(Part 2)

Part 2 will discuss:

• Physiology of blood pressure regulation,
• Medications to help control hypertension

Blood pressure regulation is a complex process involving a series of body systems, hormones and input from the nervous system all working together to achieve and maintain homeostasis.

As this is a complex topic, we will keep our focus on systems that control blood pressure: one is the RAAS system, the other is the baroreceptor reflex. Both systems rely on input from hormones, receptors, and organs to help maintain a healthy blood pressure. In addition, nervous system responses (sympathetic, parasympathetic and/or autonomic) along with vagal nerve activity help regulate blood pressure. Our focus will be primarily on the hormones, systems and organs involved in blood pressure regulation.

RAAS, the system that controls long term blood pressure

The renin-angiotensin-aldosterone system (RAAS) is a complex multi-organ endocrine (hormone) system involved in the regulation of blood pressure. It regulates sodium and water by balancing fluid and electrolyte levels and regulates sodium and water absorption in the kidney. When this system is working properly, RAAS is activated when there is a drop in blood pressure (such as reduced blood volume). Once RAAS is activated it signals systems and hormones to increase water and electrolyte absorption in the kidney. This compensates for the drop in blood volume, which increases blood pressure.

Several organs, tissues and glands are involved in the RAAS, including:

• Kidneys
• Adrenal glands
• Lungs
• Heart
• Blood vessels
• Pituitary gland

Note, there are several other hormones such as thyroid and corticosteroids that play a part in blood pressure control. These hormones can indirectly play a part in blood pressure regulation.

What are the steps in renin-angiotensin-aldosterone system (RAAS)?

Five minute scholar has a simple video that briefly explains the process

1. When blood pressure falls, kidneys release renin, an enzyme into the bloodstream
2. Once released, renin splits a protein produced by your liver called angiotensinogen. The resulting split of this protein produces the hormone called angiotensin l. This hormone is inactive.
3. In the lungs and kidneys, angiotensin converting enzyme (ACE) converts angiotensin l to angiotensin ll, an active hormone. This hormone causes small arteries to constrict, which in turn increases blood pressure. It also causes the pituitary gland to release antidiuretic hormone (ADH), also called vasopressin, and the adrenal glands to release aldosterone (a steroid hormone).
4. Aldosterone and ADH work together and cause the kidneys to retain sodium. In addition, aldosterone causes kidneys to excrete potassium through urine.
5. Water retention is the result of the increase in sodium, which in turn increases blood volume and blood pressure.

Short term blood pressure control

A short video explaining baroreflex regulation

(regulated by the nervous system and neurotransmitters)

There are baroreceptors located in the walls of blood vessels and the heart. They respond to sudden changes in blood volume-which signal the cardiovascular center of the brain to adjust the change in blood pressure. If baroreceptors detect a low blood pressure, it triggers vasoconstriction (narrowing of blood vessels) to increase the blood pressure. If high blood pressure is detected, vasodilation (widening of blood vessels) lowers the blood pressure.

In addition, there are renal baroreceptors, which are located within the kidneys. When these baroreceptors sense a sudden change in blood pressure (low blood pressure), it triggers the RAAS system to activate. The immediate response from baroreceptors results in short term blood pressure control until the RAAS system can take over.

Drug classes to control blood pressure

The following are just a few of the many medications used to control high blood pressure. Many of these drugs have other uses, from treating congestive heart failure to reducing likelihood of stroke or heart attack.

Ace inhibitors Lisinopril (Prinivil, Zestril) benazepril (Lotensin), enalapril (Vasotec) and others

ACE inhibitors prevent an enzyme in the body from producing angiotensin II which narrows blood vessels.

Calcium channel blocker – Amlodipine (Norvasc), diltiazem (Cardizem, Tiazac) and others

Calcium causes the heart and arteries to squeeze (contract) more strongly. By blocking calcium, calcium channel blockers allow blood vessels to relax and open.

Beta blockers (Not usually a first line drug to be used) Metoprolol (Lopressor, Toprol XL), atenolol (Tenormin) and others

Beta blockers work by blocking the effects of the hormone epinephrine, also known as adrenaline.

They cause the heart to beat more slowly and with less force, which in turn lowers blood pressure. They also help widen veins and arteries to improve blood flow.

Central agonist class-Clonidine (Catapres)

Central-acting agents lower heart rate and reduce blood pressure. This drug blocks signals from the brain to the nervous system that increase the heart rate and narrow blood vessels. As a result, the heart doesn’t pump as hard and blood flows more easily through the body’s veins and arteries.

Diuretics- Hydrochlorothiazide (Hydrodiuril, Microzide), furosemide (Lasix) spironolactone (Aldactone)

Diuretics work by reducing the volume in liquid in the body by releasing sodium and water. This in turn lowers blood pressure.

