Beta Blockers

Beta-adrenergic blockers, or just beta blockers, are a group of medications that are mainly used to treat cardiovascular conditions like hypertension, coronary artery disease and its manifestations like angina pectoris and myocardial infarction, as well as heart failure and arrhythmias. Beta blockers can also be used to treat essential tremor, glaucoma, and as a prophylactic treatment of migraine attacks.

Now, beta blockers work by blocking beta receptors, of which there are three types, known as beta 1, which are mainly found in the heart and kidneys; beta 2, found in the lung bronchioles as well as the arteries of skeletal muscles; and beta 3, found in adipose tissue. So beta blockers are classified into two main groups; nonselective and selective.

Nonselective beta blockers can block both beta 1 and beta 2 receptors, and include nadolol, propranolol, pindolol, and sotalol. On the other hand, selective beta blockers only block beta 1 receptors, and include atenolol, metoprolol, carvedilol, and nebivolol. So keep in mind that all beta blockers end in -lol (which is pretty funny), and they can be administered orally, intravenously, or even via the ophthalmic route.

Once administered, beta blockers block beta receptors, thereby preventing the catecholamines norepinephrine and epinephrine from binding and activating them. As a result, beta blockers decrease the sympathetic nervous system response.

Now, the main therapeutic effects of beta blockers come from the blockade of beta 1 receptors in the heart, which decreases heart contractility and slows the conduction through the atrioventricular or AV node. This helps decrease the heart rate, which ultimately decreases the cardiac output. In addition, the blockade of beta 1 receptors in the kidneys decreases the release of renin, which stimulates the adrenal glands to release aldosterone, which in turn acts on the kidneys to induce water and sodium reabsorption. So with beta blockers, there will be less renin and aldosterone, which results in natriuresis, or water and sodium excretion, reducing blood volume.

Therefore, beta blockers effectively lower the cardiac preload and the blood pressure, and can be useful for clients with hypertension. Now, when beta blockers decrease the heart rate, cardiac output, and blood volume, the net result is a decrease in the workload on the heart. This also makes them an appropriate choice for the treatment of heart failure. In addition, beta blockers help decrease the myocardial oxygen demand. This is particularly important in coronary artery disease, like angina pectoris and myocardial infarction.

Now, the most common side effects of beta blockers result from excessive blockade of beta 1 receptors in the heart, and these include bradycardia, hypotension, fatigue, and dizziness. In addition, beta blockers can cause neurological side effects like headache, depression, hallucination, and sleep problems, like insomnia and nightmares.

Male clients on beta blockers may also experience decreased libido and erectile dysfunction. Side effects can also result from blockade of beta 2 receptors, especially by the nonselective beta blockers, but also by the selective beta blockers when used in high doses. In the bronchi, this results in bronchoconstriction, or bronchospasm, which decreases airflow to the lungs and leads to dyspnea. Finally, beta blockers have shown to cause certain metabolic changes like hyperglycemia, hypertriglyceridemia, and hyperkalemia.

Moreover, beta blockers can lead to hypoglycemia unawareness, where a client with diabetes, develops hypoglycemia but does not experience the typical hypoglycemic symptoms mediated by epinephrine, like tachycardia, palpitations, tremor, and anxiety.

As far as contraindications go, beta blockers should be avoided in clients with bradycardia, hypotension, or decompensated heart failure. They are also contraindicated in clients who have a second or third degree AV block. Beta blockers should be used with caution in clients with asthma and chronic obstructive pulmonary disease, or COPD, due to their bronchoconstrictive effect, as well as in clients with diabetes due to their hyperglycemic effect. Caution should also be taken in clients with Raynaud phenomenon, a condition where clients experience recurrent vasospasm of the blood vessels supplying their fingers and toes, and this can be exacerbated by the use of beta blockers. Finally, these drugs should be used with caution in clients with severe hepatic and renal diseases, since they are metabolized and excreted by the liver and the kidneys.

Now, if your client is prescribed a beta blocker, start by performing a baseline assessment, including vital signs. Review their laboratory test results, noting their renal and hepatic function tests, electrolytes, especially sodium and potassium, blood glucose, and lipid panel. When the medication is prescribed for hypertension, assess your client for orthostatic hypotension. On the other hand, when the medication is prescribed for angina, determine the frequency and duration of angina attacks. If the medication is prescribed for an arrhythmia, also review your client’s most recent ECG. Lastly, when the medication is prescribed for heart failure, be sure to assess your client’s weight, lung sounds, and for the presence of edema or dyspnea.

Next, let your client know that hypotension can occur while taking their medication, so instruct them to change positions slowly when moving from a lying or seated position. If your client also has diabetes, be sure to let them know that their medication can mask signs of hypoglycemia, such as tachycardia and tremors; advise them to check their blood glucose regularly and to be aware of other symptoms, such as fatigue, hunger, and difficulty concentrating. And finally, ensure your client understands that they should not abruptly stop taking their medication due to the risk of rebound hypertension.

Be sure to explain how, in addition to their medication, an important part of their healthcare regimen includes dietary modifications, regular activity as tolerated, weight control, moderate alcohol intake, and smoking cessation. Then, teach them how to take their pulse and blood pressure at home, and remind them to contact their healthcare provider if they experience symptoms such as bradycardia, hypotension, hypertension, dyspnea or the development of edema.

Finally, be sure to periodically monitor your client’s heart rate, blood pressure, ECG, and evaluate for the therapeutic response, including normalized blood pressure or heart rhythm, decreased incidence in anginal pain, and absence of symptoms of heart failure.

Alright, as a quick recap … Beta blockers are medications used primarily to treat cardiovascular conditions like hypertension, myocardial infarction, heart failure, and arrhythmias. These medications work by blocking beta receptors in the heart, lungs, and kidneys, which results in decreased heart rate, blood pressure, cardiac workload, and myocardial oxygen demand. Side effects of these medications include fatigue, headache, insomnia, erectile dysfunction, orthostatic hypotension, and hypoglycemia unawareness.

When caring for a client taking a beta blocker, nursing considerations include performing a baseline assessment, and monitoring for side effects and the therapeutic effects of the medication. Client teaching is focused on self-monitoring, lifestyle modifications, and when to contact their healthcare provider.