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A U E R S & T > Chapter 23 - Chemical restraint for standing procedures > Flashcards

Chapter 23 - Chemical restraint for standing procedures Flashcards

1
Q

What factors should be considered when deciding between standing sedation and general anesthesia for a surgical procedure in a horse? (6)

A

1.Type of procedure
2.Temperament of the horse
3.Anesthetic and surgical facilities
4.Personal experience
5.Preexisting medical conditions
6.Owner compliance

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2
Q

What is the primary goal of chemical restraint for standing surgery in horses?

A

To keep the horse calm, sedated, and indifferent to environmental or noxious stimulation, while ensuring the horse remains standing with minimal ataxia.

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3
Q

Why is it important for sedatives to be administered in a quiet environment?

A

Sedatives work best when given to a quiet horse, and suboptimal drug effects may result if the horse is excited before or during drug administration.

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4
Q

What is the difference in drug onset and dosage when sedatives are administered intramuscularly (IM) compared to intravenously (IV)?

A

IM administration requires longer onset times and higher doses compared to IV administration, and the sedation is less predictable due to variable absorption.

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5
Q

What is an advantage of using constant-rate infusion (CRI) of sedatives over repeated bolus administration?

A

CRI is less cumbersome for the veterinarian, may cause fewer adverse effects, and provides a more constant level of sedation.

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6
Q

What should be considered when initiating CRI sedation to achieve the desired effects more quickly?

A

loading dose should be administered, as it takes four to five half-lives to reach steady-state plasma concentrations and sedation if no loading dose is given.

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7
Q

What factors should be considered when choosing a sedation protocol for standing procedures?

A
  1. Health status and temperament of the horse
  2. Type and duration of the planned procedure
  3. Drug availability
  4. Personal experience
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8
Q

What is the benefit of administering multiple drugs simultaneously for chemical restraint in horses?

A

Administering multiple drugs may allow the use of reduced dosages, making the procedure safer and more effective than using larger doses of a single drug.

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9
Q

What class of drugs is most commonly used for standing sedation in adult horses?

A

α2-adrenoreceptor agonists

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10
Q

Which α2-adrenoreceptor agonists are most frequently used for standing sedation in equine practice?

A
  1. Xylazine
  2. Detomidine
  3. Romifidine
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11
Q

What other α2-adrenoreceptor agonists, although not registered for horses, have been used successfully in this species?

A

Medetomidine
Dexmedetomidine

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12
Q

What are reasonable starting doses for medetomidine and dexmedetomidine in horses for standing sedation?

A

Medetomidine: 5 to 7 μg/kg IV
Dexmedetomidine: 3 to 5 μg/kg IV

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13
Q

What is a key disadvantage of using intramuscular (IM) administration of sedatives in horses?

A

Sedation by the IM route is less predictable because absorption from IM sites is variable.

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14
Q

What complications may arise if sedatives are administered to an excited horse?

A

The effects of the sedatives may be suboptimal, resulting in inadequate sedation or safety risks during the procedure.

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15
Q

What are the risks of performing painful procedures on standing horses without adequate local or regional anesthesia?

A

The horse may experience insufficient analgesia, leading to movement or ataxia, which increases the risk to personnel and may affect the success of the procedure.

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16
Q

What is the main effect of α2-adrenoreceptor agonists on the cardiovascular system?

A

Decreases cardiac output

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17
Q

Which α2-adrenoreceptor agonist provides the longest sedation?

A

Detomidine

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18
Q

What fibers are involved in the increased sensitivity to touch?

A

Aβ fibers

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19
Q

For how long do xylazine or medetomidine provide sedation in short procedures?

A

15–20 minutes

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20
Q

What side effect is reduced when α2-adrenoreceptor agonists are administered IM compared to IV?

A

Hypertensive response

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21
Q

What cardiovascular side effect is dose-dependent in α2-adrenoreceptor agonist administration?

A

Bradycardia

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22
Q

What respiratory effect is commonly associated with α2-adrenoreceptor agonists?

A

Respiratory depression

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23
Q

What happens when α2-adrenoreceptor agonists are injected intracarotidly?

A

Excitement and seizures

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24
Q

Why might α2-adrenoreceptor agonists fail to sedate stressed horses?

A

Increased catecholamines

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25
Q

Which horses need higher doses of α2-adrenoreceptor agonists?

A

Mules (approximately 50%)

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26
Q

What class of drugs should never be administered IV following α2-adrenoreceptor agonists?

A

Potentiated sulfonamides = fatal arrythmias

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27
Q

At what age are α2-adrenoreceptor agonists not recommended for foals?

A

<14 days

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28
Q

What cardiovascular effect is prevented by combining acepromazine with α2-adrenoreceptor agonists?

A

Initial hypertension

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29
Q

What happens when opioids are added to α2-adrenoreceptor agonists in terms of sedation?

A

Synergistic effect

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30
Q

Which condition can result from prolonged head lowering during sedation?

A

Facial and nasal edema

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31
Q

What drug is sometimes added to a romifidine CRI for dentistry procedures?

A

Butorphanol

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32
Q

What can be administered to treat mucosal edema in sedated horses?

A

Phenylephrine nasal drops

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33
Q

What effect is often seen in very young foals (<14d) sedated with α2-adrenoreceptor agonists?

