Hypertension Flashcards
Define Hypertension as per Hypertension Canada Guidelines
HTN:
1) First visit - if BP greater than 180/110
2) Office BP measurements >130/80 for >3 measurements on different days ( consider to send for home monitoring to rule out WCH)
3) Home measurements of average daytime >135/85, or 24 hour BP >130/80
Normal BP across age span?
Normal Adult: 95-135/ 60-80 with some permissive ranges as adults get older (up to 145/90).
For Children (greater than one year of age) Median SBP = 90 mmHg + (2 x Age in years) Minimum SBP = 70 mmHg + (2 x Age in years)
Older children and adolescents should be a fairly classic 120/80 or slightly lower.
Just look up charts…
Factors effecting BP?
BP = Cardiac Output x Total peripheral resistance (blood viscosity and arteriolar radius)
Things that effect CO:
- anxiety
- eating
- exercise
- temperature
- pregnancy
- sympathetic activation
- position change
- heart pathology
What is the Frank-Starling Law and what does it have to do with hypertension?
Cardiac output is dependant on venous return - so when increased amounts of blood flow into the heart, the heart muscle stretches and this stretch (up to a point) allows for increased force of contraction.
This means that increasing CO can increase BP (to a certain point)
What are the rapid mechanisms of BP regulation?
Baroreceptor feedback:
- low pressure at pressure receptors in carotid sinus cause rapid activation of sympathetic system = vasoconstriction
CNS ischemic response
- more powerful sympathetic stimulation but only happens once MAP falls below 50mmHg
Chemoreceptors
- similar to baroreceptors but sense changes in pH, CO2 and to a lesser degree O2
What is the role of the renin-angiotensin-aldosterone system in hypertension?
This is a vasoconstriction mechanism initiated by the kidney, it is in response to LOW blood flow to the kidney.
Renin is released by the kidney - causes the activation of angiotensin 1 which is converted by ACE in the lung to angiotensin 2 which will help
- the kidneys retain water, (via aldosterone)
- systemic vasoconstriction
- Activates the pituitary to secrete ADH (antidiuretic hormone - aka vasopressin) to increase renal retention as well
What is the role of Atrial natriuretic peptide?
This is secreted by the atria of the heart in response to stretch. It is a high blood pressure response and acts opposite to the RAAS. It acts on the kidney to increase Na+ excretion and decrease water retention
Primary vs Secondary HTN?
Primary - elevated BP with no known underlying reason. May be environmental and genetic reasons.
Secondary - underlying cause that when corrected will fix hypertension
Consequences of severe HTN?
End-organ damage:
- hypertensive encephalopathy
- Aortic dissection
- ACS
- AKI
- Stroke
- Retinal damage
Look for: headache, chest pain, syncope, vision changes, abdominal pain
Target BP for non-diabetic? Target BP for diabetic?
Target BP non-diabetic = <140/90
Target BP diabetic = <130/80
Diuretic mechanism of action? Types of Diuretics?
Diuretics act to decrease extracellular fluid volume and vascular resistance
Thiazides (Hydrochlorothiazide), loop (furosemide), K+ sparing (spironolactone)
How do B-blockers work?
Decrease cardiac contractility and renin secretion
- careful in asthmatics/ CHF
- Propanolol and metoprolol
How do Calcium channel blockers work?
Decrease smooth muscle tone and cause vasodilation, my also act directly on the heart.
Caution with dihydropyridines - headache, flushing, peripheral edema - amlodipine
Non-dihydropyridines - verapamil, diltiazam
How do ACEI and ARBs work
Block aldosterone/ Angiotensin 2 production via the ACE
Hydralazine is?
A direct vasodilator which decreases peripheral resistance - use in emergency/ resistant BP
