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OS Renal > Body Fluid Homeostasis SS - Rao > Flashcards

Body Fluid Homeostasis SS - Rao Flashcards

1
Q

Total body water (TBW) is what percent of a person’s weight?

A

60%

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2
Q

What are the major sources of fluid intake in the body?

A

Drinking water, followed by water in food and oxidative metabolic production of water

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3
Q

What are the major sources of fluid output?

A

Urine, ‘insensible’ water from skin/lung/sweat, and a little in feces

Insensible water loss is high in burn victims and fecal loss high in diarrhea

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4
Q

What is the absolute minimum daily urine output?

A

500 mL

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5
Q

What is the volume of ICF in an average person?

A

25L

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6
Q

What is the volume of ECF in an average person?

A

15L

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7
Q

What is the volume of fluid in interstitial space?

A

12L

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8
Q

What is the volume in a person’s plasma and total blood?

A

3L in plasma; 5L total blood volume; blood is 60% plasma and 40% hematocrit

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9
Q

What is the major cation and anion in the interstitium/plasma?

A

Na, Cl

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10
Q

What is the major anion and cation in the intracellular fluid?

A

K+, Protein-

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11
Q

What is the Gibbs-Donnan effect in relation to fluid compartments?

A

Explains the behavior of charged particles near a semi-permeable membrane; Na+ is greater in plasma by 2% and Cl- lower by 2% because the capillaries are more permeable than the cellular membranes, allowing negatively charged proteins to retain the Na+ through electrical interactions

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12
Q

Where is bicarbonate in highest concentration

A

Plasma and interstitium

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13
Q

Where is phosphate in highest concentration

A

intracellular

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14
Q

Where is magnesium in highest concentration/

A

intracellular

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15
Q

What are the criteria for probes that measure body fluid?

A 
Non-toxic at used concentration
Neither synthesized or metabolized
Disperses evenly
Disperses only in compartment of interest
Doesn't influence volume itself
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16
Q

What probes are used to measure plasma volume?

A

Iodinated albumin, Evans blue dye, both which bind avidly to plasma proteins

17
Q

What is the formula to measure volume of plasma?

A

Blood volume = plasma volume / (1-HCT)

18
Q

What is the formula for measuring concentration of a something in a fluid compartment?

A

Compartment volume = Q / (Q/V), where Q/V is the concentration of the probe and Q is the amount of probe injected

Applies to intra- and extracellular compartments

19
Q

What are the probes used to measure extracellular fluid volume?

A

Inulin, thiosulfate, and Na+

20
Q

ISF=

A

ECF-PV

21
Q

What are the probes used to measure total body water?

A

Radiolabelled water; antipyrene

22
Q

ICF=

A

TBW-ECF

23
Q

What forces determine the fluid movement between plasma and ISF?

A

Starling forces - hydrostatic and oncotic pressure

(Capillaries are more permeable than cell membranes)

NOT plasma osmolarity

24
Q

What forces determine the fluid movement between the intracellular and extracellular fluid?

A

Osmosis, mainly due to differences in sodium concentration causing water rearrangment

25
Q

How are osmoles different than moles?

A

Moles is amount of molecules; osmoles is amount of particles in solution

26
Q

Does osmotic pressure depend on molecule size?

A

One particle of albumin and one particle of glucose have the same osmotic pressure

27
Q

How do the osmolarities of different fluid compartments compare?

A

They are all the same, 295 mOsm/L, because water is freely permeable through barriers

28
Q

What happens to RBCs in hypotonic Na solution?

A

Swelling and lysis

29
Q

What happens to RBCs in hypertonic Na solution?

A

Shrink

30
Q

What happens to RBCs in the presence of a low Na and high urea environment?

A

Swelling, because urea is freely permeable across membranes

31
Q

Formula for estimating plasma osmolarity?

A

Plasma osmolarity = 2[Na+] + glucose + urea

32
Q

What are the steps for estimating how much fluid to give a patient?

A

Calculate ECF and ICF before depletion; calculate total mOsm in ECF and ICF now, calculate volume needed to achieve 280 mOsm, then calculate amount of fluid needed to add

33
Q

Giving isotonic saline to a normally hydrated person will change which compartments?

A

ECF only, maintain same osmolarity while increasing volume

34
Q

Gaining pure water through drinking or giving 5% glucose H20 will change which compartments?

A

Increase volume of all compartments; decrease osmolarity of all compartments

35
Q

What does excess gain of salt do to copartments?

A

Increase ECF osmolarity, draws water from ICF, increase ECF volume, decrease ICF volume, osmolarity of all compartments increased

36
Q

What does loss of NaCl do to compartments?

A

Decreases ECF osmolarity, flux of water into ICF, decrease volume of ECF, increase vol of ICF, osmolarity decreasd in all compartments

This is why you should drink electrolyte-rich drinks like Gatorade after excessive sweating instead of pure water

37
Q

What does infusion of isotonic urea do to compartments?

A

Increases volume of all compartments (water retained everywhere) without changing osmolarity of anything

OS Renal (25 decks)

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