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Questions and Answers
What is a potential side effect of Atipamezole, an antagonist of alpha-2 adrenergic receptor agonists?
What is a potential side effect of Atipamezole, an antagonist of alpha-2 adrenergic receptor agonists?
Which receptor do benzodiazepines primarily act on?
Which receptor do benzodiazepines primarily act on?
What is a common method of excretion for Diazepam?
What is a common method of excretion for Diazepam?
Which of the following benzodiazepines is specifically licensed for use in horses?
Which of the following benzodiazepines is specifically licensed for use in horses?
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What is a significant risk when using alpha-2 adrenergic receptor agonists in patients with cardiovascular disease?
What is a significant risk when using alpha-2 adrenergic receptor agonists in patients with cardiovascular disease?
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What is a primary benefit of using premedication in veterinary anesthesia?
What is a primary benefit of using premedication in veterinary anesthesia?
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Which premedication option is known for unpredictable sedation?
Which premedication option is known for unpredictable sedation?
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Which is not a characteristic of Acepromazine?
Which is not a characteristic of Acepromazine?
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What is a risk associated with the use of Acepromazine in certain dog breeds?
What is a risk associated with the use of Acepromazine in certain dog breeds?
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Which of the following is a potential side effect of Acepromazine?
Which of the following is a potential side effect of Acepromazine?
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What is the typical dosage range for administering the controlled drug to dogs and cats?
What is the typical dosage range for administering the controlled drug to dogs and cats?
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Which of the following effects is associated with the use of the controlled drug in horses?
Which of the following effects is associated with the use of the controlled drug in horses?
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What is a significant concern when using trazodone as an adjunct premedication?
What is a significant concern when using trazodone as an adjunct premedication?
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How does gabapentin primarily reduce excitatory neurotransmitter release?
How does gabapentin primarily reduce excitatory neurotransmitter release?
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When developing an anesthetic protocol, which of the following is a key consideration?
When developing an anesthetic protocol, which of the following is a key consideration?
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What is the purpose of premedication before induction of general anaesthesia?
What is the purpose of premedication before induction of general anaesthesia?
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What distinguishes sedation from general anaesthesia?
What distinguishes sedation from general anaesthesia?
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Which term describes sedation produced by opioids?
Which term describes sedation produced by opioids?
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Why is neuroleptoanalgesia beneficial in veterinary practice?
Why is neuroleptoanalgesia beneficial in veterinary practice?
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What is a key consideration when choosing sedation over general anaesthesia?
What is a key consideration when choosing sedation over general anaesthesia?
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Which statement regarding the administration of local blocks during sedation is true?
Which statement regarding the administration of local blocks during sedation is true?
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Which of the following best describes anxiolysis?
Which of the following best describes anxiolysis?
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What is a common misconception about sedation compared to general anaesthesia?
What is a common misconception about sedation compared to general anaesthesia?
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Which opioid is known for causing significant respiratory depression and is considered 100 times more potent than morphine?
Which opioid is known for causing significant respiratory depression and is considered 100 times more potent than morphine?
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What is the duration of action for Buprenorphine typically reported as?
What is the duration of action for Buprenorphine typically reported as?
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Which opioid is a full mu agonist and also functions as an NMDA receptor antagonist?
Which opioid is a full mu agonist and also functions as an NMDA receptor antagonist?
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Which of the following opioids is known to have a significant histamine release when administered intravenously?
Which of the following opioids is known to have a significant histamine release when administered intravenously?
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What is the primary mechanism by which opioids achieve analgesia?
What is the primary mechanism by which opioids achieve analgesia?
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How is Pethidine primarily administered for effective results?
How is Pethidine primarily administered for effective results?
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Which opioid serves as a mu antagonist and kappa agonist, and is often used for its sedative properties?
Which opioid serves as a mu antagonist and kappa agonist, and is often used for its sedative properties?
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Which drug is specifically noted for its limited sedative effects, except in very young or sick patients?
Which drug is specifically noted for its limited sedative effects, except in very young or sick patients?
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What is the primary effect of activating central alpha-2 adrenergic receptors?
What is the primary effect of activating central alpha-2 adrenergic receptors?
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Which alpha-2 adrenergic receptor agonist has the highest α2:α1 selectivity ratio?
Which alpha-2 adrenergic receptor agonist has the highest α2:α1 selectivity ratio?
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What is a common administration route for alpha-2 adrenergic receptor agonists?
What is a common administration route for alpha-2 adrenergic receptor agonists?
