3. Essentials of Renal Physiology Pt. I Flashcards by J L

The Kidney is A Filter
• What kind of filter that gets rid of poisons you did not know about when you built it?
• A filter that throws ____ away and then ____ back the stuff you want

everything

takes

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The Kidney is A Filter Like That
• Each kidney is made up of about one million tiny filters
• Each filter is called a ____
• Each nephron has two parts:
– A tuft of capillaries that “throws away” about a ____ of the plasma flowing through it
– A long tubule that reabsorbs about ____% of the fluid that was thrown away

• Throwing away part = tuft of capillaries surrounded by a capsule
	○ \_\_\_\_
	○ Feeds into long tubule

nephron
fifth
99
protourine

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The Nephron

* Whole thing is the nephron
* Afferent arteriole goes into glomerulus
* Blood is under \_\_\_\_ here
* Fifth of plasma squeezed into \_\_\_\_
* Remainder of blood comes out the \_\_\_\_ arteriole
* Protourine travels along long tube that resorbs majority of what got filtered in the first place
* Energetic, \_\_\_\_ way of doing things; so MUST be worth it

high pressure
BC
efferent
inefficient

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The Tubule

• No need to memorize
• Tubule is not \_\_\_\_ along its length
	○ Very different machinery that resorbs different things

uniform

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Summary Schematic

• Glomerulus
	○ Aff arteriole in and eff arteriole going out
• \_\_\_\_ occurring at (1)
	○ Fifth of aqueous portion of blood is being squeezed out
• Travels along the tube > sig amount of reabsorption
• Eff arteriole stays next to tubule and turns into \_\_\_\_ that envelopes the tubule, and all \_\_\_\_ goes in here
• Not all of ridding of toxin is during filtration; some things are thrown away on purpose > \_\_\_\_ secretion (little arrow along the capillaries); pumping from PT cap into the tubule
• Net effect of filtration minus \_\_\_\_ plus \_\_\_\_ (PT cap) = excretion
	○ Each term is different

filtration
peritubular capillaries
reabsorption
active
reabsorption
active secretion

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GFR is the Major Measure of Kidney Function

• Glomerular Filtration Rate (GFR):
– Volume squeezed through the glomerulus per minute
– About ____ml/min in a “normal-sized” adult
– ____ liters per day

• Major metric of kidney function
	○ Measure of whether the kidney is working well
• Time is minute
• 180 is many multiples of the amount of fluid in the body

125

180

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GFR is the Major Measure of Kidney Function

• Decreased GFR is evidence of ____

kidney disease

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Other Evidence of Kidney Disease
• Remember when I said that the
glomerulus throws “everything” away?
• Not quite true

• Glomerulus doesn't throw everything away
• Protourine doesn't look like \_\_\_\_
	○ Barrier that prevents things from leaving
		§ No \_\_\_\_ (RBC, platelets, etc.)
		§ \_\_\_\_ (albumin) are too big to pass through filtration space

blood
cells
large protein

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Other Evidence of Kidney Disease
• Healthy glomeruli prevent certain things from being filtered
– ____
– ____
– If these are in the urine, then kidney disease may be present even with ____ GFR

• In disease, they are present in the urine
• Diabetic kidney disease
	○ Glomerulus is damaged > protein in urine
	○ Most frequent example
• \_\_\_\_ disease
	○ Immune attacks kidney > red cells can get in the urine
		§ From only the glomerulus > concerning for AI disease
• If GFR is normal, but you have RBC from \_\_\_\_ origin or protein > concerning for kidney disease

red blood cells
protein (albumin)
normal

immune-mediated
glomerular

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How To Measure GFR?
• Substance that:
 – Is \_\_\_\_
– Not \_\_\_\_
– Not \_\_\_\_

• Got in urine via filtration, and didn't leave and nothing added

filtered
reabsorbed
secreted

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How To Measure GFR?
• Then measure:
– ____ in the blood
– The ____ it is excreted

• Can then figure out the GFR

concentration

rate

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How To Measure GFR?

