Week 10 Hypertension Flashcards
8 drugs that increase BP?
corticosteroids estrogens NSAIDs sympathomimetics cyclosporins danazol erythropoietin megestrol acetate
6 drugs/classes that decrease BP?
anasthetics anxiolytics hypnotics dopamine agonists Tricyclic antidepressants nitrates antipsychotics
why tx HTN since it doesn’t produce sxs unless rapid & severe onset?
to prevent or reduce severity of disease
atherosclerosis, CAD, AA, CHF, stroke, DM, renal and retinal disease
examples of target organ damage from HTN?
cerebrovascular disease
stroke - ischemic, or transient ischemic attack
aneurysmal subarachnoid hemorrhage
hypertensive retinopathy
left ventricular dysfunction - hypertrophy (must pump against high pressure which causes muscle to thicken; restricting blood flow)
CAD - MI, angina, CHF
Renal disease - hypertensive nephropathy; albuminuria
PAD - intermittent claudication
AA/dissection
what are the 2 main categories of the physiological etiology behind HTN?
increased cardiac output
or
increased systemic vascular resistance
3 causes of increased cardiac output?
hypervolemia (renal artery stenosis, hyperaldosteronism, aortic coarctation, pregnancy)
stress (sympathetic activation)
pheochromocytoma (increased catecholamines)
7 causes of increased systemic vascular resistance?
stress (sympathetic activation) atherosclerosis renal artery disease (increased angiotensin II) pheochromocytoma thyroid dysfunction diabetes cerebral ischemia
what are 3 mechanisms to reduce cardiac output?
reduce blood volume
reduce heart rate
reduce stroke volume
what is 1 mechanism to reduce systemic vascular resistance
dilate systemic vasculature
7 classes of anti-hypertensive drugs?
ABCDE
ACE inhibitors
Alpha-agonist
Angiotensin receptor blockers
Alpha-antagonist
B-adrenergic blockers
Ca-Channel blockers
Diuretics
Endothelin antagonists
2 demographic indications for use of diuretics?
african american
elderly
2 demographic indications for use of calcium channel blockers?
african american
elderly
3 demographic indications for use of beta blockers?
young & caucasian
post MI
CHF
5 demographic indications for use of angiotensin receptor blockers & ACE inhibitors?
DM (protect KI) CT disease (scleroderma) CHF post MI young & caucasian
How does using 2 drugs affect dosing?
effect is synergistic therefore less dosage needed, therefore diminished side effects
cardiac output x total peripheral vascular resistance = ?
arterial blood pressure
heart rate x stroke volume = ?
cardiac output
beta blockers affect which:
cardiac output
OR
total peripheral resistance
cardiac output
heart rate & stroke volume
which 3 classes of drugs affect cardiac output?
b-adrenergic receptor antagonists
angiotensin receptor antagonists
diuretics
which 6 classes of drugs affect total peripheral resistance?
vasodilators
b-adrenergic receptor antagonists
a-adrenergic receptor antagonists (a-blockers)
angiotensin receptor antagonists
centrally acting sympatholytics
angiotensin-converting enzyme (ACE) inhibitors
name the 3 physiological mechanisms that control arterial BP
- sympathetic nervous system (incl. baroreceptors)
- renin-angiotensin-aldosterone
- tonically active endothelium-derived autocoids (NO and ET-1)
ET-1 = endothelin-1 (peptide that is a vasoconstrictor) autocoid = local hormones (e.g. eicosanoids, angiotensin, neurotensin, kinins, NO)
how does a decrease in BP increase aldosterone?
decrease BP => decreased renal flow => increases renin => increased angiotensin II => increases aldosterone
how does a decrease in BP result in increasing blood volume?
decreased BP => decreased renal blood flow => decreased GFR => increased sodium & water retention => increased blood volume (which increases cardiac output)
how do baroreceptors regulate BP?
