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Anesthesiology 398 and 466 > Lecture 5 Preanesthetic Medications and Induction Agents part 2 > Flashcards

Lecture 5 Preanesthetic Medications and Induction Agents part 2 Flashcards

1
Q
  1. What are the Alpha-2 agonists used in horses
  2. What are the reversal agents?
A
  1. Alpha-2 agonists - Horses:
    • Xylazine
    • Detomidine
    • Romifidine
  2. Reversal agents:
    • yohimbine
    • tolazoline
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2
Q
  1. What are the benzodiazepines used for sedative/ tranquilizer abilities?
  2. What is the reversal agent?
A
  1. Benzodiazepines:
    • Diazepam
    • Midazolam
  2. Reversible with flumazenil
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3
Q
  1. What type of animals do you use benzodiazepines to sedate?
  2. Which don’t you use them in and why?
A
  1. Sedation more profound in:
    • Sedation more profound in pediatric (<3mos.)
    • geriatric,
    • critical patients
    • Small ruminants,
    • Neonatal foals
  2. Don’t:
    • young, healthy dogs, cats
    • Causes paradoxical excitement, hyperresponsiveness
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4
Q

How do Benzodiazepines (•Diazepam, Midazolam) effect:

  1. Cardiovascular system?
  2. Respiratory?
  3. Analgesia?
  4. Other side effects/ uses?
A
  1. Mild cardiovascular effects
  2. Enhances respiratory depression of other drugs
  3. No analgesia
  4. Muscle relaxation, Anticonvulsant effects
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5
Q

Diazepam contains propylene glycol, why do we care?

A

Pain on injection, not well absorbed, toxicity at high doses (seizure txt)

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6
Q

What are the uses for midazolam?

A
  1. Used with opioid for pre-med for very young (<3 mos.), geriatric, sick, dogs
    • 0.1- 0.2 mg/kg IM or IV
  2. Induction adjunct => ↓ Propofol induction dose
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7
Q

What drug possibly has amnesic properties?

A

Midazolam

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8
Q

What are some benefits of using Anti-cholinergics as premeds?

A
  1. ↓ vagal effects, salivary secretions
    • Modern inhalants not as irritating to respiratory tract so not used as much for this reason
  2. Still used to counter vagal effects of anesthetic drugs
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9
Q
  1. Does atropine cross the blood brain barrier/ placenta?
  2. What is the onset of action?
  3. Duration of action?
  4. Side effects?
A
  1. Crosses BBB/placenta
  2. Onset of action (minutes): 5 IM, 1 IV
  3. DOA: 60-90 minutes
  4. Side effects: sinus tachycardia, 2° A-V block
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10
Q
  1. Does Glycopyrrolate cross the blood brain barrier/ placenta?
  2. What is the onset of action?
  3. Duration of action?
A
  1. Does not cross BBB/placenta
  2. Onset of action: 3 – 5 minutes
  3. DOA: 2-4 hours
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11
Q

What are the side effects of glycopyrrolate?

A
  • Side effects: sinus tachycardia, 2° A-V block => ↑ with IV administration
    • A-V block – wait, give additional dose
    • Sinus tachycardia – self-limiting
      • Caution in geriatric or cardiac disease
    • Avoid in LA (GI statsis)
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12
Q

What is Guaifenesin (GG) used for?

A
  1. Central muscle relaxant (replaced succinylcholine to ‘cast’ horses)
  2. Action similar to benzodiazepine
  3. Adjunct for induction in horses, large ruminants, camelids
  4. Maintenance for total intra-venous anesthesia (TIVA)
    • Triple Drip => GG + xylazine + ketamine
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13
Q

What are disadvantages of using Guaifenesin

A
  1. Minimal analgesia, hypnotic at large doses
  2. Do NOT use concentrations >5%
    • hemolysis in cattle
    • jugular thrombophlebitis in horses
  3. Large volume of injection (1-2 ml/kg)
  4. Perivascular injection => sloughing
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14
Q

What are the Anesthetic Induction agents used for Dogs & Cats

A
  1. Propofol
  2. Alfaxalone
  3. ketamine/benzodiazepine
  4. Telazol (tiletamine + zolazepam)
  5. Etomidate
  6. Ketamine + Propofol
  7. Total IM injectable anesthesia
    • Dexmedetomidine + opioid + dissociative (ketamine or Telazol)
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15
Q

What are the anesthetic induction agents used in:

  1. Horses
  2. Large ruminants
  3. Small ruminants
  4. Camelids
A
  1. Horses
    • Ketamine + Midazolam +/- GG
  2. Large Ruminants
    • Triple Drip: GG + xylazine + ketamine
  3. Small Ruminants
    • Ketamine + Midazolam
    • Ketamine + propofol
  4. Camelids
    • Triple Drip Or Ketamine + Midazolam
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16
Q

What is important to know about propofol and its shelf life

A
  • Emulsion containing soybean oil, egg lecithin, no preservative =>
  • Promotes bacterial growth => discard 6 hours after opening
17
Q

What is the mechanism of action of Propofol

A
  • Works via GABA-A receptors
  • GABA is major inhibitory neurotransmitter in the CNS
18
Q

Propofol:

  1. Whats the onset?
  2. How long does it last?
A
  1. Rapid onset
  2. Rapid metabolism & redistribution
    • Noncumulative, extra-hepatic metabolism
19
Q

