HTN Flashcards
How does the renin-angiotensin-aldosterone system work?
- Renin is an enzyme secreted by specialized cells in the kidney when BP falls or decrease in sodium flowing through kidney tubules
- once in blood, renin converts to inactive liver protein (angiotensin I)
- when passing through lungs, angiotensin I is converted to angiotensin II (potent natural vasoconstrictors)
- angiotensin converting enzyme (ACE) finishes the process
What is the renin-angiotensin-aldosterone system?
key homeostatic mechanism that controls BP and fluid balance
Angiotensin II
- potent natural vasoconstrictor
- secretes ADH and aldosterone
Aldosterone
hormone from adrenal cortex
increases sodium reabsorption in the kidneys
helps the body retain water (increases blood volume and raises BP)
ADH
hormone from posterior pituitary
enhances the conservation of water by the kidneys (increases BP by increasing blood volume)
Angiotensin-converting enzyme (ACE) inhibitors
Block the affects of angiotensin II and aldosterone levels to decrease BP by lowering peripheral resistance and decreasing blood volume
Angiotensin II receptor blockers (ARBs)
block receptors for angiotensin II in arteriolar smooth muscle and in the adrenal gland
causes BP to fall
arteriolar dilation and increases sodium excretion by the kidneys
(different from ACE inhibitors because it blocks the action of angiotensin II after it is formed)
Hypertension
consistent elevation of systemic arterial BP
Primary, idiopathic or essential HTN
no identifiable cause
90%
Secondary HTN
caused by identifiable factors
ex. excessive secretion of epinephrine by the adrenal glands or by narrowing of the renal arteries
10%
Non pharmacological tx of HTN
● Exercise
● Diet
● Smoking cessation
● Alcohol intake
Nutritional therapy of HTN
● DASH diet (dietary approaches to stop hypertension)
● Low in saturated fat, total fat, and cholesterol
● High in fruits, vegetables, and low fat dairy foods
● Whole grains, poultry, fish, and nuts
● Low amounts of fats, red meats, sweets, and sugared beverages
● High in potassium, calcium, magnesium, protein and fiber
● Lower in salt and sodium
○ Sodium circulating in blood, higher BP
Recommendations for HTN
maintenance of healthy weight (weight loss is recommended for those who are overweight)
moderate activity increases strength of heart to improve BP
Factors that affect BP
- peripheral resistance
- fluid volume
- cardiac output
Cardiac output
volume of blood pumped per minute
higher CO = higher BP
CO determined by HR and stroke volume (amount of blood pumped by a ventricle in one contraction)
Peripheral Resistance
turbulence-induced friction in the arteries
Peripheral Resistance
turbulence-induced friction in the arteries
Baroreceptors
sense pressure within large vessels
Chemoreceptors
recognize pH levels of oxygen and CO2 in the blood
Stress
causes BP to rise
Depression, lethargy
BP lowers
Systolic BP
pressure in the arteries when the ventricles in the heart contract
Diastolic BP
When the pressure falls from the ventricles relaxing and not ejecting blood
Risks
When BP rises, the heart has to work harder to eject blood into the circulation
causes
- ventricular hypertrophy (thickening of vessel walls)
- angina, MI, CVA, peripheral vascular disease
- HF
- Kidney failure
- blindness
Guidelines to management of HTN
healthy BP is in the 115/75 range
first approach is a modifiable lifestyle
if pressure does not change… drugs can be added
Pharmacotherapy of HTN
Diuretics, ACE inhibitors, Angiotensin II receptor blockers, calcium channel blockers, beta-blockers
then… added vasodilators or alpha 2 agonists
used to reduce morbidity and mortality
individualized to pts risk factors, comorbid med conditions and degree of BP elevation
