Anesthesia/Pre-Anesthetics Flashcards
What is anesthesia? What is it used in veterinary medicine to provide?
state of controlled, temporary loss of sensation or awareness induced for medical purposes
- sedation
- tranquilization
- immobility
- muscle relaxation
- unconciousness
- pain control
during surgery, dentistry, grooming, diagnostic imaging, wound care, and capture/transport of wildlife
Conscious vs. unconscious:
What’s the difference between local, regional, and general anesthesia?
LOCAL: numbs a small section of the body, commonly during cataract surgery, dental procedures, or skin biopsies where the patient remains awake
REGIONAL: blocks pain in a larger part of the body, commonly during epidurals, spinal/hip/knee durgery, or an arm block for hand surgery, where the patient remains awake or have some sedation
GENERAL: unconscious and insensitive to pain or other stimuli, commonly used for invasive surgeries on the head, chest, or abdomen
What is sedation?
relaxation to the point where the patient can be easily aroused or awakened
What are the 4 stages of anesthesia?
STAGE I: analgesia without amnesia
STAGE II: excitement, nausea, vomiting, hyperreactivity, irregular respiration —> goal is to move through this stage as rapidly as possible
STAGE III: surgical anesthesia, sleep, normal respiration and blood pressure, muscle relaxation, complete loss of pain sensation
STAGE IV: medullary depression of vasomotor and respiratory centers causing coma and death (overdose)
Why are adjuncts used with anesthesia?
produces other desired effects, such as desation, muscle relaxation, analgesia, reversal, neuromuscular blockade, or parasympathetic blockade
- tranquilizers
- opioids
What are pre-anesthetic medications? What are 4 common uses?
medications used prior to the administration of an anesthetic agent to make anesthesia safe and more agreeable to the patient
- sedation to reduce anxiety and apprehension
- obtain an additive or synergistic effect so that induction can be smooth and rapid
- counteract certain adverse effects of anesthetics
- relieve from pain
How does the route of administration affect drug onset and duration?
SC: slowest onset, longest duration
IM: faster onset, shorter duration
IV: fastest onset, shortest duration
What are the 6 effects of pre-anesthetic medications and adjuncts?
- calm and sedate excited animals
- minimize adverse drug effects
- reduce dose of concurrent drugs
- smoother anesthetic induction and recovery
- analgesia
- muscle relaxation
What 4 drug classifications are commonly used as pre-anesthetics and adjuncts? What do they do?
- opioids - analgesia
- tranquilizers - pre-operative sedation and amnesia; prevent or counteract CNS stimulation caused by some anesthetics
- central muscle relaxants - muscle relaxation during anesthesia
- anticholinergic agents - prevent profuse salivation and bradycardia
What are the 3 most common drugs used as pre-anesthetics and adjuncts? 3 additional?
- opioids - Morphine
- phenothiazine tranquilizers - Acepromazine
- benzodiazepeines - Diazepam
- α2-agonists - Xylazine
- anticholinergics - Atropine
- muscle relaxants - Baclofen
Why do we use analgesics as a pre-anesthetic?
most general anesthetics are not analgesics - patient will feel pain after surgery
(true analgesics don’t provide general anesthesia)
How are opioids used as a pre-anesthetic? What 2 are most commonly used?
perioperative analgesia
- Morphine - safe, effective for mild and severe pain
- Butorphanol (+++κ, μ) - keeps analgesia, reverses sedation, respiratory depression
(can be used in combination with tranquilizers and anticholinergics)
What is an additional benefit of Morphine as a pre-anesthetic?
good sedative for dogs
How are tranquilizers used as pre-anesthetics? Which one is most commonly used?
reduces anxiety, calms, and enhances CNS depressant and analgesic effects of other anesthetics
Acepromazine
What are 3 common uses for Acepromazine?
