Treatment of HTN Flashcards
Resistance is influenced by ___ (indirectly) and ____ (directly)
Blood volume- indirect
Vessel diameter- direct
__% of all American adults have HTN
__% of adults over 65 have HTN
28%
60%
Blood pressure refers to
The force exerted by the blood upon walls of the blood vessels or chambers of the heart
HTN develops when
Blood volume is too high for the space available inside blood vessels.
What can cause an increase in blood pressure?
Increased CO or increased peripheral resistance
HTN
Sustained systolic BP of greater than 140 mmHg or sustained diastolic BP of greater than 90mmHg
4 classifications of blood pressure
Normal: less than 120/80
Pre-Hypertensive: 120-139/80-89
Stage 1: 140-159/90-99
Stage II: Greater than 160/100
Which populations have higher incidence of HTN
AA, middle age men, older
Family history increases risk
Environmental factors further predispose a person: Stress, high intake of sodium, smoking.
Why is arterial BP regulated within such a narrow range?
To provide perfusion of tissues without causing damage to vascular system. Especially arterial endothelium.
BP is directly related to
CO and peripheral resistance
Cardiac output is controlled by
HR, contractility, and filling pressure (Which is controlled by blood volume and venous tone)
Peripheral resistance is controlled by
Arteriolar tone
CO and peripheral resistance are controlled by which two overlapping systems
Baroreflexes and RAAS system
Baroreceptors act by:
Act by changing the activity of the sympathetic nervous system. Rapid, moment to moment control.
A fall in BP causes baroreceptors to send fewer impulses to cardiovascular centers in the spinal cord. Reflex response of increased sympathetic and decreased parasympathetic output. (results in vasoconstriction and increased CO)
RAAS system acts by:
Kidney provides long term control of BP by altering blood volume.
Baroreceptors in the kidney respond to reduced arterial pressure (AND to sympathetic stimulation of B1 receptors)
Kidney responds by increasing the release of renin.
Low sodium intake or greater sodium loss also results in release of renin
Which 3 stimuli trigger renin release
- Baroreceptors in the kidney notice reduced arterial pressure
- B1 stimulation thru the sympathetic system
- Decreased sodium intake or increased sodium release
RAAS flow starting with angiotensinogen
Angiotensinogen circulates in the blood and is converted to angiotensin I by renin, which is released by the kidney. Angiotensin I is biologically inactive. Angiotensin I is converted to Angiotensin II by ACE enzyme. Angiotensin II is active and is a potent vasoconstrictor, stimulates aldosterone secretion, increases peripheral resistance, decreases capacitance. Also may cause cardiac hypertrophy (myocardial fibrosis and apoptosis)
Role of aldosterone
Released by the adrenal gland. Stimulated release by angiotensin II.
Results in the reabsorption of salt from the kidney, resulting in the reabsorption of water. This will increase the volume of blood, which increases BP.
Effects angiotensin II has on the body
Potent vasoconstrictor: Increase peripheral resistance, decrease capacitance.
Stimulates release of aldosterone.
May cause cardiac hypertrophy: Myocardial fibrosis and apoptosis
Most antihypertensives lower BP by
reducing cardiac output and/or decreasing peripheral resistance. Some do a little bit of both.
Treatment strategies
Tailored to each patient
Usually use a combo- want to use different MOA
Must look at different factors including age, race, side effects, disease.
Tx example:
Vasodilator. Then add BB then add diuretic
Vasodilator: Will reduce peripheral resistance, but will result in reflex tachycardia and salt/water retention.
Add BB to decrease reflex tachycardia.
Add diuretic to decrease reflex salt/water retention.
Any of these 3 could work on their own, but some pts may need combos.
Angiotensin agents work to
Reduce peripheral resistance and blood volume.
Bc angiotensin causes constriction (increase peripheral resistance) and aldosterone release (increase blood volume)
Diuretic agents work to
Decrease sodium levels and blood volume.
Sympathetoplegic agents work to
Reduce peripheral resistance and decrease CO
Direct vasodilators work to
Decrease peripheral reisistance
Beta blockers work to
Decrease renin release, contractility, and HR
Most common reason for therapy failure
Lack of patient compliance
The pt is usually asymptomatic.
Pt may feel worse as BP is decreasing
Resistant hypertension
High BP that does not respond to tx. Remains high despite 3 drug regimen.
Most commonly use to:
Poor compliance
Excessive alcohol drinking.
Use of sympathomimetics, NSAIDs, or antidepressants.
Insufficient dose
Using multiple drugs with same MOA
RAAS system monitors
Na, K, Vascular volume, BP
