Positive Inotropes Flashcards
What are phosphodiesterase inhibitors?
A heterogeneous group of non-catecholamine non-glycoside compounds that exert a competitive inhibitory action on phosphodiesterase enzymes
PDE III inhibitors have their greatest clinical usefulness in patients who would benefit from?
Combined Inotropic and vasodilator therapy
Milrinone is a derivative of _______ with almost ____ times the inotropic potency but less adverse side effects
Derivative of Amrinone with almost 30 times the inotropic potency
MOA of Milrinone
Inhibition of PDE3 leads to increased levels of cAMP in cardiac myocytes, which enhances cardiac contractility (positive inotropic effect) and relaxes vascular smooth muscle (vasodilation) in the periphery and pulmonary vessels.
Bolus and Infusion dose of Milrinone
Bolus: 50mcg/kg over 10minutes followed by
Infusion: 0.375-0.75mcg/kg/min
Unlike Dobutamine, Milrinone rarely causes?
Tachycardia (Milrinone has strong activity in cardiac muscle cells, less nodal cell activity compared to Dobutamine)
Clinical uses of Milrinone
-Mgmt of acute LV dysfxn
-Weaning from CPB
-Increase inotropy of CHF pts who have down regulation of Beta-1 receptors
-Pulmonary Htn (decrease PAPs)
Milrinone is associated with more _______ and greater______ in SVR and BP than Dobutamine
vasodilation and greater decreases in SVR and BP
Milrinone may be preferred over other positive inotropes when?
In situations with:
high filling pressures,
elevated pulmonary artery pressure, continued need for beta blockade, decreased responsiveness to catecholamine therapy
and pts with increased risk of tachyarrythmias
Side Effects of Milrinone
Rapid administration may decrease SVR decrease Venus return and result in hypotension
Rapid admin of large dose may also increase arrhythmias
What mineral is present in the body in greater amounts than any other?
Calcium
Calcium is important for what kinds of intrinsic physiology functions?
-Neuromuscular transmission
-Skeletal muscle contraction
-Cardiac muscle contraction
-Blood coagulation
-Exocytosis necessary for release of neurotransmitters
Calcium chloride or calcium gluconate is commonly used to treat cardiac depression that may result from what kind of situations?
Delivery of volatile anesthetics
Transfusion of citrated blood
Following termination of cardio pulmonary bypass
What percent of Ionized calcium typically represents total plasma concentration?
45%
How does acidosis affect ionized calcium?
Increases ionized calcium
How does alkalosis affect ionized calcium?
Reduces ionized calcium
What is normal plasma ionized calcium concentration?
1-1.26mmol/L
(2-2.5mEq/L or 4-5mg/dL)
Onset, peak effect and duration of action of calcium chloride or calcium gluconate 500-1000mg bolus?
Onset: <1min
Peak: <1min
Duration: 10-20min
Clinical uses of Digoxin?
management of supraventricular tachydysrhythmias (paroxysmal atrial tachycardia, atrial fibrillation, atrial flutter) associated with a rapid ventricular response
rate
MOA of Digoxin on contractility
Inhibits the Na-K ATPase pump, which increases intracellular sodium levels. This effects the neighboring sodium-calcium pump that usually uses the energy from the Na-K pump to release Calcium out of the cell. When Na-K pump is blocked, calcium subsequently accumulates in the cell as well enhancing cardiac contractility.
MOA of Digoxin on HR
enhance parasympathetic nervous system activity, leading to delayed conduction of cardiac impulses through the atrioventricular node and decreases in heart rate.
Levels great than ____ng/mL are likely to cause digitalis toxicity
greater than 3
Symptoms of Digoxin toxicity
Anorexia, nausea, and vomiting are early manifestations of digitalis toxicity.
Followed by dysrhythmias.
What kind of drug is Levosimendan? How does it work?
Calcium Sensitizer
Enhance cardiac contractility by increasing the sensitivity of contractile proteins in cardiac muscles to calcium ions without increasing intracellular, calcium levels.
Not approved by FDA in US.
(binding of levosimendan
to troponin C, increasing the sensitivity of troponin to
calcium. also activates adenosine
triphosphate–regulated potassium channels (KATP),128
causing vasodilation129 and myocardial protection.130 As a
result, cardiac output is increased with decreased systemic
vascular resistance and pulmonary vascular resistance.?
