Matters of the Heart - Beta Blockers
Let’s talk cardiac pharmacology! Beta Blockers, in my opinion, are like the bread and butter of cardiovascular care medications. This classification of medication is commonly seen when caring for individuals with cardiovascular issues.
What are Beta Blockers?
Beta Blockers fall under the category of Class II Antiarrhythmics. If we are going to be technical about the name, Beta Blockers are technically Beta-adrenergic blockers. This is a classification of medications that block beta-adrenergic receptors. These receptors respond to catecholamines, such as norepinephrine and epinephrine.
When these adrenergic receptors (or adrenoceptors) are stimulated, it ignites a chain reaction within the cell that increase the transfer of calcium into the myocardial cells (myocytes). The increased calcium stimulates electrical impulses, which contracts the myocardial cells and, when stimulated together, a heartbeat.
Are you still with me?
If you’re not, its ok, that’s a lot to take in. More simply, Beta Blockers are medications that help to control the rate and rhythm of the heart, helping it beat more effectively.
Is that explanation a little easier to swallow?
As a side note, if you ever need a review to brush up on your A&P (Anatomy and Physiology) concepts, please be sure to check out Khan Academy and their series on Heart Depolarization. They also can help you brush up on other detailed A&P content with their videos and lectures. Their teaching material is always concise and makes the information easier to understand. You’re welcome for that piece of advice.
Beta blockers can block receptors in 3 areas of the body:
Beta 1 Receptors are primarily located in the tissue of the heart.
Beta 2 Receptors are primarily located in the lung tissue.
Beta 3 Receptors are primarily located in adipose tissue.
An easy way to remember which receptor a beta blocker acts on as follows:
Acts on the heart, we only have 1 heart.
Decreases the heart rate, and secondarily decrease the blood pressure.
Decreases the force of heart contractions.
Acts on the lungs, we have two lungs
Can decrease blood sugar due to interrupting glycogenesis.
Beta 3 Receptors are found in adipose tissues and excess adipose tissue gives you rolls like the number 3 has (I know, this one’s a stretch).
Beta Blockers can also be subdivided and classed as being selective or non-selective.
Non-selective Beta Blockers are indiscriminate in what beta-adrenoceptors they block, either beta 1 Receptors or beta 2 Receptors.
Beta Blocker List
Here’s a good picture to break down the different subclasses of beta blockers
By far, the most common beta blockers I come across in my everyday practice include Metoprolol (Lopressor), Atenolol, Carvedilol (Coreg), and Sotalol (Betapace). I’ve primarily seen Sotalol used in the advanced treatment of recurrent or chronic A-fib in the inpatient setting and regular (Daily) 12-lead EKGs are needed to assess QTc measurements to assess whether the medication dosage should be adjusted.
How do Beta Blockers work?
Beta Blockers block the adrenoceptors in the heart from the stimulation of norepinephrine and epinephrine (catecholamines) and enables a decrease in the firing rate of the SA and AV nodes, thus leading to a decrease in the heart rate.
Beta Blockers can also decrease the heart's workload by doing the following:
Slowing the heart rate and decreasing the heart’s oxygen requirements and decreasing afterload.
Decreasing the strength of contractions.
Remember that there are subclasses of beta blockers, Non-selective and Selective.
Non-selective Beta Blockers not only decrease the heart rate, because of blocking beta 1 receptors (heart), but they can also cause bronchoconstriction when beta 2 receptors are blocked (lungs). They block receptors more indiscriminately. Thus, Nonselective Beta Blockers, especially, should be used with caution in patients with respiratory disorders, such as Asthma, COPD, and Emphysema.
Selective Beta Blockers (also called cardioselective) have a greater affinity for blocking specific adrenoceptors, more discriminately, in this case, those located in myocardial (heart) tissue and cells. These cardioselective beta blockers solely work by blocking the myocytes response to adrenaline (epinephrine) creating a decreased heart rate and decreased heart muscle contractility.
It should be noted that all beta blockers, regardless of being cardioselective or non-selective, have the potential of negatively impacting those with respiratory issues, and may be contraindicated in some cases (see below). Use beta blockers with caution in those with emphysemic or constrictive respiratory issues.
Uses and Indications
High Blood Pressure, as a secondary method to treat hypertension, not first line in many cases.
Certain Beta Blockers, like Atenolol, are more effective in treating acute hypertension, particularly when administered intravenously.
Myocardial Infarctions (Post infarction care and as a preventative method)
Administration of Beta Blockers
If you learn nothing else from this post and series, please remember that whenever you give someone a medication that impacts the cardiovascular system, regardless of the route of administration, you should have, at minimum, a recent blood pressure and pulse rate (at least within 30-45 min of administration, possibly less than 15 minutes for some IV medications). You will avoid a lot of potential trouble by administering any cardiovascular medications with the knowledge of the Heart Rate and BP.
Have a recent BP and HR. If there are HR, MAP, or BP parameters hold the medication accordingly if the parameters aren’t met, and notify the provider. If Bradycardia or Hypotension are present and there are no parameters, consult with a more experienced nurse, a prescribing provider, and use your nursing judgment before administering the medication.
If available, have the most recent QT interval or Qtc interval measurements.
Having a knowledge of the most recent electrolyte values are helpful.
Having knowledge of a patient’s most recent renal lab values, such a BUN, Creatinine, and Creatinine clearance would be beneficial.
Mentally remember to monitor patient urine output (I&O’s) and urine characteristics as possible signs of renal impairment, which you can report to a prescribing provider.
Can give before meals for better absorption.
Patients should not abruptly discontinue beta-blocker therapy, particularly in the outpatient setting, emphasize this in teaching and encourage discussing changes in dosing or scheduling with providers, before making a change.
