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Chapter 17: Adrenergic Agonists
Terms in this set (12)
A nurse is teaching a nursing student about the two classes of adrenergic agonist drugs. Which statement by the nursing student indicates understanding of the teaching?
a. "Catecholamines may be given orally."
b. "Catecholamines often require continuous infusion to be effective."
c. "Noncatecholamines do not cross the blood-brain barrier."
d. "Noncatecholamines undergo rapid degradation by monoamine oxidase."
Catecholamines undergo rapid degradation by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Consequently, they have a brief duration of action, and continuous infusion often is required to maintain the drug's effects. Catecholamines cannot be used orally. Catecholamines do not cross the blood-brain barrier; noncatecholamines do. Noncatecholamines are not degraded by MAO.
Dopamine is administered to a patient who has been experiencing hypotensive episodes. Other than an increase in blood pressure, which indicator would the nurse use to evaluate a successful response?
a. Decrease in pulse
b. Increase in urine output
c. Weight gain
d. Improved gastric motility
Dopamine would cause an increase in urine output, because cardiac output is increased as a result of the increase in blood pressure. The effectiveness of dopamine would not be measured by a decrease in pulse, because dopamine's primary effect is to increase blood pressure. Dopamine's effectiveness would not be evaluated by a weight gain. Dopamine's effectiveness would not be evaluated by improved gastric motility.
A nursing student asks the nurse about receptor specificity of adrenergic agonist medications. What will the nurse say?
a. "As the dosage of these medications increases, drugs in this class are more selective."
b. "Dopamine is selective for dopamine receptors and has no effects on alpha or beta receptors."
c. "Epinephrine is the most selective alpha-adrenergic agonist medication."
d. "Specificity is relative and is dose dependent."
Receptor specificity is relative, not absolute, and is dose dependent. At low doses, selectivity is maximal, and selectivity declines as the dose increases. Dopamine is the only drug in this class that acts on dopamine receptors, but it also has effects on alpha and beta receptors. Epinephrine is the least selective of this class.
A patient brought to the emergency department requires sutures. The prescriber orders a local anesthetic with epinephrine. The nurse understands that epinephrine is ordered to:
a. prevent hypertension induced by the anesthetic.
b. allow a reduced dose of the anesthetic.
c. reduce anesthetic-induced nausea.
d. reduce the pain of an injection.
Epinephrine prolongs absorption of the anesthetic, because it is an alpha1 agonist. It is frequently combined with a local anesthetic for this purpose, so that the amount of anesthetic required may be reduced. Local anesthetics do not induce hypertension; therefore, epinephrine would not be needed to prevent it. Epinephrine does not act as an antiemetic and would not reduce anesthetic-induced nausea. Epinephrine is not used to reduce the pain of an injection.
A nurse is administering intravenous dopamine [Intropin] to a patient in the intensive care unit. Which assessment finding would cause the most concern?
a. Blood pressure of 100/70 mm Hg
b. Increased urine output
c. Edema at the IV insertion site
The nurse would be concerned if the patient's peripheral IV were edematous, because this could signal infiltration of the solution into the tissues. Dopamine can cause necrosis if it extravasates. Dopamine is indicated to increase the patient's blood pressure; this blood pressure reading is acceptable. When dopamine is effective at increasing cardiac output, it also causes an increase in urine output. Headache is not a contraindication to the use of dopamine.
A patient with asthma uses albuterol [Ventolin] for wheezing. The nurse assesses the patient and notes vital signs of HR, 96 beats per minute; RR, 18 breaths per minute; and BP, 116/78 mm Hg. The patient has clear breath sounds and hand tremors. What will the nurse do?
a. Ask the patient how often the inhaler is used.
b. Check the patient's blood glucose level.
c. Request an order for isoproterenol [Isuprel] to reduce side effects.
d. Stop the medication and report the tremors to the provider.
Tachycardia is a response to activation of beta1 receptors. It can occur when large doses of albuterol are used and selectivity decreases. The nurse should question the patient about the number of inhalations used. Isoproterenol can cause hyperglycemia in diabetic patients. Isoproterenol has more side effects than albuterol. Tremors are an expected side effect and are not an indication for stopping the drug.
A nurse is teaching parents how to use an Epi-Pen for their child, who has a peanut allergy. Which statement by the parents indicates understanding of the teaching?
a. "After using the Epi-Pen, we must go to the emergency department."
b. "The Epi-Pen should be stored in the refrigerator, because epinephrine is sensitive to heat."
c. "The teacher should call us when symptoms start so that we can bring the Epi-Pen to school."
d. "We should jab the device into the thigh until it is empty of solution."