- oral sedative before stressful events, like thunderstorms
- treat motion sickness and nausea associated with car or plane rides
- pre-anesthetic sedation
(NOT a pain reliever + opioids for minor procedures)
In what animals is Acepromazine approved for use? What is important to note?
horses, dogs, cats
- no reversal agent
- will cross slowly into placenta
How does Acepromazine compare to other tranquilizers? Due to this, in what 3 animals should it be used cautiously?
increased potency and long duration (10-20x Chlorpromazine)
- geriatrics
- neonates
- debilitated
What are the main 3 groups of animals that require special considerations for Acepromazine use?
- Australian shepherds - MDR1 mutation, less dose
- giant breeds, boxers, greyhounds bulldogs - less dose
- terriers and cats - higher dose
What is used to treat Acepromazine overdose?
norepinephrine
What pharmacological effects does Acepromazine have on the CNS, cardiovascular system, respiratory system, and GI system?
CNS - calming, reluctant to move, decreased interest in surroundings (sedation less pronounced in cats); NOT AN ANALGESIC
CV - peripheral vasodilation leading to hypotension, decreased heart rate, and hypothermia, protects against arryhthmias
RS - no significant depression
GI - antiemetic
What are 4 possible adverse effects of Acepromazine as a pre-anesthetic?
- CNS: reduced seizure threshold, aggression, excitement
- CV: hypotension (dose-dependent)
- penile prolapse in horses and other large animals that can lead to permanent injury
- decreased packed cell volume (PCV) up to 30%, causing anemia
How are Benzodiazepines used as pre-anesthetics? What 4 are commonly used?
produces anxiolytic, anticonvulsant, and muscle relaxant effects, and can potentiate general anesthetics
- Diazepam
- Zolazepam
- Midazolam
- Clonazepam
What pharmacological effects do Benzodiazepines have on the CNS, cardiovascular system, respiratory system, and muscles?
CNS: calming, antianxiety, anticonvulsant, appetite stimulant in cats/ruminants (NOT a sedative or analgesic)
CV, RS: minimal effect - high margin of safety
M: skeletal muscle relaxation
What shouldn’t Diazepam (Valium) be mixed with?
water-soluble drugs
- can be mixed with ketamine to induce anesthesia
What are 5 possible adverse effects of Diazepam (Valium)?
- disorientation and excitement in young, healthy dogs (paradox)
- dysphoria and aggression in cats
- muscle fasciculations (eye twitch, leg spasms) in horses
- ataxia and recumbence in large animals*
- can cause liver damage when given orally in cats
- must be give slowly IV
What are 5 possible adverse effects of Diazepam (Valium)?
- disorientation and excitement in young, healthy dogs (paradox)
- dysphoria and aggression in cats
- muscle fasciculations (eye twitch, leg spasms) in horses
- ataxia and recumbence in large animals*
- can cause liver damage when given orally in cats
- must be given slowly IV
In what animals is Midozalam commonly used? What is it typically used in combination with?
swine, rabbits, birds
ketamine - anesthesia in dogs, small mammals, and birds
In what way is Zolazepam available? What animal is it used in?
component of Telazol (reconstituted in water)
cats
What is neuroleptanalgesia?
profound state of analgesia and sedation induced by simultaneous administration of an opioid and a tranquilizer
- great sedation, no pain
What opioids are commonly used in neuroleptanalgesia? Tranquilizers?
- Hydromorphone (5X)**
- Morphine (+++μ, +κ)
- Buprenorphine ( partial μ, –κ)
- Butorphanol (partial μ, +++κ)
~ Dexmedetomidine (α2 agonist)**
~ Acepromazine (Dopa)
~ Diazepam (GABA)
~ Midazolam (GABA)
~ Xylazine (α2 agonist)
When is neuroleptanalgesia used?
when you don’t want to do general anesthesia
- sedation for minor prodecures
Describe the components of neuroleptanalgesia.
OPIOIDS = analgesia
TRANQUILIZERS = pre-operative sedation and amnesia, and prevent CNA stimulation caused by some anesthetics
(analgesic + tranquilizer)
