Water and electrolytes Flashcards by Kevin Bayaca

What is hydrostatic pressure?

it is the pressure exerted by an fluid at equilibrium due to the force of gravity
Pressure= force/area

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What is the concentration of solutions?

amount of solute per unit volume of solvent

concentration= amount solute/volume solvent

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Ion

atom or group of atoms with an electrical charge
cation +
anion-

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Valence electrons

the number of electrons in an atom’s outermost energy level (shell)

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Valency

the combining power of an atom
the absolute number of electrons that are gained,
lost, or borrowed in order to have a full outermost
energy level
Elements with 4 electrons will share them such as
Carbon
Examples:
oxygen has 6 valence electrons so its valency is 2
sodium has 1 valence electron so its valency is 1

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osmosis

the net diffusion of water across a membrane

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Osmotic pressure

the pressure that must be applied to a solution to prevent the net flow of water into it
the amount of pressure required to prevent
osmosis is called the osmotic pressure
per k= (m x v^2)/2 large and small particles exert the
same osmotic pressure

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Osmotic pressure is directly related to

the solute concentration (osmolality)

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What contributes the most to osmotic pressure of body fluids?

electrolytes; they determine the distribution of body water

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What is an osmol?

one mole of solute particles dissolved in a solution
indicator of osmotic activity
the term osmole refers to the number of osmotically active particles rather than the molar

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1 mole/1 L is equal to

1 osmol/ 1L or 1 osmM

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1 osmole is equivalent to

1 mole which is equal to 6.02 x 10^23 particles

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What osmolality do we use when referring to the body?

we utilize milliosmoles for body fluids

1 mOsm= 1/1000 osmoles

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What is osmolarity?

the osmotic concentration of a solution expressed as OSMOLES of solute per LITER of solution

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What is osmolality?

the osmotic concentration of a solution expressed as OSMOLES per KG of solution
285-295 mOsm/kg is normal osmolality for adults
275-290 mOsm/kg is normal osmolality for
children

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What is an isotonic solution?

the solution has the same solute concentration as our cells

0.9 NS or LR

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What is a hypotonic solution?

the solution has less solute concentration than our cells so water will want to move into cells and cause them to burst
ex.: D5 or .45 NS

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What is a hypertonic solution?

the solution has more solute concentration than our cells so water will want to move out of cells and cause them to shrink
Ex. 3%

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What is colloid osmotic pressure?

high MW substances such as proteins (albumin) do exert a colloid osmotic pressure (oncotic pressure)
proteins are confined in the vascular space whereas all other dissolved solutes pass freely through the capillary pores

What is the total body weight of water?

60%
in a 70 kg person 3L is plasma, 11 L is ISF, and 28 L is intracellular
We can calculate these for any body weight

What electrolytes have the highest concentrations extracellularly?

Na+, Cl-, and bicarb

What electrolytes have the highest concentrations intracellularly?

K+, Mg+, proteins, phosphate, and organic anions have the highest concentrations inside the cell

Explain the Donnan equilibrium effect.

Proteins that have multiple negative charges attracts cations, cations bring water (hydration spheres) so osmotic pull is much larger than expected for 1 protein
-electroneutrality is maintained in the plasma and ISF
the presence of negatively charged non-diffusible proteins molecules on one side of a membrane leads to an excess of diffusible cations and a deficit of diffusible anions on the same side

What is a colloid solution?

colloids are big proteins that cannot diffuse across the plasma membrane; they have negative ions so they pull water into the plasma

If we have 1 mole of Cl-. How many moles of Ca2+ will balance the charge on 1 mole of chloride?

Ca2+ is divalent thus half a mole of Ca2+ will balance 1 mole of negative charge

Conversion between mEq and moles and milligrams for 222 mg CaCl2 in 1 L of fluid

222 mg CaCl2 & MW is 111 grams/mole 111 grams/mole= 111 mg/mmole so 222 mg/111 mg/mmole= 2 mmole 2 mmoles/ 1 L For Ca2+: 2 mmoles in 1 L x valency of 2= 4 mEq/L For Cl-: 4 mmoles in 1 liter x valency of 1= 4 mEq/L of anion

Why do we use mEq/L over mg/deciliter?

mEq/L shows neutrality | Mg has to be converted to moles of ions and valence to assess neutrality

What is Van Hoff's Law & it's relationship to osmotic pressure and fluid movement?

osmotic pressure= CRT where C is concentration in osmoles/L R= ideal gas constant of 62.36 T= Temperature in Kelvin

Example of Van Hoff's Law: what is the osmotic pressure of 0.9% NaCl?

9 grams/ 1 L 9 grams/58 g/mole 0.155 moles/ 1 L or 0.155 molar x 1000= 155 mmoles/Liter NaCl dissociates into Na+ and Cl- so we have 2 osmoles (155 mmoles x 2) = 308 mOsmoles/L = 308 mOsmoles/L x 62.36 x 310 K =5,954 mmHg

What is the volume of distribution for colloid solutions?

albumin- plasma | PV/Vd = 3/3 so 100% of it stays in the plasma

What is the volume of distribution for isotonic solutions?

NS & LR Plasma and ISF 3/14= 20% fraction left in plasma

What is the volume of distribution for hypotonic solutions?

D5W plasma, ISF, ICF 3/42= 7% fraction left in plasma

What is the volume of distribution for hypertonic solutions?

3% plasma, ISF, and draws fluid in from ICF cannot calculate d/t this

Be able to calculate the Net Capillary Filtration given the Pc, Pif, πp and πif / determine which way fluid will flow

Net filtration pressure (NFP) = (Pc – Pif) – (πp – πif) Where Pc = capillary hydrostatic pressure (outward) Pif = interstitial fluid hydrostatic pressure (inward) (is usually -3mmHg) Πp = osmotic force due to plasma protein concentration (inward) Πif = osmotic force due to interstitial fluid protein concentration (outward)

What is the major extracellular ion?

Na+ & it is a good reflection of osmolality | If Na+ goes up sodium is not the issue, H2O is

Electroneutrality is maintained

in plasma and ISF

Conversion of mg/dl to mEq/Liter

mEq/Liter= (mg/dl x 10 x valence)/atomic weight

Proteins are

multi-valent (many negatively charged areas) and thus, can attract multiple cations

Osmotic pressure

is directly related to concentration of the solute and it determines how water moves

The water concentration of a solution depends on

the number of particles in the solution | we define this in osmoles

The amount of pressure required to prevent osmosis is known as

osmotic pressure

increased osmotic pressure

higher solute concentration and lower water concentration

The osmotic pressure is directly proportional

to osmolarity or the concentration of osmotically active particles in the solution

1 molecule of NaCl has XXXX the osmotic effect of 1 molecule of glucose

twice

A large force acts to move H2O across the cell membrane when

intracellular and extracellular fluids are not in osmotic equilibrium 1 mosmole = osmotic pressure of 19.3 mmHg

When the MW of a substance is low

there will be MORE molecules per a given unit weight | more molecules--> greater osmotic pressure

Plasma volume expansion equation

Plasma volume expansion= plasma volume/volume of distribution