- responsible for rapid moment to moment BP regulation
- fall in BP causes pressure-sensitive neurons to send fewer impulses to CN enters in spinal cord
- results in reflex response for increased sympathetic & decreased parasympathetic output to the heart & vasculature = vasoconstriction & increased CO
where are baroreceptors located?
aortic arch and carotid sinuses (at bifurcation of internal and external carotids)
The carotid sinus baroreceptors are innervated by the sinus nerve of Hering, which is a branch of the glossopharyngeal nerve (IX cranial nerve). The glossopharyngeal nerve synapses in the nucleus tractus solitarius (NTS) located in the medulla of the brainstem. The aortic arch baroreceptors are innervated by the aortic nerve, which then combines with the vagus nerve (X cranial nerve) traveling to the NTS. The NTS modulates the activity of sympathetic and parasympathetic (vagal) neurons in the medulla, which in turn regulate the autonomic control of the heart and blood vessels.
which baroreceptors are more sensitive?
aortic arch
OR
carotid sinus
carotid sinus
Maximal carotid sinus sensitivity occurs near the normal mean arterial pressure; therefore, very small changes in arterial pressure around this “set point” dramatically alters receptor firing so that autonomic control can be reset in such a way that the arterial pressure remains very near to the set point. This set point changes during exercise, hypertension, and heart failure. The changing set point explains how arterial pressure can remain elevated during exercise or chronic hypertension.
Baroreceptors in KI respond to reduced BP (and to sympathetic stimulation of B adrenoceptors) by releasing the enzyme ________
Renin
KI provides Long Term control of BP by altering _________
blood volume
Renin converts __________ to ________, which is then converted to _________ via ___________
Renin converts angiotensinogen to angiotensin I, which is converted to angiotensin II via angiotensin converting enzyme (ACE)
which hormone is the body’s most potent vasoconstrictor (resulting in increased BP)
angiotensin II
angiotensin II stimulates _____________ secretion
aldosterone
what are the 4 pathways that contribute to the kidney’s retention of Na+ and H2O in response to decreased BP?
- direct intrarenal hydraulic effect of reduced renal perfusion pressure
- release of aldosterone stimulated by renin system
- SNS stimulating nerves innervating renal blood vessels and tubules
- release of vasopressin (ADH) from pituitary stimulated by baroreceptor
Persistently raised arterial pressure leads to hypertrophy of which ventricle?
left
Persistently raised arterial pressure leads to narrowing of which, veins or arteries?
arteries
what are the 3 clinical variables that affect BP measurement?
cuff diameter
patient positioning
Kortokoff sounds
6 lab assessments that help in dx HTN
electrolytes, creatinine level fasting blood glucose CBC lipid profile urinalysis electrocardiography
Drug treatment is recommended if the diastolic BP is greater than ____ mmHg with other risk factors
85 mmHg
Drug treatment is recommended if the diastolic BP is ___ mmHg diastolic (and ___ mmHg systolic) without other risk factors
90 mmHg diastolic (and 140 mmHg systolic) without other risk factors
what is considered stage 1 hypertension?
systolic and diastolic
140-159 mmHg / 90-99 mmHg
what is considered stage 2 hypertension?
systolic and diastolic
> 160 mmHg / 100 mmHg
what is the BP tx goal in a HTN patient with diabetes/renal disease
less than 130/80 mmHg
what is the BP tx goal in a HTN patient?
less than 140/90mmHg
what is the tx protocol for stage 1 HTN
- lifestyle modification
- thiazide diuretic
- consider ACE(-), ARB, BB, CCB
drug combo if no achieve target BP
what is tx protocol for stage 2 HTN
- lifestyle modification
- drug combos:
thiazide diuretic
PLUS
ACE(-)
ARB
BB
CCB
always starts with 2 drugs at this stage
which 3 drug classes are vasodilators?
ACE inhibitors direct dilators (less so) Calcium channel blockers
which drug class tends to end in “-pril”
ACE inhibitors
which antihypertensive drug is preferred as first line tx in DM, CHF, CT disease
ACE inhibitors
where is the highest activity of angiotensin converting enzyme in the body?
endothelium of pulmonary vasculature
how do ACE inhibitors produce vasodilation?
inhibit formation of angiotensin II
ACE breaks down which vasodilator substance which, when inhibited by ACE inhibitors, is responsible for creating a dry cough?
bradykinin
which enzyme converts angiotensinogen to angiotensin I?
renin
angiotensin II stimulates secretion of which hormone?
aldosterone
what effect does aldosterone secretion have on blood pressure & why?
increases renal sodium absorption and increased blood volume, thereby increased BP
ACE inhibitors lower BP by reducing peripheral vascular resistance without reflexively increasing __________, _______, or ________.
cardiac output
heart rate
contractility
ACE inhibitors:
Vasodilation of both arterioles and veins occurs as a result of decreased vasoconstriction from diminished levels of _________.
