7.3 Blood Pressure Flashcards
What is the difference between primary and secondary HTN? mmHG?
primary hypertension: most common, unknown etiology
secondary hypertension: result of pathology in another organ
more than 140/90
What does HTN do to arteries? Which are most susceptible?
endothelial damage due to shearing forces on vessel walls
retinal arteries hypertensive retinopathy, blindness
renal arteries renal failure
cerebral arteries hemorrhagic stroke
increases atherosclerosis
How does HTN lead to left ventricular hypertrophy?
hypertension increases afterload, resistance against the left ventricle
left ventricular hypertrophy without increase in vascular supply –> susceptible to ischemia, infarction
left ventricle chamber has reduced volume, reduces stroke volume and cardiac output
may also encroach on right ventricle chamber size
How does HTN lead to renal disease?
increases atherosclerosis of kidney afferent and efferent arterioles of nephrons
damages fragile glomerular capillaries, filtration rate decreases, permeability increases
increased waste in blood, serum creatinine and blood urea nitrogen (BUN) increase
loss of serum proteins in urine (proteinuria)
Can lead to renal failure, end stage renal disease
What is pulse pressure? Formula?
The “throb” of pulse
= systolic-diastolic
What is MAP? How derived?
Average between systolic and diastolic
calculated: [MAP = diastolic + 1/3 (systolic – diastolic)]
theory: [MAP = CO X PVR]
What 3 factors generally impact BP?
Blood Flow
Resistance
Blood Volume
Systemically, what impacts blood flow?
local blood flow to an organ/region
bulk flow through capillaries
systemic blood flow through the entire body
How is local blood flow auto regulated?
metabolic controls: low oxygen and high waste accumulates, causes vasodilation
increased metabolic products: H+, lactic acid, K+, adenosine, prostaglandins
releases Nitric Oxide (NO) –> vasodilation
myogenic controls
stretch due to increased pressure
smooth muscle contracts –> vasoconstriction
angiogenesis (long-term)
growth of new blood vessels to increase supply to the area
What is capillary blood flow? What determines it?
movement of fluid between capillaries and tissue interstitial space
This is determined by the pressure, fluid and components that change from the arteriole to venule end of the capillary bed
Arteriole end: Fluid needs to leave the capillaries to bathe the tissues
Venous end: Fluid needs to return back to the capillaries to remove waste and retain blood flow.
Lymphatics: excess fluid and debris will be cleaned and returned to circulation through lymphatics.
How does hydrostatic pressure contribute to capillary bulk flow?
fluid, blood pressure:
arteriole –> venule blood pressure (35 –> 17 mmHg)
How does osmotic pressure contribute to capillary blood flow?
solute pressure (water follows solutes)
high concentration of plasma proteins and blood cells left in capillary (26mmHg)
low level of proteins in the interstitial fluid (0.1 to 5 mmHg)
=measure of the amount of solutes; water follows solutes
What is the definition of net filtration pressure?
sum of hydrostatic and osmotic pressures between the capillaries and ICF
What is the formula for net filtration pressure?
NFP = (OUT) – (IN)
or:
[NFP = (HPc + OPicf) – (HPicf + Opc)]
What causes peripheral edema? When supine?
Venous congestion, increased venous pressure causes a build up of pressure in the capillary beds, this leads to edema (swelling) in the lower body
standing swelling in lower extremities, ankles
lying down swelling in the sacral region, risk of bed sores
** If venous congestion is more than the lymphatic system can remove = edema
