Anesthesiology Exam 2 - Apha 2 Agonists

Front 1

What drugs are listed as Alpha 2 agonists

Back 1

Xylazine, Detomidine, Romifidine, Medetomidine/Dexmedetomidine

Front 2

Side 2: What is the major 'separating' factor between the different drugs
Side 3: Name the drugs in decreasing order of strength for this property

Back 2

Specificity for the alpha-2 receptor

Hint 2

(Dex)medetomidine>Romifidine>Detomidine>Xylazine

Front 3

Side 2: Where do these drugs work in the CNS? peripherally?
Side 3: What are the effects

Back 3

Pre-synaptic a-2 receptors
Post synaptic peripheral effects

Hint 3

CNS depression
Locus ceruleus (noradrenergic relay in the brain stem)
Spinal cord (dorsal horn nociceptive fibers)
Sympathetic nerve endings (inhibits NE release)

Front 4

Side 2: What neurotransmitter do these drugs affect
Side 3: What does this result in

Back 4

Decreases NE centrally and peripherally

Hint 4

Decreases sympathetic outflow

Front 5

Side 2: What is the mechanism of action during the first phase of CV respone
Side 3: What is the response

Back 5

Binding of a-2 receptor in vasculature

Hint 5

Vasoconstriction, increased systemic vascular resistance (SVR)
Increased blood pressure
Reflex bradycardia (treatment is controversial)

Front 6

Side 2: What is the outcome on the of treating reflex bradycardia with anticholinergics
Side 3: What is a better option

Back 6

Increase HR (already have hypertension) - increases myocardial work and O2 demand (myocardial irritability, arrhythmias)
Exacerbates hypertension (MAP>200 in dogs and horses)
Ventricular arrhythmias

Hint 6

Better to reverse alpha-2

Front 7

Side 2: What is the outcome of phase 2 of CV response
SIde 3: What effect do a-2 agonists have on CO

Back 7

Decreased NE
Decreased: HR, BP, CO

Hint 7

Decrease by 50%

Front 8

Side 2: What effects do a-2 agonists have on conduction
Side 3: What is the resulting effect

Back 8

Slow conduction via SA and AV nodes

Hint 8

arrhythmias, bradycardia, heart block (1st, 2nd, 3rd degree), ventricular arrhythmias

Front 9

Side 2: Where do a-2 agonists work to effect respiration
Side 3: What does interaction at this site result in

Back 9

Medulla

Hint 9

Mild to moderate respiratory depression
Depressed response to hypercapnia

Front 10

SIde 2: What increases the CNS depressant effects of a-2 agonists
Side 3: What disorder do sheeps have

Back 10

Mixture with other CNS depressants

Hint 10

Hypoxic syndrome

Front 11

Do a-2 agonists have analgesia effects

Back 11

yes

Front 12

What results from a-2 receptor location

Back 12

near opioid receptors - synergistic/cross react with opioids

Front 13

Side 2: What happens during reversal of a-2 agonists
Side 3: Which effect lasts longer

Back 13

Reverse sedation as well as analgesia

Hint 13

Sedation lasts longer than analgesia

Front 14

SIde 2: How do pigs react to a-2 agonists
Side 3: How do cats react to a-2 agonists

Back 14

Fairly resistant to effects

Hint 14

Emesis

Front 15

Side 2: How do horses and dogs react to a-2 agonists
Side 3: How do sheep react to a-2 agonists

Back 15

Can see aggression

Hint 15

Hypoxemia

Front 16

What causes hypoxemia in sheep

Back 16

Pulmonary intravascular macrophages (PIM) - pulmonary edema

Front 17

How do the following drugs act on horses
Side 2: Romifidine
Side 3: Detomidine

Back 17

less ataxia

Hint 17

'keep their feet on the ground'

Front 18

What is the effect on insulin, ADH, GI motility

Back 18

Decrease insulin release - mild hyperglycemia
Diureses and sodium loss (diuresis)
Decrease GI motility

Front 19

What system do a-2 agonist effect when they act on the hypothalamus

Back 19

thermoregulation

Front 20

Side 2: What effect do a-2 agonists have on muscle
Side 3: What is the result

Back 20

muscle relaxation

Hint 20

Decreased shivering - hypothermia

Front 21

Side 2: What drug has adverse effects during C-sections
Side 3: What are the effects

Back 21

Xylazine

Hint 21

Increased morbidity and mortality of puppies/kittens and dams/queens

Front 22

Side 2: How can a-2 agonists be administered
Side 2: Where are they metabolized

Back 22

IV, IM, SQ, epidurally

Hint 22

Primarily liver metabolism

Front 23

What four factors contribute to duration of action

Back 23

Dose dependent
Drug dependent
Species dependent
Synergy with other drugs

Front 24

When should a-2 agonists be avoided

Back 24

CV compromised - hypovolemia,myocardial dz, shock
C-sections
Debilitated animals (Equine colic is an exception)
Severe liver dz

Front 25

Side 2: Which drugs are reversible and what agent is used
Side 3: What can result from reversal of a-2 agonists

Back 25

Xylazine - yohimbine
Medetomidine - atipamezole
tolazoline (sometimes in cows)

Hint 25

Severe hypotension

Front 26

What is the shortest acting a-2 agonist, and also has the lowest a-2:a-1 ratio = 'dirtiest'

Back 26

Xylazine

Front 27

Side 2: Why is Xylazine used often in horses
Side 3: What are adverse effects of Xylazine in small animals

Back 27

efficacy and low cost

Hint 27

Increase morbidity and mortality

Front 28

How do cattle react to Xylazine

Back 28

Very sensitive - need 1/10 the dose of a horse

Front 29

Side 2: How does Detomidine (dormosedan) effect horses
Side 3: What is the negative aspect, when should it be used

Back 29

Stand base-wide
'keep their feet on the ground'

Hint 29

More expensive (use in painful or excited horses)

Front 30

Side 2: Why is Romifidine used primarily in horses
Side 3: What is a negative aspect

Back 30

Less ataxia (good for anesthesia recovery)

Hint 30

Less intense sedation/control than detomidine

Front 31

What is the most specific a-2 agonist

Back 31

Medetomidine

Front 32

How does Dexmedetomidine compare to Medetomidine

Back 32

Active enantiomer
Theoretically 2x as potent
Clinical experience - need 3/4 dose size to make them equi-potent
Harder to reverse (due to selectivity)

Front 33

What is the mechanism of action for a-2 antagonists

Back 33

Compete for receptor - bind, but do not activate the receptor

Front 34

What is the effect of using a-2 angtagonists as reversal agents

Back 34

Revers both sedation and analgesia
Rapid, anxious, uncoordinated, painful awakening

Front 35

Side 2: What drug is used to reverse Xylazine and Detomidine
Side 3: What drug is used to reverse Medetomidine/Dexmedetomidine

Back 35

Yohimbine (Yobine)

Hint 35

Atipamezole (Antisedan)

Front 36

Side 2: When should one be cautious of reversing a-2 agonists
Side 3: How can this be avoided

Back 36

Full IV reversal during vasoC (phase 1) = severe hypotension (removing increased SVR while bradycardic)

Hint 36

Reverse via IM, or by giving only a partial dose IV