Biochemistry Flashcards
What is hypertension a major risk factor for?
- Stroke
- IHD
- HF
- CKD
- Cognitive decline
- Premature death
- CAD
- Myocardial ischaemia
What is a hypertensive urgency?
- 180mmHg systolic or 110mmHg diastolic
- Symptoms include headache, SOB, nosebleed, severe anxiety
- Management: oral medication, outpatient
What is a hypertensive emergency (malignant)?
- Target organ damage - brain, heart, kidneys
- Systolic 180mmHg or diastolic 120mmHg
- Encephalopathy can occur - cerebral arteries lose ability to regulate blood flow in cerebral capillaries and so leaking of fluid into interstitial space > cerebral oedema > increased pressure > brain dysfunction
What is the function of beta receptors in the heart and blood vessels?
- Heart: increased contractility (adenylate cyclase > ATP>cAMP > protein kinase A > Ca)
- Blood vessels: release of cAMP causes relaxation of the artery
Where are baroreceptors found?
Nerve endings in all thoracic and neck arteries. 2 major populations: carotid sinus and arch of aorta. They are activated on stretch e.g. high BP.
- They are important in maintaining postural BP
Describe chemoreceptors
- Sensitive to low O2, high CO2 and acidosis
- Chemoreceptor organs: 2 carotid bodies (in each bifurcation), 1-3 aortic bodies
- Reduction in blood flow (<80mmHg) causes metabolic stimulation
What is the atrial volume reflex?
Atrial stretch to pressure causes:
- Reflex dilation of renal afferent arteriole causing increased glomerular capillary pressure > increased filtration of fluid to renal tubule so fluid loss by kidneys
- Reduced secretion of anti-diuretic hormone from hypothalamus causing reduction in water resorption from renal tubule > fluid loss by kidneys
What is the role of angiotensin II?
Increased sympathetic activity, tubular NaCl reabsorption and K excretion with H2O retention, aldosterone secretion and is a potent vasoconstrictor. Causes the release of ADH secretion from the posterior pituitary which causes resorption of water from the collecting ducts.
What is hyperaldosteronism?
Increased aldosterone > decreased K and decreased H = hypokalaemic alkalosis
What are the causes of hyperaldosteronism?
- Unilateral aldosterone producing adenoma or Conn’s syndrome (50-60%)
- Bilateral adrenal hyperplasia (40-50%)
What are the pathologies caused from type 2 diabetes and hypertension?
- Increase in wall thickness
- No change in lumen diameter
- Impairment of endothelial function
What are the pathologies caused from essential hypertension?
- Increase in wall thickness
- Reduction in lumen diameter
- Increase in wall to lumen ratio
- Preservation or mild impairment of endothelial function
What are the renovascular causes of secondary hypertension?
- Acute elevation in serum creatinine (at least 30%) after ACEi or ARB
- Diffuse atherosclerosis, unilateral small kidney or asymmetry in renal size of more than 1.5cm that cannot be explained by another reason
- Recurrent flash pulmonary oedema
- Abnormal urinalysis
What drugs cause a temporary rise in BP related to use?
- Oral contraceptive pill
- NSAIDs
- Stimulants e.g. cocaine, methylphenidate
- Calcineurin inhibitors
- Antidepressants
What conditions cause elevated BP?
- Pheochromocytoma (tumour of adrenal gland) - triad of headache, palpitations and sweating
- Primary aldosteronism - unexplained hypokalaemia with urinary K wasting
- Cushing’s syndrome - central obesity, proximal muscle weakness and ecchymoses
- Sleep apnea syndrome - daytime somnolence, fatigue and morning confusion
- Coarctation of aorta - diminished or delayed femoral pulses, low or unobtainable BPs in legs
- Hypothyroidism
- Primary hyperparathyroidism - elevated serum calcium
Who is at risk of hypertension?
- FH
- Caribbean or African descent
How are renal artery stenosis and RAAS system linked?
In renal artery stenosis, blood flow through the afferent arteriole is reduced which results in activation of the RAAS system which results in systemic hypertension and the efferent arteriole to constrict maintaining GFR.
When is same day referral recommended?
If the clinic blood pressure is 180/120 mmHg and higher with:
- signs of retinal haemorrhage or papilloedema
- life-threatening symptoms such as new onset confusion, chest pain, signs of heart failure, or acute kidney injury
- they have suspected phaeochromocytoma (for example, labile or postural hypotension, headache, palpitations, pallor, abdominal pain or diaphoresis).
