11B H2O/electrolyte & Fluid Physiology Flashcards Preview

AS - N927 Chem/Physics > 11B H2O/electrolyte & Fluid Physiology > Flashcards

Flashcards in 11B H2O/electrolyte & Fluid Physiology Deck (33)
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1

Homeostasis

Given physiologic function or variable remains w/in predictable range (time averaged mean) over time
When ↑↓ disturbed, restored to baseline

2

Hydrostatic Pressure

Pressure exerted by any fluid at equilibrium d/t gravitational force

3

Concentration

Amount solute (particles) per unit solvent volume

= Amount solute / Volume solvent

4

Ion

Atom or group of atoms w/ an electrical charge +/-
Cation (+)
Anion (-)

5

Octet Theory

All elements need 8e¯ in outer orbit
Stable & unreactive
Elements w/ 4e¯ share (Amphoteric)
< 4e¯ tend to lose
> 4e¯ tend to gain

6

Valence e¯

# electrons in an atom outermost energy level (shell)
NOT the same as valency
Chloride 7 valence e¯

7

Valence Osmosis

Atom combining power
Absolute number electrons gained, lost, or borrowed in order to fill outermost energy level
Chloride 1 valency

8

Equivalents

Represents electroneutrality (balanced +/-) in solutions
Electroneutrality maintained in plasma & ISF
Total # ionic charges in solution (ion moles) and considers each ion valence (charge)
1 Mole Cl¯ = 1Eq
1 Mole Ca2+ = 2Eq

9

mEq

Electrolyte chemical activity
1/1,000
NaCl = mEq +/-

10

mg/dL → mEq/L

mg/dL = (mEq/L x Atomic weight) / (10 x valence)
mEq/L = (mg/dL x 10 x valence) / Atomic weight

11

Conversions mEq/Moles/mg

222mg CaCl2 in 1L fluid
GMW = 111g/Mol = 111mg/mMol
222mg/(111mg/mMol) = 2 mMol in 1L
2mMol/L = 2mM
2mM CaCl2 → 2mM Ca2+ + 4mM Cl¯
Ca2+ 2mMol x valency 2 = 4mEq/L cation
Cl¯ 4mMol x valency 1 = 4mEq/L anion
Electroneutrality maintained when salt dissolves

12

Osmosis

Net water diffusion across membrane
H2O movement across selectively permeable membrane

13

Osmotic Pressure

Pressure that must be applied to solution to prevent net flow water into (osmosis)
Number particle correlates to osmotic pressure
Large (glucose) and small (Na+) particles exert the same osmotic pressure
Smaller mass = higher velocity
K = (mv^2) / 2
Directly r/t solute concentration (osmolality)
H2O moves from high to low osmolality areas
Indirect measure H2O & solute concentration
↑ osmotic pressure → ↑ solute concentration ↓ H2O

14

Osmol

Amount per unit volume
Expresses solute concentration
1 mole (GMW) of solute particles dissolved in solution
Osmoles refers to osmotically active particles in solution

1 Mole / 1L = 1 Molar = 1M
1 osmol / 1L = 1 osmMolar = 1 osmM

1 Osmole = 1 Mole solute particles = 1,000 mOsm
Total number particles in solution measured in osmoles

15

OsmolaRity

Chemistry term
Osmotic concentration of solution
Osmoles of solute per liter of solution
Unable to measure actual L fluid in body - estimate
Molar solution # moles of solute per liter of solution
Osmoles/L solution
Directly proportional to osmotic pressure

16

OsmolaLity

Physiological term - most correct clinically
Body weight in Kg (measurable)
Osmotic concentration of solution
Osmoles of solute per Kg of solution
Molal solution # moles of solute per Kg of solution
Osmoles/Kg solution

17

Total Body Water

60%
70Kg x 0.6 = 42L
Extracellular
- Plasma (3L)
- Interstitial (11L)
Intracellular 28L

18

Sodium

Na+
1° extracellular cation
Accurately reflects osmolality
H2O moves out
↑ osmolality
↑ Na+ concentration

19

Potassium

K+
1° intracellular cation

20

The Donnan Equilibrium

Negatively charged non-diffusible protein molecules (Albumin) on one membrane side leads to an excess diffusible cations and deficit diffusible anions on same side
Proteins are multi-valent (many negatively charged areas) therefore attract multiple cations

21

Van Hoff's Law

π = CRT
Osmotic pressure in mmHg π
C = solute in osmoles/L
R = Ideal gas constant 62.36
T = temperature in °Kelvin

1 mOsm = 19.3mmHg

22

Calculate Osmotic Pressure

0.9% NaCl = 0.9g/100ml = 9g/L
NaCl GMW = 23 +35.5 = 58.5g/mole
(9g/L) / (58.5g/mole) = 0.154moles/L
154mMoles/L
Na+Cl¯ dissociates in solution to Na+ and Cl¯ ions
1 Mole NaCl = 2osmoles
154mMoles/L x 2 = 308mOsm/L = Isotonic

23

Adult Osmolality

285-295mOsm/Kg

24

Pediatric Osmolality

275-290mOsm/Kg

25

Isotonic

No net movement

26

Hypertonic

400mOsm
Water moves out into solution → cells shrink

27

Hypotonic

200mOsm
Water moves into cells → cells swell

28

Colloid Osmotic Pressure

Oncotic pressure
Donnan equilibrium effect results in colloid osmotic pressure in the plasma
Increases effect by 50% as compared to proteins alone

29

Isotonic Crystalloid

NS or LR
Stays in extracellular fluid - plasma & ISF
20% (3/14) left in plasma
No impact on intracellular
Exception - dehydrated cell

30

Hypotonic Crystalloid

D5W
Dextrose used in metabolism leaving hypotonic H2O
7% (1/14) left in plasma
Equilibrates across all three compartments