Hypertension, hypotension and therapeutic interventions Flashcards
What is the equation for aterial blood pressure
ABP = CO x TPR
How can we lower blood pressure
well if we look at the equation
drugs that can lower CO, and lowerTPR can reduce blood pressure
How do we physiologically maintain our blood pressure
Baroreceptor reflex
- Autonomic nervous system
- this is very fast response
- could target and
- this is very fast response
- Heart
- Vessels
Renin-angiotensin-aldosterone system
- Kidneys → alter blood volume → slower
- Vessels → this is faster
this means there’s lots of places we can target drug wise
How do we determine drug choice
what factors do we look at
- Age
- Genetics (Black African/Caribbean)
- they also take comorbidities/health status
- includes pregnancy
What are the classes of drugs
Class A, C, D, B
What are class A drugs
Angiotensin-converting enzyme (ACE) inhibitors
Angiotensin (AT1) receptor antagonists
Name a class A drug (ACE)
Eg lisinopril, enalapril… end with pril
How do class A drugs wotk
- lower angiotensin 2
- ACE enzyme is inhibited to stop the conversion of angiotensin 1 to 2
- we use ACE to degrade vasodilator kinins e.g bradykinin
- which reduces TPR and CO
What are the side effects of class A drugs
- Dry cough( can disrupt sleep)
- may be due to kinins in the lungs not as great degradation which can act as irritants
- may be due to demographics (some evidence evidence→ women more than men, older age, and having an east asian origin may be your more likely t have a cough)
-may cause severe sudden hypotension is taken with diuretics
What is the first line of drugs given to patients that have mild uncomplciated, younger patinets
ACE inhibtors
What other class A drug do we have
Angiotensin (AT1) receptor antagonists
Name some AT1 receptor antagonists
Eg Losartan, irbesartan…. (sartan ending)
How do AT1 receptor antagonists work
Mechanism
- decrease vasoconstriction by decreasing angiotensin 2
- indirect effect
- have antagonist action at AT1 receptor
- this decreases TPR and CO
- they have no major side effects as yet (not associated with cough) → maybe because they don’t affect ACE itself, which affects the kinins
we may use this if ACE doesnt work
What are class C drugs
Calcium channel blockers
Name a class C drug
Eg amlodipine (pine ending)
How do class c drugs work on hypertension
the whole mechanism is not there, but you should know it
reduces TPR which reduces blood pressure
What are the side effects of class c drugs
- impact on heart function
- have effect in smooth muscle in GI tract for example
What is the first line of treatment for uncomplicated, mild hypertension
Class C drugs
What are class D drugs
Diuretics (D for diuretics)
Drugs act at various sites in the kidney nephron
Clinically - First line treatment for uncomplicated, mild hypertension
How does Class D drugs
-Has a biphasic mechanism (2 stage mechanism)
- Initially
- it increases water/Na+ excretion from kidneys → which impacts blood volume
- which reduces CO
To compensate -Thiazide/thiazide-like are better than loop diuretics
They may be better because
- Longer-term effects = which causes arterial dilation which causes decrease TPR?
- maybe due to: sodium depletion can decrease intracellular calcium in smooth muscle cells
What are the side effects of Class D drugs
hypokalemia
its a diuretic
What types od drugs act on the peripheral symathteic nervous system
Beta adrenoreceptor antagonists (beta blockers)
Name same beta blockers
Eg propranolol ( beta 1&2), atenolol ( beta 1)→ aka the olols
How do beta blockers help with hypertension
- decreases heart rate/contractility which decreases cardiac output
- decreases renin secretion which decreases angiotensin 2 which decreases TPR and CO
What are the side effects of beta blockers
- Beta 2 action can cause bronchospasm
- there may be an exercise intolerance
What does it say clinically now about beta blockers
to avoid them
What other receptor can you effect in the peripheral sns
Alpha1 adrenoceptor antagonists
Name some alpha1 adrenoceptor antagonists
Eg prazosin, doxazosin
How do alpha 1 adrenorecpetors work
- target alpha one which causes vasoconstriction
- Block vasoconstriction
- primarily on arteriole side
- decreases TPR and CO
What are the side effects of alpha 1 adrenoreceptors antagonists
postural hypotension
What are alpha 1 adrenorecpeor antagonists used for
Clinically used for
- people with severe hypertension
- or for patients with other cardiac/renal problems
How are drugs that treat hypertension and hypotension catagorised into
there;s two
- ones that directly reducd RAAS (A+B)
- ACE inhibitors, A2 receptor antagonists and beta blockers
- Ones that have no direct effect on RAAS (C+D)
- calcium channel blockers and diuretics
If someone has worsening hypertension what do we do
- we can increase the dose of the drug
- increasing the dose means increasing the side effects
How do we combot the side effects of increading drug doses
- we use combination therapy
- this can decrease toxic effects
- and increase the chance of successful therapy
How do we combine the drugs
- A+C
- or A+d
- but we try to avoid C+D (but it can be done)
What are the possible causes of hypotension
bleeding, burns, shock
If someone has shock what drugs can we use
- adrenaline (aka a Sympathomimetics)
- which increases cardiac output, and increase blood pressure
How do we help people with chronic hypotension
they are often told to increase salt intake, but not much is done clinically
