Hypertension Flashcards
(15 cards)
Define hypertension
- Known as high blood pressure
- When systolic or diastolic blood pressure or both, is above normal all the time
If not treated, hypertension results in a greatly increased risk of thrombosis, strokes and renal failure.
Define stage 1 hypertension
140/90 mmHg or higher in clinic, and the a minimum of 135/85 in follow up self-readings with provided cuff.
Define stage 2 hypertension
Clinical blood pressure is 160/100, and subsequent home readings with provided cuff are 150/95 mmHg or higher.
Define severe hypertension
- Clinical blood pressure is 180/110 or higher
Define primary hypertension
- risk factor induced hypertension
Define secondary hypertension
Hypertension that rises as a result of another condition, such as a renal damage.
List the main risk factors for hypertensoin
- Age (blood pressure rises with age)
- Obesity
- Excessive alcohol intake
- High salt intake
- Genetic susceptibility
- High plasma cholesterol
- Smoking
Explain how hypertension can cause problems for the heart muscle, as well as vessels of the body
- hypertension increases heart worload, the left ventricle gradually enlarges causing ventricular hypertrophy
- This resulting increase in heart mass is acompaned by an increase in oxygen requirements for the heart, and since the coronary circulation cannot keep pace, ischaemia may occur leading to myocardial infarction
- Furthermore, increased blood pressure can result in aneurysms and atherosclerosis
Give the mechanism of action of Beta-Blockers (specifically how the effect blood pressure) and examples of types of Beta Blockers
- Beta blockers act as a competitive antagonist for Beta 1 receptors on the heart, reducing sympathetic tone on the heart
- This occurs since the capability of noradrenaline/adrenaline to bind to these receptors on the heart is reduced
The results are:
- decreased cardiac output
- Decrease in sympathetic activity by the CNS
- Also decrese of renin release
Examples:
Propanolol (Non-selective beta 1 and Beta 2)
Atenolo (beta 1 selective)
Give the mechanism of ACE inhibitors with regards to blood pressure, and examples.
- Prevents conversion of angiotensin 1 to angiontensin 2 by ACE
- Angiotensin 2 cannot therefore exert it’s vasoconstrictive efffects, nor can it stimulate the secretion of Aldoesterone - therefore preventing blood pressure increase
ACE inhibitors do NOT affect cardiac contractility, so cardiac output is normal.
Examples:
- Captopril
- Enalapril
- Lisinopril
Side effects:
- Dry cough - There is a reduced of bradykinin a peptide that activates sensory nerves in lung tissue therefore s the accumulation of bradykinin in bronchial mucosa.
- Sudden fall in blood pressure on the 1st dose
Give the mechanism of Angiotensin 2 receptor blockers, and give examples
- Losartan
- Candesartan
- Blocks the Angiotensin 2 Type 1 Recetpor (AT1) - which has a role in mediating the constrictive effects of Angiotensin 2 and aldosterone - since Angiotensin 2 stimulates AT1 receptors on adrenal gland to release aldosterone)
Give the mechanism of alpha adrenceptor blockers and give examples of these drugs
- reversible antagonists of alpha 1 adrenoreceptors in smooth muscle of blood vessels
- thereby prevents sympathetic activity on blood vessels, preventing vasoconstriction and causing vasodilation
- This decreases total peripheral resistance, whilst also acting on the kidneys to prevent renin production
- This causes the reduction of blood pressure
- Examples
- Phentolamine (a1 and a2)
- Prazosin, Doxazosin (a1 specific)
Give the mechanisms of Calcium channel blockers and give examples
- prevent calcium influx upon membrane depolarisation of heart cells, also prevents calcium influx into sarcoplasm from SR in vascular smooth muscle contraction )
- This reduces peripheral resistance (calcium entry is blocked in vascular smooth muscle cells)
- Reduces cardiac output (calcium entry is blocked in cardiac muscle cells
There are two types of calcium channel blockers:
- Those which physically block calcium ions passing through pores - Open channel blockers
- Verapril and Diltiazem
- Those which bind to an allosteric site (basically a site away from the main receptor component) and causes a change in the receptor in a way that limits channel opening - ALLOSTERIC MODULATION CALCIUM CHANNEL BLOCKER
Some drugs can be better suited for smooth muscle in vessels, whilst some can be more for cardiac muscle
Give the mechanisms for diuretics and how they reduce blood pressure. Give examples
- increase the volume of urine production
- this is done because sodium reabsorption is decreased and water retention is decreased,
- Usually thiazides are used, which inhibit sodium reabsorption in the distal renal tubule. Thiazides also have a vasodilator effect, further reducing blood pressure
- Example is Bendroflumethiazide
- Side effects are hypokalaemia
Describe the responses to changes in posture and the mechanisms resulting in postural hypotension in the elderly
- When moving from a supine to standing positino, the effect of gravity causes venous pooling in any vessels below the heart, causing venous pressure
- As a result, cardiac filling is reduced as less blood reaches the heart - stroke volume and cardiac output fall
- Arterial blood pressure drops, but the baroreceptor reflex corrects it almost immediately
- If for some reason there is already peripheral vasodilation (for example, if you are on an anti-hypertensive), you can get cerebral-hypoperfusion and the person can faint
As mentioned, baroreceptor reflex is involved. Upon standing the pressure is redcued, so baroreceptors decrease their firing rate - this increases sympathetic outflow from CNS, increasing HR and contractility - you also get peripheral vasoconstriction which increases blood pressure
Failure of this mechanism causes Postural Hypotension:
- this is defined as a decrease of 15+mmHG in blood pressure upon standing, and maybe associated with symptoms of lightheadedness or lead to collapse
- Normally the baroreceptor reflex is sufficient to bring blood pressure back up, however this can be affaected with alpha adrenoceptor blockers - these drugs inhibit vasoconstriction normally initiated by the baroreceptor reflex upon postural change