Vasodilation also occurs directly from increased levels of ________ because it is not being broken down.
angiotensin II
bradykinin
route of administration of ACE inhibitors?
orally
how long is the onset of action?
for captopril?
enalapril (prodrug)
rapid
captopril: minutes (does not need to be transformed to more active form)
enalapril: hours
which 2 ACE inhibitors do not need to undergo hepatic conversion to active metabolites? (and therefore may be preferred in patients with severe hepatic impairment)
captopril
lisinopril
which demographic are ACE inhibitors most effective in?
young, caucasian (under 55 yoa)
ACE inhibitors are as effective in african americans as caucasians when combined with which other class of antihypertensives?
diuretics
ACE inhibitors are particularly useful for tx HTN associated with other risk factors, such as? (4)
post-MI
diabetes
Kidney disease
stroke
ACE inhibitors are effective in the management of chronic CHF, unlike which other class?
beta blockers
why are ACE inhibitors effective in patients post-MI?
help reduce deleterious remodeling that occurs post-infarction (dilatation, hypertrophy, and the formation of a discrete collagen scar; Hypertrophy is an adaptive response during postinfarction remodeling that offsets increased load, attenuates progressive dilatation, and stabilizes contractile function)
Thrombolysis is of proven value in the acute infarction, in which the primary objectives are limiting infarct size and salvaging ischemic myocardium. Once infarct evolution has occurred, pharmacological intervention may minimize infarct expansion and ventricular dilatation and improve the long-term prognosis.
The mechanism of improvement with ACE inhibition is related in part to peripheral vasodilatation, ventricular unloading, and the attenuation of ventricular dilatation.
It is recommended that patients with left ventricular dysfunction or heart failure be treated with ACE inhibitors without delay after infarction. Alternatively, all patients should be treated with ACE inhibitors initially, with a review of the need for continuation later on the basis of left ventricular function assessment.
Adverse effects of ACE inhibitors (8)
- persistent dry cough (10-30% of patients;d/t elevation of - bradykinin)
- rashes
- altered/loss of taste
- hypotension
- hyperkalemia (K+ levels must be monitored & supplements used cautiously)
- reversible acute renal failure (CI in severe renal artery stenosis)
- swelling of mucus membranes - angioedema (rare but life-threatening)
- fetal malformation - SHOULD NOT BE USED BY PREGNANT WOMEN
ACE (-) herbal interactions (6)
- cayenne (predispose to cough)
- ephedra (antagonise hypotensive effect)
- rhubarb (improves Captopril effect on decreasing progression of chronic KI failure)
- antacids significantly decrease absorption of ACE (-)
- Lithium increases toxic concentrations of ACE inhibitors
- theoretically: anything that lowers BP, e.g. theanine, CoQ10, olive, liquorice, reishi, stinging nettle, fish oil, garlic black cohosh.
ACE (-) nutrient interactions (2)
potassium (accentuates hyperkalemia)
zinc (ACE (-) deplete body of zinc)
What class of antihypertensives ends in “-sartans”
Angiotensin receptor blockers
e.g. losartan, valsartan
ARBs are receptor antagonists that block _________ receptors on bloods vessels and other tissues such as the heart.
type 1 angiotensin II (AT1)
Why do ARBs not cause an increase in bradykinin?
ARBs do not inhibit ACE
Why do ARBs not have the side effects of dry cough & angioedema?
ARBs do not increase bradykinin levels
Why should ACE (-) and ARBs not be combined for the tx of HTN?
- similar mechanisms and adverse effects
- no real BP benefit & increase side effects when taken together
this combo is reserved for very ill patients: advanced HF, proteinuric nephropathy
How do Centrally Acting Adrenergic Drugs work?
These drugs decrease the BP by reducing the firing rate of sympathetic nerves [decrease in sympathetic tone, decrease CO]
This action is mediated by activation of α2-adrenergic receptors in the CNS to inhibit sympathetic vasomotor centers [MOSTLY CENTRAL!]
describe adrenergic receptors
The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline). Many cells possess these receptors, and the binding of a catecholamine to the receptor will generally stimulate the sympathetic nervous system.
What are the 2 Centrally Acting Adrenergic Drugs that we learn in class?
Clonidine
Methyldopa
What is clonidine indicated for?
mild/moderate HTN not responding to diuretics
also opioid withdrawal
Are clonidine and methyldopa a2 adrenergic agonists or antagonists?
a2 adrenergic agonists
what are the 3 mild adverse effects of clonidine?
sedation
drying of nasal mucosa
edema
who is methyldopa indicated for?
- patients with renal insufficiency
- pregnancy
3 most common adverse effects of methyldopa?
sedation
impotence
rare hepatic necrosis (life-threatening)