Review of Hemodynamics Flashcards
A patient is taking a beta1-adrenergic drug to improve the stroke volume of the heart. The nurse caring for this patient knows that this drug acts by increasing:
a. cardiac afterload.
b. cardiac preload.
c. myocardial contractility.
d. venous return.
C
Beta1-adrenergic agents help increase the heart’s stroke volume by increasing myocardial contractility. Cardiac afterload is determined primarily by the degree of peripheral resistance caused by constriction of arterioles; increasing afterload would decrease stroke volume. Beta1-adrenergic agents do not affect afterload. Cardiac preload is the amount of stretch applied to the cardiac muscle before contraction and is determined by the amount of venous return. Beta1-adrenergic agents do not affect cardiac preload. Venous return is determined by the systemic filling pressure and auxiliary muscle pumps and is not affected by beta1-adrenergic agents.
A nurse is caring for a patient who is receiving a drug that causes constriction of arterioles. The nurse expects to observe which effect from this drug?
a. Decreased stroke volume
b. Increased stroke volume
c. Decreased myocardial contractility
d. Increased myocardial contractility
A
Constriction of arterioles increases the load against which the heart must pump to eject blood. Increased constriction of arterioles would decrease, not increase, the stroke volume of the heart. Myocardial contractility is determined by the sympathetic nervous system, acting through beta1-adrenergic receptors in the myocardium.
A patient with a history of hypertension is admitted for a procedure. If the patient’s arterial pressure decreases, which clinical manifestation would the nurse expect to see?
a. Decreased heart rate
b. Increased heart rate
c. Decreased blood pressure
d. Syncope
B
When arterial pressure decreases, the vasoconstrictor center causes constriction of nearly all arterioles, leading to an increase in peripheral resistance, constriction of veins, increasing venous return, and subsequent acceleration of the heart rate. A decrease in arterial pressure would not cause a decrease in the heart rate or blood pressure, nor would it cause syncope.
A nurse is teaching a nursing student how blood can return to the heart when pressure in the venous capillary beds is very low. Which statement by the student indicates a need for further teaching?
a. “Constriction of small muscles in the venous wall increases venous pressure.”
b. “Negative pressure in the left atrium draws blood toward the heart.”
c. “Skeletal muscles relax to allow the free flow of blood.”
d. “Venous valves help prevent the backflow of blood.”
C
Skeletal muscle contraction, along with one-way venous valves, help create an “auxiliary” venous pump that helps drive blood toward the heart. Constriction of small muscles in venous walls helps increase venous pressure. Negative pressure in the left atrium sucks blood toward the heart. Valves, which are one-way, work with the contraction of skeletal muscles to create a venous pump.
A nurse is assessing a patient with heart failure. The patient complains of shortness of breath, and the nurse auscultates crackles in both lungs. The nurse understands that these symptoms are the result of:
a. decreased force of ventricular contraction.
b. increased force of ventricular contraction.
c. decreased ventricular filling.
d. increased ventricular filling.
A
In the failing heart Starling’s law breaks down, and the force of contraction no longer increases in proportion to the amount of ventricular filling. The result is the backup of blood into the lungs and the symptoms of shortness of breath and crackles caused by fluid. Increased ventricular contraction would not result in a backup of blood into the lungs. Changes in ventricular filling are not the direct cause of this symptom.
A patient with hypertension is admitted to the hospital. On admission the patient’s heart rate is 72 beats per minute, and the blood pressure is 140/95 mm Hg. After administering an antihypertensive medication, the nurse notes a heart rate of 85 beats per minute and a blood pressure of 130/80 mm Hg. What does the nurse expect to occur?
a. A decrease in the heart rate back to baseline in 1 to 2 days
b. An increase in the blood pressure within a few days
c. An increase in potassium retention in 1 to 2 days
d. A decrease in fluid retention within a week
A
When blood pressure drops, the baroreceptors in the aortic arch and carotid sinus sense this and relay information to the vasoconstrictor center of the medulla; this causes constriction of arterioles and veins and increased sympathetic impulses to the heart, resulting in an increased heart rate. After 1 to 2 days, this system resets to the new pressure, and the heart rate returns to normal. The blood pressure will not increase when this system resets. Increased potassium retention will not occur. Over time, the body will retain more fluid to increase the blood pressure.
A patient is taking a drug that interferes with venous constriction. The nurse will tell the patient to:
a. ask for assistance when getting out of bed.
b. expect bradycardia for a few days.
c. notify the provider if headache occurs.
d. report shortness of breath.
A
A drop in venous pressure reduces venous return to the heart, and as blood pools in the extremities, orthostatic hypotension can occur. Patients taking drugs that reduce venous constriction should be cautioned to ask for assistance when getting out of bed. Bradycardia, headache, and shortness of breath are not expected effects.
