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Clinical Anesthesia > Muscle Relaxants and Ancillary Drugs > Flashcards

Muscle Relaxants and Ancillary Drugs Flashcards

1
Q

What is an Ancillary Drug/ Medication?

A

An ‘additional’ drug added to improve the overall wellbeing and stability of the patient

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2
Q

What are the 4 classifications of Ancillary Drugs used in vet medicine?

A

1) Anticholinergics
2) Sympathomimetics
3) Bronchodilators
4) Doxapram

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3
Q

What part of the brain is the centre of the autonomic nervous system?

A

Hypothalamus

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4
Q

The sympathetic nervous system is made up of short _______ and long _______ fibres

A
  • Preganglionic (myelinated)

- Postganglionic (unmyelinated)

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5
Q

All preganglionic fibres use ________ as the neurotransmitter, regardless of sympathetic or parasympathetic nerves

A
  • Acetylcholine

note: which bind to Nicotinic receptors within the ganglion

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6
Q

What are the neurotransmitters and receptors involved in the Parasympathetic pathway to the Heart and vessels?

A

Preganglion ACh-Nicotinic receptor

Postganglion ACh-Muscarinic receptor

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7
Q

What are the neurotransmitters and receptors involved in the Sympathetic pathway to the Heart and vessels?

A

Preganglion ACh-Nicotinic receptor

Postganglion Norepinephrine- Beta + alpha adrenoreceptors

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8
Q

What are the neurotransmitters and receptors involved in the Sympathetic pathway to the Sweat Glands and Vessels?

A

Preganglion ACh-Nicotinic receptor

Postganglion ACh-Muscarinic receptor

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9
Q

What are the neurotransmitters and receptors involved in the Sympathetic pathway to the Renal vessels?

A

Preganglion ACh-Nicotinic receptor

Postganglion Dopamine-Dopaminergic receptor

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10
Q

What are the neurotransmitters and receptors involved in the Sympathetic pathway to the Adrenal medulla, and subsequent Heart and vessels?

A

Preganglion ACh-Nicotinic receptor

Epinephrine and Norepinephrine travel in the blood and bond to Beta + Alpha adrenoreceptors

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11
Q

What is the purpose of using Anticholinergics in a patient?

A

Anticholinergic medications are a class of drug that block the neurotransmitter acetylcholine in the central and peripheral nervous system. They are used to block a wide variety of conditions associated with activation of the parasympathetic nervous system.
Thus resulting in the following:
Heart: Increased HR and Contraction
Lungs: Bronchodilation
Pupils: Dilation
Salivary Glands: Decreased salivation
Arterioles: Vasoconstriction
Sweat Glands: Increased Sweating
Adrenal Glands: Release of adrenaline and noradrenaline
GI Tract: Decrease peristalsis- Caution with colic
Bladder: Relaxation

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12
Q

What are the 2 most commonly used Anticholinergics in vet medicine?

A
  • Atropine

- Glycopyrrolate

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13
Q

What is Atropine used to treat?

A
  • Bradycardia

- Integral part of CPR (cardiac-pulmonary resuscitation)

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14
Q

What routes can Atropine be administered?

A
  • IV
  • IM
  • Down the trachea
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15
Q

Atropine is not considered helpful in rabbits, why?

And what drug should be used for rabbit bradycardia?

A

Rabbits possess Atropinase, and therefore rapidly metabolize atropine, rendering it ineffective
- Glycopyrrolate used be used instead

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16
Q

What are the main side effects associated with Atropine?

A
  • 2nd degree AV block (P waves with no QRS wave)

- Paradoxical bradycardia due to activation of certain subtypes of Muscarinic receptors, leading to bradycardia

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17
Q

When is Atropine contraindicated?

A
  • Patients with pre-existing tachycardia (e.g. shock or fever patients)
  • Hyperthyroidism
  • Phaeochromocytoma
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18
Q

What is the benefit of using Glycopyrrolate over Atropine?

A
  • Slower onset of action, with a more controlled increase in HR
  • Longer duration of action
  • Does NOT cross the BBB
  • Does NOT cause pupil dilation
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19
Q

What is a Sympathomimetic?

A

A type of drug that produces effects characteristic of the sympathetic nervous system by stimulating sympathetic nerves

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20
Q

What are the subclassifications of Sympathomimetics, and give examples?

A
  • Mixed inotropes + vasopressors: Dopamine, Adrenaline, Noradrenaline and Ephedrine
  • Positive inotropes: Dobutamine
  • Vasopressors: Phenylephrine, Vasopressin
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21
Q

What Bronchodilators are used in vet medicine?

