ANESTHESIA OVERVIEW

  1. What are examples of alpha-2 agonists?
    Answer: Xylazine (Rompun®), medetomidine (Domitor®), dexmedetomidine (Dexdomitor®), detomidine (Dormosedan®), romifidine (Sedivet®), and clonidine (Catapres®).

  2. What are the primary clinical effects of alpha-2 agonists?
    Answer: Sedation, analgesia, and muscle relaxation.

  3. Which alpha-2 agonists are most commonly used in small animals?
    Answer: Dexmedetomidine.

  4. Which alpha-2 agonists are commonly used in large animals?
    Answer: Xylazine.

  5. What is the mechanism of action for alpha-2 agonists?
    Answer: They act as agonists at presynaptic alpha-2 adrenergic receptors, decreasing norepinephrine release from adrenergic nerve terminals, which leads to sedation, decreased sympathetic activity, analgesia, and hypotension.

  6. What is the primary advantage of alpha-2 agonists?
    Answer: Their effects can be pharmacologically reversed using alpha-2 antagonists.

  7. How are alpha-2 agonists commonly administered?
    Answer: They can be administered intravenously (IV), intramuscularly (IM), subcutaneously (SQ), or orally.

  8. What is the onset of action for alpha-2 agonists when administered IV?
    Answer: Within minutes.

  9. What is the duration of action for dexmedetomidine in small animals?
    Answer: Typically 1–2 hours.

  10. Why do alpha-2 agonists have variable effects depending on the species?
    Answer: Different species have varying numbers and distributions of alpha-2 adrenergic receptors.

  11. What are the cardiovascular effects of alpha-2 agonists?
    Answer: Initial transient hypertension followed by prolonged hypotension, bradycardia, second-degree AV block, and decreased cardiac output.

  12. Why do alpha-2 agonists initially cause hypertension?
    Answer: Due to intense peripheral vasoconstriction.

  13. What causes the prolonged hypotension seen with alpha-2 agonists?
    Answer: Decreased sympathetic outflow and norepinephrine release.

  14. Why might bradycardia occur with alpha-2 agonists?
    Answer: Due to vagal stimulation and decreased sympathetic activity.

  15. How do alpha-2 agonists affect cardiac output?
    Answer: They decrease cardiac output by up to 30–50%.

  16. What respiratory changes do alpha-2 agonists cause?
    Answer: Decreased respiratory rate with variable effects on tidal volume.

  17. Are the respiratory effects of alpha-2 agonists typically clinically significant?
    Answer: At normal doses, respiratory effects are generally of minor concern.

  1. How do alpha-2 agonists affect gastrointestinal motility?
    Answer: They decrease intestinal motility, which can predispose animals to ileus.

  2. What effect do alpha-2 agonists have on blood glucose?
    Answer: They increase blood glucose by inhibiting insulin release.

  3. How do alpha-2 agonists affect urine production?
    Answer: They increase urine production due to decreased vasopressin secretion.

  4. Do alpha-2 agonists cause vomiting?
    Answer: Yes, they often induce vomiting in cats and sometimes in dogs.

  1. Which species are highly sensitive to xylazine?
    Answer: Ruminants, particularly cattle.

  2. What is the recommended dose of xylazine in cattle compared to horses?
    Answer: About 1/10th of the dose used for horses.

  3. What are examples of alpha-2 antagonists?
    Answer: Atipamezole (Antisedan®), yohimbine, and tolazoline.

  4. Which reversal agent is most commonly used for dexmedetomidine?
    Answer: Atipamezole.

  5. How should atipamezole be administered?
    Answer: Intramuscularly (IM) for routine reversal; IV only in emergencies.

  6. What is the effect of alpha-2 antagonists?
    Answer: They reverse sedation, analgesia, and cardiovascular effects of alpha-2 agonists.

  7. What is a common use of alpha-2 agonists in veterinary practice?
    Answer: Sedation for minor procedures, pre-anesthetic medication, or short-term analgesia.

  8. Why should alpha-2 agonists be used cautiously in animals with cardiovascular disease?
    Answer: Due to their effects on blood pressure, heart rate, and cardiac output.

  9. Why is it important to monitor animals after administering alpha-2 agonists?
    Answer: To watch for potential adverse effects like bradycardia, hypotension, or respiratory depression.

  10. What are common adverse effects of alpha-2 agonists?
    Answer: Bradycardia, hypotension, vomiting, decreased GI motility, increased blood glucose, and increased urine production.

  11. How can the bradycardia caused by alpha-2 agonists be managed?
    Answer: Use of reversal agents or atropine in certain cases, though caution is needed to avoid worsening hypertension.

  12. What can happen if alpha-2 antagonists are overdosed?
    Answer: Excitement, muscle tremors, or hypotension.