Contrl Of Blood Pressure - The Patient With Hypertension Flashcards
What is the ideal normal blood pressure
- BP is measured in millimetres of mercury (mmHg)
* The normal or ideal adult blood pressure is considered to be between 90/60mmHg and 120/80mmHg
What is hypertension
• Sustained increase in blood pressure
Stage 1 hypertension >= 140/90 clinic or >= 135/85 home
Stage 2 hypertension >=160/100 clinic or >=150/95 home
Severe hypertension >= 180 systolic or >= 110 diastolic
What causes hypertension?
• In around 95% of cases the cause is unknown - combination of genetic, lifestyle, environmental, combination etc
– ‘essential’ or primary hypertension
• Where the cause can be defined it is referred to as secondary hypertension – examples • renovascular disease • chronic renal disease • hyperaldosteronism • Cushing’s syndrome
• With secondary hypertension – important to identify and treat the underlying cause or will struggle to reduce bl
Why is it important to treat hypertension?
• Hypertension – the silent killer
• Although hypertension may be asymptomatic, it can have unseen damaging effects on
– heart and vasculature
– potentially leading to heart failure, MI, stroke, renal failure and retinopathy
Describe the relationship between blood pressure and ratio of actual to expected mortality
Mortality increases are blood pressure increases - relationship particularly strong with systolic
Name some diseases attributable to hypertension
Coronary heart disease Heart failure Stroke Cerebral haemorrhage Chronic kidney failure Hypertensive encephalopathy Retinopathy Peripheral vascular disease Aortic aneurysms Left ventricular hypertrophy Myocardial infarction Coronary heart disease
All vascular
Describe how hypertension can lead to various diseases
Pls see slide for diagram
How can organ damage be assessed
By clinical history ad physical examination - brain, eyes, heart, kidneys, arteries
What is the effect of intervention?
Every 10mmHg reduction in blood pressure results in: • 17% reduction for coronary heart disease
• 27% reduction for stroke
• 28% reduction for heart failure
• 13% reduction in all-cause mortality
How is blood pressure regulated?
• Pressure = flow x resistance
• mean arterial BP = CO x TPR
• CO = SV x HR
- if bp falls, heart can combat by increasing stroke volume or heart rate
• Both short and long term regulation
• Short term regulation
– baroreceptor reflex
– adjust sympathetic and parasympathetic inputs to the heart to alter cardiac output
– adjust sympathetic input to peripheral resistance vessels to alter TPR
What is the baroreceptor reflex
Nerve endings in the carotid sinus and aortic arch are sensitive to stretch.
Increased arterial pressure stretches these receptors.
Decreased pressure stretches less
Increases stretch detracted by baro receptors - feedback to medulla - reduce sympathetic - reduce vasocostrition - relative bradycardia
• The baroreceptor reflex works well to control acute changes in BP
• Produces rapid response to changes in BP
• Does not control sustained increases because the threshold for baroreceptor firing resets
Happens in seconds to minutes
Describe medium and longer term contorl of blood pressure
• Complex interaction of neurohumoral responses
• Directed at controlling sodium balance and thus extracellular fluid volume
• Plasma is part of the extracellular fluid compartment
– control of extracellular fluid volume controls plasma volume
– water follows Na+ therefore controlling total body Na+ levels controls plasma volume
What are 4 parallel neurohumoral pathways which control circulating volume and hence BP?
- Renin-angiotensin-aldosterone system
- Sympathetic nervous system
- Antidiuretic hormone (ADH)
- Atrial natriuretic peptide (ANP)
Control BP in part by controlling sodium balance and extracellular fluid volume
What is the renin-angiotensin-aldosterone system
• Renin is released from granular cells of juxtaglomerular apparatus (JGA)
• Factors that stimulate renin release: a) Reduced NaCl delivery to distal tubule b) Reduced perfusion pressure in the kidney causes the release of renin detected by baroreceptors in afferent arteriole
c) Sympathetic stimulation to JGA increases release of renin
What stimulates renin release
Decreased circulating volume
Decreased NaCl delivery to the macula densa
Sympathetic stimulation to juxtaglomerular apparatus
Decreased renal perfusion pressure (sensed by renal baroreceptors)
Renin is released from the granular cells of the afferent arteriole in response to reduced perfusion pressure