Cardiovascular Flashcards
Name three positive inotrope medications
Pimobendan, dopamine, dobutamine
What is the purpose of positive inotrope medications?
Increase cardiac contractility
What’s the mechanism of action of dopamine and how does that affect the patient?
Acts on beta-1 receptors to stimulate norepinephrine release. This causes increased cardiac contractility, increased heart rate, arterial constriction, and increased blood pressure.
Which drug, dopamine or dobutamine, should be avoided in patients with severe cardiac disease and why?
Dopamine as it will cause an increase in cardiac afterload.
How can loop diuretics activate RAAS?
They cause a decrease in renal blood flow which triggers the release of renin, which begins the RAAS cascade.
Name three diuretics
Furosemide, spironolactone, torsemide.
Which diuretic spares potassium and avoids activating RAAS?
Spironolactone
What is the suffix of all ACE inhibitors?
Pril
What is the mechanism of action of an ACE inhibitor?
It essentially prevents RAAS by inhibiting angiotensin converting enzyme (ACE) which prevents the conversion of angiotensin 1 to angiotensin 2.
Name the two most common ACE inhibitors in vet med?
Enalapril, benazepril.
Where are beta-1 receptors located?
In the heart
Define cardiac preload
The volume of fluid in the heart prior to contraction.
Define cardiac afterload
The ventricular pressure at the end of cardiac contraction. Essentially, the pressure the heart has to push against to contract.
Where are alpha receptors located?
Arteries
What hormones stimulate alpha receptors to constrict arteries and increase blood pressure and venous return?
Epinephrine and norepinephrine
Where are beta-2 receptors located?
Lungs and skeletal tissue
When stimulated, what do beta-1 receptors do?
Increase heart rate and cardiac contractility.
When stimulated, what do beta-2 receptors do?
Cause bronchodilation and vasodilation in skeletal muscle.
How can pimobendan assist in cardiogenic shock?
It balances vasodilation and increases cardiac contractility.
How do positive inotropes increase cardiac contractility?
They increase available calcium for protein binding or they increase protein sensitivity to calcium.
What is the mechanism of action for dobutamine?
It acts on beta-1 receptors to increase cardiac contractility to increase blood pressure and peripheral perfusion.
Where is angiotensin converting enzyme (ACE) produced?
The lungs.
Which cardiac medication is a calcium channel blocker that acts primarily as an arterial vasodilator?
Amlodipine.
What is diltiazem used for and what is its primary mechanism of action?
It is used to treat supraventricular tachycardia (SVT) and it is a calcium channel blocker.
Which drug is most useful in the management of atrial fibrillation to slow AV nodal conduction?
Digoxin
Which cardiac medication is derived from the poisonous foxglove plant?
Digoxin
Which two cardiac drugs, when combined, have a marked affect at reducing the ventricular response rate of atrial fibrillation?
Digoxin and diltiazem
What is lidocaine’s mechanism of action and what does it treat?
Lidocaine is a sodium channel blocker that is used to manage ventricular arrhythmias in dogs.
What is sotalol’s mechanism of action and what does it treat?
Sotalol is a nonselective beta-adrenergic blocker and a potassium channel blocker. It’s primary use is to treat ventricular tachyarrhythmias.
Name the three most common beta blockers.
Propranolol, atenolol, and sotalol.
What is the specific mechanism of action of beta blockers?
They block beta one and beta two receptors which promotes a steady heart rate and slightly reduces cardiac contractility.
Which medication has a variety of mechanism of actions and can work as a beta blocker, a sodium channel blocker, and a calcium channel blocker?
Amiodarone
In what instances would amiodarone be used?
It is useful for both ventricular and atrial arrhythmias and can be useful when traditional anti-arrhythmic drug therapies do not work.
What is the most powerful vasodilator in veterinary practice?
Nitroprusside.
What is nitroprusside’s primary use?
It reduces preload and afterload assisting in treatment of severe hypertension and CHF.
In what location of the body would nitroglycerin be applied in an acute situation and why?
It should be applied to a hairless area of the abdomen, because perfusion to the ears may not be sufficient for drug uptake.
Which medication is commonly used for feline urinary obstruction but can also be used as an alpha receptor blocker to decrease blood pressure?
Prazosin.
Which medication is commonly used for feline urinary obstruction but can also be used as an alpha receptor blocker to decrease blood pressure?
Prazosin.
Which rhythms during CPA are considered shockable?
Ventricular fibrillation and pulseless ventricular tachycardia.
Which ECG rhythms are not shockable during CPA?
Pulseless electrical activity and asystole.
If the first defibrillation is not successful, should you adjust the joules on the defibrillator?
Yes, you should double the joules for the next attempt.
If a canine patient has refractory shockable rhythms, what are drugs to consider administering?
Lidocaine and esmolol.
If a patient has had 15 minutes of unsuccessful CPR, is it reasonable to administer sodium bicarbonate? What if you don’t have an acid base status?
Yes. Even without an acid base status, the patient is most likely acidotic due to persistent unsuccessful CPR.
How many times is it acceptable to repeat atropine if the initial dose did not benefit CPR? Why?
Atropine should not be repeated. It has a long half-life and will accumulate when repeated.
What is the difference on ECG between pulseless VT and PEA?
The heart rate will be above 200bpm if it’s VT. PEA usually has a low heart rate.
What is the difference on ECG between pulseless VT and VF?
VT will have consistent complexes that are the same size, VF will have chaotic complexes varying in size.
What medication would be beneficial to cats, but not dogs when multiple defibrillations have failed to initiate ROSC on a shockable rhythm?
Amiodorone.
How often is it acceptable to repeat epinephrine during CPR?
Every 4 minutes or every other rotation of CPR.
Why would you immediately initiate compressions again after defibrillating instead of pausing and examining the ECG?
It will take at least 2 minutes of compressions to get consistent contractions of the heart to return after defib.
In what situation would vasopressin be more beneficial than epinephrine at causing peripheral vasoconstriction?
Vasopressin’s efficacy is not dependent on pH like epi, so if the patient is severely acidotic, vasopressin will be more effective.
When should open chest CPR be initiated if a feline or small canine patient is not responding to closed chest CPR? Why?
Open chest CPR is not recommended in cats or small dogs. Due to their size, you have almost equal chances of attaining ROSC with closed chest CPR.