• Substances that are: 
– Filtered
– Not reabsorbed 
– Not secreted
• No \_\_\_\_ produced by the body have these perfect qualities

• No natural substances that produce these qualities
	○ No metric of GFR in our own \_\_\_\_

substances

bodies

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How To Measure GFR?

• Artificial Substances:
– \_\_\_\_
– \_\_\_\_
– \_\_\_\_
• Need to be \_\_\_\_
• Not \_\_\_\_
• Only used in \_\_\_\_

• Inulin is most classic one
• Iothalamate and iohexol > \_\_\_\_ substances
• Not practical in clinical setting
	○ Need a reason to inject something into somebody

inulin
iothalamate
iohexol
injected
practical
research
CT scan contrast

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How To Measure GFR?
• Endogenous Substance: Creatinine
– Made by \_\_\_\_
– \_\_\_\_
– Not \_\_\_\_
– BUT, does have some \_\_\_\_
• About \_\_\_\_%
• (This is variable)

muscle
filtered
reabsorbed
secretion
20

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How To Measure GFR?
• In the past, kidney function was often estimated just by looking at serum levels of creatinine
• Serum level of creatinine will ____ if GFR drops

• Certain cxn of creatine in blood, and kidney is removing > something happens that decrease how much you're removing > so now the creatine will increase in blood

rise

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Theoretical Curve

* Normal GFR of \_\_\_\_ with a normal creatine
* If GFR halves > the creatine will \_\_\_\_

100

double

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Issues with Creatinine
• It’s Made By Muscle
• People with more muscle produce more ____ in day
• Creatinine of ____ mg/dl may be normal for some

* Same creatine in two different people an mean two different things
* 1.5 is moderately abnormal; may not be abnormal for someone who has a lot of \_\_\_\_

creatinine
1.5
muscle mass

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Issues with Creatinine
• But not others

• 1.5 would be \_\_\_\_ for someone with not as much muscle mass

abnormal

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Issues with Creatinine

This problem can be solved by collecting urine for ____ hours
This allows the amount of creatinine produced to be measured
____ concentration is also measured
Volume of plasma that has been “cleared” of creatinine can then be calculated• Once creatine level is ____ > you test the levels > will account for muscle mass

24
plasma creatinine
steady state

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Creatinine Clearance Equation

• Assume that all creatinine is removed by ____, then:
– GFR = [____]/SCr
– This assumption is imperfect, since some creatinine is removed by ____
• 24-hour urine collection is ____ – It is used clinicaly, but rarely

• Easy way to mess up: what to do with urine in the morning
	○ Will get incorrect result
	○ 8 hours of sleep > first time you pee > 1/3 of creatinine excretion done in the day
	○ Get up in morning > empty bladder don't \_\_\_\_ that; save everything until next day, and make sure save urine from morning void from that \_\_\_\_ and when they're done and they bring it in
	○ If you collect both mornings > \_\_\_\_ hours collection
	○ If didn't collect either > \_\_\_\_ hour collection
	○ And assume you collected over 24 hours > everything will be off

GFR
UCr x V
secretion
impractical

save
32
16

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Next Step
• Can kidney function be estimated from blood tests alone?
The problem here is creatinine generation and the fact that it is not the ____ between different
people. Bodybuilders will have different levels than a 90yo person.
Is there another way to measure this beside the 24 hour collection?

same

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Cockcroft-Gault Equation
• Oldest equation
• In 249 patients, measured:
1. \_\_\_\_-hour urine creatinine excretion 
2. \_\_\_\_ level
• Used \_\_\_\_ regression to derive:

CCr (mL/min) = (140-age) x weight (kg) / Cr (mg/dL) x 72

• Doesn't measure GFR, but \_\_\_\_ excretion
• 249 patients is not a lot using a linear regression
	○ Linear regression - forcing a line over a cloud of dots
	○ Body really works like a \_\_\_\_; linear will never do it perfectly bc forcing into a line
• Measured serum creatinine level as well
	○ Way to estimate actual creatinine clearance from this?
• Not \_\_\_\_ truth

