Beta Blockers NCLEX Pharmacology Review

Beta blockers are medications that help decrease blood pressure, slow down the heart rate, and treat dysrhythmias. This review will discuss the mechanism of action of beta blockers, what conditions they treat, nursing implications, side effects, and patient education.

Don’t forget to take the beta blockers quiz after reviewing this material.

Beta Blockers Lecture

Beta Blockers Nursing Pharmacology Review

Name?

Beta blockers block the BETA receptors sites in the body so norepinephrine and epinephrine can NOT bind to the receptor site and elicit a sympathetic nervous system response.

Sympathetic nervous system: it’s the “fight or flight system”….it works to save your life from danger.

When BETA receptors sites are stimulated by the SNS and have norepinephrine and epinephrine bind to them, the person can experience (note these are just some of the responses created by the sympathetic nervous system):

• Increase heart rate and blood pressure
  • This increases cardiac output and the workload on the heart, but it requires a lot of oxygen demand by the myocardium.
• Increase strength of heart contractions
  • This helps to increase cardiac output.
• Bronchodilation
  • The bronchioles will dilate so breathing can be easier and more oxygen can enter the blood. Remember this oxygen is needed because the myocardium demands it for this type of nervous system response.
• Increase blood sugar for energy via glycogenolysis in the liver.

Beta blockers will block many of these actions, and this can be helpful in certain conditions when the workload of the heart needs to be decreased or the heart is beating too fast (dysrhythmias).

It’s very important to know that there are different types of beta receptors in the body….beta 1, beta 2, and beta 3.

Beta 1 receptors are mainly located in the HEART (remember you have one heart) and in the kidneys (specifically the juxtaglomerular cells that release renin).

Beta 2 receptors are located in the bronchioles of the LUNGS (remember you have two lungs), GI system, vascular smooth muscle and skeletal muscle, and ciliary body of the eye.

Beta 3 receptors are located in the fatty/adipose tissue of the body.

Types of Beta Blockers

All generic beta blockers names end in “LOL”.

Selective beta blockers are selective to only beta 1 receptors. These medications are sometimes referred to as cardioselective because they mainly target the heart since it’s mainly made up of beta 1 receptors.

• Atenolol, Esmolol, Metoprolol etc.

Nonselective beta blockers block BOTH beta 1 and beta 2 receptors. They’re not selective to one certain type of beta receptor. Therefore, they will target the heart and kidneys too, but will also target the GI system, LUNGS, vascular smooth muscle etc. These medications have more of a peripheral effect than the selective beta blockers.

It’s important to remember what patient populations cannot take the nonselective beta blockers and side effects they may cause for exams.

• Propranolol, Sotalol, Timolol etc.

Mechanism of Action of Beta Blockers (how they affect the body)

• Slow heart rate (both selective and nonselective)
  • Beta receptors (mainly beta 1) are in the cardiac nodal tissue and conduction system of the heart. These areas control our heart rate. Beta blockers slow down how they work, so they’re helpful with dysrhythmias like supraventricular tachycardia.
    • Monitor for AV blocks like 2 or 3 degree and severe bradycardia (contraindicated)
    • Mask tachycardia during hypoglycemic episodes in diabetics because these medications keep the heart rate from increasing (remember they slow down the heart rate).
  • Decrease the strength of contractions (both selective and nonselective)
    • Beta receptors (mainly beta 1) are in the cardiac myocytes that control the strength of the heart’s contractions. Beta blockers cause a negative inotropic effect because they make the contractions weaker. This helps ease the workload on the heart and decrease oxygen consumption by the myocardium (great for treating stable angina due to coronary artery disease).
      • Watch for the development or worsening of heart failure…not to be used in patient with uncompensated heart failure or cardiogenic shock.
    • Lowers blood pressure (both selective and nonselective)
      • Beta receptors (mainly beta 1) are in the juxtaglomerular cells of the kidneys. Beta blockers will prevent angiotensin II from being created in the RAAS because it inhibits the release of RENIN by the juxtaglomerular cells. Remember angiotensin II normally causes vasoconstrictor, but there will be vasodilation instead and the influence of aldosterone will be decreased (so less water is reabsorbed by the kidneys) and this will decrease blood volume and in turn decrease the blood pressure.
        • Watch for hypotension.
      • Decrease intraocular pressure (only nonselective)
        • The ciliary body of eye has beta 2 receptors. The ciliary body of the eye is responsible for the production of aqueous humor. In patients with glaucoma, the high eye pressure is high due to a high amount of aqueous humor collecting in the eye. Nonselective beta blockers (example eye drops like Timolol) will decrease the production of aqueous humor and help decrease intraocular pressure.
      • Bronchoconstriction (only nonselective)
        • Nonselective affect beta 2 receptors which are found in the bronchioles of the lungs. These medications should NOT be used in patients with asthma or COPD due to the risk of bronchoconstriction.
      • Hypo/hyperglycemia (only nonselective)
        • Educate the diabetic patient to monitor glucose closely.
      • Peripheral vasoconstriction (only nonselective)
        • Avoid in patients with peripheral vascular disease. These medications may cause cold feet and hands and erectile dysfunction.

Used For?

Hypertension, stable angina (CAD), dysrhythmias (example SVT), compensated heart failure, migraines, glaucoma (example: Timolol), tremors, anxiety

Side Effects, Responsibilities, Education?

“Beta Block”

Bradycardia and blocks….2 or 3 degree heart blocks

• monitor EKG and teach patient to monitor heart rate at home for bradycardia

Exacerbate heart failure due to negative inotropic effect

• monitor for pulmonary edema, swelling in extremities, jugular venous distention, weight gain, I and O’s, daily weights…TEACH patient to monitor self at home

Taper off (beta blockers are typically tapered off over 2 weeks or so)… TEACH patient to NEVER just stop taking because the body will have withdrawal issues like rebound hypertension, ischemia that leads to angina etc.

Asthma & COPD patients can’t have nonselective beta blockers due to bronchoconstriction… Propranolol, Sotalol, Timolol etc.

Blood glucose monitored closely in diabetes (TEACH). They need to monitor for hypo/hyperglycemic AND the masking of hypoglycemia due to NO TACHYcardia experienced with blood glucose drops.

Low blood pressure (hypotension)…TEACH patient to monitor blood pressure at home.

Orthostatic hypotension: monitor and teach….slowly changes positions when going from a sitting to lying position to standing.

Circulation impaired due to peripheral vasoconstriction (NONselective)

• peripheral circulation is circulation to the vessel to the hands, legs, feet, and arms
• Erectile dysfunction, cold feet and hands, leg cramps…NOT for patient with peripheral vascular disease

Know overdose signs and symptoms: Bradycardia, heart blocks, low blood pressure, mental status changes: very lethargic or fainting, difficulty breathing due to bronchospasm, heart block… TEACH patient to monitor for these as well.

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