CV drugs Dr. Maney

Question 1

What are the CV drug classes that we are concerned with regarding anesthesia

Answer 1

• Anticholinergics
• Antiarrhythmics
• Vasopressors/Inotropes

Adrenergic agonists

vasopressin

Question 2

What is the ultimate CV goal with anesthesia

Answer 2

Oxygen delivery to tissues! (DO2)

Question 3

Equation to determine Cardiac Output (CO)

Answer 3

CO = HR x SV

Question 4

How do anticholinergics affect HR

Answer 4

Helps to correct:

Too low → decr CO

Question 5

How do antiarrhythmics fit into the CV equation

Answer 5

Helps correct rhythym:

Too high or irregular → decr CO

Question 6

Inotropes correct

Answer 6

Contractility, they fix:

Too low → decr CO

Question 7

Most anesthetic drugs cause vasodilation so pressors help with

Answer 7

Afterload/preload

make sure pt has adequate intravascular volume

Question 8

2 anticholinergics

what receptors do they affect

what is their effect

Answer 8

Atropine, Glycopyrolate

competative antagonists at muscarinic ACh receptors (antimuscarinic), decr parasympathetic tone

incr fire rate of SA node (chronotropy) & conduction speed through AV node (dromotropy)

Question 9

Where are the muscarinic receptors we are concerned about

what CS might we see when activated

Answer 9

M2: heart, CNS, airway smooth mm

bradycardia

Question 10

Clinical indications to use anticholinergics

Answer 10

bradycardia 2° to incr vagal tone

incr vagal tone can be caused by:

opioids, brachycephalic conformation & doxies, ophtho, GI, vomiting, intubation

Question 11

Side effects of Atropine/Glycopyrrolate

Answer 11

Ileus & colic (concern for horses & ruminants)

incr viscosity of saliva

mydriasis (atropine) - contraindicated in glaucoma

Question 12

what can be seen with atropine/glyco administration

Answer 12

paradoxical bradycardia

more likely at low doses

may lead to AV block, sometimes severe/persistent

Question 13

Atropine

Answer 13

IV, IM, SQ, IT

Onset: ≈ 1 m IV

DoA: 30-60 m

may cause marked tachycardia

crosses BBB & placenta

Question 14

Glycopyrrolate

Answer 14

IV, IM, SQ

Onset: 1-5 m IV

DoA: 2-3 h

may cause mild tachycardia (<atropine></atropine>

does NOT cross BBB or placenta & no mydriasis

NOT for emergency use (slow onset)

Question 15

Anti arrhythmics

Answer 15

Class 1B - Lidocaine

Na channel blocker

Use for VPDs. Vtach

Short acting: bolus → CRI

Criteria for use: hypotension/inadequate perfusion, R-on-T, multiform VPDs, HR>180

Class II - Beta blockers

use for severe sinus tachycardia or SVT

rarely used during anes except:

tachycardia associated w/ pheochromocytoma

Esmolol most common

Question 16

Dopamine

Answer 16

Dose dependent receptor agonism:

Low dose: incr renal perfusion, Dopamine receptor agonist

Med dose: incr inotropy & chronotropy, Beta agonist

High dose: incr inotropy, chronotropy & vasoconstriction, Beat and Alpha agonist

Short 1/2 life, must be CRI

Common first line tx for hypotension in cats

Question 17

Ephedrine

Answer 17

Mixed agonist

• Primary α

• Also ß1, ß2

• May see a reflex bradycardia due to vasoconstrictive effects

• May cause CNS stimulation (increases MAC)

• DoA: 20-30 minutes

• Less effective after repeated dosing

Question 18

Norepinephrine

Answer 18

Mixed agonist

• Primary α ⇒ vasoconstriction

• Also ß1

• Indicated for refractory shock or non-responsive hypotension (usually a 2nd or 3rd line treatment)

• Short acting, use as a CRI

Question 19

Epinephrine

Answer 19

Non-selective agonist: α, ß1, ß2

• Indications: CPR or anaphylactic shock

• Arrhythmogenic (vFib)

Question 20

Phenylephrine

Answer 20

α-1 agonist ONLY → vasoconstriction, increased BP

 May decrease cardiac output and perfusion

 Careful patient choice and titration

 Causes splenic contraction – used to treat nephrosplenic

entrapment in horses

 Short half-life, must be given as a CRI

 Useful topically for nasal edema in horses

 (7th semester sheep lab too)

Question 21

Dobutamine

Answer 21

ß agonist

• Primarily ß1 ⇒ increased inotropy, minimal effects on chronotropy

• Mild ß2 effects (vasodilation)

• Used commonly in equine anesthesia (~100% of horses under inhalant GA)

• Short half-life, must be given as a CRI

Question 22

Isoproterenol

Answer 22

ß1 and ß2 agonist

• Clinical use in veterinary medicine restricted to medical tx for 3rd

degree AV block (ß1effect) and bronchodilation (ß2 effect)

• Short half-life, give as a CRI

Question 23

Vasopressin (ADH)

Answer 23

Non-adrenergic sympathomimetic →Vasoconstriction via V1 receptors

 Indicated for refractory shock or non-responsive hypotension as a CRI

 May cause profound vasoconstriction and tissue ischemia – monitor patients closely!

 Used in CPR interchangeably with epinephrine

Question 24

Strategies for hypotension

Answer 24

If bradycardic give anticholinergic.

Try turning down vaporizer, if pt is light give MAC sparing drug then decr vaporizer

Opioid, benzo, lidocaine, ketamine, etc

Give crystalloid fluid bolus & evaluate response

If still hypotensive:

CV drugs, tx underlying cause (i.e. vasodilation → vasopressor, decr contratility→ inotrope)