Sodium

what are the 3 main elements involved in total body volume regulation by the kidney?

sodium, potassium, and water

what are the components of the BMP/Chem 7?

BMP: basic metabolic panel (chem-7) —> sodium, potassium, chlorine, bicarbonate, BUN, creatine, and glucose

what are the normal values of the BMP/Chem 7

Na: 140

K: 4.3

Cl: 104

HCO3: 24

BUN: 12

creatine: 0.8

glucose

hyponatremia means what regarding lab values?

in terms of lab values, hyponatremia means that there is a sodium concentration less than 140 mEq/L, closer to 120 mEq/L

what does hyponatremia really mean regarding the body?

hyponatremia means that the body is too dilated; there is too much water in the body

hypernatremia means what regarding lab values?

in terms of lab values, hypernatremia means that there is a sodium concentration greater than 140 mEq/L, closer to 160 mEq/L

what does hypernatremia really mean regarding the body?

hypernatremia means that the body is too concentrated; there is not enough water in the body

what are the 2 basic conditions that cause hyponatremia?

1) intake of too much water (drank a tremendous amount of water)

2) your kidneys are not able to excrete out the extra water

what are the 2 main causes for the kidneys to not get rid of extra water

1) ADH/vasopressin acting on kidney to tell it to hold onto the water

2) kidneys are not working (diseased/injured) —> cannot pee anymore

what are the 2 basic conditions that cause hypernatremia

1) not drinking enough water

2) kidneys are excreting extra water leading to dehydration

serum sodium concentration is a reflection of what?

a reflection of water balance (NOT total body Na)

why is total body sodium NOT the same as serum sodium concentration?

total body sodium refers to the total quantity of sodium in your entire body, including sodium stored in the extracellular fluid (ECF), intracellular fluid (ICF), and bone; whereas serum sodium concentration is the concentration of sodium in your blood serum or plasma that represents the ratio of sodium to water in the serum, not just the amount of sodium alone

describe the relationship between total body sodium and serum sodium concentration

1) you can have a normal total body sodium, but if you have too much water, your serum sodium will be diluted —> hyponatremia

2) if you're dehydrated, even with normal or low total body sodium, serum sodium concentration can be high —> hypernatremia

how do you assess for too much or too little total body sodium?

total body sodium is assessed by the examination of the extracellular volume (ECV)

remember that sodium is like mary and water is like her little lamb, meaning?

water follows sodium everywhere!

what are low and high values for urine osmolarity

low: ~50 mOsm/kg

high: >100 mOsm/kg

what does volume depletion tell you about total body sodium?

volume depletion means there is too little salt in the body (to fix this: eat more salt or administer some salt)

why does hyponatremia cause brain swelling?

1) hyponatremia definition is: serum Na <135 mEq/L (relatively too much water)

2) lets say you drank so much water which is causing the hyponatremia

3) the ECV has decreased osmolality now as a result of the excess water

4) the water in the ECV is naturally going to go across the barrier into the ICV where there is a higher concentration (higher osmolality) in order to even things out (water just does this; it naturally balances out)

5) the water going into the ICV is going to expand the size of the cells

6) anywhere else in the body, this is not life threatening, but in the brain, it can cause cerebral edema (brain swelling) which can be accompanied with headaches, seizures, and coma

when comparing serum osmolarity with urine osmolarity, should the urine osm be high (concentrated urine) or low (dilute urine) if the person has extra water in their body and needs to pee it out?

1) if the person has extra water in their body and needs to pee it out, it means they have hyponatremia

2) in order to determine if the hyponatremia is a problem of too much water intake or a kidney problem, you would look at urine osmolarity

3) if the kidneys are working correctly, you would want urine osmolarity to be low —> enough water has been filtrated out into the urine to decrease the osmolarity (this is good)

what does edema tell you about total body sodium

edema means there is too much salt in the body (to fix this: stop eating so much salt or make kidneys pee out more salt)

if the urine osm was high (concentrated) in the face of hyponatremia, what hormone is at work?

due to the action of ADH (anti diuretic hormone), there is most likely a diluting problem (prevents water from being excreted so there is higher concentration in the urine)