24
serum creatinine
creatinine
curve
mathematical

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Cockcroft-Gault Equation

CCr (mL/min) = (140-age) x weight (kg) / Cr (mg/dL) x 72

• Multiple the above by ____ for women

• Additional factor for women
• What is the added information here?
	○ How \_\_\_\_ you are, how \_\_\_\_ you are, and whether or not you're a \_\_\_\_
	○ Can add several other factors about human beings; but what are we trying to get at > all related to \_\_\_\_
	○ Gives a sense of how to fail:
		§ Every single 30 y/o of a given weight have less muscle mass than a male? \_\_\_\_!
		§ Is everyone who is age 50 of a given weight and gender the same? \_\_\_\_!

0.85
old
weight
woman
muscle mass
no
no

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Cockcroft-Gault Equation
• Because it’s the ____ equation, is used for many ____ guidelines
• ____ used clinically because of many limitations:
– It’s not 1976
• Body weight today is more likely to come from ____
• Laboratory creatinine assays have ____
• Because of this it tends to ____ creatinine clearance
– Weight can be surprisingly ____ to get

• Can be difficult to weigh someone than to get their blood drawn
	○ Stand them up, out of bed, roll scale into room
	○ Different scales get different results
	○ Data that is often missing - people don't enjoy seeing their weight

Study These Flashcards

oldest
drug dosing
rarely

fat
changed
over-estimate
difficult

MDRD Equation • Modification of Diet in Renal Disease Study was an RCT in which subjects had: – GFR measured by ____ clearance – v measured – Many other lab data as well • Used to derive the “MDRD equation” – Simplified form of this equation is the ____ clinical tool for estimated GFR today • Mot frequently used equation • Purpose of study > not designed to create this equation ○ Looking at low protein diets and whether prevented progression of chronic kidney disease ○ Derived equation form data set ○ Initially a complicated one > then made a simple one

iothalamate serum creatinine dominant

GFR = 175 x Screat-1.154 x age-0.203 x 1.212 [if black] x 0.742 [if female] * Needs a ____ * Data ____ to obtain * What happened to body weight though? * Output of the equation is ml/min/1.73m2 Body Surface Area * Body Surface Area (BSA) is calculated by ____ and ____ • CG can be done on a piece of paper; for this a person will need a calculator/computer ○ In setting of research, or via EMRs • All you need: ____, whether they're ____and ____ • Weight made it part of the ____ • Output of equation isn't just clearance; but clearance per ____ (1.73m^2 is normal - arrive here via height and weight together) ○ Problem: data about human being and have creatinine, and to figure out how much filtering (muscle mass); adding information is age, whether you're black and whether you're female § Imperfection - being black, is not that much data; and same about woman § Will all different ____ ○ Equation performs ____ because of these inconsistencies

calculator/computer easy weight height ``` age black female unit body surface area muscle masses poorly ```

MDRD eGFR Co-incided with New Definition of ____ ``` • Estimated GFR became definiton of CKD ○ Stage I: § Kidney ____, but GFR within normal range (>____) ○ Stage II: § Kidney damage with ____ decrease ○ Stage III: § ____ decrease ○ IV: § ____ ○ Kidney failure § GFR ```

``` damage 90 mild moderate severe 15 ```

Limitations of MDRD • Derived from a population with average GFR ____ ml/min/1.73m2 – Few patients with ____ GFR • Tends to ____ GFR in patients with true GFR>____ ml/min/1.73m2 • People in the MDRD all have CKD ○ The average true GFR was 40 • First question: who did they study? • Equation performs poorly for people with ____ > gives them one that is lower than their true GFR

40 normal/near normal under-estimate 60 mild/GFR

eGFR Alone Can Only Define CKD if < 60 ml/min/1.73m2 • Only GFR, and no protein/imaging issues; the earliest you can truly diagnose is ____ ○ Bc ____ GFR so frequently • Stage II > so frequent underestimation > need to find other things wrong: ____ in urine (glomerular), protein in urine, or ____ showing you're missing one or structural damage (cysts, etc.) • Issue communicating with patients ○ Referred and don't have other problems > stage III § Why didn't get ____ earlier? Did doc miss? Just an issue with the above

