3. Essentials of Renal Physiology Pt. I Flashcards
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
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
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
The Tubule
• No need to memorize • Tubule is not \_\_\_\_ along its length ○ Very different machinery that resorbs different things
uniform
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
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
GFR is the Major Measure of Kidney Function
• Decreased GFR is evidence of ____
kidney disease
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
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
How To Measure GFR? • Substance that: – Is \_\_\_\_ – Not \_\_\_\_ – Not \_\_\_\_
• Got in urine via filtration, and didn't leave and nothing added
filtered
reabsorbed
secreted
How To Measure GFR?
• Then measure:
– ____ in the blood
– The ____ it is excreted
• Can then figure out the GFR
concentration
rate
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
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
How To Measure GFR? • Endogenous Substance: Creatinine – Made by \_\_\_\_ – \_\_\_\_ – Not \_\_\_\_ – BUT, does have some \_\_\_\_ • About \_\_\_\_% • (This is variable)
muscle filtered reabsorbed secretion 20
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
Theoretical Curve
* Normal GFR of \_\_\_\_ with a normal creatine * If GFR halves > the creatine will \_\_\_\_
100
double
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
Issues with Creatinine
• But not others
• 1.5 would be \_\_\_\_ for someone with not as much muscle mass
abnormal
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
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
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
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
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
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
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»_space; Plasma vol»_space;
SVR»_space;
CO»_space;
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
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
