11B H2O/electrolyte & Fluid Physiology

Question 1

Homeostasis

Answer 1

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

Question 2

Hydrostatic Pressure

Answer 2

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

Question 3

Concentration

Answer 3

Amount solute (particles) per unit solvent volume

= Amount solute / Volume solvent

Question 4

Ion

Answer 4

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

Question 5

Octet Theory

Answer 5

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

Question 6

Valence e¯

Answer 6

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

Question 7

Valence Osmosis

Answer 7

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

Question 8

Equivalents

Answer 8

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

Question 9

mEq

Answer 9

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

Question 10

mg/dL → mEq/L

Answer 10

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

Question 11

Conversions mEq/Moles/mg

Answer 11

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

Question 12

Osmosis

Answer 12

Net water diffusion across membrane

H2O movement across selectively permeable membrane

Question 13

Osmotic Pressure

Answer 13

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

Question 14

Osmol

Answer 14

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

Question 15

OsmolaRity

Answer 15

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

Question 16

OsmolaLity

Answer 16

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

Question 17

Total Body Water

Answer 17

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

Question 18

Sodium

Answer 18

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

Question 19

Potassium

Answer 19

K+

1° intracellular cation

Question 20

The Donnan Equilibrium

Answer 20

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

Question 21

Van Hoff’s Law

Answer 21

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

Question 22

Calculate Osmotic Pressure

Answer 22

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

Question 23

Adult Osmolality

Answer 23

285-295mOsm/Kg

Question 24

Pediatric Osmolality

Answer 24

275-290mOsm/Kg

Question 25

Isotonic

Answer 25

No net movement

Question 26

Hypertonic

Answer 26

400mOsm

Water moves out into solution → cells shrink

Question 27

Hypotonic

Answer 27

200mOsm

Water moves into cells → cells swell

Question 28

Colloid Osmotic Pressure

Answer 28

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

Question 29

Isotonic Crystalloid

Answer 29

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

Question 30

Hypotonic Crystalloid

Answer 30

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

Question 31

Isotonic Colloid

Answer 31

5% Albumin
All volume remains in plasma 100%
Unable to cross endothelium ჻ confined to plasma
Donnan effect to pull additional fluid into vasculature

Question 32

Hypertonic Crystalloid

Answer 32

3% saline
Equilibrates across extracellular compartments - plasma & ISF
Pulls fluid from intracellular to extracellular

Question 33

Plasma Volume Expansion

Answer 33

How much fluid stays in the plasma?
PV expansion = PV / Vd
↑ Vd ↓ plasma volume expansion