``` stage III under-estimated blood imaging detected ```

For Stage 1 or 2, Additional Evidence of CKD is needed • ____ • ____ • Abnormal Kidneys on ____

proteinuria hematuria imaging

Summary • Glomerular Filtration is the Major Metric of Kidney Function • Estimation of GFR is helpful with: – ____ of medications – Assessment of ____ of disease – Decisions about ____ • Regulation of ____ is critical to maintenance of homeostasis (this will be the next talk)

dosing severity therapy tubular reabsorption

Two important parameters - ____ - ____

effective vasc vol | tonicity

Effective Vascular Volume ECF vol >> Plasma vol >> SVR >> CO >> Effective vascular volume • EFV ○ How well loaded the ____ is ○ Not a volume > an idea of how well ____ your vital organs are ○ If low > not sending enough blood to the vital organs in the proportion they need • Plasma volume ○ How much ____ you have • SVR ○ How ____ your BV are • CO ○ How well the ____ is working • The part the kidney controls is the ____ through control of ECF

``` arterial space perfused blood volume dilated/constricted kidney plasma volume ```

Body Fluid Compartments Total body water (TBW): ECF (____) - ____ ICF (____) - ____ • TBW ○ Makes up ____% of body weight is split into: § ECF □ 1/3 of TBW § ICF □ 2/3 of TBW § Black line separating > every cell membrane in body □ One ubiquitous protein in every membrane: ____ □ As a result of this pump: Na+ in the ECF, and K+ in the ICF

Na+ 1/3 K+ 2/3 50-70 Na-K ATPase

ECF Volume is the Major Determinant of Plasma Volume ECF: Plasma (____) Interstitial fluid (____) ``` • Take ECF and breaks up further: ○ Plasma volume § 1/4 of the ECF § ____ to blood volume ○ Interstitial fluid § 3/4 of the ECF ```

1/4 3/4 major contributor

Body Fluid Spaces: Water makes up 50-70% of total body weight Total body water (TBW): – ____ intracellular fluid (ICF) – ____ extracellular fluid (ECF) compartment • ____ Plasma and ____ Interstitial Fluid 70 kg man TBW = 70 x 0.6 = 42 L ICF = 42 x 2/3 = 28 L ECF = 42 x 1/3 = 14 L Plasma =14x1/4=3.5L • Plasma volume makes up ____ of the TBW ○ Keeps you alive ○ If not high enough > heart wont be able to pump sufficient blood to the organs • What's IF then of TBW?

``` 2/3 1/3 1/4 3/4 1/12 ```

Definitions: Osmolality and Tonicity: • Osmolality = ratio of ____r – Calculated Osmolality = 2 x [Na+] + Glu/18 + Urea/2.8 – Normally = 2x(140) + 100/18 + 10/2.8≈____ mOsm – Osmolality can be directly measured by the ____ • Particles in water > has an osmolality ○ Important for osmotic shift ○ Large number of particles > traps ____ § Why starch exist > 20 glucoses, each is one particle > then link and make starch > one whole particle and store without the cell ____ • Take all the particles in serum that we measure > can calculate the osmolality ○ Euro's wouldn't need the divisions ○ Normal serum value: 140; normal glucose: 100; and a normal urea: 10 > 290 is a normal serum osmolality ○ Can ____, AND measure by the ____

