NBME 22 Serum potassium concentration (NBME Answers)

NBME 22 Answers

nbme22/Block 2/Question#40 (reveal difficulty score)
A previously healthy 7-year-old girl is ...
Serum potassium concentration 🔍 / 📺 / 🌳
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+17
submitted by ∗mcl(658),

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To pnedxa no ths,i wtah ew tkinh hppeans hitw sik'rosnanP esdiaes ad(n poki)nnaiasmisnr si na iacmealbn bwtenee maenipod dan n.iaeytclocleh tI kesma mero eesns fi you kloo ta isth rgaa,idm ipngya pauacilrrt tteanonti ot eht irentdic aay.phtw ssoL fo cgdnaierimpo A)(D surnnoe rmfo teh sausaittnb garin ()SNc stlerus ni notsacnt ontciaativ of ehost ACh niecetgsr ns,enrou ihwhc iatyutlmle steulrs ni ioibinnith fo amusalth morf iiitntagni mneevm.sot Te,ehferor sugni corngtiliienchas ephl ithw nnsaomnrkiaiips orncadsey ot a.odhll

+8
submitted by kobeandming23(8),

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ADK sia)i(dosc ;gt& iumsatPso fhtssi tou fo the cell ;t&g eriayhkmekpa

AF ,2190 pg 758

mumenrider4ever While you will have a high serum potassium, your total body potassium will be low due to very low intracellular potassium (which is where the majority of the body's potassium is usually). This is why you give potassium to patients with DKA +1

passplease Why do you not get an increased bicarbonate concentration? +

briangibbs3 Bicarb acts as a buffer and binds up excess H+ in DKA +

jurrutia In other words, DKA a is a cause of metabolic acidosis. Hallmark of MA is low bicarb. +1

skonys Also INsulIN shifts K+ INto cells. Insulin is used as a treatment for hyperkalemia. This person has DKA thus low Insulin so shes expected to have hyperkalemia because insulin isn't shiting K+ into cells. Theres also the DKA acidosis too. +

+3
submitted by ∗osgoodschlatter10(41),

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KAD si a taest of cdredasee ;snulini ecsni we nkwo ttha uninsli suaesc a ihsft of K+ into het lcels owl evlsle of iuinlsn lliw petvner tish and lrestu ni nIkypmair lae.he ,dntdaoii due ot recgmypihayel adn high ECF atmolilsyo ewtar lilw hifts tuo fo hte cells into eht FEC nad K+ sfthsi otu twhi teh etarw whihc illw furteh creneasi the myaherpelaik

dentist I know Insulin cause shift K+ into cells due to closing of ATP-sensitive K channels (blocking K from leaving)? Does it increase K in the cells by another mechanism? +

makinallkindzofgainz @dentist - Insulin stimulates the Na+-K+-ATPase pump, this drives K+ into the cell (Source: Amboss) +

castlblack Another mechansim = acidosis causes hyperkalemia due to H+/K+ antiporters. H+ is high in blood so shifts into cells via this antiporter, which shifts K+ out. --potassium section of acid/base chapter in Costanzo physiology +

+2
submitted by ∗skip_lesions(17),

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yhW odluw eehrt be raeymikalhep fi ltoat oydb poastmius si cdsaedere ni ?ADK

drdoom super high blood glucose; super high glucose spillage into urine; lots of peeing = volume depleted (“osmotic diuresis”) +

alphatnf because insulin normally stimulates Na/K ATPase, which sequesters K inside cell. lack of insulin means that there will be more K outside of the cell causing hyperkalemia. however, you are still total body K depleted due to osmotic diuresis. so the hyperkalemia is mainly due to a shift of K from the intracellular (where the vast majority of your K is inside your body is) to the extracellular space. +1

alphatnf *where the vast majority of your K is inside your body +

+1
submitted by ∗llpierso(3),

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I rnaenddsut why +K si isaecn.red tuB wyh t'isn oldhrice soal sdraei?nec iTsh is a ibtomaecl acd,isois so rcibab lwli be wlo nda +H iwll eb hh.ig You deen na noi ot aclenba rehagcs g--;t& ireasdcen er?dloich

llpierso Nevermind, thought about this more: DKA causes an anion gap acidosis (hence normal chloride and elevated keto-anions). +2

+0
submitted by ∗empem28(1),

totally buy the answer of K+ being increased, but can somebody explain why her extreme dehydration (decreased skin turgor, excess urine output) wouldn't lead to an increase in serum [Na+]?