What are the main anesthetic uses of propofol

A
  1. Sedation (subanesthetic doses do not cause excitement),
  2. Induction
  3. CRI for maintenance of anesthesia
20
Q
  1. What are some added uses other than induction for propofol?
  2. What happens if you accedently do a perivascular administration
A
  1. Other uses:
    • Neuroprotective
      • Decreased cerebral metabolic O2 rate (CMRO2), Cerebral blood flow (CBF), and intracranial pressure (ICP) => neuroprotective
    • Anticonvulsant
  2. non-irritating
21
Q

What are Propofol precautions

A
  1. Myocardial depression, hypotension
  2. Hypoventilation => apnea
  3. Directly related to dose & rate of administration => give slowly
  4. potentiates bradycardia
  5. Myoclonic muscle twitching
  6. Not analgesic
  7. Cumulative in cats
  8. Contaminated => endotoxemia
22
Q
  1. What has been added to Propofol 28?
  2. why?
  3. This additive can be toxic to what species and can you still use it in that species?
A
  1. Contains benzyl alcohol as preservative
  2. Shelf life 28 days from opening
    • Bacteriostatic – still need sterile technique
  3. toxic to cats at high doses
    • Ok for induction dose
      • Use pre-med to lower the dose
    • no repeated dosing, no CRI
23
Q

What type of drug is Ketamine

A
  • NMDA receptor antagonist
  • Dissociative anesthetic (catalepsy, amnesia, analgesia)
24
Q

Ketamine advantages?

A
  1. Indirect sympathomimetic CV stimulation (↑HR, CO, BP)
  2. Good analgesia
  3. Metabolized in the liver
  4. Excreted unchanged in urine in cats
25
Q

Uses of ketamine?

A
  1. IM pre-med – need to use with good sedative/muscle relaxant
    • Dexmedetomidine, benzodiazepine
  2. IV induction
    • Ketamine 4mg/kg + Midazolam 0.2mg/kg
    • Ketamine 2mg/kg + Propofol 2mg/kg
26
Q

What are some ketamine precautions?

A
  1. Muscle Rigidity => use with alpha-2 agonist or BNZ
  2. May cause seizures
  3. Direct myocardial depression in critically ill patients
  4. Rough recovery
    • Avoid in very short procedures
  5. Transient respiratory depression
  6. Salivation
  7. Increases intraocular pressure, cerebral blood flow, and intra-cranial pressure
  8. Eyelids remain open, pupil centered in globe
27
Q

What is Telazol? (brand name)

A

Tiletamine (dissociative) + zolazepam (benzodiazepine)

28
Q
  1. What are telazols uses?
  2. What is important to know when injecting IM?
A
  1. Uses:
    • Can be used alone for short term restraint (dogs 6-9mg/kg), anesthesia (cat 9-11mg/kg)
    • Combine with dexmedetomidine to lower dose, avoid rough recoveries
    • Induction 1-2mg/kg IV
  2. Pain with IM injection
29
Q

What are disadvantages of using telazol

A
  1. Copious salivation => combine with dexmedetomidine (anti-sialologue) or anti-cholinergic
  2. Eyes remain open, pupils dilated, maintain palpebral reflex
  3. Maintain laryngeal/pharyngeal reflexes, can have spontaneous movement
30
Q
  1. How do cats recover from telazol and why?
  2. Dogs?
A
  1. Cats: zolazepam lasts longer so recovery is smoother
  2. Dogs: rough recoveries due to short DOA of zolazepam
31
Q
  1. How does Alfaxalone (Alfaxan®) work?
  2. Whats the duration?
  3. time of onset?
  4. Is it cumulative?
A
  1. Steroid structure and interacts with GABAA receptors
  2. Ultrashort duration,
  3. rapid acting,
  4. non-cumulative
32
Q
  1. Alfaxalone (Alfaxan®) uses
  2. Does it affect respiratory system?
A
  1. Induction: Dogs – 2.0 – 3.0 mg/kg, Cats 5.0- 6.0mg/kg
    • give ¼ dose every 15 seconds until ET intubation can be acheived
  2. Dose & rate dependent respiratory depression
33
Q

Alfaxalone advantages

A
  1. Rapid induction & recovery
  2. Rapid metabolism and short half life
  3. May be administered as CRI or repeated IV injections for 1 hr without accumulation
34
Q

Alfaxalone disadvantages

A
  1. Apnea
  2. Vasodilation and hypotension with high doses
  3. ↓ recovery quality with high doses => delirium, excitement
  4. Not analgesic
35
Q
  1. Etomidate uses?
  2. Advantages?
A
  1. Rapid induction and recovery
  2. Advantages
    • Minimal myocardial depression/hypotension
    • Noncumulative
    • Decreases CBF, ICP and IOP
    • Anticonvulsant
36
Q

Etomidate precautions

A
  1. Osmolality (4600 mOsm/kg)
  2. Pain when injected by itself
  3. Phlebitis/thrombosis with CRI
  4. Hemolysis – undiluted
  5. No analgesia
  6. Suppresses adrenal response to ACTH
  7. Myoclonic muscle twitching
  8. Expensive
37
Q

What is a good induction protocol for critically ill patients like GDV, septic/hemo abdomen, severe heart disease

A
  • Opioid + Benzodiazepine
    • Fentanyl 5-10 mcg/kg IV
    • Midazolam 0.2 mg/kg IV

Anesthesiology 398 and 466 (22 decks)

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