particles/water 290 lab water shrinking calculate lab

Tonicity • Tonically active osmoles are confined to one side of cell membrane or the other • Also called “effective osmoles” • Examples: – Effective osmoles: ____, K, ____, Mannitol – Ineffective osmoles: ____, Ethanol – Glucose can behave as either effective or ineffective (depending on ____) • Tonicity can NOT be directly measured by the ____ • TA osmoles have two properties ○ Osmotically ____ ○ Confined to one side of ____ or the other • Cl- ○ Anion of Na+ ○ Largely ____ • Mannitol ○ Artificial ○ Doesn't go into ____ ○ Used to suck fluid ____ of cells • Urea and ethanol distribute across the entire TBW • Glucose ○ Can behave as either depending on insulin ○ Tehcnically: ____, usually outsdie of cells § But in presence of insulin > pumps into cells > metabolized or changed into a starch • Tonicity CANNOT be directly measrued by lab; but you can do it for the ____ ○ Tonicity; have to see if cells ____ or swole ○ No ____ term! (unlike osmolality)

``` Na Cl urea insulin lab ``` active membrane EC cells out effective osmolality shrunk urea

Tonicity • Since it cannot be measured, “best guess” is to calculated it: • Calculated Tonicity= 2 x [Na+] + Glu/18 • This is the same as the calculated osmolality, except that the ____ term is removed • Na+ is always partnered with something that is also tonically ____ ○ Double it ○ And then take glucose and divide by 18 § Because of unit to turn it into the same units as we have for the sodium

urea | active

Why do we care about Tonicity? Tonicity Dictates ____ K+ restricted to ____ and Na restricted to ____ • Water moves across ICF and ECF to maintain equal ____ across both compartments • Water is moving in and out of cells to maintain ____ tonicity • Add tonically active osmole outside that cannot get into the cell ○ Like NaCl, and raise it > H2O will move inside to ____ in order (down it's own gradient) > shrink cell until cxn of ____ matches the cxn of Na+ outside ○ Tonicity: changes cause fluid shifts across membranes > cause shrink/swell > changes in ____

``` water distribution ICF ECF tonicity equal out K+ cell size ```

Why do we care about Tonicity? • Add RBC into isotonic > looks ____ • Add into salt but hypotonic (not as high as isotonic) > water will go into cells > ____ • Add cells into solution that is hypertonic > water drawn out of cells > ____ up • Take RBC and drop into pure H2O > swell and explode > won't see any RBC > ____ • Disorder in tonicity (systemic) > never causes a problem in ____ function ○ Another organ will undergo changes that are lethal before the RBC gets messed up; the only organ that's entirely surrounded by bone > the ____ § Isotonic: nice ____ § Equivalent of swollen RBC > swell your brain > no sulci and get ____ of your brain outside the foramen magnum § Shrink brain > tear dura > ____

``` same swell shrivel hemolysis RBC brain ``` sulci herniation subdural hematoma

Basic physiology • Tonicity ○ Regulate via is not via salt bc it would have big impacts on volume § Via ____ □ Has some impact on volume □ Impact tonicity bc by def is by number of tonically active osmoms divided by water § Tonicity detected by ____ > two nuclei control thirst and ADH release □ ADH ® Hormone released by post pit acts on kidney and tells to hang onto ____ ® If off > urine volume will increase and it will be ____ § ADH and thirst impact water balance □ V thirsty and high ADH > will hang onto ____ □ ADH switched off, and thirst switched off > pee out a lot of ____ • Two circles are separate, but one can perturb the other ○ Tonicity circle decides that you're ____, and says you need water (upreg water and ADH) § 1/3 of water goes into ECF (not great vol exapnder); if at this time, you're at upper limit of what ECF circle thinks you're at ____ □ As soon as extra water pushes you over limit > downregulat RAT > pee out ____ rich urine ○ Separate unless body has to choose which one is more important § Body in this situation; will always choose ____ over anything else § Significant intravascular volume depletion (>10%) > body will forget tonicity, hangs onto ____ no matter what > hang onto ADH and maybe thirst > try to retain water even though not a great volume expander (better than nothing) > so desperate, get whatever I can get • Underpins thigns that are important: ○ Way the body works ○ Way we intervene when we need to change something (in problems of ECF volume and tonicity) § Importatn in disorders of tonicity

``` water hypothalamus water dilute water water hypertonic hypervolemia salt ECF volume water ```

