Sympathomimetic medications: Nursing pharmacology

Definitions & Key takeaways

Sympathomimetic medications are drugs that mimic the effects of the sympathetic nervous system. They work by mimicking the effect of endogenous catecholamines, like norepinephrine and epinephrine, and can be used to treat conditions such as cardiac decompensation, shock, anaphylaxis, bronchospasm, and bradycardia post-cardiac arrest. Some common examples of sympathomimetic medications include dobutamine, dopamine, norepinephrine, epinephrine, and isoproterenol.

Once administered, these medications stimulate two types of adrenergic receptors, alpha, and beta. With alpha-adrenergic receptor stimulation, vasoconstriction occurs, whereas stimulation of beta-1 adrenergic receptors causes increased heart rate and contractility, and stimulation of beta-2 adrenergic receptors causes vasodilation and bronchodilation.

Common side effects of sympathomimetics include gastrointestinal disturbances, hypertension, and arrhythmias. Nursing considerations for clients receiving sympathomimetics include monitoring their hemodynamic status; titrating doses as needed; monitoring for side effects; and assessing for the desired therapeutic response. Client education is focused on what to expect during treatment.

Chapters:

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Introduction0:00–0:24

Sympathomimetics are medications that mimic the effect of endogenous catecholamines, like norepinephrine and epinephrine.
As a result, these medications activate the sympathetic nervous system, which in turn triggers the fight or flight response, ultimately increasing the heart rate and blood pressure, as well as slowing down digestion.
This response maximizes blood flow to the muscles and brain. Now, sympathomimetic medications include dobutamine, dopamine, norepinephrine, epinephrine, and isoproterenol.

Sympathomimetic medications0:24–0:43

All of them are administered intravenously, while isoproterenol can also be given intramuscularly, and epinephrine can also be administered intramuscularly, as well as through endotracheal tube or inhalation.Once administered, sympathomimetic medications act by stimulating adrenergic receptors.

Mechanism of action0:43–2:33

Now, there are two main groups of adrenergic receptors: the alpha receptors, and beta receptors. Alpha adrenergic receptors are mainly located on the walls of blood vessels of the skin, as well as the gastrointestinal and genitourinary systems, and when stimulated, they cause vasoconstriction and decreased blood flow to these tissues.
On the other hand, beta receptors have two main subtypes: beta-1 and beta-2. Beta-1 adrenergic receptors are mainly located in the heart, and when activated, they increase the heart rate and contractility, which helps pump out more blood.
On the other hand, beta-2 adrenergic receptors are found on smooth muscle cells in the walls of blood vessels supplying skeletal muscles and the brain, so their activation leads to vasodilation and increased blood flow to these tissues; and in the lungs, they cause bronchodilation.
Each type of adrenergic agonists stimulate these receptors to a different degree, which makes them useful to treat different conditions.
But in general, all of them activate beta-1 receptors, so they all increase heart contractility, helping in the treatment of conditions where the cardiac output is decreased.Now, all of these medications can be used to treat cardiac decompensation and shock.
In addition, dopamine can also be used to treat bradycardia and post-cardiac arrest after shock. Norepinephrine is mainly used to treat acute hypotension and shock.
Epinephrine is used to treat cardiac arrest, shock, and anaphylactic reactions; and because of its action on beta-2 adrenergic receptors, it’s also useful to treat acute asthmatic attacks and bronchospasm.
Finally, isoproterenol is used in the treatment of cardiac arrest, episodes of heart block, congestive heart failure, shock, and bronchospasm that may occur during anesthesia.Now, most side effects of these medications are the result of their action on adrenergic receptors.

Side Effects2:33–3:14

Clients on sympathomimetics may also experience gastrointestinal side effects, such as nausea and vomiting. Sympathomimetics can also be associated with cardiovascular side effects, including hypertension, and tachycardia, while more serious side effects of adrenergic agonists include angina and arrhythmias, while excessive hypertension can even result in cerebral hemorrhage.
Dopamine, epinephrine, and norepinephrine have a boxed warning for extravasation, which can lead to tissue necrosis, sloughing, and gangrene.
Finally, epinephrine can cause hyperglycemia in clients with diabetes.As far as contraindications go, all sympathomimetic medications should be used with caution during pregnancy and breastfeeding, as well as in elderly clients and those with hypertension or coronary artery disease.