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What is a potential synergistic effect of alpha-2 adrenergic receptor agonists?
What is a potential synergistic effect of alpha-2 adrenergic receptor agonists?
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Which of the following is NOT an effect associated with alpha-2 adrenergic receptor agonists?
Which of the following is NOT an effect associated with alpha-2 adrenergic receptor agonists?
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What is a common duration of action for alpha-2 adrenergic receptor agonists?
What is a common duration of action for alpha-2 adrenergic receptor agonists?
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Which of the following drugs is specifically mentioned as an alpha-2 adrenergic receptor agonist for dogs?
Which of the following drugs is specifically mentioned as an alpha-2 adrenergic receptor agonist for dogs?
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What is the typical onset time for intravenous administration of alpha-2 adrenergic receptor agonists?
What is the typical onset time for intravenous administration of alpha-2 adrenergic receptor agonists?
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Study Notes
Premedication & Sedation
- Premedication involves administering medication(s) before anesthesia.
- Anxiolysis is a state of mental calm and relaxation, reducing locomotor activity, anxiety, and concern for the environment. Response to stimuli is lessened.
- Sedation is a state of mental calm, sleepiness, and disinterest in the environment, with poorer responsiveness to stimuli compared to anxiolysis.
- Narcosis is sedation produced by opioids.
- Neuroleptoanalgesia is the joint administration of a sedative drug and an opioid analgesic, often used for pain relief during surgery.
Learning Objectives
- Outline the reasons for premedication before general anesthesia.
- Explain the rationale and patient safety considerations for sedation versus general anesthesia.
- Describe the pharmacology of commonly used sedative drugs and opioids in veterinary anesthesia.
- Explain the principles of neuroleptoanalgesia in veterinary premedication and sedation.
Sedation vs General Anesthesia (GA)
- Sedation: Airway control (regurgitation/aspiration) may be problematic, monitoring and ventilation can be more difficult. Local blocks administration presents a challenge. Can take longer. Recovery might be slower to completely return to a functional state.
- GA: Airway control is good (regurgitation/aspiration is less likely), there is good monitoring and ventilation, and local blocks can be easily administered. Faster and recovers quicker to a functional state.
Why Premedicate?
- Decrease anxiety, stress, and catecholamine release.
- Ensure patient and staff safety and well-being.
- Facilitate handling.
- Facilitate IV catheter placement.
- Pre-emptive analgesia and balanced anesthesia.
- Promote smooth induction, maintenance, and recovery.
- Decrease autonomic nervous system (ANS) activation during surgery.
Premedication Options
- Acepromazine
- Alpha-2 agonists (e.g. medetomidine, dexmedetomidine)
- Benzodiazepines (e.g. diazepam, midazolam)
- Opioids (e.g. fentanyl, morphine, butorphanol, methadone, buprenorphine, pethidine/meperidine)
- Ketamine (discussed in another lecture).
Acepromazine
- Phenothiazine class
- Used in dogs, cats, and horses (SC, IM, IV, PO).
- Unpredictably sedative, especially in combination with other drugs.
- Slow onset of action (30-40 minutes IM).
- Long duration of action (4-8 hours).
- No reversal agent.
- High protein binding.
- Metabolized by the liver, excreted in urine and faeces.
- Crosses blood-brain barrier and placenta.
- Potential for side effects like "locked in syndrome".
Acepromazine (continued)
- Anti-adrenergic (alpha-1 receptor blockade), leading to vasodiation, hypotension, and hypothermia.
- Anti-dopaminergic (D1 & D2 receptor blockade).
- Weak antihistaminic (H1 receptor blockade).
- Potential for side effects like sedation extrapyramidal effects at high doses, including excitation, tremors, rigidity.
- Potential for inducing syncope in hypovolemic animals.
- Potential for anti-arrhythmic effect. Prolonged profound sedation can be a factor for breeds with MDR-1 gene mutations (Collies and Shepherds).
- Potential proconvulsant effect in dogs with epilepsy.
- Extremely low risk of priapism in stallions in contemporary use.
Alpha-2 Adrenergic Receptor Agonists
- Medetomidine, Dexmedetomidine, Xylazine, Detomidine, Romifidine, Zenalpha
- Selectively bind to alpha-2 adrenergic receptors.
- Activation of central and peripheral pre & postsynaptic alpha-2 receptors.
- Effects also on alpha1 & imidazoline receptors.
- Effects on the central nervous system (CNS) (cerebral cortex, locus coeruleus, rostroventral lateral medulla, noradrenaline release, and CNS neurotransmission).