ECF Volume: Na Content • Na is restricted to ____ compartment • Na is the major osmole in ECF compartment • Total body Na content determines ____ • Stable hemodynamics is dependent on ____ Stable ECF volume is maintained by Na balance ____ (dietary) = ____ (renal and extrarenal) – ____ of Na is the major way of regulate Na content in body – Extrarenal Na loss can outpace Na intake under certain conditions (diarrhea, burns, blood loss) leading to total body Na loss and abnormally low ____ (hypovolemia) * ECF volume is equivalent to sodium content * Most common worldwide of extrarenal Na loss: ____

``` ECF compartment ECF volume stable ECF volume intake output renal excretion ECF volume ``` diarrhea

How Do We Evaluate Volume and Tonicity? ``` • Effective vascular volume: – Labs for this are ____ – This is a ____ evaluation • History • Physical Exam – ____, Lung Exam for Crackles, ____, Acute Change In Weight, ____. ``` • Tonicity: – Clinical exam for this is ____ – This is a ____ evaluation • Serum sodium and ____ • Clinical decision ○ Pattern that requires more than one piece of information, and requires seeing and examining the patient ○ Impossible - need to recognize a pattern of things to recognize one "animal" from another ○ Volume status - need a lot of things to determine ○ History § Puking and a lot of diarrhea □ Hypovolemia ○ Physical exams § Crackles - fluid in the ____; and may be volume overload § Peripheral edema □ Normal tissue should spring back out; but edematous feels like ____ § Very helpful: ____ change in weight □ Weigh patients daily □ Change weight by 2 kg > likely to be from ____ § Most specific finding: loss of ____ □ Someone's armpit > small amount of sweat; no sweat > ____ □ Can have ax sweat and can still be volume depleted; very ____ but not very ____ ® Ninja analogy • Tonicity ○ Clinical exam > nonspecific and unreliable ○ Lab diagnosis! § Key for this

``` unreliable clinical jugular venous pressure peripheral edema axillary sweat ``` unreliable lab osmolality alveoli memory foam acute fluid axillary sweat specific sensitive

Serum Sodium Concentration Does Not Asses Total Body Sodium • Chem 7: ○ TL is sodium ○ K below ○ Cl next ○ Bicarbo below ○ BUN ○ Creatinine below ○ Glucose • Cations, anions, kidney • ____ is checked on daily basis on in-patients ○ Tells you nothing about ____ Na+ cxn • Effective intravascular volume is impacted by plasma volume, which in turn is impacted by ____, which then impacted by ____ • Tonicity is impacted osmolality, which is related to cxn of ____ • Check Na everyday; and people mistake that for how much Na in your body ○ Cxn doesn't tell you how big the ____ is

``` Na+ total body ECF volume total body Na Na volume ```

Volume Disorder = Abnormal Total Body Na Content ``` • Normal total body Na = ____ • Too much Na = Volume ____ • Too little Na = Volume ____ – Not the same as ____ – Dehydration implies too little water for the amount of solute in the body (____) ``` • Dehydration is diff from volume depletion ○ Voluem depeletion > disorder in total Na+ body content ○ Dehydration > too little water > hypernatremia/hypertonicity

``` euvolemia overload depletion dehydration hypernatremia ```

Tonicity Disorder= Abnormal Ratio of Water to Solute ``` • In general: • Normal tonicity: – Normal Serum Sodium (____) • Low tonicity: – Too much water relative to solute – ____ • High Tonicity: – Too little water relative to solute – ____ ``` * High tonicity = dehydration * Can substitute for hyper/hypoaqeumia

