PPT 11: antihypertension Flashcards
What is the equation to calculate MAP
DBP+1/3(SBP-DBP)
What are factors that affect blood pressure?
peripheral resistance
vessel elasticity
blood volume
cardiac output
What is the Hydraulic equation
BP=CO x PVR
What are the 3 main sources of peripheral resistance?
blood vessel diameter
Blood viscosity
total vessel length (overweight ppl have inc. # of vessels)
where are baroreceptors located?
carotid arteries
aortic arch
How do the kidneys attempt to fix hypotension?
RAA cascade: hypotension in renal arterioles stimulates renin production. Renin -> angiotensin 1 -> angiotensin 2
angiotensin 2 causes vasoconstriction, stimulates aldosterone (inc. sodium absorption, intravascular volume)
What are the 4 types of antihypertensive agents?
diuretics
sympathoplegics (a2 agonists)
direct vasodilators
anti-angiotensins
Why is methyldopa better than clonidine for pregnant women?
Doesn’t cross the placental barrier like clonidine does
used for 2nd and 3rd trimester HTN
BP maintained by regulating:
- cardiac output (systolic)
- peripheral vascular resistance (diastolic)
What is systolic pressure? What is the normal range?
peak arterial pressure (120 mmHg)
What is diastolic pressure? What is the normal range?
lowest arterial pressure (70 - 80 mm Hg)
______ propels the blood to the tissues
MAP
What are the causes of primary hypertension?
- CV disease - most common
- obesity, age (over 40), diabetes, heredity, stress, smoking, renal failure, CV disease, stroke
Differentiate between the stages of hypertension
Normal - 120/80
Prehypertension (between)
Hypertension 140/90
Stage 1 (between)
Stage 2 - 160/100
What is driving venous pressure?
back pressure driving venous tone
skeletal muscle squeezes veins
one way valves
Cardiac output equation
CO = SVxHR
What are the four anatomic sites of BP control?
- Resistance - arterioles
- capacitance - venules
- pump output - heart
- volume - kidneys
Cardiac output is a function of what 3 things?
- Stroke volume
- Heart rate
- Venous capacitance (Preload)
How much do diuretics typically lower BP?
Lower BP – 10-15 mm Hg in most patients
What are the main sympathoplegics used for lowering BP?
Clonidine and methyldopa
Dexmedetomidine (sedation)
How do sympathoplegics lower BP?
- Primary antihypertensive activity due to α agonist activity in brainstem, decreasing sympathetic stimulation
- Bind more tightly to α2 than α1
What kind of agonist is clonidine?
Partial agonist
Why can’t clonidine be given to a pregnant patient?
Lipid soluble, rapidly enters brain
Clonidine works to lower BP by stimulating the alpha receptors in the ________
arterioles
What are more common uses for clonidine?
ADHD, Tourettes, Withdrawal symptoms
- Off label use: Anxiety, PTSD; Sedative – prolong anesthesia
What are the side effects of clonidine?
Sedation, Dry Mouth
Which adrenoceptor antagonists can be used to lower BP?
Beta Blockers - Propanolol, Metropolol, Atenolol, Esmolol, Labetolol
Alpha 1 blockers - Phentolamine, Prazosin, Terazosin, Doxazosin
How do alpha 1 blockers lower BP?
- Block α1 receptors in arterioles and venules
- Dilates both resistance and capacitance vessels
- BP is reduced more in upright position
- Retention of salt and water
- Most effective when used with a β blocker or a diuretic
How do beta blockers lower BP?
- Lowers BP, prevents reflex tachycardia
- Decreases cardiac output
- Inhibits renin production
Differentiate between beta selectivity of beta blockers and their use in lowering BP
Propanolol - Antagonizes β1 & β2 receptors
β1 selective - Metoprolol, Atenolol, Esmolol (ultra-short acting), and Labetolol
- β1 has less systemic side effects and more selective for cardiac β1 receptors