Stabilizing Dogs With Upper Airway Obstruction & Heat Stroke

The upper airway system includes the nares, pharynx, and trachea and is vital for gas exchange, air humidification, filtration of air particles, and thermoregulation.¹ Upper airway obstruction in dogs may lead to life-threatening respiratory dysfunction with subsequent heat-induced injury; alternatively, hyperthermia may cause upper airway obstruction.^1,2 Upper airway obstruction and heat stroke are often concurrent.

Upper airway obstruction is typically caused by laryngeal paralysis, tracheal collapse, or brachycephalic obstructive airway syndrome.^1-5 Common physical examination findings include a prolonged inspiratory phase of respiration, panting, and stridulous or stertorous breathing. Patients with severe obstruction may become cyanotic and orthopneic. Stabilization involves rapid intervention with oxygen therapy, sedation, and active thermoregulation.^1,2,5,6 Oxygen therapy can be provided in various forms depending on the severity of obstruction, and emergency intubation may be needed prior to referral to a specialty clinic.^1,2

Step-by-Step: Stabilizing Dogs With Upper Airway Obstruction & Heat Stroke

Step 1: Evaluate Respiratory Pattern & Effort, & Provide Sedation

Using low-stress handling techniques, observe the patient for evidence of respiratory obstruction (eg, cyanosis, stertor/stridor, prolonged inspiratory effort, excessive panting), and perform a triage examination (ie, measure heart rate, pulse, pulse quality, respiratory rate, respiratory effort, and body temperature) to assess for presence of shock.

Author Insight

Low-stress handling includes gentle, quiet, and calm handling techniques and should be used concurrently with sedation (see Step 2) to avoid patient struggling. An oxygen cage can also be used, if available, to facilitate observation of the respiratory pattern until sedation begins to take effect. Respiratory obstruction can often be detected based on abnormal respiratory sounds and a prolonged inspiratory phase.

Step 2: Provide Oxygen Support & Sedation

Provide oxygen support during evaluation and stabilization based on severity of respiratory distress, patient tolerance, and availability of supplies. Administer an IV or IM sedative based on patient stability.

If an oxygen cage is available, briefly place the patient in the cage and administer an IM sedative while supplies are gathered for further intervention. Monitor the patient for persistent or worsening respiratory signs. If an oxygen cage is not available, provide continuous flow-by oxygen.

Author Insight

Sedation can reduce anxiety associated with respiratory distress and increase airway diameter and is thus essential for dogs with upper airway obstruction.¹

Commonly used sedatives include butorphanol (0.1-0.5 mg/kg IM or IV), acepromazine (0.005-0.02 mg/kg IV; 0.01-0.05 mg/kg IM), and dexmedetomidine (0.5-2 micrograms/kg IV; 3-5 micrograms/kg IM).^1,2,5,7 Congestive heart failure should be ruled out as the cause of respiratory compromise before sedatives (eg, dexmedetomidine, acepromazine) with the ability to alter cardiovascular parameters are considered. Butorphanol has minimal cardiovascular effects. Reversal agents for dexmedetomidine and butorphanol (atipamezole and naloxone, respectively) should be available in case of cardiovascular compromise.

Flow-by oxygen is a good first choice for oxygen therapy and can be given via a mask (if tolerated by the patient) to increase oxygen concentration. Endotracheal intubation is the most rapid and effective method of stabilization for patients with severe obstruction.

Step 3: Perform Endotracheal Intubation (Optional)

In cases in which orotracheal intubation is indicated, establish IV access if possible. Administer an anesthetic induction agent (eg, propofol, 3-4 mg/kg IV).⁸ If IV access is not possible, perform induction with IM medications (eg, butorphanol [0.2-0.3 mg/kg] with midazolam [0.2-0.3 mg/kg] ± alfaxolone [1 mg/kg]).⁷ Establish IV or intraosseous access as soon as possible.

With the patient in sternal recumbency, use a laryngoscope to briefly evaluate the oropharynx and larynx if possible,⁸ and insert an appropriately sized cuffed endotracheal tube. Confirm correct placement of the tube, then tie the tube to the maxilla or head and connect to a manual resuscitator bag or anesthetic machine to provide oxygen and ventilation as needed. Maintain sedation via intermittent bolus administration or IV CRI.

Author Insight

A multimodal approach to induction (eg, butorphanol [0.1-0.2 mg/kg IV] in addition to propofol [2 mg/kg IV] or butorphanol [0.1-0.2 mg/kg IV] and ketamine [2 mg/kg IV] in addition to propofol [2 mg/kg IV]) can reduce the dose of a single induction agent, thereby reducing both respiratory depression and cardiovascular compromise.⁷

Orotracheal intubation should be considered in patients with severe obstruction or signs of obstruction persist or progress following initial intervention. Several endotracheal tube sizes should be available, as airway swelling and edema may make intubation difficult. All cardiovascular parameters should be closely monitored while the patient is sedated and intubated. The endotracheal tube should be kept in place until the patient is stabilized and ready for transport to a referral facility. Anesthesia and intubation may be required during transport. Sedation can be maintained with IV CRIs of propofol (0.05-0.1 mg/kg/minute), butorphanol (0.025-0.3 mg/kg/hour), and/or a benzodiazepine (0.25-0.5 mg/kg/hour).^7,9

Step 4: Measure Patient Temperature

If body temperature was not previously measured due to patient anxiety or the need for immediate intubation, measure body temperature after the airway is secured or the patient is stabilized with sedation or endotracheal intubation. Continue to monitor temperature every 5 to 10 minutes.

Step 5: Provide Thermal Regulation (Optional)

In patients with rectal temperature >103°F (39.5°C), provide active cooling via administration of room-temperature IV fluids, wetting the patient with tap water, and nearby placement of a fan.⁶ Discontinue active cooling once the patient’s temperature reaches 103°F (39.5°C), as rectal temperatures often continue to drop.^1,2,4,6 Maintain rectal temperature between 99°F and 102.5°F (37°C-39°C) prior to transport.³

Author Insight

After active cooling, the patient should be kept at the low end of a normal temperature (eg, 99°F-100.5°F [37.2°C-38.1°C]) to avoid a drive to pant.

Step 6: Consider Additional Medications

Consider administration of a short-acting, anti-inflammatory glucocorticoid (eg, dexamethasone sodium phosphate, 0.05-0.2 mg/kg IM, IV, or SC or 0.14 mg/kg IV) to reduce airway swelling and edema and/or parenteral antiemetics to prevent aspiration if the patient will be sedated or intubated during transport.^1,2,9