BIOMED 10/23c Hemodynamics Flashcards
total body water
50-70% of body weight
total body water composition
○ 2/3: intracellular fluid
1/3: extracellular fluid
What composes extracellular fluid
(1/3 of total body water)
contains:
1. plasma
2. interstitial fluid
what is plasma?
it has a lot of soluble proteins (free and have a negative charge) - albumin
the proteins are too large to diffuse along the capillary membrane
what is interstitial fluid?
everything that is part of tissues that is outside the cells and the blood vessels
- ultra filtrate of plasma
- ion composition is similar to plasma
- difference: capillary wall
why does plasma have more proteins than interstitial fluid?
proteins are too large to diffuse along the capillary membrane, whereas the solutes are gases are able to
what separates plasma from interstitial fluid?
cell membrane
where are the gases, fluids, and solutes exchanged?
microcirculation!
Arterioles > capillaries (1 single endothelial layer thick) > venules > veins > heart > arteries
AND lymphatic network
what is the importance of the lymphatic network
fluid balance maintenance
how are gases and solutes exchanged?
DIFFUSION
SOLUTES:
– Lipid soluble substances (O2, CO2) diffuse through the endothelial cells
– Water-soluble substances (ions, glucose, amino acids) diffuse through
pores
– Plasma proteins are too large to diffuse
GASES:
through endothelial cells
Vesicular transport is minimal
what is flow determined by?
- resistance to flow
- pressure gradient between capillary and interstitium
- fluid exchange along the capillary
what determines a fluid’s resistance to flow?
- diameter of vessels
2. permeability of capillary wall
what is the major vessel that determines the overall impact of the diameter on the resistance?
arterioles! they are the most dynamic to change in diameter
What is the permeability of the capillary wall a function of?
Pore Size!
Capillaries in different tissues have different pore sizes
what are the different capillary pore sizes for different tissues?
– Cerebral = tight junctions between endothelial cells; capillary is NOT leak; K is low; pores are very small; Blood brain barrier
– Muscular = larger, INTERMEDIATE; K is intermediate (permeability constant)
– Glomerular = LARGE; very leaky capillaries in kidney to filter blood and make urine
– Bone marrow = VERY LARGE
what determines the pressure gradient between the capillary and the interstitium?
starling forces
- hydrostatic pressure
- osmotic/oncotic pressure
what is hydrostatic pressure?
blood pressure inside the vessel walls
Pc = capillary hydrostatic pressure (~30mmHg)
Pi = interstitial hydrostatic pressure (~-1)
PUSHES FLUID OUT OF CAPILLARY for FILTRATION
what is osmotic pressure?
due to negatively charged proteins that are too big to diffuse out of the capillary
Pic = capillary oncotic pressure (-26mmHg)
Pii = interstitial oncotic pressure (close to 0)
PULLS WATER INTO THE CAPILLARY for ABSORPTION
what is the difference between osmosis, osmotic pressure, and osmotic force?
– Membrane permeable to fluid, but not to solutes
– Osmosis = flow of fluid due to differences in concentration of solute in a membrane
** Diffusion is when the ion/solute moves through membrane
– Osmotic pressure = amount of pressure required to stop the flow of fluid from low to high concentration (from chamber 2 to 1)
– Osmotic force = pulls water into the capillary
what defines the fluid exchange between interstitium and capillary?
the balance between the osmotic pressure and the hydrostatic pressure
what determines the fluid exchange along the capillary?
changes in osmotic and hydrostatic pressure
arteriolar: delta P > delta Pi
- net filtration OUT of vasculature (3ml/min)
venous: delta P < delta Pi
- net absorption INTO the vasculature (2.7ml/min)
why don’t we get swelling even though net movement out of vessel is more than what is inside?
10% of what isn’t reabsorbed is picked up by the lymphatic vessels and finds its way back to the vasculature
what causes edema?
accumulation of fluid in interstitial space
what is non-inflammatory edema
- lymph system malfunction
2. disruption/altering in starling forces
what happens when lymph system malfunctions?
fluid is transudate (low protein concentration) and we get pitting edemas
what are the reasons for lymph edema?
◊ Primary = congenital
◊ Secondary = most common, resulting from trauma or surgery; UE swelling -> resection of lymph nodes following a mastectomy
Generally unilateral, unless bilateral mastectomy
how do you fix the symptoms of lymph edema?
compression wraps increase hyrdostatic pressure in the interstitium and decreases the pressure gradient and decreases fluid filtration of out the capillaries
what happens when the starling forces are altered?
edema occurs when there is an increase in hydrostatic pressure and a decrease in oncotic pressure
what kind of inflammation is a malfunction of the lymph system
non-inflammatory
why do we get increased hydrostatic pressure in capillary?
decreased flow through venous system; increased venous resistance caused by some sort of mechanical blockage
what happens after hydrostatic pressure in the capillary rises?
- increased filtration
2. increased fluid accumulation and edema
what are causes of increased capillary hyrdostatic pressure?
- DVT
2. Heart Failure
what is the edema response to a DVT?
- Unilateral edema distal (due to increased filtration)
- Redness
- Inflammatory response in the vein itself -> painful, hot swollen limbs - phlebitis
what causes edema when there is heart failure?
- left sided heart failure:
- Right ventricular output exceeds left ventricular output
- Pressure Backs up in pulmonary vasculature
- Fluid accumulates in the PULMONARY tissue
- Interstitial accumulation
- Fluid in alveoli and interferes with gas exchange - right sided heart failure:
- output of left ventricle exceeds right ventricular output
- Peripheral edema (bilateral LE)
- most edema in the bilateral dependent position
what is the impact of decreased oncotic pressure on edema?
when plasma protein concentration is decreased -> oncotic pressure decreases -> absorption decreases -> fluid accumulates -> edema
what is the most common plasma protein that drives oncotic pressure?
albumin
50-60% of plasma protein
normal concentration = 3.5-5.5 g/dL
Oncotic pressure is normally 25 mmHg
what happens in hypoalbuminemia
plasma protein concentration is decreased and it leads to decreased oncotic pressure this absoroption decreases and fluid accumulates as edema
where can hypoalbuminemia stem from?
