Water & Electrolytes Flashcards
body water content varies with
age, body size, composition
decreases with age and body size
body water is distributed into 3 extracellular fluids
interstitial, plasma, lymph
interstitial fluid
directly bathes cells, provides medium for exchange of nutrients and metabolic products to and from plasma and cells
lymph fluid
transcellular (cerebral spinal, pleural, pericardium, joints
lymph has WBC = lymphocytes, remove waste and toxins
water loss sources
major: urine
smaller: feces
varied amounts in respiratory t ract and skin
water intake sources
major: beverages and foods (25% foods)
minor: metabolism- formed from cellular biochem reactions
AI for water set for?
intake to balance losses
set for moderately active temperate climate
*highly active in hot climate = 6-10L
estimate at 1mL per kcal
Recommendation based on body weight= 20-45mL of water/kg
type of water loss and controllable
urine, controllable
feces, effected by dietary fibre
insensible, non controllable, sweat and breath
how was AI derived
set to prevent dehydration
maintaining normal osmolarity of healthy US population
electrolyte concentration/ kg or L of water
AI water
men = 3.7L
women = 2.7L
UL for water
no, but hypotonicity is fatal- electrolyte imbalance
marathon athletes, endurance
cation conc in plasma, interstitial, intracellular
plasma= 153
interstitial = 153
ICF= 195
anion con in plasma, interstitial, ICF
plasma= 153
interstitial=153
ICF=195
osmolality conc in plasma, interstitial, ICF
intracellular and extracellular electrolytes are about 300 in all 3 fluids
which cation and which anion are highest conc in plasma and interstitial fluids
Na+ and Cl- and some HCO3-
which cation and which anion are highest conc in ICF
K+ and PO4-3 phosphate and protein
sodium functions
water, pH and electrolyte regulation
nerve transmission
muscle contractions
sodium deficiency
anorexia, nausea, muscle atrophy, poor growth, weight loss
food sources of sodium
table salt, processed and snack foods, cured meats, seafoods, condiments, milk, cheese, bread
AI for sodium
1500mg 19-50years
Canadians are much higher intake
potassium functions
water, electrolyte, and pH balances
cell membrane polarization
potassium deficiency
muscular weakness, cardiac arrythmias, paralysis
potassium food sources
fruits, veg, legumes, buts, dairy
potassium AI
3400mg males
2600mg females
both 19+
can overall low potassium intake
chloride functions
fluid and pH balance, component of gastric HCl- **denatures tertiary and quaternary protein structures for digestion
chloride deficiency
weakness, lethargy, hypokalemia, metabolic acidosis (acid-base balance)
chloride food sources
table salt, seafood, meat, eggs
chloride AI
2300mg 19-50 years
can over bc salt
hyponatremia
diluted plasma due to overconsumption of water
hypernatremia
loss of water without solutes, solutes very high
hypervolemia
too much fluid in extracellular, too much IV, kidney failure
hypovolemia
deficiency of fluid in ECF, severe diarrhea, vomiting, bleeding
hydrostatic pressure, hydro and colloid
fluid/capillary pressure
hydrostatic pressure = 25mmHg, heart pumping
interstitial fluid colloid osmotic pressure= 5mmHg, opposes hydrostatic
hydrostatic pressure, interstitial hydraulic and plasma osmotic
interstitial hydraulic= -6mmHg NEGATIVE
plasma osmotic= 28mmHg (oppose hydraulic), major reabsorption force countering filtration force
Starling’s equation
net result of four forces= 8mmHg filtration pressure
ECF volume/osmolarity controls
sustaining ECF volume and osmolarity is vital to blood presssure and cv system function
hormones that control ECF volume/osmolarity
vasopressin - retain water constrict vessels
renin-angiotensin-aldosterone system- increase Na
natriuretic peptides- increase Na and water, decrease bp and fluid
CV system
where is sodium stored in body
30-40% bone surface
UL for Sodium
No, Chronic Disease Risk Reduction
prevent CV disease and lower bp
absorption of Na
95-100% from small intestine and proximal colon
mechanisms of Na absorption
- Na/glucose transporter, small intestine
- electroneutrak Na and Cl cotransport exchange transporter, small intest and colon
- electrogenic system, colon, lesser used bc Can have such a high amount that Na doesn’t need to be reabsorbed usually
how is Na transported
free in blood
serum Na conc maintained in narrow range 135-145mEq/L
Na functions and interaction with other nutrients
maintain osmotic pressure, nerve transmission conduction, muscle contraction, dietary Na intake increase urinary Ca excretion
aldosterone controls
Na excretion
Na deficiency may occur bc of
excessive sweating
Na is measured in labs by
routinely, 24 hour urinary sodium excretion level
chloride absorption mechanisms
follows Na
1. Na/glucose cotransport system, Cl follows actively absorbed Na in small intestine
2. electroneutral Na/Cl cotransport absorption, Cl absorbed in exchange for HCO3 as Na is absorbed in exchanged for H+ ions, small intest and colon
3. eletrogenic Na absorption, Cl follows absorbed Na passively
Cl functions
- form gastric HCl- acid
- released by WBC to destroy foreign substances
- exchange anion for HCO3- in RBC (chloride shift, acid-base balance)
Cl excretion
through GI tract, skin, kidneys
loss reflects Na loss
Cl AI
2300mg
T of F: Cl deficiency is rare
T
Cl levels evaluated by
serum conc, dependent on plasma volume
K severe deficiency
hypokalemia
less than 3.5mmol/L
cardiac arrhythmia can occur
K moderate deficiency
increased bp
kidney stones
increased bone turnover
risk of CVD, stroke
Food sources of K
tomato juice/paste, prune juice, carrot juice, banana, wild Atlantic salmon, clams, potatoes, squash, legumes
role of K in acid buffering
K intake in F&V with bicarbonate anions like citrate will combine with K-anion slat to buffer dietary acid production from high protein foods, then alkali-K salts can decrease urinary calcium excretion (good for bone health)
K AI
Men= 3400mg = 9 servings of F&V
women=2600mg= 7 servings
% of K absorption
over 85%
where is K absorbed
small intestine, some colon
how is K absorbed
passive diffusion or K+/H+ ATPase
stimulated by insulin
muscles release K back into plasma between meals
K function and interactions with other nutrients
proper ICF to ECF ratio to maintain cell’s resting membrane potential
water and acid–base balance
cellular metab
decrease urinary excretion of Ca
K excretion
mainly kidneys, some sweat
K deficiency caused by
loss of fluid and electrolytes, hypokalemia
assessed by plasma/serum K conc
hypertension
8 mill Can diagnosed
over 140/90
DASH Diet trials
Na restriction decreased bp slightly
increase K intake beneficial
Ca intakes:
supplements: no effect on bp
= meet Ca needs with rich food sources
what does DASH stand for, what foods does it recommend
Dietary Approach to Stop Hypertension
reduce bp effectively, without drugs
like 2007 CFG, whole grains, meat alts, fresh F&V
not eating processed foods
