NBME Answers : freebie's page

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submitted by aneurysmclip(209), visit this page

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basically polycystic kidneys won't work properly, they've hinted at this with the s.creat of 4mg/dl. thus the kidney won't do what its supposed to do. REMEMBER to check whether they are asking SERUM changes or URINE changes

Kidneys normal function - reabsorb HCO3- , its not doing that now > decreased HCO3

PTH - would cause increased Calcium reabsorption in kidneys, but kidneys aren't able to reabsorb calcium > PTH responds to low calcium levels and levels increase

PO4 ties into PTH as well, PTH acts be DECREASING PO4 reabsorption. Since kidneys aren't working ie: not responding to PTH > there would be increase in PO4

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pg32 Sometimes these questions are made more difficult by trying to decipher the order in which these changes happen (first cause). In my mind, whenever I see a question on renal insufficiency, I know that phosphate in the serum will increase. In response, Ca will decrease and in response to that, PTH will increase. Lastly and unrelated, HCO3 will decrease because the kidneys aren't absorbing HCO3 as they usually do. +15

baja_blast I also think there is decreased 1alpha hydroxylation of Vitamin D, which would increase PTH secretion +3

freebie This questions is testing the consequences of renal failure --> "MAD HUNGER" mnemonic in FirstAid +1

submitted by hello_planet(43), visit this page

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The other comment is partially incorrect. If the drug molecules dissolve in blood, they do not have an anesthetic effect. If they have a low blood solubility, they do NOT dissolve in blood well which leads to a faster anesthetic effect.

The potency is related to the lipid solubility because the drug has to be lipid soluble to cross the blood-brain barrier. A drug with a higher lipid solubility will be able to reach a therapeutic dose in the brain at a lower administered dose, so lower lipid solubility = more potent.

This question asked about a quick induction time, so we want a drug with a low blood solubility so the drug will not dissolve in the blood and will more quickly cross into the brain.

In other terms, a low blood:gas partition coefficient = low blood solubility = short induction time.

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hello_planet Ugh, it appears you can't edit comments. I meant that a higher lipid solubility = more potent. +1

drdoom nice explanation! +1

ringarosie agree, with explanation and "aside" +

freebie Correct. Anyone confused on this should go watch the Boards & Beyond anesthesia video covering this topic. +

kcyanide101 The explanation also applies to the blood gas coefficient. Another factor that affects induction is Aterio/Venous conc. The higher it is the lower the induction as it shows the peripheral tissue is taking it up.......... Here's a youtube video that simplify's it https://www.youtube.com/watch?v=Zsjs_mDc_AM +