Hemodynamics & Fluid Disorders (10/23c) [Biomedical]

Question 1

Fluid in the Body

Answer 1

Total body water = 50-70% of body weight

⅔ intracellular, ⅓ extracellular (contains plasma and interstitial fluid)

Question 2

Extracellular and intracellular differ in ___ concentration

Answer 2

ion

Question 3

Plasma and interstitial fluid differ in ___ concentration

Answer 3

protein

Plasma contains a lot more soluble proteins with negative charge (EX: albumin)

not much in interstitial bc too big to diffuse across capillary membrane

Question 4

Exchange occurs in the microcirculation

Answer 4

Gasses, solutes, and fluids exchanged between vasculature and tissue

Microcirculation involves arterioles, capillaries, venules, arteries, veins, and lymphatic network

Question 5

How are gasses and solutes exchanged?

Answer 5

Capillary cell walls are only 1 endothelial cell thick

At cell junctions, the pores can increase as cells pull away and cause leakage

Gasses and solutes exchange by diffusion

Vesicular transport is minimal

Question 6

Gasses and solutes exchange by diffusion

Answer 6

Lipid soluble substances (O2, CO2) diffuse through the endothelial cells

Water solubles (ions, glucose, amino acids) diffuse through pores

Plasma proteins are too large to diffuse

Question 7

Fluid flow is determined by

Answer 7

Resistance to flow

Pressure gradient between capillary and interstitium

Question 8

Resistance to flow

Answer 8

Determined by permeability of the capillary wall (K)

Cerebral capillary K is very low → not leaky
- mechanism behind blood-brain barrier

Muscle capillary K is intermediate

Glomerular capillary K in kidney is very high → is leaky

Question 9

Pressure gradient between capillary and interstitium

Answer 9

Determined by Starling Forces

• hydrostatic pressure
• oncotic pressure

Question 10

Starling Forces - Hydrostatic Pressure

Answer 10

the mechanical pressure of blood on vessel walls

tends to push fluid out of the capillary

Pc = capillary hydrostatic pressure

Pi = interstitial hydrostatic pressure
- much lower than Pc

Question 11

Starling Forces - Oncotic Pressure

Answer 11

pressure due to negatively charged proteins that are too big to leave capillary

tends to pull fluid into the capillary

𝜋c = capillary oncotic pressure

𝜋i = interstitial oncotic pressure
- nearly 0 since few proteins outside

Question 12

Osmosis

Answer 12

flow of fluid due to differences in solute concentration across a membrane

Fluid goes from low → high solute concentration

Question 13

Osmotic Pressure

Answer 13

amount of pressure we would have to apply to stop the flow of fluid

Question 14

Fluid Exchange Along the Capillary - Arterial End

Answer 14

ΔP > Δ𝜋

Net filtration, or movement of fluid out of the vasculature (out of capillary, into interstitium)

Generally 3 mL/min

Question 15

Fluid Exchange Along the Capillary - Venous End

Answer 15

ΔP < Δ𝜋

Net absorption, or movement of fluid into the vasculature (out of interstitium, into capillary)

Generally 2.7 mL/min

Question 16

Filtration vs Absorption

Answer 16

90% of what we filter is reabsorbed

The lymph vessels pick up the remaining 10% (0.3 mL/min) and return it to the blood via the vena cava

Question 17

Edema

Answer 17

results when fluid remaining after absorption exceeds capacity of lymph vessels to collect and return

accumulation of fluid in the interstitial space

Question 18

Edema - Causes

Answer 18

Disruption of lymphatic system

Altered Starling Forces

• increased hydrostatic pressure
• decreased oncotic pressure

Increased capillary permeability

Question 19

Edema - Disruption of Lymphatic System

Answer 19

Lymphedema — edema causes by dysfunction of or damage to lymph system

Primary = congenital

Secondary = resulting from trauma or surgery

Question 20

Edema - Altered Starling Forces, Increased Hydrostatic Pressure

Answer 20

Increased venous resistance

Increased capillary hydrostatic pressure

• increased filtration
• increased fluid accumulation → edema

Question 21

Causes of increased venous resistance in edema - DVT

Answer 21

Usually unilateral

Swollen limb due to increased filtration

Tenderness along venous distribution, erythema and heat due to inflammation of vein (phlebitis)

Question 22

Causes of increased venous resistance in edema - Heart Failure

Answer 22

Pulmonary Edema (left sided failure)

