Lecture 11- Controlling Blood Pressure In Patient With Hypertension Flashcards
What is hypertension?
Sustained increase in blood pressure
What is the normal range for blood pressure in an adult?
90/60mmHg to 120/80 mmHg but normal can vary
Stage 1= over 140/90
Stage 2= over 160/100
Severe= over 180 systolic or 110 diastolic
Primary vs secondary hypertension?
With primary the cause is unknown in 95% of cases
Secondary cause can be defined eg chronic renal disease, Cushing syndrome etc
Treat cause in secondary
Some diseases attributable to hypertension?
MI Coronary heart disease Aortic aneurysm Retinopathy Peripheral vascular disease Heart failure
How do you know if you have hypertension?
It is asymptomatic
How does high blood pressure lead to damage?
Increased afterload- LV hypertrophy and heart failure. O2 demand increased leading to MI and ischaemia
Arterial damage- atherosclerosis and weakened vessels leading to aneurysm, MI, retinopathy etc
How do you check for organ damage with hypertension?
Look at functioning of kidneys, brain, arteries, heart and eyes
What is blood pressure?
Flow X resistance
Calculating mean arterial BP?
Calculating cardiac output?
CO X TPR
CO= SV X HR
How is blood pressure regulated in the short term?
Baroreceptors reflex involving sympathetic and parasympathetic inputs to heart and vasculature
How is blood pressure regulated in the medium to long term?
Through neurohumoral responses and sodium balance and so extracellular fluid volume
Controlling sodium levels controls extracellular fluid volume
What are the four parallel neurohumoral pathways that control circulating volume and BP?
Renin angiotensin-aldosterone system
Sympathetic nervous system
ADH
ANP (lowers, others raise)
Renin angiotensin aldosterone system (RAAS)?
Can be targeted by ACE inhibitors which reduces sodium reabsorption and prevents the breakdown of bradykinin which acts as a vasodilator.
What stimulates renin release from the juxtaglomerular apparatus?
Reduced NaCl delivery to distal tubule
Reduced perfusion pressure in kidney
Sympathetic stimulation to JGA
How does the RAAS work?
Angiotensinogen converted to angiotensin I by renin. Angiotensin I is converted to angiotensin II by ACE (angiotensin converting enzyme).
Angiotensin II then causes vasoconstriction sodium reabsorption and stimulates aldosterone which also helps retain sodium
What angiotensin II receptors are there?
AT1 and AT2.
AT1 has main actions. Arterioles=vasoconstriction Kidney= sodium reabsorption Sympathetic= adrenaline secretion Adrenal cortex=aldosterone release Hypothalamus=thirst and ADH secretion
How does ACE (angiotensin converting enzyme) interact with bradykinin?
Converts angiotensin I to angiotensin II and causes bradykinin to be broken down into fragments
Role of bradykinin in blood pressure?
Acts as a vasodilator
Why are ACE inhibitors effective drugs and give an example of one?
They prevent angiotensin I being converted to angiotensin II and they also prevent bradykinin from being broken down which prevents those compounds from exerting their BP elevating actions.
EG Ramipril and lisinopril
Sympathetic nervous system control of BP?
Vasoconstriction and reduced renal blood flow and glomerular filtration.
Increased sodium reabsorbance and stimulation of renin release from juxtaglomerular cells.
ADH and blood pressure?
Increased water reabsorption
Stimulated by increased plasma osmolarity or severe hypovolaemia
Stimulates sodium reabsorption and causes vasoconstriction
Natriuretic peptides and BP control?
Produced and stored by atrial myocytes. Release in response to stretch of low pressure sensors. Cause sodium excretion to reduce circulating volume. Opposite effects to others (vasodilation etc)
Role of prostaglandins?
Oppose effects of RAAS and sympathetic nervous system.
Reduce sodium reabsorption and cause vasodilation etc
Dopamine?
Formed in kidney from L-Dopa. Causes vasodilation, reduces NaCl absorption etc
