Hypertension 1 Flashcards
What is Systolic BP?
- Pressure of the blood against the artery walls when the heart contracts
- 120mmHg
What is Diastolic BP?
- Pressure against the artery walls when the heart relaxes between beats
- 80mmHg
Define Prehypertension
- Systolic between 121-139mmHg
OR
- Diastolic between 81-89mmHg
Define Hypertension
- Systolic 140 or above
OR
- Diastolic 90 or above
Function of Arteries
Deliver molecules to tissues
Function of Veins
Take molecules from tissues
What is the importance of proper systolic and diastolic BP?
- Blood needs to be pumped out of the heart as well as taken into the heart
- Proper values of both systolic and diastolic pressure are crucial for proper function of the vascular system
What is the function of Baroreceptors and where are they located?
- Detects changes in BP
- Location:
- internal carotids
- aortic arches
What is the function of Chemoreceptors and where are they located?
- Detects changes in pH (H+, O2, CO2)
- Location
- internal carotids
- aortic arches
What does a low pH indicate?
Inefficient blood flow and oxygenation
What are major factors affecting BP?
- Peripheral resistance
- Cardiac output
The amount of blood pumped is dependent on?
- Heart rate
- Heart contractility
- Heart muscle health (metabolism)
Define Cardiac Output
- The volume of blood pumped by the heart per minute (mL of blood/min)
- The more blood pumped into the system, the higher the BP is
- CO = HR x SV
Define Peripheral Resistance
- Hydrostatic ‘back pressure’ working against heart attempt to pump the blood into the CV system
What are the important hydrostatic parameters affecting BP?
- Proper blood flow would depend on hydrostatic parameters
- Force by which blood is pushed through the system
- Volume of blood in the system
- Diameter of conducting vessels
- achieved by sympathetic nervous system
What are the treatment aims of hypertension?
- Decrease arterial BP by decreasing:
- cardiac function-related (CO)
- blood volume (Peripheral resistance)
- Drugs affecting diameter of arteries (vasodilators) aren’t used in treatment of high BP but for other CV conditions e.g. angina
- could impact BP therapy
Discuss Primary (Essential) Hypertension
- Raised blood pressure with ‘no clear single identifiable cause’
- Factors are involved with blood pressure control including:
- adrenergic nervous system
- the RAAS
- renal function changes
- hormonal factors (e.g. vasopressin, adrenal hormones)
- vascular endothelium
- haemodynamic changes (e.g. changes in CO and peripheral vascular resistance)
Discuss Secondary Hypertension
- Refers to elevated blood pressure that can be attributed to a specific cause
- Causes:
- pregnancy
- pheochromocytoma
- aorta constriction
- hyperthyroidism
- Cushing’s syndrome
- Primary hyperaldosteronism
- Renoparenchymal diseases of the kidney
- Renovascular disease
- Certain prescription, non-prescription and natural health products can also precipitate or worsen hypertension
- treat primary cause
Discuss Resistant Hypertension
- Blood pressure that remains above treatment goal despite concurrent use of three antihypertensive agents of different classes, one of which should be a diuretic
- If patient has blood pressure controlled with 4 or more medications = resistant hypertension
What is the treatment aim of antihypertensive medications?
- To reduce the risk of CVD, target organ damage and mortality associated
- May be achieved by lowering SBP to <140mmHg and lower DBP to <90mmHg
- Majority of patients require a combination of lifestyle modifications and medications to achieve target blood pressures
How do you calculate BMI and what is a healthy BMI range?
BMI = weight (kg)/height (m)2
- Healthy range: 18.5-22.9
- Obese: 27.5 and above
What are non-modifiable risk factors?
- Increasing age (>55y)
- male gender
- family history of premature CVD (men <55 years or women <65 years) in a primary/first-degree relative
What are modifiable risk factors?
- Sedentary lifestyle
- Poor dietary habits
- Smoking
- Dyslipidaemia
- Stress
- Abdominal obesity (BMI >25; waist circumference >102 cm in men or >88cm in women)
- Impaired glucose tolerance or diabetes mellitus
Target organ damage
- Cerebrovascular disease
- Coronary artery disease
- Chronic renal disease
- Peripheral artery disease
What are lifestyle modifications in hypertension treatment?
- Weight reduction
- Physical activity
- Healthy diet
- Salt intake
- Alcohol intake
- Smoking
- Emotional Stress
What is the MOA of aldosterone?
What happens if aldosterone receptors are blocked?
- Upregulates expression of epithelial sodium channels (ENaC) in the collecting duct, increasing Na+ absorption as well as Na+/K+ pump level
- Overall effect: increase in BP
- If aldosterone receptors are blocked, blood pressure decreases
What happens when reuptake of Na+ from urine?
Reuptake of Na+ from urine brings water with it into the blood and raises BP
Define Preload
Volume of blood in ventricles at end of diastole
Define Afterload
Resistance in left ventricle must overcome to circulate blood
Functions of Angiotensin II?
- Retention of Na+ by kidney (via aldosterone)
- H2O retention by kidney (via Na+ uptake and vasopressin)
- Salt appetite
- Increased drinking (via Subfornical organ)
- Increased BP
What is the long-term regulation of Renin-Angiotensin-Aldosterone System (RAAS)?
- Fall in blood pressure
- Release of Renin
- Angiotensinogen
- Angiotensin I
- Angiotensin II
- Two pathways
- Aldosterone > sodium retention > BP increase
- Vasocontriction > BP increase
- Two pathways
What are juxtaglomerular cells?
- Specialised smooth muscle cells which act as mechanoreceptors which stretch in response to increase in BP of the afferent arteriole
- also synthesise and secrete the enzyme renin which serves to activate the inactive precursor, angiotensinogen (made by the liver), into angiotensin I
Two major functions of ATII
- Vasoconstriction
- Aldosterone Release
