Lecture 8: Hypertension

Question 1

What is hypertension?

Answer 1

• Persistent raised blood pressure
• Normal blood pressure: 120/80 mm Hg
• Treat when systolic > 140
• Diastolic > 90

Question 2

How do we measure BP?

Answer 2

Measure in the brachial artery in the arm

Question 3

What is white coat hypertension?

Answer 3

• BP may be artificially high bc you are being checked medically, making you nervous
• Can be circumvented via ambulatory blood pressure monitoring (ABPM)
  
  • Inflates once an hour during the day n night
  • BP measured automatically n transferred onto a disk
• Can also be overcome w home BP measurement but they’re not calibrated

Question 4

Describe the diagnosis of hypertension in the clinic

Answer 4

• High BP -> 140/90 mmHg or higher
• ABPM: ensure at least 2 measurements per hour during person’s waking hours
  
  • Average value of at least 14 measurements taken during person’s waking hours

Question 5

Describe the diagnosis of hypertension in the home blood pressure monitoring (HBPM)

Answer 5

• For each BP recording, 2 consecutive measurements are taken, at least 1 minute apart n with the person seated
• BP is recorded twice daily, morning n evening
• BP recording continues for at least 4 days, ideally for 7 days

Question 6

What are you measuring when you take a blood pressure?

Answer 6

• Ausculation
  
  • Listening to any sounds from the body (e.g. heart)
• Korotkoff sounds
• Inflate cuff n use statoscope to listen to brachial artery
  
  • Inflate cuff so high to stop blood flow -> no sound
  • Slowly let pressure off -> pressure falls
  • Point when you hear the first sound (systolic BP)
  • Pressure in cuff is low enough to allow blood to go thru = systolic BP
• Sound increases in volume [more blood blow]
• Turn pressure down further -> hear no more sound [no more turbulence] = diastolic pressure

Question 7

What is mean arterial pressure?

Answer 7

• MAP = (SP + (2 * DP)/3)
• Not just average BP as uneven amount of time spent at rest
• ~2/3 diastolic and ~1/3 systolic
• Mean closer to diastolic

Question 8

What are the causes of hypertension?

Answer 8

• 90-95% primary essential hypertension
  
  • Probably a complex genetic disorder
• Secondary hypertension
  
  • Renal causes [increase BP -> not providing volume of liquid]
  • Endocrine disorders [hormones that cauese artery restriction]
  • Aortic coarctation [part of the aorta is occluded]
  • Preeclampsia (pregnancy)
  • Neurogenic hypertension (overactivity of the SNS)
  • Endocrine tumours: primary hyperaldosteronism, phaeochromocytoma, renin secreting tumour
  • Drug induced: amphetamines, NSAIDS, steroids

Question 9

Why treat hypertension?

Answer 9

• Hypertension increases the risk of
  
  • Stroke (occlusion in the brain)
  • Coronary events (myocardial infarction, angina)
  • Aortic aneurysm (bulging in blood vessel, aorta [pressure] -> fatal)
  • Heart failure
  • Renal failure
  • End organ damage

Question 10

Symptoms of hypertension

Answer 10

• Headaches [high pressure]
• Dizzy
• Flushing
• Awareness of heart beat
• Nosebleeds
• None (most common): silent killer

Question 11

Signs of hypertension

Answer 11

• Level of blood pressure
• Cardiomegaly/left ventricular hypertrophy [heart has to work w high pressure -> increase in muscle mass]
  
  • Can be observed in an echocardiogram
• Abnormal renal function
  
  • Blood test
• Proteinuria or haematuria
  
  • Urine test
• Hypertensive retinopathy

Question 12

How is hypertension managed?

Answer 12

• Patient education/lifestyle changes
  
  • Stop smoking
  • Loss of weight
  • Exercise
  • Reduce salt intake
  • Diet
  • Relaxation therapy
• Drug treatment
• Surgery

Question 13

What is the effect of excess weight on BP?

Answer 13

• Weight n BP are linked
• Likely that wight interacts w various factors controlling BP at different points over lifetime

Question 14

What determines BP?

Answer 14

• How much blood is ejected
  
  • Determined by cardiac output
    
    • Heart rate
    • Stroke volume
      
      • Filing pressure (Starling Law’s: more blood that comes back to heart, stretches the fibers in heart -> bigger CO)
      • Contractility (determined by SNS)
  • Total peripheral resistance
    
    • Diameter of arterioles
    • Small lumen -> higher pressure

Question 15

What are the 2 major mechanisms for controlling BP?

