3. Hypertension Flashcards
What is BP?
- Driving force to perfuse organs with blood (force per unit area acting on vessels)
- Is not uniform throughout the body
- Commonly measure and report systolic (SBP) and diastolic (DBP)
equation for Mean Arterial Pressure
- Mean Arterial Pressure = cardiac output X total peripheral resistance
- MAP = DBP + (SBP-DBP)/3)
what is the effect of sympathetic activity when blood pressure is low?
- activation of B1 adrenoceptors on the heart –> ↑ cardiac output
- activation of a1 adrenoceptors on smooth muscle –> ↑ increased venous return
- activation of B1 adrenoceptors on kidney –> renin release
What is the effect of renin?
• converts angiotensinogen to angiotensin I which is converted to angiotensin II by ACE in lungs
• angiotensin II:
- increases sympathetic activity
- increase Na, Cl and water reabsorption and K+ excretion
- increases aldosterone secretion so increased Na, Cl and water reabsorption and K+ excretion
- causes arteriole vasoconstriction
- increases ADH secretion
• all increase blood pressure
What is the effect of vasoconstriction?
↑peripheral resistance requires ↑ BP to drive blood through the systemic circulation
Original
WHat vascular changes does hypertension cause?
Remodelling, thickening and hypertrophy
what substances are increased due to hypertension?
Increased vasoactive substances including ET-1, NAd, angII
effects of Hyperinsulinemia and hyperglycaemia?
lead to endothelial dysfunction and increased reactive oxygen species - NO signalling reduced
what are the combined effects of hypertension?
• permanent and maintained medial hypertrophy of vasculature with ↑↑TPR and ↓compliance
of vessels
• End organ damage (renal, peripheral vascular disease, aneurysm, vascular dementia, retinal
disease)
• “Hypertensive heart disease” LVH → dilated cardiac failure
• Increased morbidity and mortality
what factors make defining hypertension difficult?
• Labile, age, sex and population differences
define hypertension
“An elevation in blood pressure that is associated with an increase in risk of some harm”
• NICE say 140/90 mmHg = hypertension ≥ 40% population of England
causes of hypertension
Essential/primary/idiopathic hypertension – 90% of cases
The rest:
secondary hypertension – to other pathology
pre hypertension
isolated systolic/diastolic hypertension
white coat/clinic - real phenomenon
How should the patient be when taking BP?
Seated, relaxed, arms supported
Which arm should be measured?
Both
- if more than 15 mmHg difference repeat
- use arm with higher reading
How often should BP be taken?
Measurements over period of visits +/- ABPM/HBPM
When is emergency treatment required?
BP > 180/120 + clinical signs
What should be the target BP for different hypertension patients?
- 140/90 < 80 years old inc. type II diabetes
- 150/90 > 80 years old
- 135/85 type 1 diabetes
what is the desired bp?
120/80 mmHg
What is stage 1 hypertension?
Clinic blood pressure ranging from 140/90 mmHg to 159/99 mmHg and subsequent ABPM daytime average or HBPM average blood pressure ranging from 135/85 mmHg to 149/94 mmHg.
What is stage 2 hypertension?
Clinic blood pressure of 160/100 mmHg or higher but less than 180/120 mmHg and subsequent ABPM daytime average or HBPM average blood pressure of 150/95 mmHg or highe
What is stage 3 hypertension?
Clinic systolic blood pressure of 180 mmHg or higher or clinic diastolic blood pressure of 120 mmHg or higher
What is prehypertension?
120/80 - 140/90
What advice should be given to prehypertension/hypertension patients?
- Promotion of regular exercise
- Modified healthy/balanced diet
- Reduction in stress and increased relaxation
- Limited/reduced alcohol intake
- Discourage excessive caffeine consumption
- Smoking cessation
- Reduction in dietary sodium
All contribute to cardiovascular disease risk reduction
what are the Primary hypertension therapeutic agents?
- Angiotensin converting enzyme (ACE) inhibitors (ACEi)
- Angiotensin (AT1)receptor blockers (ARBs)
- Calcium channel blockers (CCBs)
- Diuretics – thiazide and thiazide-like
- “Other agents”
What are is the action of ACEi?
Limit the conversion of Angiotensin-I to Angiotensin-II by inhibiting circulating and tissue ACE
what is ACE and what is its action?
- ACE found on luminal surface of capillary endothelial cells, predominantly in the lungs
- ACE catalyses conversion of angiotensin-I to potent, active vasoconstrictor - angiotensin-II
what are the actions of angiotensin II?
• Angiotensin-II affords action through AT1 (and AT2 receptors)
• AT1 receptor subtype typical of classic angiotensin-II actions
- vasoconstriction
- stimulation of aldosterone which acts at distal renal tubule
- cardiac and vascular muscle cell growth
- vasopressin (ADH) release from posterior pituitary
What are the effects of ACEi?
• vasodilation (↓ PVR →↓afterload)
• reduction in aldosterone release (↑Na + H2O exc.)
• reduced vasopressin (ADH) release (↑ H2O
exc.)
• reduced cell growth and proliferation
What ACE independent pathway can produce AngII?
Angiotensin II can be produced by chymases
What receptors do ARBs work on?
Angiotensin I receptors
What are 2 ACEi?
Lisinopril and ramipril
What is the effect of ACEi on bradykinin?
Prevents breakdown of bradykinin, therefore increasing its effects
Why does build up of bradykinin cause cough?
sensitisation of airway sensory nerves and an enhancement of the cough reflex
What are the possible side effects of ACEi?
- Hypotension!
- Dry cough (10-15% - BK association)
- hyperkalaemia (low aldosterone ↑ K+)
- renal failure
- angioedema (BK more common in black population)
How may ACEi lead to renal failure?
Prevent formation of AngII, main vasoconstrictor of efferent arteriole, reduce GFR
When is ACEi more likely to cause renal failrue?
esp. renal artery stenosis where constriction of efferent arteriole needed
What are the warnings/contraindications to ACEi?
• X Renal artery stenosis, AKD, pregnancy, (CKD - caution), idiopathic angioedema
What are the important considerations/interactions of ACEi?
- Drugs that increase K+,
- NSAIDs (prevent prostaglandin production, prevent AA vasodilation),
- other antihypertensive agents