rida
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A diabetic teenager is found to have a pH of 7.1 and normal electrolyte levels (Na+ = 140 mM, K+ = 4 mM, Cl– = 103 mM) except for a bicarbonate of 11 mM (normal 22 to 28 mM). The urine tests positive for ketone bodies, mostly due to acetoacetic acid and acetoacetate (CH3C=OCH2COOH and CH3C=OCH2COO–), which have a pK of 4.8. In this case, it is assumed that acetoacetate is the only significant anion in the blood besides chloride, and that each acetoacetate anion binds and removes one sodium cation during excretion by the kidney. Given that the patient has a normal glomerular filtration rate of about 7 L of blood per hour without any retention of acetoacetate/acetoacetic acid, the rates of sodium, acetoacetate, and acetoacetic acid loss will be
A. 10 mmol/h of each species
B. 50 mmol/h of sodium and acetoacetate, virtually no acetoacetic acid excretion
C. 100 mmol/h of sodium and acetoacetic acid, virtually no acetoacetate excretion
D. 200 mmol/h of sodium and acetoacetate, virtually no acetoacetic acid excretion
E. 300 mmol/h of each species
Explain please???? :?
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| mash
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is it 200 mmol/h?
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| rida
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yea your right, how did you get that?
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| mash
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it is a state of met acidosis
Anion gap is (Na +K) -( Cl + HCO3) = (140+4) - (103 + 11) =30
this AG is due to acetoacetate
pH = pK + log acetoacetate/acetic acid
=>7.1 = 4.8 + log acetoacetate/ acetic acid
=> log acetoacetate/acetic acid = 2.3 =>99% of acetic acid is in ionized form i.e acetoacetate
so, it will be excreted
=>acetoacetate/acetic acid ~ 100
(ketone bodies r freely filtered)
filtered load = GFR* plasma conc= 7L/h*30mmol/L=210mmol/L
bcoz acetoacetate anion binds and removes one sodium cation during excretion so, Na+ loss wud also be same
99% is in acetoacetate form so, acetoacetic acid excretion wud almost be nil
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| mash
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rida, cud u plz give the explanation given by usmleasy?
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| rida
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sorry mash, been trying to find that question again, can't seem to find it, if i do, will post it here. However, i do think it was basically what you said.
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| rida
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 Couldn't find it mash, sorry about that, and time's up so it won't let me log in, should have saved it :cry:
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| mash
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rida, its alright !
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