Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
54 Cards in this Set
- Front
- Back
|
List the cardiac glycosides
|
1. Digoxin
2. Digitoxin 3. Ouabain |
|
|
List the nonglycosides and noncatecholmaines that are similar to cardiac glycosides.
|
1 Phosphodiesterase III inhibitors
2. Calcium 3. Glucagon |
|
|
What is the mechanism of action of digitalis?
|
1. Direct effect on the heart
2. Alterations in ANS activity |
|
|
What does digitalis mean?
|
Term used for cardiac glycosides that occur naturally.
|
|
|
What are the direct effects on the heart by digitalis?
|
1. Inhibition of Na-K pump on the sarcolemma or cardiac cell membranes.
2. Increase in intracellular Na and Ca a. Inotropic effect |
|
|
How does digitalis affect ANS activity?
|
1. Increases PSNS
2. Activates vagal nuclei and nodose ganglion in CNS 3. Slows conduction through the AV node |
|
|
How does digitalis work on A-fib?
|
It tries to normalize electrical activity by delaying Phase 4.
|
|
|
List clinical uses for digitalis.
|
1. Periop management of suprventricular tachydysrhythmias with rapid ventricular response
2. Tx of chronic CHF |
|
|
List electrocardiographic effects of digitalis.
|
1. Prolonged P-R segment
2. Shortened QT intervals 3. ST depression 4. Diminished amplitude or inverted T waves |
|
|
List effects of digitalis.
|
1. Increased myocardial contractility
2. Improved renal function 3. Enhanced PSNS |
|
|
What percentage of pts treated with digitalis will experience toxicity?
|
20%
|
|
|
What causes ectopic cardiac dysrhythmias seen in digitalis toxicity?
|
Excessive intracellular calcium.
|
|
|
What population is more prone to digitalis toxicity? Why?
|
Elderly, due to decreased renal clearance.
|
|
|
List causes for digitalis toxicity.
|
1. Hypokalemia
a) increases cardiac glycoside binding 2. Hypomagnesemia 3. Hypercalcemia 4. Decreased renal function and muscle mass 5. Increased SNS activity |
|
|
List causes of decreased potassium levels.
|
1. Diuretics
2. Epi 3. Stress 4. Hyperventilation |
|
|
How is digitalis toxicity diagnosed?
|
By checking plasma concentration:
1. Adults: >3 mg/L 2. Children: 2.5-3.5 mg/L |
|
|
What are some early signs of digitalis toxicity?
|
1. Anorexia
2. Nausea 3. Vomiting |
|
|
What will an EKG show in digitalis toxicity?
|
Atrail tachycardia with prolonged PR up to incomplete or complete heart block.
|
|
|
What cardiac dysrhythmia do pts die from in digitalis toxicity?
|
V-fib
|
|
|
How do you treat digitalis toxicity?
|
1. Correct hypokalemia, hypomagnesmia, and arterial hypoxemia.
2. Treat cardiac dysrhythmias a. Phenytoin b. atropine c. lidocaine 3. Insert temporary artificial transvenous cardiac pacemaker |
|
|
What is used for life threatening digitalis toxicity?
|
Fab fragments
|
|
|
What are fab fragments?
|
Antibodies to digitalis.
|
|
|
What is the greatest disadvantage of preop prophylactic digitalis?
|
The narrow therapeutic-to-toxic dose difference to pts with no obvious ned for the drug.
|
|
|
What is another disadvantage of preop prophylactic digitalis?
|
There may be difficulty in differentiating between anesthetic-induced cardiac dysrhythmias and those due to digitalis toxicity.
|
|
|
What are positive effects of preop prophylactic digitalis?
|
1. Decreased occurrence of postop supraventricular cardiac dysrhythmias in elderly patients.
2. Decreased evidence of impaired cardiac function in pts with CAD recovering from anesthesia. |
|
|
How does quinidine interact with digoxin?
|
Quinidine increases plasma concentrations of digoxin.
|
|
|
How does succinylcholine interact with digitalis?
|
1. Increased PSNS activity
2. Increased cardiac dysrhythmias |
|
|
How do sympathomimetics, pancuronium, and IV calcium interact with digitalis?
|
Increases likelihood of cardiac dysrhythmias.
|
|
|
What drugs protect against digitalis-enhanced cardiac automaticity?
|
1. Fentanyl
2. Enflurane 3. Isoflurane |
|
|
How is digoxin metabolized?