Part 1

High blood pressure (HBP) has been called the silent killer and with good reason. It is estimated that at least 20 percent of the population with high blood pressure have no symptoms.

In part 1 we will discuss:

• Symptoms of hypertension
• Health risks of uncontrolled hypertension
• Stages of hypertension
• Types of hypertension
• How to take blood pressure at home

Part 2 will discuss:

Physiology of blood pressure regulation, lifestyle, nutrition, and medications to help control hypertension.

Symptoms associated with hypertension:

• Ringing in ears
• Headache
• Dizziness
• Confusion
• Visual disturbances
• Difficulty breathing
• Chest pain
• irregular heartbeat
• In severe cases blood in urine

In the US alone nearly half of adults in the United States (47%, or 116 million) have hypertension, defined as a systolic blood pressure greater than 130 mmHg or a diastolic blood pressure greater than 80.

Health Risks of Uncontrolled Hypertension

Uncontrolled hypertension increases your risk of kidney disease, cognitive decline, heart disease and stroke and more.

Stages of Hypertension

(The top number is systolic and measures the pressure in your arteries when your heart beats

The bottom number is diastolic -when the heart muscle relaxes.) 

All blood pressure measurements over 120/80 mm Hg are considered elevated in adult population

As of 2021 AHA blood pressure guidelines:

• Normal = less than 120 and less than 80
• Elevated = 120-129 and less than 80
•  Stage 1 = 130-139 or 80-89
• Stage 2 = 140 or higher or 90 or higher
• Hypertensive Crisis (call your care provider immediately) = Higher than 180 and/or higher than 120

Types of Hypertension

Primary Hypertension

Caused by one or more of the following: poor diet, smoking hereditary alcohol, lack of exercise, obesity.

• Blood pressure is high on three or more visits to care provider.
• May have no symptoms, but you may experience frequent headaches, tiredness, dizziness, or nose bleeds.

Secondary Hypertension 

Caused by a medical condition or medication.

 Examples include:

•  Airway obstruction during sleep and sleep apnea.
• An abnormality in the arteries supplying blood to the kidneys
• Adrenal gland tumors
• Thyroid disease
• Medications that can cause HPB:
• Pseudoephedrine, (Sudafed) 
• NSAIDS (non-steroidal anti-inflammatory drugs 
• Select antidepressants
• ADHD medications
• Birth control pills
• Decongestants
• Steroids and immunosuppressants

Resistant Hypertension

• Defined as 3 or more hypertension medications prescribed and blood pressure still not controlled.
•  20-30 percent of HBP patients have resistant hypertension. 
• May be genetic.
• More common in obese, older female patients. 
• Underlying cause may be diabetes or kidney disease. 

Isolated Systolic Hypertension 

• Blood pressure defined as systolic over 140, diastolic is normal- below 90. 
• Most common in people over the age of 65 and is due to the loss of elasticity in the arteries.

Malignant Hypertension 

• Rare, occurs in less than 1 percent of patients diagnosed with high blood pressure. 
• More common in younger adults, especially African American men.
• This hypertension type occurs in only about 1 percent of people with hypertension.
•  It is more common in younger adults, African American men, and women who have pregnancy toxemia.
• Blood pressure rises rapidly and can be a medical emergency.  
• Symptoms include numbness in the arms and legs, blurred vision, confusion, chest pain, and headache.

White Coat Syndrome

• White coat syndrome is a condition in which your blood pressure is high at your healthcare provider’s office, but you get a normal reading at home.
• Can be an underlying risk for future health problems.
• Left untreated, patients have a 36 percent increased risk of heart disease, 33 percent increased risk of death and 109 percent increased risk of death from heart disease.
• Previously believed this syndrome was exclusively due to anxiety from clinic visits, however closer monitoring of blood pressures taken outside clinic setting point to unstable blood pressure readings. 

How to Take Blood Pressure at Home

Here is a short video on how to properly take blood pressure

Blood pressure should be taken at the same time in the same setting as often as your care provider recommends.

Excerpt from AHA

• Don’t eat or drink anything 30 minutes before you take your blood pressure.
• Empty your bladder before your reading.
• Sit in a comfortable chair with your back supported for at least 5 minutes before your reading.
• Put both feet flat on the ground and keep your legs uncrossed.
• Rest your arm with the cuff on a table at chest height.
• Make sure the blood pressure cuff is snug but not too tight. The cuff should be against your bare skin, not over clothing.
• Do not talk while your blood pressure is being measured.
• Take 2 readings, at least 1-2 minutes apart
• Log your results. Attached is a pdf supplied by the AHA to log your readings