Hypertension Flashcards
What is hypertension defined as in children?
A systolic and/or diastolic pressure greater than the 95th percentile for age, gender, and height on at least 3 occasions
What can hypertension be classified into?
- Essential
- Secondary
What is essential hypertension?
When no specific cause can be identified
What are the majority of cases of secondary hypertension caused by?
- Renal parenchymal disease
- Renovascular disease
- Coarctation of aorta
What are the less common causes of secondary hypertension?
- Raised ICP
- Phaeochromocytoma
- Congenital adrenal hyperplasia
What is the most common presentation of hypertension in children?
Incidental finding
What are the symptomatic presentations of hypertension?
- Headache
- Facial palsy
- Acute emergency
What are the acute emergency presentations of hypertension?
- Congestive cardiac failure
- Cerebrovascular accident
- Hypertensive encephalopathy
What are haemodynamics defined as?
Physical factors that govern blood flow
What is blood flow determined by?
- The blood pressure gradient between arterial and venous blood
- Resistance provided by blood vessel and viscosity of blood
Why is the blood inside arteries and smaller branches always under pressure?
- Constant tension in the walls of the arteries
- Peripheral resistance
What is meant by peripheral resistance in the context of haemodynamics?
The resistance offered to the passage of blood as it passes into smaller and smaller vessels
What provides the tension in the walls of arteries?
Muscle and elastic tissue
What happens to the pressure exerted on blood inside arteries when the left ventricle contracts?
There is a surge of pressure
What is the result of the surge of pressure produced by the contraction of the left ventricles?
It causes the larger arteries to distend and then recoil due to their own elasticity, causing a pulsation
What produces a greater change in arterial pressure during left ventricular contraction?
A greater stroke volume
What is the aortic pulse pressure?
The maximal change in aortic pressure during systole
How is the aortic pulse pressure calculated?
The systolic minus the diastolic pressure
What factors determine the systolic and diastolic blood pressure?
- Cardiac output
- Total peripheral resistance
What factors determine the rise in aortic pressure from diastolic to systolic?
- The compliance of the aorta
- The ventricular stroke volume
Which vessel has the greatest compliance in the arterial system?
The aorta
Why is the compliance in the aorta important?
It dampens down the pulsatile output of the left ventricle - if the aorta were rigid, the pulse pressure would be very high
Why is the energy from ventricular contraction not instantly transferred around the circulation after each heartbeat?
Because the circulatory system is elastic, and has resistance and other impediments to flow
What is the result of the energy from ventricular contraction not being instantly transferred around the circulation?
The energy of venous flow is several heartbeats behind that of ventricular ejection
What factors is blood pressure determined by?
- Cardiac output
- Peripheral resistance
What is the clinical relevance of BP being determined by cardiac output and peripheral resistance?
Clinical disorders that either raise cardiac output or peripheral vascular resistance can raise BP
What is cardiac output determined by?
- Stroke volume
- Heart rate
What is the most commonly affected factor leading to an increase in cardiac output?
An increase in stroke volume
What can cause a rise in stroke volume?
Rise in intravascular volume
What can cause a rise in intravascular volume?
Fluid retention
What can cause excessive fluid retention?
- Decreased fluid output
- Salt retention
What can cause decreased fluid output?
Oliguric renal failure
What can cause salt retention?
- Excessive salt intake
- Activation of the renin-angiotensin-aldosterone system (RAAS)