- Effects on spinal cord, peripheral nerves, and organs (analgesia, muscle relaxation).
- Different a2:a1 selectivity ratios can be used for clinical treatment.
- Administered as SC, IM, IV, oral, transmucosal, nasal, intrarectal, intravaginal.
- Short onset (1-2minutes IV, 15-20 minutes IM).
- Duration of action depends on the drug (30-120 minutes)
- Synergism with opioids and benzodiazepines.
- Decrease dose of induction/inhalational agents (MAC sparing effect).
- Dose-dependent effects on sedation, analgesia, cardiovascular effects, etc.
- Potential side effects: emesis, decreased gut motility, ruminants (bronchoconstriction, pulmonary and vasoconstriction), pulmonary edema, hypoxemia, muscle relaxation, hyperglycemia, diuresis, reflex bradycardia, and peripheral vasoconstriction. Also bradycardia can persist.
Antagonists of Alpha-2 Adrenergic Receptor Agonists
- Atipamezole, Yohimbine, and Tolazoline
- Reversal agents for alpha-2 agonists.
- Atipamezole can be used with xylazine and detomidine.
- Yohimbine and Tolazoline (MK-467) mostly used to reverse cardiovascular effects.
Benzodiazepines
- Diazepam, Midazolam
- GABA A receptor agonists.
- Schedule IV drugs
- IV and IM (midazolam only)
- Dose range from 0.1-0.4mg/kg IV
- Hepatic metabolism (active metabolites). Duration of action varies (1-4 h (midazolam), 4-12 h (diazepam)).
- Potential for hepatic necrosis in cats.
- Renal and biliary excretion.
- Flumazenil is an antagonist.
- Minimal cardiovascular depression.
- Minimal respiratory depression.
- Primarily used for inducing anxiety and anticonvulsant properties.
- Anxiolytic/sedative, anticonvulsant, central muscle relaxation, co-induction agent.
Opioids
- μ, κ, and δ receptors .
- Primary endogenous ligands: β-Endorphin, leucine- and methionine-enkephalin, dynorphin A.
- Full agonists (e.g., methadone, fentanyl), partial agonists (e.g., buprenorphine), antagonists (e.g., naloxone).
- Dose-response relationships.
- IV, IM, SC, poor PO absorption.
- Hepatic metabolism, (remifentanil: plasma esterases).
- Excretion: urine & bile.
- Cardiovascular (bradycardia, respiratory depression, histamine release).
- Urinary retention, gastrointestinal motility (ileus, constipation; horses, colic risk).
- Hyperthermia or hypothermia
- Antitussine properties
- Analgesia properties (mu receptor).
- Potential for inducing or exacerbating hyperalgesia.
Opioid Specifics
- Fentanyl: μ agonist, potency 100x morphine, onset 1-2 mins, short duration (20 minutes), bolus (1-2mcg/kg). CRI(5-10mcg/kg/hr), IV/transdermal patches, respiratory depression, schedule II, licensed in dogs.
- Butorphanol: partial μ agonist, κ agonist, onset 30 mins. long duration (6-8 hours), mild resp/cardio effects, less nausea/vomiting, schedule III, licensed in dog, cat, horse.
- Methadone: full μ agonist, NMDA receptor antagonist, onset 3-4 hrs, not very sedative (except in sick/young patients), schedule II, licensed in dog, cat.
Adjuncts to Premedication
- Trazodone: anxiolytic/sedative, tricyclic antidepressant, serotonin reuptake inhibitors (SSRIs), serotonin 1 & α1-adrenergic receptors antagonist, histamine 1, 3-7 mg/kg PO SID/BID/TID 1-2 h before travel.
- Gabapentin: neuropathic pain/seizures, blocks Ca²⁺ channels, side effects might include sedation, ataxia, vomiting, diarrhea, increased appetite, 100mg/cat 1-2 hrs before vet visit.
Choosing the Perfect Drug Combination
- Tailor anaesthetic protocols to patient needs
- Consider species variations and patient characteristics (aggressive/anxious, age, cardiovascular stability, comorbidities).
- Evaluate the desired outcomes (procedure, duration, pain level).
References
Include the BSAVA and Wiley Blackwell veterinary anesthesia books.
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Description
Test your knowledge on veterinary anesthesia, particularly focusing on the use of benzodiazepines and alpha-2 adrenergic receptor agonists. This quiz covers potential side effects, specific drug uses, and the benefits of premedication in animals. Perfect for veterinary students and professionals alike!
