Fluid + Electrolytes Flashcards
fluid accounts for _____% of our body weight. how does intracellular weight % compare to extracellular %?
60% of our weight
20% extracellular
40% intracellular
___% of our body weight is plasma fluid. ____% is interstitial fluid
5% plasma
15% interstitial
t/f: gastrointestinal fluid contributes 2% of our body weight
false… very low amt(
t/f: body has innate mechanism to correct for fluid imbalance
true: conserve or expel
obligatory water loss + quantity
amt of water needed to expel daily nitrogenous wastes, sodium, urea, etc. (aka: urine can only be concentrated so much)
-approx. 500 mL/d
4 ways we lose water
- sweat
- breath(water vapor)
- urine
- feces
how much water is excreted in the breath/d? how much in feces/d?
about 250 mL for a sedentary person in breath
200 mL in feces
3 ways we can take in water
- drinking
- eating water rich foods
- water as a byproduct of normal metabolic rxns
rank the macronutrients in terms of catabolic water derivatives
CHO (15 mL/100 kcal), fat (11 mL/100 kcal), protein (10 mL/100 kcal)
up to _____% of daily water intake can be derived from foods, depending on foods chosen
20
why does water not have an RDA and only an AI? (3 reasons)
because it’s too highly variable to have a recommendation for everyone. varies based on body size, ambient temp, and physical activity
t/f: hydration status can easily be tested
false! no one good test…
t/f: even very dry foods like peanuts have water contents
true!
4 biomarkers of hydration status
- blood
- urine volume
- urine color
- thirst
what is the caveat to testing hydration status?
must look at several biomarkers because other conditions (other than dehydration) can cause abnormally low of one biomarker
what two things are tested in the blood to determine hydration status
[Na], [BUN]
what could cause elevated levels of BUN and plasma sodium besides dehydration
kidney failure(cannot excrete materials well)
where does BUN come from?
deamination of AA…
what can cause a normal [BUN] even if someone is dehydrated?
BUN comes from deamination of proteins, so if the ind. eats a low protein diet, they will not have an elevated [BUN] in time of dehydration
t/f: the kidneys continue to filter, even if we are severely dehydrated
true!`
what is the normal and dehydrated ranges for urine volume?
normal= 100 mL/hr
dehydrated=
low urinary volume can also be caused by what disorder in addition to dehydration?
kidney failure
what are 3 things that can darken urine besides a dehydrated state?
antibiotics, supplements, some foods
what is the best way to determine if a patient is drinking enough?
ASK them how much they’ve drunken in the past 24 hr!
negative water balance is detected two ways in the body… what are these receptors and what do they sense?
osmoreceptors: sense increased plasma osmolarity
baroreceptors: sense decreased plasma volume
what hormone is released to increase water reabsorption if we are in negative water balance? where is it released?
ADH(vasopressin) from pituitary gland
what is the mechanism for water balance called?
the renin-angiotensin system
up to what % of water can a healthy person lose and still be at very low risk of death?
7-10%
how fast one might die from dehydration is dependent upon what?
ambient temperature
what are two major effects of dehydration?
- with only 2% of water loss–> cognitive function impaired
2. motor control impaired`
how do altitude and cold temperatures affect H20 needs?
- altitude: drier air… more water vapor lost in breath; hypoxia induced diuresis
- cold exposure induces diuresis
caffeine is both a __________ and ___________
laxative and diuretic
what is the half life of caffeine in healthy adults?
4-6 hr
what other beverage besides coffee has a diuretic effect until metabolized?
alcohol(ethanol)
why is a lot of water needed to digest CHO?
starches, especially need a lot of water molecules so enzymes can hydrolyze bonds between glucose molecules
what happens to water balance on a low- CHO diet?
ketones will be produced–> very acidic(must maintain blood pH!) and must be excreted so water pulled out with them
what is the AI for water for men and women(include both parts!)
men: 3.7 L/d with 3 L directly from fluids
women: 2.7 L/d with 2.2 L directly from fluids
t/f: there is a UL for water
false(too variable)
______________ occurs when there is an imbalance of intake and output of water that causes a very positive water balance
water intoxication(output can not keep up with intake)
water intoxication can lead to ____________, where electrolyte levels in the blood esp. Na are too low
hyponatremia
who are the common individuals water intoxication is seen in?
marathon runners drinking water not electrolyte drinks at stations
during water intoxication, fluid can accumulate in the blood, but also the _________, impairing function
brain(yikes!)
t/f: according to the latest data, water consumption is adequate for adults
false!
who drinks more water- kids or adults? why is this even more shocking?
kids
**they also have a smaller body size so they drink more but have a lower requirement!
sodium’s 3 concentration-maintaining functions
- helps maintain blood osmolarity and pressure
- action potentials(nerve firings)
- extracellular fluid and cell shape
what are sodium’s two transport functions?
involved in symport of some nutrients(ex. SGLT1 for glucose transport)
activates Na/K ATPases
Na/K pumps in the body require approx what percentage of our daily intake of calories to run?
30-40%!
what fraction of young people are Na sensitive?
about 1/3
t/f: Na sensitivity increases with age
true!(efficiency of excreting Na is reduced with age, so greater effect on BP)
what happens if a Na sensitive person eats a lot of Na?
BP greatly increases(more so than a non-sensitive person)
the ___________ component of BP is most greatly affected by Na intake
diastolic
how does excess Na create a higher BP? (2 ways) how is one of these processes affected by age?
- Na is involved in muscle signaling–> excess causes vasoconstriction of smooth muscle in arterial walls
- excess Na draws fluid into blood vessels–> puts mechanical force on arterial walls
* *if arteries are stiff(happens with age), BP even further increased b/c vessels cannot stretch to accommodate excess fluid
how does Na affect kidney function? what is the implication of this?
kidneys must work harder to excrete–> chronically high Na intake can cause kidney injury in the LT
**snowball effect: kidneys become worse at filtering, which heightens BP and damages kidneys more!
t/f: the RDA for sodium is 2300 mg
false! that is the UL!!
the AI for sodium is
1500 mg/d
t/f: keeping sodium far below 1500 mg/d has been shown to be beneficial, esp. for patients over the age of 50
false! no additional benefit seen by decreasing sodium levels to below 1500 mg/d
what is the avg. American sodium intake?
3500 mg/d
what is the problem with the food label’s handling of sodium reporting?
reports sodium in foods as a % DV, which implies that ind MUST get their sodium intake(DV is used on other parts of the label for things like CHO and vitamins, where the DV really should be met)
3 body sites that chronically high sodium intake affects + how they are affected
- kidneys: injury + failure
- arteries: increased pressure, fibrosis, decreased elasticity–> atherosclerosis???
- heart: cardiac hypertrophy(due to increased force needed), diastolic disfunction
what is the worst food group/eating behavior for Americans’ intake of sodium?
frequent intake of moderately high Na foods(not really, really salty)–> adds up an pushes us over the recommendations
what is one of the worst lunches for sodium intake?
sandwich with deli meat and cheese(sodium in bread AND fillings!)
what is the AI for K? how does the American avg. intake compare to this?
AI=4700 mg
avg intake= oNLY 2000MG!
t/f: the UL for K is 7500 mg/d
false! no UL
what are the 3 best sources of K?
fruits, veg, whole grains
