Antidysrhytmics Flashcards
What are two examples of, and the mechanism of action for Class I antidysrhythmic?
Examples are Procainamide, and lidocaine.
Blocks sodium ion channels and suppresses ectopic foci by raising threshold for depolarization. It also slows conduction velocity.
What are the 5 classes of antidysrhythmics?
I sodium channel blockers II beta adnergic antagonists III potassium channel blockers IV calcium channel blockers V misc
What is an example of, and the mechanism of action for Class II antidysrhythmic?
An example is metoprolol
Beta adnergic antagonists slow heart rate, and decrease conduction velocity through AV node.
The competitively inhibit catecholamine activation of beta receptor sites.
What are two examples of, and the mechanism of action for Class III antidysrhythmic?
Examples are amiodarone and bretylol
Potassium channel blockers delay depolarization extending the action potential and lengthening the refractory period.
What are two examples of, and the mechanism of action for Class IV antidysrhythmic?
Examples are verapamil, and cardizem.
Calcium channel blockers slow conduction through the AV node, decrease automaticity of etopic foci and the SA node, and decrease velocity of cardiac contraction.
What are two examples of Class V antidysrhythmics?
Examples are adenosine, and digoxin
Chronotropy
Heart rate
Inotropy
Myocardial contractility
Dromotropy
Myocardial conduction
Phase 4 of cardiac muscle cell action potential
Begins cycle, cardiac cells are at rest,waiting for automaticity or transfer of an impulse from adjacent cardiac cell.
Coincides with diastole of the heart.
Phase 0 of cardiac muscle cell action potential
Begins with rapid influx of sodium ions through channels in the cardiac cell.
Potassium slowly begins to exit the cell, and depolarization occurs, altering the electrical charge present in the cell.
Phase 1 of cardiac muscle cell action potential
Sodium influx decreases while potassium continues to leave the cell slowly.
Phase 2 of cardiac muscle cell action potential
Begins movement of calcium into the cell while potassium continues to leave the cell.
Phase 3 of cardiac muscle cell action potential
Calcium movement ceases with continued outflow of potassium.
Myocardial contraction and depolarization happen during phase 2 and 3
What are the indications for lidocaine and procainamide? Which one is refractory to the other?
V-tach and v-fib
Procainamide refractory to lidocaine for v-fib and pulseless v-tach
What contraindication do procainamide and lidocaine share?
2nd and 3rd degree heart block
Contraindications for procainamide
Myasthenia gravis, and 2nd/3rd degree heart block
Contraindications for lidocaine
Supra ventricular dysrhythmias, stokes-Adams syndrome, 2nd/ 3rd degree heart block,hypersensivity to amide type local anesthetics and bradycardias
Precautions that lidocaine and procainamide share
CHF, and h/r impairment
Precautions for procainamide
Hypotension,cardiac enlargement, CHF,AMI, ventricular dysrhythmias due from digitalis, h/r impairment, or bronchial asthma
Lidocaine precautions
H/r impairment, CHF,hypoxia,respiratory depression, hypovolemia, myasthenia gravis, shock, elderly
Lidocaine description
Lidocaine is an antidysrhythmic that suppresses automaticity and raises stimulation threshold of the ventricles. Also causes sedation, anticonvulsant, and analgesic effects.
Procainamide description
Procainamide prolongs ventricular depolarization, slows conduction,and decreases myocardial excitability.
What are the 4 stop points of procainamide?
- Up to 17 mg/kg to effect, then1-4 mg/min
- Ectopic resolves
- QRS widens more then50% from original
- Hypotension ensues
Adult dose for procainamide
20-30 mg/min IV drip @6-8 mg/kg
Pedi dose for procainamide
15 mg/kg over 30-60 min
Lidocaine dose for adult
1-1.5 mg/kg q 3-5 min max of 3 mg/kg
Post conversion drip of 2-4 mg/min (1 g/250 cc)
Elderly dosing for lidocaine
1/2 of adult
Pedi dose of lidocaine
1mg/kg q 3-5 min max of 3 mg/kg
Post conversion 20-50mcg/kg/min
