Feline anesthesia

Anesthesia for Cats

  • Presenter: Jill Maney, VMD DACVAA, Modified and delivered by Dr. Miguel Martinez, LV Dip ECVAA

Objectives

  • Describe appropriate premedication, induction, and anesthetic maintenance protocols for healthy cats.

  • Discuss complications and methods for avoiding and treating them.

  • Overview of recently FDA-approved drugs for cats.

Anesthetic Mortality Rates

  • Dogs: 0.05-0.17%

  • Cats: 0.11-0.24%

    • Cats generally exhibit higher mortality rates compared to dogs.

    • Mortality rates for cats are significantly higher than in humans (0.001% to 0.0001%).

Challenges in Anesthesia for Cats

  • Cats are generally more difficult to anesthetize than dogs due to:

    • Smaller body size.

    • Increased risk of hypothermia.

    • Potential for accidental overdose.

    • Equipment malfunction.

    • More complex intubation process.

    • Differences in drug metabolism; cats may be more sensitive to adverse effects of certain drugs.

Pre-Anesthetic Considerations

  • History Taking:

    • Similar considerations as in dogs, but cats often hide disease until it's advanced.

    • Requires asking specific questions; outdoor vs. indoor living affects infectious disease and trauma risks.

    • Signs of pain may be subtle and hard to detect.

Cat Breeds and Associated Risks

  • Certain breeds such as Maine Coons are prone to hypertrophic cardiomyopathy (HCM).

  • Anesthesia in HCM breeds carries risk of fatal arrhythmia or congestive heart failure (CHF).

  • Random Feline MDR1 mutation discovered; no current evidence associating it with sedatives/anesthetics/analgesics.

    • If a murmur is detected, recommend a cardiologist consult before elective anesthesia.

    • HCM can be present without observable murmurs.

    • Use point-of-care proBNP SNAP tests for cardiac disease screening.

Premedications

  • Opioids:

    • Options include oxymorphone and methadone for lower excitement levels.

    • Fentanyl may be used as a continuous rate infusion (CRI) for analgesia.

    • Buprenorphine provides good analgesia but has a ceiling effect.

    • New opioid options include Simbadol (SQ every 24 hours) and Zorbium (transdermal application).

    • All can result in post-operative hyperthermia.

  • Sedatives:

    • Dexmedetomidine is effective but requires higher doses than in dogs and can be antagonized.

    • Acepromazine provides sedation without analgesia.

    • Benzodiazepines can cause excitement and are better given IV at induction.

At-Home Premeds

  • Gabapentin (50 mg per cat) and Trazodone are recommended.

  • Oral transmucosal options include dexmedetomidine +/- buprenorphine, methadone, or acepromazine.

IM Anesthesia

  • Alfaxalone or ketamine IM combinations are effective for fractious cats.

  • Monitor closely after injection and intubate once laryngeal reflexes are lost.

  • Use cat-specific techniques for restraint, such as the "burrito technique" or using a "cat nabber".

IV Induction Agents

  • Agents include propofol, alfaxalone, etomidate, and ketamine (telazol).

  • Be cautious with propofol to avoid Heinz body anemia from repeated doses.

  • Avoid chamber or mask induction due to potential stress responses and arrhythmias.

Intubation Techniques

  • More difficult in cats than in dogs; caution required to avoid damage to the larynx and trachea.

  • Use lidocaine to reduce laryngeal spasm risks.

  • Ensure adequate depth before attempting intubation.

  • Monitor cuff inflation carefully and adjust to prevent damage.

V-Gel Supraglottic Airway Device

  • An alternative to endotracheal intubation designed for easier placement by inexperienced personnel.

  • Six sizes available based on cat weight; single use (~$20 each).

Anesthesia Maintenance

  • Inhalant anesthetics require a higher minimum alveolar concentration (MAC) in cats than in dogs.

  • Injectable anesthetics (CRI) options include alfaxalone or propofol alongside adjunct drugs like opioids and benzodiazepines; avoid lidocaine CRI.

Complications During Anesthesia

  • Watch for pulmonary edema/fluid overload; manage blood volume around 60 mL/kg.

  • Monitor for hypotension and provide adjustments as necessary, including using vasopressors.

  • Neurological Complications:

    • Risk of blindness or neurological deficits.

    • Avoid using spring-loaded mouth gags which can compromise cerebral blood flow.

    • Address other causes of cerebral hypoxia like low cardiac output or hypoxemia.

Drug Toxicity and Risks

  • Acetaminophen is toxic to cats leading to methemoglobinemia.

  • NSAIDs can have renal/GI effects; only 2 approved for use in cats: Robenacoxib and Meloxicam.

  • Robenacoxib: Approved for 24 hours over 3 days; evidence of safe longer usage interval.

  • Meloxicam: Approved for a single SQ dose only in the US; concerns about kidney injury.

Blood Transfusions in Cats

  • Recognize the three blood groups (A, B, AB) and Mik antigen.

  • Mandatory typing and cross-matching before transfusions.

  • Type A is prevalent in most domestic cats in the US, while Type B is more common in specific breeds (e.g., Himalayan).

Recently FDA Approved Drugs

  • Buprenorphine Transdermal Solution (Zorbium): Approved for postoperative pain control in cats, offering analgesia for 4 days.

  • Frunevetmab (Solensia): Targets osteoarthritis pain by binding to nerve growth factor (NGF) and preventing pain transmission, administered monthly.

Questions?