Vasodilators Flashcards
A nurse is administering a vasodilator that dilates resistance vessels. The nurse understands that this drug will have which effect on the patient?
a. Decreased cardiac preload
b. Decreased cardiac output
c. Increased tissue perfusion
d. Increased ventricular contraction
C
Vasodilators that dilate resistance vessels, or arterioles, cause a decrease in afterload, which allows cardiac output and tissue perfusion to increase. A decrease in preload would be the result of dilation of capacitance vessels, or veins. Dilation of arterioles increases cardiac output. Ventricular contraction results when preload is increased.
A patient is taking a vasodilator that relaxes smooth muscles in veins. To help minimize drug side effects, the nurse caring for this patient will:
a. caution the patient not to get up without assistance.
b. encourage the patient to increase fluid intake.
c. tell the patient to report shortness of breath.
d. warn the patient about the possibility of bradycardia.
A
Postural hypotension occurs when moving from a supine or seated position to an upright position. It is caused by relaxation of smooth muscle in veins, which allows blood to pool in veins and decreases venous return of blood to the heart. Patients taking such drugs should ask for assistance when getting up to prevent falls. Prolonged use of vasodilators can lead to expansion of blood volume and fluid overload, so increasing fluid intake is not appropriate. Shortness of breath is a symptom associated with heart failure. Tachycardia can occur when the blood pressure drops as a result of the baroreceptor reflex.
A nurse is caring for a patient with hypertension and diabetes. The patient’s prescriber recently ordered an angiotensin-converting enzyme (ACE) inhibitor. Which statement by the patient indicates understanding of the nurse’s teaching about this drug?
a. “ACE inhibitors only dilate veins, so I may have more edema in my ankles.”
b. “ACE inhibitors prevent the nervous system from causing increased blood pressure.”
c. “This drug can also cause shortness of breath because of bronchoconstriction.”
d. “This drug will help lower my blood pressure and will benefit my kidneys.”
D
ACE inhibitors reduce blood pressure and help preserve renal function in people with diabetes. ACE inhibitors dilate both veins and arterioles. ACE inhibitors work on the renin-angiotensin-aldosterone system, not the nervous system. ACE inhibitors do not have effects on the bronchioles of the lungs.
The nurse is caring for a patient who is taking a vasodilator that dilates capacitance vessels. The nurse will expect which effect in this patient?
a. Decrease in cardiac work
b. Increase in cardiac output
c. Increase in tissue perfusion
d. Increase in venous return
A
Vasodilators that dilate capacitance vessels, or veins, lead to a decrease in venous return to the heart, which reduces preload and the force of ventricular contraction. The resultant effect is a decrease in cardiac work. With a decrease in ventricular contraction, cardiac output is reduced, as is tissue perfusion. Dilation of veins causes a decrease in venous return.
A nurse is reviewing the phenomenon of reflex tachycardia with a group of nursing students. Which statement by a student indicates understanding of this phenomenon?
a. “Baroreceptors in the aortic arch stimulate the heart to beat faster.”
b. “Reflex tachycardia can negate the desired effects of vasodilators.”
c. “Reflex tachycardia is more likely to occur when beta blockers are given.”
d. “Venous dilation must occur for reflex tachycardia to occur.”
B
Reflex tachycardia, which is a compensatory mechanism in response to decreased blood pressure, can negate the desired effect of a vasodilator by eventually increasing blood pressure. Baroreceptors relay information to the vasomotor center of the medulla; the medulla sends impulses to the heart. Beta blockers are given to counter reflex tachycardia. Reflex tachycardia can be produced by dilation of both arterioles and veins.
A female patient with essential hypertension is being treated with hydralazine (Apresoline) 25 mg twice daily. The nurse assesses the patient and notes a heart rate of 96 beats per minute and a blood pressure of 110/72 mm Hg. The nurse will request an order to:
a. administer a beta blocker.
b. administer a drug that dilates veins.
c. reduce the dose of hydralazine.
d. give the patient a diuretic.
A
This patient is showing signs of reflex tachycardia, so a beta blocker is indicated to slow the heart rate. Patients with heart failure who take hydralazine often require the addition of isosorbide dinitrate, which also dilates veins. There is no indication for reducing the dose of hydralazine. A diuretic can be given with hydralazine if sodium and water retention is present.
A nurse is obtaining a medication history on a newly admitted patient, who reports taking minoxidil for hypertension. Admission vital signs reveal a heart rate of 78 beats per minute and a blood pressure of 120/80 mm Hg. What is an important part of the initial assessment for this patient?
a. Evaluating ankle edema
b. Monitoring for nausea and vomiting
c. Noting the presence of hypertrichosis
d. Obtaining a blood glucose
A
Fluid retention is a common and serious adverse effect of minoxidil, because it can lead to cardiac decompensation. If present, a diuretic is indicated. Nausea and vomiting may occur with this drug but is not a serious side effect. Hypertrichosis occurs in about 80% of patients taking the drug, but its effects are cosmetic and not life threatening. It may be important to monitor the blood glucose level in some patients, because the drug can alter glucose tolerance, but this effect is not as serious as fluid retention.
A patient is admitted with severe hypertensive crisis. The nurse will anticipate administering which medication?
a. Captopril PO
b. Hydralazine (Apresoline) 25 mg PO
c. Minoxidil 20 mg PO
d. Sodium nitroprusside (Nitropress) IV
D
Sodium nitroprusside is the drug of choice for hypertensive emergencies and is given intravenously. ACE inhibitors, such as captopril, are not used. Hydralazine may be used but should be given IV. Minoxidil is effective, but its severe side effects make it a second-line drug.
A nursing student asks a nurse why a patient in hypertensive crisis is receiving both intravenous sodium nitroprusside (Nitropress) and oral hydralazine (Apresoline). The nurse will explain that this is done to prevent:
a. cyanide poisoning.
b. fluid retention.
c. rebound hypertension.
d. reflex tachycardia.
C
Sodium nitroprusside acts rapidly and is given only intravenously. Rebound hypertension occurs immediately when the IV is stopped, so an oral antihypertensive should be given simultaneously. Cyanide poisoning can occur with sodium nitroprusside, but giving hydralazine does not counter this adverse effect. Hydralazine does not prevent fluid retention or reflex tachycardia.
Which medications are most likely to cause postural hypotension? (Select all that apply.)
a. Minoxidil
b. Diltiazem (Cardizem)
c. Prazosin (Minipress)
d. Captopril (Capoten)
e. Losartan (Cozaar)
C, D, E
Postural, or orthostatic, hypotension is defined as a fall in blood pressure related to a change in position. Minoxidil and diltiazem dilate arterioles; therefore, they are not likely to cause postural hypotension. Prazosin, captopril, and losartan all reportedly can cause orthostatic hypotension.