- Liver
- Nephrotic disease
- Burns
- Protein-calorie malnutrition
what happens when there is protein calorie malnutrition?
Yields to gut edema and protein continues to spiral downward
can also seen petally and pre-tibially
how do you treat hypoalbuminemia from protein calorie malnutrition?
- Treatment: IV line to inject nutrition mixture to raise protein levels
- Total parenteral (right into the veins)
what is inflammatory edema?
- not pitting
- accompanied by redness, heat, and pain
how does inflammatory edema occur?
Leaky capillaries (increase in capillary permeability) - INFLAMMATORY (mechanism differs from the lymph and starling forces) - fluid is exodate and has a high protein content - pores are getting bigger so proteins can squeeze out
what is the process of inflammatory edema?
Mast cells release histamine -> diffuses to endothelial cells -> retract and increase pore size -> receptors are expressed for rolling, adhering, and migrating
define effusion
Accumulation of fluid in enclosed space
-joint or pleural
define depended edema
edema in the lowermost region
define anasarca
generalized edema
define ascites
accumulation of fluid in peritoneal cavity, causing abdominal swelling
compartment syndrome
Limb-threatening ↑ in pressure in
fascial compartment due to
bleeding or swelling of tissue in that
compartment
early signs and symptoms of compartment syndrome
– Numbness, paresthesias along cutaneous distribution of nerves in that compartment – Severe, progressive pain, worse with stretch or squeezing of affected muscles – Taut, shiny skin
late signs and symptoms of compartment syndrome
– Paralysis
– Diminished pulses
overall, edema results from?
– Disruption of lymphatic system – ↑ Hydrostatic pressure • Deep vein thrombosis – ↓ in oncotic pressure • Protein calorie malnutrition – ↑ Capillary permeability • Acute inflammation
treatment for compartment syndrome
fasciotomy - cut open fascia to relieve the pressure
in the absence of compensatory mechanisms, hemorrhage triggers:
Venous Return Drops -> Decreased Stroke Volume -> Decreased CO -> Decreased BP
what is pulse pressure?
systolic - diastolic
when pulse pressure drops, SV drops
what are compensations for hemorrhage?
- elevated HR
- cool, pale skin
- decreased urine output
why do we get elevated HR during hemorrhage?
in response to fall in BP, baroreceptors and carotid sinus send signal to medulla where we get the increase in firing; Decrease in Parasymp; Increase in Symp activity to HR and BVs;
Yields increased HR, Contractility, TPR, and venoconstriction
why do we get cool pale skin in response to hemorrhage?
Peripheral
vasoconstriction
– ↓ blood flow to
skin→ cool, pale skin
why do we get decreased urine output during hemorrhage?
Renin-angiotensin-aldosterone system
- Increased BP yields increase in angiotensin II that augments vasoconstriction
- > Yields increased thirst, sodium reabsorption, and water!
- Aldosterone also yields increased fluid volume and decreased fluid output
↑ Blood pressure by – ↑ Total peripheral resistance • Peripheral vasoconstriction → ↓ blood flow to skin→ cool, pale skin
– ↑ Fluid volume
• ↑ Na+ and H2O resorption
→ ↓ Urine output
when there is a ___ in ____ pressure we get retention of fluid in blood volume that yields ____ _____ pressure
decrease
capillary hydrostatic pressure
increased
arteriolar pressure
what does circulatory shock result from?
• failure of compensatory mechanisms
• Results from hypoperfusion of tissues
– Cellular hypoxia → Anaerobic metabolism →
Metabolic acidosis → Cell injury or death
what are signs/symptoms of shock
– Weak, rapid pulse – Hypotension – Low urine output – Altered mental status • Anxiety → Confusion → Loss of consciousness
what are the main stages of shock?
- initial
- compensatory
- progressive
- refractory
what is initial stage of shock?
– Cellular hypoxia → reliance on anaerobic metabolism
-high likelihood to come back from
what is compensatory stage of shock
– Hypercapnia and Acidosis → Hyperventilation
– Activation of baroreceptor reflex and renin-angiotensin
system to increase BP
-mid likelihood to come back from shock
what is progressive stage of shock?
– If compensatory mechanism fail, ↑metabolic acidosis
• General vasodilation → ↓ peripheral resistance
• Histamine release → fluid leakage, edema
-less likely to come back from this
what is refractory shock?
– Irreversible damage to cells → Organ failure → Death
-most often leads to death
what are different types/causes of shock?
- hypovolemic
- cardiogenic
- obstructive
- distributive
what is hypovolemic shock?
– Fluid loss due to hemorrhage, burns,
vomiting/diarrhea
what is cardiogenic shock?
– Failure of cardiac pump
what is obstructive shock?
– Obstruction of blood flow due to tamponade, aortic
stenosis, pulmonary embolism
what is distributive shock?
– Septic, anaphylactic, neurogenic
what does hemorrhage yield?
• Hemorrhage → ↓ Venous Return → ↓ CO
what are the responses to hemorrhage summarized?
– Baroreceptor Reflex • ↑ SNS activity → ↑ HR, ↑ Contractility, ↑ TPR → ↑ BP – Renin – Angiotensin – Aldosterone • ↑ TPR, ↑ Fluid Retention → ↑ BP