|
1. Skeletal muscle is the tissue reservoir
2. 35% cleared by kidneys 3. Elimination half-time of 31-33 hours |
|
|
How should the dose of digoxin be adjusted in the case of increased creatnine levels?
|
Decrease the dose by 50%.
|
|
|
How should the dose of digoxin be adjusted in the case of renal failure?
|
Decrease the dose by 75%.
|
|
|
What should the maintenance dose of digoxin be?
|
Equal to the daily clearance of the drug.
|
|
|
What are selective phophodiesterase inhibitors?
|
Noncatecholamine, nonglycoside cardiac inotropic agents.
|
|
|
What is the mechanism of action for phosphodiesterase inhibitors?
|
1. Competitive inhibitory action on an isoenzyme fraction of PDE (PDE III).
2. Decreased hydrolysis of cAMP and cGMP in myocardium and vascular smooth muscle. 3. Increased intracellular cAMP allows inward movement of calcium ions. |
|
|
What is the overall effect of the actions of phosphodiesterase inhibitors?
|
1. A positive inotropic effect with vascular, diastolic relaxation.
a. Enhanced removal of calcium from myoplasm. 2. Airway smooth muscle relaxation. |
|
|
What are phosphodiesterase inhibitors used for?
|
Management of acute cardiac failure.
|
|
|
What is amrinone?
|
A bipyridine derivative that acts as a selective PDE III inhibitor.
|
|
|
What is the pharmacodynamic effect of amrinone?
|
Positive inotropic and vasodilator effects manifesting as:
1. Increased cardiac output 2. Decreased left ventricular end-diastolic pressure |
|
|
List side effects of amrinone.
|
1. Hypotension
2. thrombocytopenia with chronic tx |
|
|
How should amrinone be prepared?
|
It does not need to be mixed with anything. Put 5 vials into a 250 ml bag.
|
|
|
How does amrinone improve cardiac output?
|
1. Positive inotropic effect.
2. Decreases SVR. |
|
|
What are the cardiovascular actions of glucagon? What 2nd messenger is involved in these responses?
|
1. Increases myocardial contractility.
2. Increases cardiac output. cAMP is involved. |
|
|
List 3 cardiac effects of digitalis.
|
1. Enhances myocardial contractility.
2. Decreases heart rate 3. Slows impulse propagation through the AV node. |
|
|
What are the 2 principle uses of digoxin?
|
1. CHF
2. Supraventricular dysrhythmias |
|
|
Diitalis produces its positive inotropic effect by what mechanism?
|
1. Inhibition of the sodium-potassium pump.
2. Sodium accumulates in the cell. 3. Sodium-calcium exchange is accelerated. 4. Calcium accumulates in the cardiac cell. 5. Contractility increases. |
|
|
In what phase of the cardiac cycle does digitalis work to slow heart rate?
|
Phase 4.
|
|
|
What are the 3 signs of digitalis toxicity?
|
1. Atrial or ventricular cardiac dysrhythmias.
2. Prolonged PR interval. 3. GI disturbances a. Anorexia b. Nausea c. Vomiting |
|
|
What three electrolyte disturbances enhance digitalis toxicity?
|
1. Hypokalemia
2. Hypercalcemia 3. Hypomagnesemia |
|
|
Why does hypokalemia enhance digitalis toxicity?
|
Increased binding of digitalis to the Na-K pump in cardiac cells results in excessive drug effect.
|
|
|
Why should hyperventilation be avoided during anesthesia for the pt who is taking digitalis?
|
It may cause hypokalemia, which increases the likelihood of digitalis toxicity.
|
|
|
Identify 5 drugs or treatments for cardiac dysrhythmias due to digoxin toxicity.
|
1. Procainamide
2. Phenytoin 3. Propanalol 4. Lidocaine 5. DC countershock |
|
|
A pt showing s/s of digitalis toxicity begins having PVCs. What drugs could be given to treat this? Which of these drugs is particularly useful in suppressing cardiac ventricular dysrhythmias associated with digitalis toxicity?
|
Phenytoin (0.5-1.5 mg/kg IV over 5 minutes) or lidocaine (0.5-1 mg/kg IV) is useful in the initial treatment of digitalis-induced ventricular irritability. Small doses of propanalol have also been effective. Phenytoin is particularly useful in suppressing ventricular dysrhythmias associated with digitalis toxicity.
|
|
|
Why should verapamil, quinidine, or amiodarone be avoided in the digitalized pt?
|
They can increase digitalis concentration on promote digitalis intoxication.
|