A
  • Salbutamol

- Terbutaline

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22
Q

What receptors do sympathomimetics exert their effect on?

A
  • Adrenoreceptors (alpha and beta)

- Dopamine receptors

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23
Q

What are the effects of Adrenaline and Noradrenaline binding to the alpha and beta adrenoreceptors?

A

Alpha adrenoreceptor = vasoconstriction

Beta adrenoreceptor = Smooth muscle relaxation, platelet aggregation, increased inotropy and chronotropy, and increased lipolysis

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24
Q

What are the effects of Dopamine binding to the Dopamine receptors?

A

Within the CNS: Reduces pituitary hormone output, and modulates extrapyramidal activity

Peripherally: Vasodilation of renal and mesenteric vasculature, and inhibits further noradrenaline release

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25
Q

When would you use Adrenaline in the patient?

A
  • CPR
  • Anaphylaxis
  • Severe hypotension and bradycardia associated with sepsis
  • Added to local anesthetics to cause vasoconstriction, reduced blood flow and prolonged effects of the anesthetic
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26
Q

What are the effects of Adrenaline administration on the CVS and Respiratory system?

A

CVS: increased chronotropy and inotropy, vasodilation of the heart, improvement of O2 delivery to the tissues

RS: Bronchodilation

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27
Q

When would you use Noradrenaline in the patient?

A
  • Severe hypotension and bradycardia associated with sepsis
28
Q

What are the effects of Ephedrine binding to alpha and beta adrenoreceptors?

A
  • Increased blood pressure and + inotropic effect

- Bronchodilation

29
Q

What type of drug is Dobutamine, and what is its use?

A
  • Synthetic analog of Dopamine
  • Positive inotrope and chronotrope
  • Useful in severe congestive heart failure
  • Rarely causes arrhythmias
30
Q

How must Dobutamine be adminstered to the patient?

A

On a CRI (IV)

31
Q

When is Phenylephrine (vasopressor) typically used in patients?

A

When the patient has adequate cardiac function and cardiac output, BUT the patient has hypotension (such as seen with an epidural, or sepsis)

  • used as a spray for nasal edema in horses
  • used to induce splenic contraction in horses
32
Q

What is the caution associated to using Phenylephrine in patients?

A
  • causes vasoconstriction, and can reduce tissue perfusion
33
Q

What is the use of Vasopressin in the patient?

A
  • Increases heart contractility
34
Q

What are the effects of Salbutamol?

A
  • Bronchodilation
  • Tachycardia in high doses
  • Relaxes the gravid uterus
  • Can lead to muscle tremors
35
Q

What are the effects and uses of Terbutaline?

A
  • Bronchodilation

Commonly used prior to bronchoscopy and broncho-alveolar lavage

36
Q

What kind of drug is Doxapram?

A

Central Nervous System Stimulant

37
Q

What are the effects and uses of Doxapram?

A
  • Stimulate respirations after anesthesia
  • Increase respirations in neonates who have a low-frequency, gasping, erratic pattern of breathing after receiving oxygen

Note: This drug doesn’t seem to have any real purpose or use

38
Q

How is muscular relaxation achieved in vet medicine, give examples

A
  • Centrally acting agents: Benzodiazepines, Guaifenesin, Alpha2 agonists
  • Peripherally acting agents: Neuromuscular blocking drugs (Depolarizing and Non-depolarizing)
39
Q

When can Neuromuscular blocking drugs be used?

A

Only used if:

  • appropriate hypnosis, unconsciousness and analgesia is provided
  • the patient can be monitored regularly
  • the patient is intubated and mechanical ventilation can be given
40
Q

What are the risks associated with using Neuromuscular blocking drugs?

A
  • Paralysis of the muscles, including respiratory muscles can occur
  • They DONT provide hypnosis, unconsciousness or analgesia
41
Q

Neuromuscular blocking agents block the action of ________ at the _______

A
  • Acetylcholine

- Neuromuscular Junction

42
Q

What is the difference between Depolarizing and Non-depolarizing Neuromuscular blocking agents?

A
  • Depolarizing: are non-competitive at the Nicotinic-Acetylcholine receptor
  • Non-depolarizing: are competitive at the Nicotinic-Acetylcholine receptor
43
Q

What is the effect of Neostigmine?

A

ACh-esterase antagonist

44
Q

What is the effect of Pralidoxime?

A

ACh-esterase agonist

45
Q

What is the effect of Hemicholinium?

A

Disruption of ACh pathway by decreasing the recycling of ACh

46
Q

What is the effect of Vesamicol?

