparotomy sponge was soaked with 30 mL of hypertonic saline and placed in the back of the oral cavity to reduce swelling associated with the surgery. The patient was then repositioned for bilateral wedge resection. This portion of the procedure was completed without complications. Total anesthetic time was 120 minutes.

The patient was then transferred to the recovery ward, where the CRIs were discontinued, the sponge was removed from the back of the oral cavity, and the esophagus was suctioned with minimal return. Dexamethasone-SP (0.15 mg/kg IV) and acepromazine (0.005 mg/kg IV) were administered. While awaiting extubation, the nebulizer was connected to a loose-fitting oxygen mask and the diluted epinephrine solution (0.05 mg/kg epinephrine mixed with 0.9% saline to create a 5-mL nebulization solution)³ was prepared and placed in the nebulizer (TABLE 1 AND FIGURE 1).

Figure 1. The patient in recovery receiving nebulized epinephrine.

The patient’s laryngeal reflexes returned, indicating the patient was capable of protecting its airway from aspiration. The ETT was deflated and removed 40 minutes after discontinuation of the propofol and dexmedetomidine CRIs, with no regurgitation observed in the ETT or oral cavity. After extubation, nebulization was initiated while ensuring the patient maintained adequate airflow. The breathing system was connected to an adapter, and the nebulization was delivered via a mesh nebulizer, producing droplets at a rate of 0.25 mL/min for 10 minutes. Throughout nebulization, the patient’s electrocardiogram was monitored, and no increase in HR was detected.

• Mentation: Quiet, alert, and mildly sedated
• Spo₂: 98%
• HR: 120 bpm
• RR: 12 breaths/min with referred upper airway noises
• Temperature: 37.4 °C (99.3 °F)
• Mucous membrane: Pink, moist

Discussion

Anesthetic management of patients undergoing BOAS corrective surgery is generally straightforward, but the recovery phase carries significant risks. During the immediate postoperative period, oxygen saturation and breathing effort should be closely monitored, particularly within the first few hours following extubation. Studies report a 6.6% morbidity and mortality rate in English bulldogs, with 87.5% of deaths occurring within the first 3 hours postoperatively due to respiratory complications.⁴

Additionally, a study has demonstrated that nebulized epinephrine effectively reduces airway obstruction in dogs with severe BOAS, especially in those with a preoperative BOAS index above 70% and postoperatively in most cases.³ Pugs, particularly those with a high BOAS index, showed the most improvement, likely due to their smaller glottic size, which is more susceptible to mucosal edema.³ Nebulized epinephrine was associated with minimal side effects, with nausea being the most common, possibly caused by stress or the epinephrine itself.³

This treatment shows promise for emergency stabilization and postoperative care, although careful patient selection and monitoring are essential due to potential risks such as stress-induced airway obstruction and rare adverse effects. Further research is necessary to explore its impact on mucosal edema, the risk of rebound edema, and optimal dosing frequency.³