4. Hypertension Flashcards
What is BP determined by?
By the cardiac output and the resistance of the blood vessels to blood flow
How do you work out BP?
BP = CO x SVR
“Systolic BP”
The maximum BP during ventricular contraction
“Diastolic BP”
The minimum level of BP measured between the contractions of the heart
“Hypotension”
Blood pressure less than 90/60
“Postural hypotension”
AKA. Orthostatic hypertension
Reduction in systolic BP of 20mmHg or more after standing for at least one minute
May also see in increase in diastolic BP by 10mmHg or more
Associated with dizziness and fainting
When does postural hypotension tend to occur/how can it be caused?
More frequent in older patients - especially those with diabetes
Can be caused by drugs such as antihypertensives (diuretics, vasodilators), alcohol
CNS symptoms occurring with hypotension
Dizziness
Impaired cognition (espeically in the elderly)
Lethargy and Fatigue
Visual disturbances due to hypo-perfusion of the brain e.g. blurred vision, tunnel vision etc
Symptoms of hypotension associated with the muscles
Paracervical (upper back) ache
General fatigue
Symptoms of hypotension associated with the heart
Angina - due to hypo-perfusion of the heart, especially during exercise
“Prehypertension”
Aka. High normal BP
Systolic - 130-139
Diastolic - 85-89
What should be implemented for patients with prehypertension?
Should encourage lifestyle changes - this group has an increased risk of becoming hypertensive
NB. These are not candidates for drug therapy
“Isolated systolic hypertension”
Systolic BP greater than 140mmHg and a diastolic less than 90mmHg (SO high systolic but normal diastolic)
Less serious than full hypertension
What should be implemented for patients with isolated systolic hypertension?
Lifestyle changes - diet low in sodium, rich in whole grains, fruits and vegetables due to the presence of nitrate which can be converted to nitric oxide
Should encourage weight loss, increased physical activity and reduced alcohol consumption
If these do not reduce the systolic hypertension to safe levels then drugs should be used
“Hypertension”
When the systolic and diastolic are persistently greater than 140/90
Persistently meaning that the diagnosis must be based on repeated measurements on separate occasion days or weeks
Why is the recognition of hypertension so important?
Cardiovascular mortality risk is proportional to increased BP
Elevated BP is a major cause of stroke, coronary heart disease, renal impairment and peripheral vascular disease
What is the impact of hypertension on the heart?
Leads of a thickening of the left ventricle - concentric hypertrophy
This causes the lumen diameter of the ventricle to decrease
“Concentric hypertrophy”
The walls of the ventricle hypertrophy and increase, causing the size of the ventricle chamber to decrease
SO to maintain the CO in this instance, the HR must increase
“Eccentric hypertrophy”
The whole ventricle enlarges
The wall may or may not increase in thickness
The enlarged heart is weaker and this can lead to heart failure
What clinical impact might hypertension have on the eyes?
Damage to the retina - arteriolar narrowing and abnormalities
Can cause damage to the eyes that appears as ‘silver wiring’ and ‘cotton wool spots’
IMAGES ARE IN MILLAR PP _ RECOGNISE THESE
“Primary hypertension”
90-95% of the causes of hypertension
Aka. ‘essential’ or ‘idiopathic’
There is no obvious underlying cause
Strong polygenic familial trent
“Secondary hypertension”
About 5% of the cases
There is a clear underlying cause e.g. renal or renovascular disease, endocrine disease, coarctation of the aorta, iatragoenic (hormonal/oral contraceptive/NSAIDS), Thyroid or parathyroid disease
How is BP normally controlled? (year 1)
- Baroreceptors in the carotid artery via the neuronal system
- Renin-angiotensin-aldosterone system via the hormonal system
Describe the control of BP via the baroreceptor system
Immediate control - works in seconds - a rapid response system
This is important during changes in posture or during exercise
Describe the control of BP via the RAAS system and give the mechanism
Responsible for the maintenance of steady, longterm BP
Pathology in this system can lead to chronic hypertension
Mechanism:
- Angiotensinogen to angiotensin 1 via renin
- Angiotensin 1 to angiotensin 2 via ACE
- Angiotensin 2 causes the release of aldosterone
- Aldosterone increases Na+ reabsorption from the collecting duct of the kidney (upregulates ENaC channels) and hence also increases the reabsorption of Cl- (follows Na+) - this results in an increased BP
- Angiotensin 2 also has a sympathetic effect on the body which causes an increased BP
- Also results in an increased secretion of ADH
What are some clinical signs of hypertension (would be present in the blood)?
Elevated levels of renin angiotensin 2
What is the impact of elevated levels of renin and angiotensin 2?
What does this mean for treatment?
Leads to excess sodium retention
Leads to retention of water via raised ADH
SO dietary salt restriction should always be part of treatment and diuretics should be used
“Hyponatremia”
If the extracellular fluid sodium is below 135mmol/L
Serious as it can lead to brain swelling
Symptoms of hyponatremia
Mild:
Loss of energy and fatigue
Confusion
Muscle weakness
Severe: (these are all due to teh swelling of the brain) Nausea and vomiting Headache Spasms Restlessness and irritability Seizures Coma
What is the suggested link between diabetes and hypertension?
Suggested that diabetes damages the kidneys and can hence result in an increased release of renin
What is the link between obesity and hypertension?
Obesity causes increased release of renal renin
This causes increased formation of angiotensin and sodium retention
This then results in hypertension (increased sodium and water retention)
How is hypertension treated? (Ladder of treatments)
Lifestyle changes - exercise, diet (increased fruit and veg, reduced salt intake), reduced weight
Thiazide diuretic e.g. Bendroflumethazide
Thazide + beta blocker or ACE inhibitor
Angiotensin receptor blocker
Calcium channel blocker
Alpha blocker
