11B H2O/electrolyte & Fluid Physiology

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

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

Amount solute (particles) per unit solvent volume = Amount solute / Volume solvent

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

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

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

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

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

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

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

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

Net water diffusion across membrane H2O movement across selectively permeable membrane

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

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

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

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

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

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

K+ 1° intracellular cation

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

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

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

285-295mOsm/Kg

275-290mOsm/Kg