Hypertension + Antihypertensives Flashcards
Equations to work out mean arterial pressure
DBP + PP/3
or
CO x TPR
Blood pressure regulation mechanisms
- autonomic sympathetic activity
- RAAS system
- autacoids e.g. bradykinin, nitric oxide
Response of sympathetic activity in decrease in BP
- activation of B1 adrenoreceptors on heart > increase CO
- activation of a1 adrenoreceptors on smooth muscle > vasoconstriction > increased venous return + peripheral resistance
- activation of B1 adrenoreceptors on kidneys > renin release > RAAS
- increase in BP
Response of RAAS in a decrease in BP
- drop in renal blood flow
- renin released
- angiotensinogen > AngI > AngII > increased peripheral resistance
- increased aldosterone > increased Na+ + H2O retention > increased blood volume > increase CO
- increased ADH > water reabsorption > increased blood volume
- increase in BP
Stages of hypertension
- stage 1: >140/90mmHg
- stage 2: >160/100mHg
- stage 3 > 180 systolic or >110 diastolic
Increase in 20 systolic + 10 diastolic each time
What is target blood pressure for <80 years old?
<140/90mmHg
Range for pre hypertension
120/80mmHg - 140/90mmHg
What advice should be given to pre hypertensive patients?
- promote regular exercise + healthy diet
- reduce stress + promote relaxation
- discourage excessive caffeine consumption
- smoking cessation
- reduce sodium intake
What classifications of drugs are used to treat primary hypertension?
- ACE inhibitors ACEi
- angiotensin recpetor blockers ARB
- calcium channel blockers CCB
- diuretics - thiazide + thiazide like
How do ACEi help hypertension?
- limit conversion of angiotensin I > angiotensin II but inhibiting circulating + tissue ACE
- reduction in AngII activity:
-vasodilation
-reduction in alsoderone release
-reduced ADH release - lower BP
What is target blood pressure for >80 years old?
<150/90mmHg
What is desired blood pressure?
120/80mmHg
Adverse effects of ACEi
- dry cough (bradykinin accumulation)
- hypotension
- hyperkalaemia (lower aldosterone > ^ [K+])
- worsen renal failure
- angioedema
Contradictions of ACEi
Renal artery stenosis
AKD
Pregnancy
Idiopathic angiodema
Why is dry cough a possible side effect of ACEi?
- ACE also converts bradykinin into peptide fragments
- accumulation of bradykinin can cause dry cough
Suffix for ACEi
-pril
Suffix for angiotensin II receptor antagonists
-sartan
Adverse effects of ARBs
- hypotension
- hyperkalaemia (low aldosterone > ^ [K+])
- worse renal failure
What are possible side effects of ACEi that are not an issue with ARBs?
Dry cough
Angioedema
No effect on bradykinin
Contraindications of ARBs
Renal artery stenosis
AKD
Pregnancy
Important drug interactions with ACEi +ARBs
- potassium sparing drugs
- NSAIDs
- other hypertensives
How do angiotensin II receptor antagonists work?
- AngII blockers
- bind to AT1 receptors
- limit action of angiotensin II
- lower BP
Why do ACEi and ARBs precipitate hyperkalaemia?
Lower aldosterone
Causes increase in [K+]