Answer 15

• Baroreceptor/SNS
  
  • Controls BP minute to minute
• ECF volume/plasma renin activity
  
  • Longer term effects

Question 16

Describe the baroreceptor reflex

Answer 16

• Baroreceptors are located in the carotid sinus n aortic arch
• When there is a fall in BP -> decrease frequency of nerve impulse in baroreceptors -> inhibit parasympathetic nervous system n stimulate SNS -> increase in heart rate
• RESULT
  
  • Increases heart rate n artery contraction [β receptors in the heart] ->increase in CO n total periphery resistance -> increase in BP
  • Increase in venous return -> stretching of heart muscle -> increase cardiac output
• EXAMPLE
  
  • Hemorrhage/loss of blood, baroreceptors keep alive
    
    • Fast heart rate -> try to increase BP to maintain organs

Question 17

What things can you aim to change to reduce BP?

Answer 17

• Cardiac output (stroke volume * heart rate)
  
  • Diuretics: reduce BP
  • ACE inhibitors: reduce blood volume
  • Angiotensin II receptor antagonists: reduce blood volume
  • β-blockers: reduce heart rate n contractility
• Reduce total peripheral resistance
  
  • Vasodilators
  • Calcium channel antagonists
  • ACE inhibitors
  • Angiotensin II receptor antagonists
  • α-adrenoreceptor blockers
• Some drugs do both: ACE inhibitors, angiotensin II receptor antagonists

Question 18

How do ACE inhibitors n angiotensin II receptor antagonists work?

Answer 18

• Renin-angiotensin-aldosterone system
• Liver secretes angiotensinogen (inactive) into blood stream
• Converted by renin, which is secreted by the kidney, into angiotensin I (inactive)
• Angiotensin I converted to angiotensin II (active)
• Causes adrenal cortex to cause aldosterone release
• Acts on BP

Question 19

What are the effects of angiotensin II?

Answer 19

• Vasoconstriction of arterioles
• Stimulates Na+ reabsorption in PCT
  
  • Cl- and water follow passively
• Stimulates aldosterone secretion (adrenal cortex)
• Stimulates vasopressin secretion from posterior pituitary gland
• Stimulates thirst

Question 20

What are ACE inhibitors?

Answer 20

• All ACE inhibitors end w “pril” suffix
• Reduce arterial resistance n blood volume
• Causes rapid fall in BP n persistent dry cough
  
  • Block the breakdown of bradykinin (mediator released in response to inflammation)
  • Bradykinin is broken down to inactive peptides via ACE
  • Thus ACE inhibitors block this process -> buildup of bradykinin -> can persist in throat -> dry cough

Question 21

What are angiotensin II receptor antaogonists?

Answer 21

• Angiotensin II receptor antagonists
• End w “sartan” suffix
  
  • Osartan, candesartan, valsartan
• Well tolerated side effect profile
• Once daily dosing
• No significant adverse effects
• Cost effects

Question 22

What are Ca channel antagonists?

Answer 22

• Block L-type Ca channels
• Dihydropyridines end w “dine”
  
  • Vasodilators -> reduce TPR
  • Blocking Ca channels in muscles -> prevents contractions
• Unwanted side effects
  
  • Headaches
  • Flushing
  • Ankle swelling

Question 23

What are β-adrenoreceptor blockers?

Answer 23

• e.g. atenolol (lol suffix)
• Used to be first line therapy but not anymore [significant reduction in blood pressure but ppl were still dying, other agents are more effective at reducing the incidence of stroke n CVS mortality]
• Mode of action unclear but reduce cardiac output, alter baroreceptor reflex sensitivity
• May also suppress renin secretion
• Contra-indicated: asthma sufferers
  
  • β-receptors in lungs that cause dilation in bronchioles, block receptors -> more likely to get asthma attack
• Can cause peripheral vasoconstriction -> cold hands n feet

Question 23

Explain the reflex tachycardia

Answer 23

• Alpha 1 are in blood vessels
• Alpha 2 are presynaptic n inhibit noradrenaline release
• Non-selective alpha antagonists block both alpha 1 n alpha 2 -> more noradrenaline -> activates β receptors -> increase in heart rate

Question 23

What are thiazide diuretics?

Answer 23

• Cause mild diuresis
  
  • Bendroflumethiazide
• Work at the beginning of the distal convoluted tubule in kidneys to increase water n sodium loss
• Work to reduce blood volume, CO n mean arterial pressure [more excretion from the kidney]
  
  • Take in the morning to avoid nocturnal diuresis
• Use low doses
• Cause hypokalemia
• Most effective in elderly or patients of African origin

Question 24

What is malignant (accelerated) hypertension?

Answer 24

• V high BP (diastolic > 140 mm Hg)
• Medical emergency
• Symptoms
  
  • Nausea
  • Dizziness
  • Headache
  • Blurred vision
  • Kidney failure
  • Retinopathy
  • Heart failure
• Treatment
  
  • IV vasodilators
  • Oral β blockers
  • Calcium antagonists
  • Not ACE inhibitors (immediately) as rapid fall in BP could lead to cerebral infarction n blindness