Cardiac Pharmacology Flashcards
What is th Bohr Effect
The presence of carbon dioxide aiding in the release and delivery of oxygen from hemoglobin.
What is the amount of blood that is pumped out of the heart per unit of time?
Cardiac Output
What is the lowest pressure reached right before ventricular ejection?
Diastolic blood pressure (DBP).
What is the pressure that drives blood into the tissues, averaged over the entire cardiac cycle?
Mean Arterial Pressure (MAP).
What are catecholamines?
Endogenous products that are secreted into the bloodstream and travel to nerve endings to stimulate an excitatory response.
One of a group of similar compounds having sympathomimetic action
What is the link between atrial depolarization and ventricular depolarization?
AV Node
What is the peak pressure reached during ventricular ejection?
Systolic blood pressure (SBP).
What enzyme is responsible for the breakdown of cAMP?
Phosphodiesterase.
What is A-fib?
A cardiac arrhythmia in which normal atrial contractions are replaced by rapid irregular twitchings of the muscular wall.
What is vasopressor?
An agent that causes vasoconstriction (increase SVR)
Used to increase BP
Also results in an increase in coronary perfusion pressure
What is an inotropic agent?
It is an agent affecting the strength of muscular contraction.
- Can be positive (increase contraction strength) or negative (decrease contraction strength)
What is V-fib?
A cardiac arrhythmia in which normal ventricular contractions are replaced by rapid movements of the ventricular.
What three factors does tissue perfusion depend on?
Cardiac function, vascular tone, and vascular volume.
If a patient was in cardiogenic shock and had a decreased CO, would a pulse oximeter attached to the index finger be an accurate way to measure oxygenation status?
No, if perfusion was limited due to decreased CO the patient’s pulse rate in the finger may not be adequate enough for the proper functioning of a pulse oximeter.
What is a Chronotrope
- An agent that affects heart rate
- Can be positive (increase HR) or negative (decrease HR)
What is a Dromotrope
- An agent that affects the rate of conduction
- Can be positive (increase conduction velocity) or negative (decrease conduction velocity)
What is a vasoactive drug
An agent that affects blood vessel tone (dilation/contraction)
Where are alpha Adrenergic Recpetors located
- Primary located in the peripheral vasculature where they will regulate smooth vascular tone
- Alpha 1 receptors are located in the peripheral blood vessels
- Alpha 2 receptors are located in the presynaptic sympathetic neurons and CNS
Alpha Recpetor Stimulation
- Agonist stimulation results in vasoconstriction and therefore
- Increased arterial blood pressure
- Increased coronary and cerebral perfusion pressure
- Will regulate cardiac, vascular, bronchiolar, and GI smooth muscle tone
- Will have a minimal inotropic effect due to the fact that there is few alpha receptors in the myocardium
Stimulation of Alpha 2 Receptors
- Alpha 2 receptors are located in the presynaptic sympathetic neurons and CNS
- Stimulation here inhibits the release of norepinephrine resulting in vasodilation
Examples of Alpha Agonists
- Norepinephrine +++
- Epinephrine++
- Dopamine (high dose) +++
Where are Beta 1 Receptors Located
Located within the heart (mostly in the sinus node and ventricles)
Agonist Stimulation of Beta 1 Receptors
- Increased heart rate (positive chronotrope)
- Increased myocardial contraction (positive inotrope)
- Increased rate of conduction (positive dromotrope)
Negative Effects of Stimulation of Beta 1 Receptors
- Increased myocardial irritability
- Increased myocardial oxygen demand
Beta 2 Receptors
- Located in the heart, vascular bed and bronchial smooth muscle
- Agonist stimulation will result in bronchodilation (primary effect) and peripheral vasodilation (minimal effect, opposes alpha one stimulation)
Dopaminergic Receptors
- Located in the smooth muscle in the cerebral, coronary, renal, and splanchnic vascular beds
- Agonist stimulation will results in vasodilation and therefore increased blood flow to these areas
After administration of epinephrine, stimulation of what receptor type is likely to produce a net effect of tachycardia?
B1 receptors because they are densely populated in the myocardium.
Why do patients receiving a phenylephrine infusion has developed reflex bradycardia?