A

Inhibition of ACh returning to the vesicle

47
Q

What is the effect of Non-depolarizing NMBA (Neuro-muscular blocking agents)?

A

Post-synaptic AChR antagonist

48
Q

What is the effect of ACh and Succinylcholine?

A

Post-synaptic AChR agonist

49
Q

What is the effect of Iathratoxin (e.g. red back spider)?

A

ACh exocytosis agonist

50
Q

What is the effect of botulism?

A

ACh exocytosis antagonist

51
Q

What is the effect of Myasthenia gravis?

A

Destruction of motor endplates

52
Q

What is the only depolarizing NMBA found in vet medicine?

A

Succinylcholine

53
Q

What is the duration of action and recovery period of Succinylcholine?

A
  • Duration of action = 3mins

- Recovery = 10 - 12 mins (but longer in dogs due to lower levels of plasma cholinesterases)

54
Q

What are the side effects and contra-indications associated with Succinylcholine in the patient?

A
  • CVS: bradycardia
  • Increased K+ release: causing arrythmias and caution in renal disease and burn patients
  • Increase IOP: NOT for use in patients with ocular problems

Contraindicated in:

  • Eye injuries/ disease
  • Myopathies
  • Patients predisposed to Malignant Hyperthermia (e.g. certain pig breeds)
  • GDV
  • Burn Victims
  • Birds
55
Q

Between depolarizing and non-depolarizing NMBA’s, which are more commonly used in vet medicine, and why?

A

The Non-depolarizing agents are more commonly used

  • Cause paralysis without muscle contraction
  • Doesnt cross the BBB
56
Q

What type of drug is Atracurium, Cis-atracurium, Mivacurium, Vecuronium and Rocuronium?

A

A Nondepolarizing Neuromuscular Blocker

57
Q

What is the benefit and risks of using Atracurium?

A

Benefits:

  • Minimal cardiovascular effects
  • Valuable in critically ill patients who cannot receive standard inhalant anesthesia concentrations
  • 3-5 mins onset of action

Risks:

  • Possible histamine release, thus must be given slowly
  • Many potential drug interactions
  • One of its metabolites is Laudanosine- which can cause seizures
58
Q

What is the benefit and risks of using Cis-Atracurium?

A

Benefits:

  • 4x more potent than Atracurium
  • Minimal cardiac effects
  • No release of histamine
  • Produces less Laudanosine, and thus less likely to cause seizures

Risks:
- Still produces small amounts of Laudanosine

59
Q

What is the benefit and risks of using Mivacurium?

A

Benefits:
- Fast onset: 2mins

Risks:

  • Short duration: 15 mins
  • Histamine release, which can lead to hypotension
  • caution must be used in dogs
60
Q

What is the benefit and risks of using Vecuronium?

A

Benefits:
- Minimal cardiac effects

Risks:

  • Not to be used in liver disease patients, due to metabolism
  • Not to be used in renal disease patients, due to excretion
  • Not to be used in biliary disease
  • No analgesic or sedative actions
61
Q

What is the benefit and risks of using Rocuronium?

A

Benefits:
- Faster onset compared to all other Nondepolarizing Neuromuscular Blockers

Risks:

  • Intermediate duration
  • High doses = vagolytic
  • Anaphylactoid reactions reported in some patients
  • No analgesia or sedation
62
Q

How are Non-depolarizing Neuromuscular Blockers be reversed?

What caution must be known before giving the reversal agent ?

A
  • Use Anticholinesterases
    e. g. Neostigmine and edrophonium

They act by reducing ACh metabolism, therefore more is available at the junction for competition with the remaining blockers

caution: anticholinesterases also affect muscarinic receptors, thus can lead to bradycardia, salivation, bronchospasm and diarrhea
- -> To reduce this, administer an anticholinergic

63
Q

What is the Anticholinesterase of choice when needed to reverse a NDNB?

A

Edrophonium + Atropine (atropine increases its onset)

64
Q

What is the drug of choice when trying to diagnose Myasthenia gravis?

A

Edrophonium

65
Q

What are the 2 Anticholinesterases used in vet medicine?

A

Edrophonium (+ atropine)

Neostigmine (+ glycopyrrolate)

66
Q

What are the indications for Neuromuscular Blockades?

A
  • Ocular surgery for eye position
  • Deep abdomen/ chest cavity surgery
  • Arrest ventilation e.g. for thoracic surgery
  • Limb relaxation
  • When immobility is paramount e.g. intracranial surgery
  • When patients need to be ventilitated in the ICU

Clinical Anesthesia (17 decks)

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