eunatremia hyponatremia hypernatremia

Summary ECF Volume Disorder= Abnormalities in ____ Content Too little sodium: Volume ____ Too much sodium: Volume ____ Osmolar Disorders= Abnormalities of ____ Balance Too much water (relative to sodium): ____ Too little water (relative to sodium): ____

``` total body sodium depletion overload water hyponatremia hypernatremia ```

Types of IV Fluids • IVF used to give NaCl > ____ – Often called “normal saline” – Tonicity is comparable to the aqueous portion of ____ ``` • IVF used to give water > 5mg/dl ____ – Often called “D5W” – Giving pure water IV would lyse ____s – 5mg/dl dextrose is close to iso-osmolar initially, but the dextrose gets ____ • This leaves behind ____ ``` • Gave pure water > drop RBC into a beaker > explode; won't have any systemic problems in RBC with regards with tonicity bc brain will die first ○ Can have a problem ____ > pure water > locally RBC will explode > sterile water has a red label; but used to mix with other things; never inject by itself! ○ Add 5 mg/dl dextrose into the water > give pure water § Solution is ____ bc of the dextrose, and will get pumped into cells and metabolized and go away § Liter of D5W distributed over entire body > slight decrement in serum sodium; won't get a sudden drop that'll cause hemolysis • ____to give salt and volume expand • ____ fluid to give water

``` isotonic saline blood dextrose red cells metabolized water ``` locally isotonic isotonic hypotonic

Add 1.5 Liters Normal Saline • What happens to tonicity? ○ Stay the ____ ○ Fluid is isotonic > no change in tonicity • What happens to ECF ○ ____ ○ Will icnrease by 1.5L § Bc of sodium containing and isotonic > 100% of it stays in ECF volume • What happens to ICF ○ Stays the ____ ○ Unchanged!

same increases same

New Case • Add 420 mEq Dry NaCl: • Tonicity ○ Add tonically active osmom without any water > ____ ○ Ratio will ____ • ECF volume ○ ____ ○ Sodium is trapped EC; sucks water from IC • ICF volume ○ ____ ○ Pulling water from inside cell

increase increase increase decrease

New Case • Add 1.5 D5W: • Tonicity ○ ____ ○ Water without tonically active osmom > ____ the ratio (increase denominator without changing nominator) • ECF volume ○ Water by itself > nothing to trap it ○ ____; 40% of it will stay the same • ICF volume ○ ____ ○ 2/3 or 60% of water > will go into cells

decrease decreases increase increase

Impact on ECF • 1.5 L Normal Saline: 17 L > ____ L • 1.5 L D5W: 17 L > ____ L – But [Na] decr’d from 140mEq/L > ____ mEq/L • 420mEq NaCl: 17 L > ____ L – But [Na] incr’d from 140mEq/l > ____ mEq/L ``` • ECF ○ Normal saline § ECF goes up 1.5L ○ D5W § Goes up .6 L § But [Na] serum ____ ○ Dry salt § Goes up .9 L § But [Na] serum ____ ```

18.5 17.6 135 17.9 145 dropped increased

ECF Volume ≠ ____ • In these three examples, note that extracellular volume ____ (albeit by a different amount in each case) independently of changes in body fluid ____ (and the plasma sodium concentration). • In fact, sodium concentration either increased, stayed the same, or decreased. • Volume expanded all the patients; but ____ did different things every time

[Na concentration] increased osmolality [Na]

– A normal euvolemic person will ____ the salt and water out in urine and go back to 17L – [Na] 140mEq/L > 135 mEq/L, but: – Normal person will pee the extra ____ out –[Na] 140mEq/l > 145mEq/L, but: – Normal person would drink and/or pee out the extra ____ * In the real world > the types of changes would only happen in someone without working * Normal kidneys > attenuated, because of peeing and drinking and maintaining homeostasis

pee water Na kidneys

Take Home Points: • Body’s primary goal is to defend adequate ____ – Na handling is critical for this • An important secondary goal is to defend ____ – Water handling is critical for this • Water and Na Handling are typically ____ • ECF Volume ≠ [____ Concentration]

circulation tonicity independent Na

Final Summary * GFR is the major metric of ____ * Reabsorption of Na by the kidney plays a major role in maintaining ____ * Reabsorption of Water by the kidney plays a major role in maintaining ____ and preventing brain ____

kidney function euvolemia tonicity swelling/shrinkage

3. Essentials of Renal Physiology Pt. I Flashcards

(58 cards)