After using the Epi-Pen, it is important that the individual get medical attention as quickly as possible. The effects of epinephrine fade in 10 to 20 minutes, and the anaphylactic reaction can be biphasic and prolonged. Epinephrine is sensitive to heat, but storing the device in the refrigerator can compromise the injection mechanism; the device should be stored at room temperature in a dark place. Individuals who need an Epi-Pen must have the device with them at all times; any delay in treatment can be fatal, because anaphylaxis can occur within minutes after exposure. The Epi-Pen contains 2 mL of epinephrine, but only 0.3 mL is injected; the device will not be empty with a successful injection.
Because they cause vasoconstriction, alpha1-adrenergic agonists are especially useful for:
a. causing hemostasis in skin and mucous membranes.
b. producing mydriasis to facilitate ophthalmic examinations.
c. slowing the heart rate in tachycardic patients.
d. treating hypotension.
The vasoconstrictive effects of alpha1-adrenergic agonists, such as epinephrine, help produce hemostasis in skin and mucous membranes. These agents can increase blood pressure but are not the primary drugs used except in emergency situations. Alpha1 receptors in the radial muscles of the iris, not vasoconstriction, cause mydriasis. Reflex bradycardia is a side effect and not a clinical use of these agents.
A patient is admitted to the intensive care unit for treatment of shock. The prescriber orders isoproterenol [Isuprel]. The nurse expects this drug to increase tissue perfusion in this patient by activating:
a. alpha1 receptors to cause vasoconstriction.
b. alpha1 receptors to increase blood pressure.
c. beta1 receptors to cause a positive inotropic effect.
d. beta2 receptors to cause bronchodilation.
Isoproterenol is used for shock because of its actions on beta1 receptors in the heart. It has a positive inotropic effect, which improves cardiac output and thus increases tissue perfusion. Isoproterenol does not affect alpha1 receptors. Although it activates beta2 receptors to cause bronchodilation, this is not indicated for the treatment of shock.
A nursing student asks the nurse why epinephrine, and not other adrenergic agonists, is used to treat anaphylactic shock. What will the nurse tell the student?
a. "Epinephrine is the only adrenergic agonist that may be given parenterally."
b. "Epinephrine has the ability to activate multiple types of adrenergic receptors."
c. "Other adrenergic agonists have more severe adverse effects and are not safe in the doses needed to treat anaphylaxis."
d. "Other adrenergic agonists have little or no effects on beta2-adrenergic receptors."
Epinephrine is used to treat anaphylactic shock because of its ability to activate multiple adrenergic receptor types. Activation of beta1 receptors helps to increase cardiac output and improve blood pressure as well as suppress glottal edema. Activation of beta2 receptors helps to counteract bronchoconstriction. Activation of alpha1 receptors also causes vasoconstriction, which improves blood pressure. Isoproterenol may also be given parenterally but does not activate multiple receptor types. Other adrenergic agonists, such as albuterol, are more specific to beta2 receptors and have fewer side effects.
A nursing student asks why albuterol, which is selective for beta2 receptors, causes an increased heart rate in some patients. How should the nurse respond?
a. "Adrenergic agonists can lose their selectivity when given at higher doses."
b. "Bronchodilation lowers blood pressure, which causes a reflex tachycardia."
c. "Some patients metabolize the drug differently and have unusual side effects."
d. "Systemic effects are intensified with inhaled doses."
Although albuterol affects the beta2 receptors, at higher doses it may also activate beta1 receptors, causing an increase in the heart rate. Bronchodilation does not lower the blood pressure, and activation of beta1 receptors actually may increase it. Tachycardia is a common side effect. The inhaled route reduces the likelihood of systemic side effects.
A patient is receiving dobutamine [Dobutrex] as a continuous infusion in the immediate postoperative period. The patient also is receiving a diuretic. What adverse drug reactions are possible in this patient? (Select all that apply.)
A, B, E
Angina, dysrhythmias, and tachycardia are the most common adverse effects of dopamine; general anesthetics can increase the likelihood of dysrhythmias. Dopamine elevates blood pressure by increasing cardiac output. Diuretics complement the beneficial effects of dopamine on the kidney, so urine output would be increased, not decreased.
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