Contraindications and cautions3:14–4:41

In addition, dobutamine is contraindicated in clients with hypertrophic cardiomyopathy with outflow tract obstruction. On the other hand, norepinephrine should be used with caution when there’s hypovolemia or mesenteric or peripheral thrombosis, and clients on this medication should have adequate blood volume to avoid reduced blood flow, ischemia, and tissue hypoxia from the vasoconstriction.
Dopamine is also contraindicated in clients with tachyarrhythmias, ventricular fibrillation, pheochromocytoma, and hypovolemia.
Next, isoproterenol is contraindicated in clients with tachyarrhythmias or angina pectoris, as well as in those experiencing cardiac glycoside toxicity.
Finally, epinephrine shouldn’t be given to clients with closed-angle glaucoma and those having a non-anaphylactic shock.
Regarding interactions, dobutamine should not be combined with certain medications like COMT inhibitors, as it increases the risk of severe hypertension.
Dopamine, epinephrine, and norepinephrine shouldn’t be used in combination with monoamine oxidase or MAO inhibitors and tricyclic antidepressants or TCAs.
Finally, sympathomimetic toxicity is increased when combining sympathomimetics, and the risk of serious arrhythmias is greater.
Alright, when caring for a client prescribed norepinephrine to treat hypotension caused by septic shock, begin by assessing their hemodynamic status, including vital signs, central venous pressure, pulmonary artery pressure, cardiac output, cardiac index, ECG, and other parameters as needed; as well as their weight; orientation and level of consciousness; and their respiratory status and SpO2.

Nursing Considerations & Client Education4:41–6:18

Then, explain to your client or caregivers that norepinephrine will help increase their blood pressure by causing their blood vessels to constrict.
Also, let them know that medication will be given as a continuous infusion, and that the dose will be adjusted as needed, and reassure them that you will be monitoring closely to assess the client’s response to treatment.Now, after infusing the prescribed fluids, begin the norepinephrine infusion through your client’s central line, starting at the lowest prescribed dose and titrating as needed to maintain the target blood pressure.
During the infusion, continue to monitor their hemodynamic status, intake and output, and level of consciousness. Also, be sure to check for side effects like paresthesias or coldness of their extremities.
Lastly, monitor your client’s IV site for signs and symptoms of extravasation, such as pallor, swelling, and cool or firm skin near the catheter tip; if this occurs, immediately stop the infusion, notify the healthcare provider, and prepare to administer the antidote phentolamine mesylate locally into the subcutaneous tissue.Finally, when caring for a client receiving norepinephrine, be sure to closely monitor for side effects, and evaluate for the desired therapeutic response of blood pressure stabilization.
Alright, as a quick recap… Sympathomimetics are medications that mimic the effect of endogenous catecholamines, like norepinephrine and epinephrine, and can be used to treat conditions such as cardiac decompensation, shock, anaphylaxis, bronchospasm, and bradycardia post-cardiac arrest.

Review6:18–7:29

Sympathomimetic medications include dobutamine, dopamine, norepinephrine, epinephrine, and isoproterenol. Once administered, these medications stimulate two types of adrenergic receptors, alpha and beta.
With alpha-adrenergic receptor stimulation, vasoconstriction occurs, whereas stimulation of beta-1 adrenergic receptors causes increased heart rate and contractility and stimulation of beta-2 adrenergic receptors causes vasodilation and bronchodilation.
Side effects of sympathomimetics include gastrointestinal disturbances, hypertension, and arrhythmias. Nursing considerations for clients receiving sympathomimetics include monitoring their hemodynamic status; titrating doses as needed; monitoring for side effects; and assessing for the desired therapeutic response.
Client education is focused on what to expect during treatment.
Sympathomimetic medications: Video and Uses | Osmosis