Hypertension Flashcards
What units are used to measure blood pressure?
Blood pressure expressed in mmHg - milimeters of mecury
What equation is used to calculate blood pressure?
Blood pressure = Cardiac output x systemic vascular resistance
Why do mammals have a high blood pressure (3 reasons)?
There are three main answers as to why mammals have high ABP:
1. Allows dynamic distribution of blood on demand through parallel vascular beds (shower analogy) - arterioles are the taps that dictate local flow
2. Necessary to sustain glomerular filtration pressures – important
3. Keeps cardiac afterload relatively constant
What two systems are responsible for regulating blood pressure?
Baroreceptors & sympathetic nervous system = short-term ABP control
Carotid baroreceptors – drives vasocontraction, increase CO (contraction) and increase venous return by vasoconstricting veins - mechanism to increase Blood pressure
Kidneys (and RAAS) = long-term ABP control
Blood pressure falls – renin activates – angiotensin I converted into angiotensin II – AngII is a potent vasoconstrictor and drives water retention
What might cause high blood pressure?
Known cause ~10%
1. CO increased – exercise and hyperthyroidism
2. Sensors confused – renal artery stenosis and baroreceptor dysfunction
3. Kidneys – advanced CKD and NSAIDS
4. Sympathetic activated – Stress, phaeochromocytoma, sleep apnoea and cocaine
5. RAAS activated – hyperaldosteronism, cushing syndrome and iatrogenic glucocorticoids
6. Increase in TPR – Coarctation - narrowing of the aorta – increase resistance
90% primary (‘essential’) hypertension - No known/obvious cause - due to environmental/ cultural / genetic risk factors
What is hypertension?
Pathologically high BP – enough to cause disease
Blood pressure for which treatment with anti-hypertensive therapy is likely to do more good than harm
Accepted to be 140/90 in most guidelines - higher than this associated with significant risk of stroke, MI and heart failure (other conditions as well)
What do most drugs treating hypertension try to change?
Most drug therapy to treat peripheral resistance – target the sympathetic nervous system and Renin-angiotensin system
Whar are the different post-ganglionic sympathetic receptors and what effects do they exert when stimulated?
Post-ganglionic fibres release noradrenaline –acts on alpha / beta adrenoceptors:
1. alpha1 = vasoconstriction
2. beta1 = tachycardia
3. beta2 = vasodilatation, bronchodilatation
Role of calcium in smooth muscle contraction?
All vascular smooth muscle contraction diven by intracellular calcium
Calcium may enter:
1. From extracellular space through voltage and ligand-gated channels
2. From SR (e.g. in response to Gq signalling from alpha1 / ET / AT1 / V1 receptors)
How could we intervene to treat hypertension?
Lifestyle measures – low NaCL, high K, high fresh and vegetables, moderate EtOH, physical activity and weight reduction, smoking
Procedures – sympathetic denervation, carotid barocreceptor stimulation and AV fistula (Connect artery with vein)
Drugs – Calcium channel blockers, ACEi or ARBs, alpha- and beta-adrenergic receptor anatagonists, thiazide diuretics and K-sparing diurectics
Aims to reduce water retention and/or block the different pathway inputs into the smooth muscle cells lining blood vessels
Outline the treatment timeline for hypertension?
Note - differences according to age, ethnicity and health status.
T2DM status trumps ethnicity and age – important to emphasize individualizing therapy based on whole patient / patient preferences etc
Start with lifestyle modifications
First line
Age over 55 and/or Black African/Carribean - Calcium channel blocker
Type II diabetes, below 55 & not Black African/Carribean - ACEi/ARB
Second line - diuretic use
1. Thiazide
2. Spironolactone