Patients on phenylephrine infusions develop a reflex bradycardia due to the unopposed alpha 1 stimulation in the vasculature causing increased SVR.
Why would you use drug that will alter CO and SVR
- Stabilize hemodynamic status and avert cardiovascular collapse
- Restore perfusion pressure
- Improve CO and organ perfusion
Cautions of CO and SVR Drugs
- The increase BP and increase HR increases myocardial oxygen demand and may cause myocardial ischemia
- β1 properties markedly increases myocardial oxygen consumption which may exacerbate myocardial infarct/ischemia
Epinephrine Mechanism of Action
- Both an alpha and beta adrenergic agent
- Both vasopressor and inotropic, chronotropic, and dromotropic properties
- Will increase both cerebral and coronary prefusion pressure
Epinephrine Effect on Heart Rate
- Increase rate firing of the SA node
- Increased rate of conduction through the AV node
- Decreased refractory time
- This can make the heart prone to arrhythmias
Epinephrine Beta 2 Stimulation
The beta two stimulation will result in bronchodilation, the peripheral vasodilation will not win out against the strong alpha effects (though there will be some vasodilation occurring via the B2 stimulation)
Indications for Epinephrine
- Cardiac arrest
- Given as a bolus
- Used in pulseless arrhythmias, VF, VT, PEA, asystole
- Epinephrine makes VF more responsive to defibrillation
- Hypotension
- Given as an infusion
- Anaphylaxis and severe allergic reactions
- Given via SQ/ IM
Epinephrine Routes of Administration
- Can be given via the ETT
- 2-2.5 mg in 10 cc normal saline
- i.e. 2-2.5 x normal bolus of 1 mg
- 2-2.5 mg in 10 cc normal saline
- Other Routes
- Inhaled in 5 mg for adults and therefore 5 mL of 1:1000
What is the major determinant of blood pressure and ventricular contractility?
CO and the volume of blood filling in the ventricles (preload).
What are two determinants of MAP?
Systemic vascular resistance and CO.
What is stroke volume?
The amount of blood ejected from the heart during systole.
What would be the 1st line therapy to improve the hypotension if a patient has just suffered severe blood loss due to the arterial lines becoming dislodged?
Fluids are the mainstay for improving hypotensive episodes.
What measurement would likely be alerted if a patient’s hemodynamic parameters are currently being measured and patient’s fluid overloads?
CVP would be increased.
What is the clinical indication for the use of Levophed?
The need to increase MAP
- Hypotension due to a low SVR
- Ex. Distributive shock (septic, anaphylactic, neurogenic)
- Should be used with extreme caution in cardiogenic shock
- The higher BP achieved may severely limit the blood flow to flow organs
- In non septic patient can produce severe renal and splanchnic vasoconstriction
- Is an important endogenous neurotransmitter
Why is the use of isoproterenol which can be used to relax the smooth muscle of the bronchi, limited and what is the brand name?
Limited because of its pronounced stimulatory effect on the HR. Isuprel.
Why is Norepinephrine more appropriate treatment than dopamine in treating a patient with septic shock?
There is an increased risk of tachyarrhythmias as compared to the risk with other vasopressors.
What is the indication of epinephrine in advanced life support?
Potent vasoconstrictor.
What medications would be indicated to increase blood flow to the myocardium and the CNS during CPR?
Epinephrine.
Norepinephrine (Levophed)
Mechanism of Action
- Powerful alpha and beta 1 receptor agonist
- The beta 1 effect is primarily an increase in myocardial contraction
- The effect on Hr is less prounced
Dopamine (Intropin)
MEchanism of Action
- A precursor to norepinephrine
- Will agonise the effect of norepeine
- Stimulates alpha, beta 1, and dopaminergic receptor
Dopamine
Low Dose
-
Low Dose (1-5 ug/kg/min)
- Renal dose
- Causes vasodilation of renal and splanchnic arteries increasing urine output
- No longer used to treat oliguria
Dopamine
Moderate Dose
- Cardiac dose
- Beta one effects dominate
- The effects on the renal system are enhanced due to an increase cardiac output
- Used to treat bradycardias
Dopamine High Dose
-
High Dose (10-20 ug/kg/min)
- Vasopressor dose
- Alpha effects are seen increasing SVR and splanchnic vasoconstriction