A

Recumbency, use benzodiazepines + opioids instead

34
Q
A

Base-apex electrocardiogram (paper speed 25 mm/sec) showing a second-degree atrioventricular (AV) block in a horse. Note the progressive prolongation of the PQ interval before one beat drops that is characteristic of a Wenckebach or Mobitz type I second-degree AV block (in contrast, the PQ interval remains constant prior to the P-wave, which suddenly fails to conduct to the ventricles in a Hay or Mobitz type II second-degree AV block). This is a typical arrhythmia observed in horses sedated with α2-adrenoreceptor agonists. AUER book

35
Q

Which horses need lower doses of α2-adrenoreceptor agonists?

A

Draft horses

36
Q

Which α2-adrenoreceptor antagonist is most selective?

A

Atipamezole

37
Q

When should α2-adrenoreceptor antagonists be used?

A

Emergency situations

38
Q

What is abolished by using α2-adrenoreceptor antagonists?

A

Analgesic effect

39
Q

What side effects may occur after α2-antagonist administration?

A

Agitation, stress

40
Q

Which antagonists are associated with anecdotal fatalities?

A

Yohimbine, tolazoline

41
Q

Name the 3 α2-antagonist

A
  1. Yohimbine
  2. Tolazoline
  3. Atipamezole
42
Q

What should be avoided during treatment of hypotension?

A

Epinephrine

43
Q

Which drug is preferred for treating vasodilation-induced hypotension?

A

Phenylephrine

44
Q

Name the 5 phenothiazine and dosage of the most known

A

Acepromazine 0.02-0.05 mg/kg IV
IM 0.02-0.05 mg/kg
PO 0.1 mg/kg
2. Chlorpromazine
3. Propiopromazine
4. Propionylpromazine
5. Promethazine

45
Q

How does acepromazine affect packed cell volume (PCV)?

A

Decreases PCV by 20% due to RBç sequestration

46
Q

What is the mechanism behind PCV decrease with acepromazine?

A

Splenic sequestration

47
Q

What side effect is observed in stallions after acepromazine administration?

A

Priapism

48
Q

In which horses should phenothiazines be avoided?

A

Epileptic patients

49
Q

How long can acepromazine effects last in some horses?

A

6–10 hours

50
Q

What effect does acepromazine have on thermoregulatory control?

A

Loss of control be careful in foals and ponies

51
Q

What dosage of acepromazine can cause penile prolapse?

A

0.01 mg/kg

52
Q

What is a controversial effect of phenothiazines?

A

Platelet function

53
Q

Which side effect is more severe with IV administration of acepromazine compared to IM or oral?

A

Hypotension

54
Q

Does the ACP diminish GI motility?

A

yes acepromazine diminishes GI motility

55
Q

It is important to remember before sedating a horse with acepromazine that the negative effects on blood pressure and PCV can persist for more than _____ hours

A

acepromazine that the negative effects on blood pressure and PCV can persist for more than 10 hours

56
Q

Is there an antagonist available for ACP?

A

No

57
Q

Why are butyrophenones not recommended in horses?

A

Unpredictability, side effects

58
Q

Which benzodiazepines are commonly used in horses?

A

Diazepam, midazolam, zolazepam

59
Q

What neurotransmitter do benzodiazepines facilitate?

A

GABA

60
Q

What are the effects of benzodiazepines on muscle relaxation?

A

Excellent relaxation

61
Q

Why should benzodiazepines not be used for standing sedation in adult horses?

A

Unreliable sedation

62
Q

Which type of horse are benzodiazepines reliable sedatives for?

A

Neonatal foals

63
Q

What effects can opioids produce when used alone in horses?

A

Restlessness, agitation

64
Q

What can block the dosage-dependent increase in spontaneous locomotor activity caused by opioids?

A

Naloxone, acepromazine

65
Q

What severe side effects can occur at higher doses of propofol in horses?

A

Ataxia, muscle weakness

66
Q

Which drugs are considered for long-term tranquilization in horses?

A

eserpine, fluphenazine, chlorpromazine

67
Q

What can benzodiazepines cause in adult horses at higher doses?

A

Severe ataxia

68
Q

Which route should midazolam be administered if IM is the only option?

A

IM route

69
Q

What side effect can benzodiazepines stimulate that is beneficial in managing chronic grass sickness?

A

Food intake

70
Q

What concerns arise with prolonged benzodiazepine sedation in foals?

A

Hypoglycemia, hypothermia

71
Q

Which antagonist is used to reverse benzodiazepines?

A

Flumazenil 0.01-0.04 mg/kg IV slowly

72
Q

What is the mechanism of action of benzodiazepines?

A

Benzodiazepines produce their pharmacologic effects by facilitating the actions of γ-aminobutyric acid (read gamma aminobutyric acid GABA), the principal inhibitory neurotransmitter in the CNS

73
Q

Advantages of benzodiazepines (2)

A
  1. excelent muscle relaxation
  2. minimal cardiovascular respi depression
74
Q

Can you give midazolam IV and IM

A

Yes, midazolam can be given both ways but dizepam is only IV

75
Q

What are the side effects of benzodiazepines

A

Anxiolytic
hypnotic
anti-convulsive
no analgesia
unreliable sedation
severe ataxia

76
Q

Benzodiapines provide analgesia?

A

No ANALGESIA ! It provides sedations and recumbency but not analgesia, that is why it has to be combined with opioid or local anesth in foals

77
Q

In what situation should antagonists be used with benzodiazepines?

A

Respiratory depression

78
Q

What side effect can opioids cause in healthy, pain-free horses?

A

Excitement, dysphoria

79
Q

What type of sedation is produced when opioids are combined with benzodiazepines in foals?

A

Good-quality sedation

80
Q

What do opioids act via to produce their effects?

A

Opioid receptors

A U E R S & T (123 decks)

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