Antihypertensives: Beta Blockers Part 3

After going through the different kinds of volume depletion drugs, we’ll be discussing what beta-blockers are. Beta-blockers are commonly given to hypertensive clients to manipulate the conduction system of the heart.

Decreasing Blood Pressure

There are a couple of ways to lower blood pressure. First is taking off the workload by decreasing the fluid volume, through the use of diuretics and ACE inhibitors. And the second is to decrease the rate of conduction inside the heart through the use of beta-blockers.

Defining Beta-blockers

Beta-blockers are negative chronotropic drugs that block the SA node of the heart increased, inappropriate contractions. But how do beta-blockers work?

Beta-blockers block the beta-adrenergic receptors – beta-1 and beta-2. Beta receptors can be found either in the heart or the lungs. Beta-1 receptors can be found in the heart, while beta-2 receptors are inside the lungs. To easily recall this information, beta-1 is for the heart because there’s only one heart; on the other hand, beta-2 is for the lungs because there are two lungs. In the case of beta-blockers, they block receptors found inside the heart that triggers accelerated contractions.

Beta-Blocker Mechanism

If beta-2 is stimulated by giving a client beta-2 agonist, this will cause bronchial dilation. However, if beta-2 is provoked, beta-1 is also triggered; meaning, the heart rate will rise, leading to tachycardia. This is the reason why clients who are receiving treatment for breathing problems have increased heart rate. So, beta-blockers technically decrease heartbeats.

The “-Lol” Drugs

Beta-blockers end in “-lol,” like laugh out loud. Some popular examples are atenolol and metoprolol.

What to Watch-Out-For

There are four Bs that healthcare providers need to be aware of when administering beta-blockers. What are these four Bs?

  1. Bradycardia

Bradycardia means that the heart rate has dropped to less than 60 beats per minute. Obviously, the aim for giving beta-blockers is to slow down the client’s heart rate, but not to kill the client by continuously administering anti-hypertensive drugs. Therefore, to determine if it is safe to give beta-blockers to a client who is taking several anti-hypertensive drugs, blood pressure must be taken.

Since beta-blockers affect the beta receptors in the heart, there will be no direct effect on blood pressure, but it is essential to observe the client’s trend or status.

So, how are anti-hypertensive medications given?

Give the client the least heavy dose first. Meaning, volume depletion medications must first be given before messing with chronological or electrical conduction drugs. Some volume-depleting drugs are:

  • Diuretics
  • ACE inhibitors
  • Angiotensin II receptor blocker (ARBs)

Major nursing exams and the NCLEX® tend to ask trick questions that are related to this kind of dilemma. Remember that if the scenario is questionable, the answer is most probably to hold the next dose of anti-hypertensive.

  1. Decreased blood pressure

Another side effect of beta-blockers is depreciating blood pressure. As mentioned, beta-blockers do not directly affect blood pressure; however, since it influences stroke volume resulting to decreased cardiac output, there is a possibility of decreasing blood pressure as well.

  1. Bronchoconstriction

This might be a bit confusing, but the logic behind this side effect is that anytime beta-1 is blocked since it’s non-specific, beta-2 is also blocked. If albuterol is given, there is a probability of causing an increased pulse rate.

  1. Blood sugar

Beta-blockers interact with insulin release, masking the signs and symptoms of low blood sugar and bradycardia.

To check out our previous beta-blocker lectures, and to find out more nursing-related videos, drop by our Simple Nursing website and YouTube channel.

Cardiac Output: Systolic & Diastolic Blood Pressure

Blood pressure is determined by two factors – systolic and diastolic pressure. In this discussion, we’ll go through the traffic jam that happens within the blood vessels, the factors that influence pressure increase, and how peripheral pressure heightens.

The Traffic Jam

Think of your blood pressure as a morning drive with your car. If you’re driving on a freeway, there are only two things that matter to arrive at work on time – how many lanes are open and how many cars are on the freeway.

The most important between the two is the lanes that are open during that moment because, no matter how many the car is, for as long as the lanes opened are sufficient to sustain the volume, there wouldn’t be a traffic jam.

On the other hand, if there is only one lane that’s opened at that time, cars are going to be backed up, causing the traffic jam. A blocked freeway, or in this case, blood vessel, can either be due to a number of reasons, and either way, limited passage will cause bottleneck, resulting to increased pressure.

Factors that Shuts Down the Freeway

There are four different factors that influence the closing down of lanes or the narrowing of the pathways of the blood vessels. These four areas are essential in the therapeutic clinical objectives when dealing with blood pressure issues. So, what are the reasons why the lanes of the freeway are narrowing or shutting down?

  1. Increase platelet congregation

Platelet congregation is simply platelets surrounding or attaching to the lining of the blood vessels. As platelets attach to the vessels, it causes narrowing. Furthermore, tissue damage will occur.

  1. Stress

Increased stress is element that increases the risk of a narrowed pathway, this is because stress influences the increase of adrenaline which stimulates the sympathetic nervous system or the fight and flight response; thus, severe vasoconstriction occurs.

  1. Injury

Critical injury to certain sites, especially to the blood vessels, is also a qualifying factor for the constriction of passageways. What causes injury to the freeway?

  • Smoking
  • Diabetes – insulin is a corrosive agent that damages the lining of the blood vessels, causing inflammation and constriction
  1. Fatty deposits

High level of fats or cholesterol is detrimental to the body. Fats, much like platelets, attach to the lining of the blood vessels, causing the narrowing of the freeway. To prevent this from happening, high density lipoproteins (HDL) or the good cholesterol should be increased; while low density lipoprotein (LDL) or the bad cholesterol should be decreased.

Plaque Formation

Now, we have laid down the four main causes of the shutting down or narrowing of the freeway, which results to an increase in peripheral pressure. To review, we have platelet congregations, stressors, injuries, and fatty deposits.

Plaque is another thing that you need to take note of when understanding blood pressure. Plaque is just an inflammation of the veins wherein deposits underneath the vein have broken through and has protruded. Plaque is said to be one of the primary reasons for increasing peripheral pressure.

In our next lesson, we’ll be discussing how volume affects blood pressure when there is no narrowing of the pathways.