IV medications can either quickly do a lot of good or quickly do a lot of bad." So here are some tips to help you stay as close to “good” as possible:
The patient should ALWAYS actively be monitored on a bedside or a remote telemetry monitor when IV infusion or bolus injections of cardiovascular and vasoactive medications are administered.
By actively monitored, I mean when you push the medication, a licensed professional who is certified to interpret ECG/EKGs should be watching the monitor and heart rhythm/rate throughout the time you administer the medications. This can be yourself, or another qualified provider.
DO NOT PUSH IV cardiac or vasoactive drugs rapidly. This is for your patient’s safety, comfort, and for the preservation of peripheral IV sites.
Many of these medications are recommended to be pushed over 2-5 mins, according to the usage and concentration, always use a reputable drug reference, such as Mosby’s 2019 Nursing Drug Reference, or your facility pharmacist when considering how quickly an IV medication should be administered.
There are very few IV cardiac medications that are required to be administered rapidly.
Beta Blocker Side Effects
Nausea and Vomiting
Feelings of tiredness and weakness at the onset of therapy.
Beta Blocker Overdose
In the case of overdose, toxicity, or poisoning (whatever you want to label it as) with beta blockers, High-dose glucagon is considered to be a first-line antidote.
If the overdose manifests itself by causing bradycardia, hypotension, near-syncope, be sure to stop the therapy and contact a Physician or Advanced Practice Provider (APP: NP, PA, etc..). Of course, also activate your institutions emergency response system according to your unit and facility policies and nursing judgment.
Other Medications that may be used to reverse symptoms produced by an overdose of beta blockers are as follows:
Atropine - to treat bradycardia and increase the HR and Cardiac OutPut, especially when the patient is symptomatic.
In cases of worsening hypotension, using Trendelenburg Positioning (Bed tilted with head lower than feet) could be beneficial in some cases. Use your nursing judgment and assess the extent and severity of the hypotension and consider the patient's comfort.
The literature reports that Trendelenburg can be useful, but its effectiveness can vary greatly depending on pathology.
Contraindications, Precautions, and other considerations
A number of contraindications for beta-blockers are self-evident. Since beta blockers, by their nature, decrease the heart rate and contractility of the heart, if someone is experiencing bradycardia or decreased cardiac output, beta blocker administration should be non-existent or limited, according to the clinical assessment of a prescribing health care provider. The following are some conditions, situations, and medications that are considered contraindicated to Beta Blockers.
Pt. Experiencing Heart blocks, especially 2nd or 3rd degree AV Blocks
Tread carefully with those who have 1st degree AV blocks as well.
Moderate to Severe Renal Disease or impairment.
Those with COPD, Emphysema, Asthma, or similar inflammatory and constrictive respiratory disease processes.
Perform regular respiratory assessments when patients with Respiratory issues, as mentioned above, are on a beta blocker.
Sustained or Acute Bradycardia
Sustained or Acute Hypotension
Thyroid or Renal impairment and disease.
I personally have developed the habit of taking a HR and BP measure, myself, just before administering cardiac meds or meds that impact the cardiovascular system. As mentioned above, ALWAYS have a recent set of HR and BP measurements PRIOR to the administration of any cardiovascular medication. Recent, should less than 30-45 mins, at minimum, but remember to follow your institution's policy.
When it comes to quickly-absorbing oral medications or IV administration of cardiovascular medications, you may need to check follow up HR & BP measurements sooner and more frequently, as they take effect quicker.
Do not push an IV cardiac medication without a patient being on a hard-wire bedside monitor or a remotely monitored telemetry monitor.
If a patient is on a remotely monitored telemetry monitor, always ensure another licensed professional is aware that you are pushing a vasoactive or cardiovascular medication, so that they can monitor for abrupt changes in heart rhythm or rate that could indicate emergent situations.
It is preferred that you have a bedside monitor and observe the patient heart rhythm, yourself when pushing cardiovascular medications intravenously.
There are very few cardiac medications that should be administered via rapid IV push.
A diligent prescribing provider will give you hold parameters for both oral and IV beta blockers. If there are no parameters, be proactive and ask for parameters, early on. This keeps you from wondering if you should give a medication when a BP, HR, or MAP is “borderline”.
Remember, oral medications labeled ER (extended release) work over longer periods of time and have a longer a longer half-life. These oral medications (in tablet or capsule form) should not be crushed or chewed by the patient (yes I’ve seen people chew their meds).
Know the difference in the name of a medication in its standard and extended release formulations. For example Metoprolol Tartrate (Lopressor) = the standard normal half-life metoprolol. Metoprolol Succinate (Toprol XL) = the extended release option, with a longer half-life.
It’s not completely uncommon to see a patient on both on a combined therapy with an extended release medication, PRN doses of shorter acting medications in the inpatient setting, especially with people whose conditions are resistant to the therapy.
Always monitor a patient’s response to combined therapy. If you notice the patient trending towards hypotension, bradycardia, or if they develop symptoms of dizziness, syncope, or severe weakness, alert the prescribing provider before administering more of the medications.
Patients, especially in the initial few weeks of starting the therapy, should not change positions from lying to sitting or from sitting to standing, quickly. This will help prevent orthostatic hypotension and Syncopal episodes.
It’s not uncommon for patients to report mild weakness or tiredness with the initiation of therapy, but this usually resolves within a few weeks. Severe and worsening weakness and tiredness should be reported to the prescribing provider by the nurse, or the patient is in the outpatient setting.
Some individuals may find wearing support hose in preventing orthostatic hypotension.
Sources and References
Disclaimer: This material should be used to supplement your understanding of the cardiovascular system. Any use of the information given in this post series is at your own risk and should be verified prior to making it a part of your nursing practice. There may be affiliate links associated with some products but we promise that we will never recommend anything that we don’t use ourselves.