• right ventricular output exceeds left
• pressure backs up
• fluid accumulation in pulmonary tissue

Peripheral Edema (right sided failure)

• left ventricular output exceeds right
• pressure backs up
• fluid accumulation peripherally (bilateral LE)

Question 23

Edema - Altered Starling Forces, Decreased Oncotic Pressure

Answer 23

Albumin accounts for 50-60% of plasma protein

• normally 3.5-5.5 g/dL
• oncotic pressure ~ 25 mmHg

Decreased protein in plasma leads to decreased oncotic pressure

• decreased absorption
• fluid accumulation → edema

Question 24

Hypoalbumenia

Answer 24

low albumin concentration in plasma

Causes

• liver disease
• nephrotic tissue
• burns
• protein calorie malnutrition

Question 25

Edema - Increased Capillary Permeability

Answer 25

Histamine release causes: Contraction of endothelial cells opens pores Fluid, proteins, and WBCs leak out of capillary Fluid accumulation → edema

Question 26

Noninflammatory Edema

Answer 26

CAUSE - altered Starling forces - disruptions of lymphatic system FLUID - transudate (low protein content) CLINICALLY - pitting - generally dependent region - no signs of inflammation (except w/ DVT or phlebitis)

Question 27

Inflammatory Edema

Answer 27

CAUSE - increased capillary permeability FLUID - exudate (high protein content) CLINICALLY - nonpitting - signs of inflammation

Question 28

Edema Terms - Dependent

Answer 28

edema in lowermost region

Question 29

Edema Terms - Anasarca

Answer 29

generalized edema

Question 30

Edema Terms - Effusion

Answer 30

accumulation of fluid in enclosed space In the joint, pleural space

Question 31

Edema Terms - Ascites

Answer 31

accumulation of fluid in peritoneal cavity, causing abdominal swelling

Question 32

Edema Terms - Compartment Syndrome

Answer 32

limb-threatening increase in pressure in fascial compartment due to bleeding or swelling of tissue in that compartment EARLY SIGNS - numbness, paresthesias along dermatomes in that compartment - severe progressive pain, worse with stretch or squeezing of affected muscles - taut, shiny skin LATE SIGNS - paralysis - diminished pulses

Question 33

Immediate Effect of Hemorrhage on CV System

Answer 33

``` Decreased blood volume → decreased venous return → decreased stroke volume → decreased cardiac output → decreased blood pressure ```

Question 34

Hemorrhage and Baroreceptor Reflex

Answer 34

``` Increased SNS activity → increased HR → increased contractility → increased TPR → increased BP ```

Question 35

Hemorrhage and Renin-Angiotensin-Aldosterone System

Answer 35

Increased fluid volume → increased Na+ and H2O reabsorption → decreased urine output

Question 36

What causes cool, pale skin?

Answer 36

Increased TPR → peripheral vasoconstriction → decreased blood flow to skin → cool pale skin

Question 37

Circulatory Shock

Answer 37

Results from hypoperfusion of tissues Cellular hypoxia → anaerobic metabolism → metabolic acidosis → cell injury or death

Question 38

Signs of shock

Answer 38

Weak, rapid pulse Hypotension Low urine output Altered mental status - anxiety → confusion → unconscious

Question 39

Stages of Shock

Answer 39

Initial Compensatory Progressive Refractory

Question 40

Stages of Shock - Initial

Answer 40

Cellular hypoxia → reliance of anaerobic metabolism

Question 41

Stages of Shock - Compensatory

Answer 41

Hypercapnia and acidosis → hyperventilation Activation of baroreceptor reflex and RAA system to increase BP

Question 42

Stages of Shock - Progressive

Answer 42

If compensatory mechanism fails, increase metabolic acidosis General vasodilation → decrease peripheral resistance Histamine release → fluid leakage, edema

Question 43

Stages of Shock - Refractory

Answer 43

Irreversible damage to cells → organ failure → death

Question 44

Types/Causes of Shock - Hypovolemic

Answer 44

fluid loss due to hemorrhage, burns, vomiting/diarrhea

Question 45

Types/Causes of Shock - Cardiogenic

Answer 45

failure of cardiac pump

Question 46

Types/Causes of Shock - Obstructive

Answer 46

obstruction of blood flow due to tamponade, aortic stenosis, or pulmonary embolism

Question 47

Types/Causes of Shock - Distributive

Answer 47

septic, anaphylactic, neurogenic