Cardiovascular Drugs Flashcards
What are the primary effects of inhalant anesthetics on the CV system?
Vasodilation and inotropy at higher doses
What are the primary effects of propofol/alfaxalone/thiopenal on the CV system?
Negative inotropy and vasodilation especially at higher doses
What are the primary effects of opioids on the CV system?
Bradycardia; can be profound
What are the synthetic agonist of adrenergic receptors?
Isoproteronol, ephedrine, dobutamine, and phenylephrine
What are the endogenous agonist of adrenergic receptors?
Epinephrine, norepinephrine, and dopamine
What are the post-synaptic effects of alpha-1/2 receptors?
Vasoconstriction Minimal Inotropy (alpha-1)
What are the effects of beta-1 receptors?
Inotropy, chronotropy, lusitropy, dromotropy
What is lusitropy and dromotropy?
Lusitropy- relaxation
Dromotropy- conduction velocity of the AV node
What are the effects of beta-2 receptors?
Some inotropy, vasodilation
What is the endogenous agonist of cholinergic receptors?
Acetylcholine
What are the effects of muscarinic receptors?
M1- increased gut motility
M2- increased cardiac parasympathetic tone
M3- salivation/vasodilation
What are synthetic cholinergic agonists?
Bethanechol and pilocarpine
What is the first drug that is usually used for surgical bradycardia?
Atropine
What are some other things you can do to correct bradycardia before giving atropine?
Stop or reduce any bradycardia inducing drugs.
Inhalants, opioids, etc
What are most bradycardias due to?
Excessive vagal tone
Brachiocephalics, visceral manipulation, ocular pressure, drugs
What is sometimes induced when atropine is given and will it resolve?
2nd degree AV block, typically will resolve fairly quickly
What can be given if a bradycardia isn’t due to vagal tone?
Give a beta-agonist
What is isoproterenol good for?
Increasing HR while decreasing BP with an non-vagal bradycardia
What are causes of low BP?
Low HR/SV/CO
Low blood volume
Vasodilation with no reflex tachycardia
What are some ways to increase SVR?
Alpha agonists
Phenylephrine, norepi, or ephedrine
What are some ways to increase SV and CO?
Beta agonists
Dopamine, dobutamine, ephedrine
What are effects of alpha agonists?
Alpha-1/2: vasoconstriction, decrease CO/SV at high doses
Alpha-1: mild inotropy
What is phenylephrine used for in horses?
As a nasal spray to reduce nasal edema
What are some effects of ephedrine?
Bronchodilation, promotion of release of NE from terminals
Should ephedrine be used in “sick” animals?
No, more appropriate of elevating BP in healthy animals
What is an indication for using dopamine?
Increase BP and HR
Does dopamine case vasoconstriction or dilation?
Vasodilation- esp in kidneys, mesentary, and coronary vessels
Is dobutamine or dopamine more appropriate for horses, dogs, and cats?
Horses- dobutamine
What are the effects of dobutamine?
Intropy>chronotropy
Low doses produce desired effect in horses
Are the BP effects of dopamine dose dependent in small animals?
Yes
Are the BP effects of dopamine dose dependent in horses?
No, no change in BP until very high doses
What are the effects of dobutamine in small animals?
Dose dependent increase in CO but no increase in BP except at high doses
What are the effects of phenylephrine in small animals?
Dose dependent increases in BP, no change in CO, increased SVR in high doses
What are the effects of dobutamine in horses?
Rapid increase of BP at low doses with increased CO
What is a major issue with using norepinephrine?
Profound vasoconstriction- must maintain organ perfusion
When is norepinephrine usually used?
Serious hypotension esp with sepsis and shock
What is the pathophysiology of hypotension in septic patients?
Circulating vasodilatory mediators
What is norepiephrine sometimes combined with?
Dobutamine
When should epinephrine be used over norepinephrine?
Cardiac arrest, acute anaphylaxis, tachycardia, or bronchoconstricion
What receptors are more affected by epinephrine at low doses?
Beta adrenergic
What receptors are more affected by epinephrine at high doses?
Alpha adrenergic
What is vasopressin?
Antiduretic hormone (ADH)
When is vasopressin used?
In catecholamine resistant hypotension with shock/sepsis
What is a major concern with vasopressin?
Potent vasoconstriction- must maintain organ perfusion
What is a side effect of atropine/glycopyrrolate that contraindicates its use in cardiac patients?
Increased myocardial O2 consumption
What can beta agonists lead to?
Tachycardias with ventricular arrhythmias
What can alpha agonists lead to?
Hypertension- can be profound
What can vasoconstrictors lead to?
Tissue necrosis esp if injected outside of the vein
When are ventricular arrhythmias most common?
During the peri-anesthetic period and are usually not due to cardiac pathology
When should ventricular arrhythmias be treated
If they result in poor CO/BP- typically will be sustained and rapid
What drug is used to treat ventricular arrhythmias?
Lidocaine IV
What is the MOA of lidocaine?
Na channel blocker- stabilization of neuronal membranes
NOT a negative inotrope
What are some good side effects of lidocaine?
- Reduction of MAC and anesthetic requriements
- Improves bowel motility
- Useful for pain neuropathies
- Some free radical scavenging
T/F: Lidocaine is neurotoxic especially at excessive doses
True
It can also cause cardiovascular collapse at 3x toxic dose
What condition may cause primary hypertension?
Renal disease or catecholamine producing tumors
Typically managed with Ca channel blockers or ACE inhibitors
What drugs are used to manage the cardiac effects of hyperthyroidism?
Beta blockers
What are drugs used to treat hypertension?
Arterial dilators- hydralazine
Venous (capacitence) dilators- nitroprusside
Mixed dilators- alpha antagonists, prazosin, ACE inhibitors
When is nitropursside used?
Acute hypertensive emergencies (short acting infusion)
