Electrolytes Flashcards
How much of total body weight (blood volume) is plasma?
4%
What is the range of total body water in % of weight? what causes the variance?
45-75%
dependable on sex, body fat, skeletal muscle, and age
what is the typical body water for males and females? (%wt)
male - 60%
femae - 50%
what is the %wt body water for a newborn, 1 year old, and adult?
nb - 75%
1yo - 65%
adult - 50%
where is the capillary membrane and what is its function?
between plasma and interstitial fluid
allows easy movement of electrolytes and water
where is the plasma (cell) membrane and what is its function?
located between interstitial fluid and intracellular fluid
limits movement of electrolytes through tightly regulated pumps/channels but allows free movement of water
What is the Na concentration in the plasma, interstitial, and intracellular? Also state for K, Ca, Cl, and HCO
Order from plasma to interstitial to intracellular:
Na: 140, 146, 12
K: 4, 5, 150 (only one higher intracellularly)
Ca: 5, 1, 10^-7
Cl: 103, 104, 3
HCO: 24, 27, 10
what occurs once ion gradients are established?
little ion movement between ECF to ICF
water moves easily across membranes based on osmotic forces
Na added to ECF - does not change amount in ICF, only ECF
What %body wt is intracellular fluid? extracellular?
intra - 40%
extra - 20%
what is ICF?
volume within cells that is very tightly controlled
most ICF located in skeletal muscle
what is ECF?
volume not within cells that isn’t as tightly controlled
What causes water and solute movement between plasma and interstitium?
starling forces
What is Pc?
hydrostatic pressure in capillary that increases with incr. venous pressure (leads to edema)
what is pii?
oncotic (colloid) pressure in interstitium
what is Pi?
hydrostatic pressure in interstitium
what is pic?
oncotic pressure of plasma early in capillary
what are the relative pressure measurements for the following: Pc pii Pi pic
Pc = 37-20mmHg pii = 0mmHg Pi = 1mmHg pic = 25mmHg
where do preload and afterload occur?
after - in artery after left ventricle (arterial resistance)
pre - in veins before right atrium (venous return)
where do preload and afterload occur?
after - in artery after left ventricle (arterial resistance)
pre - in veins before right atrium (venous return)
what is hypertension in terms of preload and afterload?
increase in afterload
what is the difference between left sided and right sided heart failure?
left: blood backs up in lungs (drowning feeling - could be life threatening)
right: blood backs up in periphery (edema)
what on the cell maintains ICF solute/electrolyte levels?
Na/K ATPase
what drives water movement?
difference in osmolality
What is the major osmotically active cation outside the cell?
Na
what is the major osmotically acitve cation inside the cell?
K
what allows movement of fluid between plasma and interstitial space?
changes in pic and Pc move fluids and electrolytes
what allows movement between plasma and intracellular fluid?
sodium (osmolality changes and water movement)
K (resting membrane potential changes)
what is K responsible for?
determining intracellular osmolality
what could occur if there is a change in extracellular K relative to intracellular K?
major effects on resting membrane potential which could cause electrical conductance issues
how does the body respond to changes in potassium? (acute and chronically)
acute - drive potassium in or out of cells
chronic - distal nephron Na delivery/renal actions of aldosterone
how do you treat hypokalemia?
slowly administer K (diet or IV)
how do you treat hyperkalemia? (short term and long term)
short term: stimulate beta-adrenergic receptor, cause alkalosis (H leaves, K enters), insulin in emergencies, and Ca (depolarize threshold potential)
long term: aldosterone (K secretion)
how do you treat hyperkalemia? (short term and long term)
short term: stimulate beta-adrenergic receptor, cause alkalosis (H leaves, K enters), insulin in emergencies, and Ca (depolarize threshold potential)
long term: aldosterone (K secretion)
what is osmolality?
instrument measurement of solutes in a solution reported as mOsmol/Kg of solvent
what is osmotic pressure?
a pressure that needs to be applied to a solution to prevent movement of water across semipermeable membrane
what is tonicity?
osmotic pressure gradient of two solutions separated by a semipermeable membrane which must be selective in blocking movement of solutes
what is tonicity?
osmotic pressure gradient of two solutions separated by a semipermeable membrane which must be selective in blocking movement of solutes
what occurs when cell is put in the following solutions?
isotonic
hypotonic
hypertonic
iso - nothing
hypo - cell swells
hyper - cell shrinks
what is the equation to calculate osmolality?
(2 x [Na]) + [glc] + [BUN]
BUN = blood urea nitrogen
what is a normal range of calculated osmolality? what is its accuracy compared to real measured osmolality?
280-300mOsm/L
within 10mOsm/L of measured values
what happens in the body when you ingest a large amount of water?
1) water absorbed from gut into plasma (dilution of Pna and decr. osmolality)
2) osmotic gradient now favours fluid movement into cells
3) water moves into cell to balance osmotic gradient
4) cell size increases (hypotonic result)
when is cell size increasing an issue? what is usually associated with it?
brain
low Pna associated with brain cell swelling
what is hypervolemia? hypovolemia?
hyper - too much fluid
hypo - not enough fluid
why is Na important in determining total body water?
changes in plasma [sodium] changes plasma osmolality, which changes water distribution and hormone levels (vasopressin and aldosterone)
what happens in the body when you ingest a large amount of water? (4steps)
1) water absorbed from gut into plasma (dilution of Pna and decr. osmolality)
2) osmotic gradient now favours fluid movement into cells
3) water moves into cell to balance osmotic gradient
4) cell size increases (hypotonic result)
why is Na important in determining total body water?
changes in plasma [sodium] changes plasma osmolality, which changes water distribution and hormone levels (vasopressin and aldosterone)
what does vasopressin do?
released from post pit and increases water reabsorption in collecting duct of kidney?
what does aldosterone do?
released from adrenal medulla and increases sodium reabsorption in distal tubule of kidney
what happens when there is loss of Na? (4steps)
1) plasma [Na] drops, decreasing plasma osmolality (turn vasopressin off, incr. aldosterone release)
2) water moves into cells to balance osmolality
3) fluid shifts from ECF to ICF, decreasing plasma volume
4) plasma osmolality is slightly decreased (aldosterone retains sodium)
What is Pc?
hydrostatic pressure in capillary that increases with incr. venous pressure (leads to edema)
determines fluid and electrolyte movement within ECF
what is hypervolemia? hypovolemia? what does this reflect?
hyper - too much fluid (too much Na)
hypo - not enough fluid (too little Na)
what happens when there is loss of Na? (4steps)
1) plasma [Na] drops, decreasing plasma osmolality (turn vasopressin off, incr. aldosterone release)
2) water moves into cells to balance osmolality
3) fluid shifts from ECF to ICF, decreasing plasma volume
4) plasma osmolality is slightly decreased (aldosterone retains sodium)
what happens when there is an increase in Na? (4steps)
1) plasma [Na] rises, increasing plasma osmolality (vasopressin release)
2) water moves out of cells to balance
3) plasma osmolality still slightly elevated when balanced
4) vasopressin retains water in kidneys
why calc osmolality if you can measure it?
shows importance of Na
if measured osmolality is greater than calc osmolality, that can indicate that something is increasing osmolality other than sodium, glc, or BUN (indicates foreign substance in blood)
what is the osmolal gap? what is the usual value?
the difference between measured and calc values and can detect presence of unknown substance
usually 10mOsmol/L
what does a high osmolal gap indicate?
poisoning with alcohol or antifreeze
what does a high osmolal gap indicate?
poisoning with alcohol or antifreeze
what is electroneutral?
cations = anions
