Moslem Doctor
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kaplan mention that there is no increase in co2 level in metabolic alkalosis and acidosis how this can be ?
when we add H ion it must shift to left and co2 increase!
and also when we add bicarbonate must shift to left and co2 increase
so how they say it is not increase? can any one explain ?
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Say ye: "We believe in Allah, and the revelation given to us, and to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we bow to Allah (in Islam)." Holy Quran
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| drpkaur
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hi there,
here is some input from my side see if u go through those lines in kaplan notes u'll find that in metabolic acidosis -gain in fixed acid ,incr H ions forces the reaction towards left decreasing bicarbonates ,forcing the reaction towards left will produce some CO2 but by convention if there is no respiratory compensation ,therefore no change in PCo2 ...it means that there is no significant change in PCo2 in uncompensated state but if there is respiratory compensation -compensation is hyperventilation right it means increased washing out of Co2 it leads to decrease in pco2.......moreover there will be kidney compensatory mechanism too-increased excretion of acid and generation of new bicarbonate...
rest u can make out for metabolic alkalosis from notes if u understood metabolic acidosis...
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| p53
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this may be helpful:
http://www.prep4usmle.com/forum/thread/22900
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"Everything should be made as simple as possible, but not simpler." - Albert Einstein
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| Moslem Doctor
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thank u both for your interest
my friend drpkaur the Question was why co2 level will not be markedly increase ? kaplan book write just it will be increase but not effective increase but why?
Dear friend p53 thanks for your always interest in helping us iam so thankfull for u really
i checked the link u post and want to discuss with u about some points
((OK, but your question is again ununswered - why equal increase in H and HCO3 due to rise in PCO2 results in respiratory acidosis, where is HCO3 to compensate H? you said that 'HCO3 increases, but slightly'. It isn't right - HCO3 increases exactly as much as H. Then why doesn't it compensate H? BECAUSE THEIR STARTING CONCENTRATIOS IN ECF ARE VERY DIFFERENT - the [H+] in the normal state is 40 nanoequivalents (nEq/L) per liter, whereas the [HCO3-] is regulated to 24 milliequivalents (mEq/L). Note that mEq is 1000 times more than nEq. A change of pH from 7.4 to 7.2 requires a rise in H from 40 to 60 nEq/L (a 50% increase). The total amount of HCO3 also rises by the same amount (20 nEq/L), however because the amount of HCO3 in the ECF is much more large, this change is relatively insignificant. The actual change in [HCO3-] is on the order of a 0.001% increase. ))
moslem doctor: i see this has nothing to do with the Question becuz whate ever was the normal diff between the level of hydrogen idons and bicarbonate it is not the proplem , the ph is alterd by H ion increase , so in respiratory acidosis yes bicarbonate will increase as same as H ion ,but once H ion increase it is acidosis and ph become low , even if there is equal amount of bicarbonate produced and u yourself said that in next post
post number 12
((You should notice that pH is created only by concentration of H+. As you said 'pH is the log of 1/[H+]'. Other cations (for example Na+ and K+) and anions (for example HCO3- and Cl-) don't have any business with pH. For pH it doesn't matter how much [HCO3-] you have, matters only how much [H+] you have - more than in water (pH falls), less than in water (pH rises), or exactly the same as in water (neutral pH, =7). ))
but i still confused why when we add H ion no co2 increase although it has to shift to left and they say it remain unchanged without compensation , can this be becuz the normal breathing (withouth compenstion ) has the ability to remove any increase in co2 results from adding H ion or adding Hco3?
or this can be explained by that huge diff level between H ion and bicarbonate ions in starting point , so when u add some H ion or bicarbonate ions , it dont shift by marked way to produce co2 as it need high level from ions to stimulate shift and be propotional to the big diff between H ion and bicarbonate in start point ?
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Say ye: "We believe in Allah, and the revelation given to us, and to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we bow to Allah (in Islam)." Holy Quran
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| drpkaur
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well moslem doctor,
You asked abt the metabolic alkalosis and metabolic acidosis that's why i cleared my points on that issue but i don't know now you are writing abt resp acidosis ..i think you yourself making this matter confusing and complicated....hope u understand
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| doc179
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I think this is what you are asking... you want to know why CO2 level does not increase in metabolic acidosis... its because you hyperventilate to get it the normal or below normal level which is a compensatory mechanism , if the pt had a lung problem then he would not hyperventilate and CO2 level rises and it becomes a combined acidosis.
In met.alkalosis ( in acid - base mostly we talk abt H+ ) either the HCO3- is more or the H+ is less( most likely its less H+ ) so you need to make more H+ or excrete more HCO3- to compensate and hence the reaction does not shift to the left but shifts to the right. so CO2 does not increase.
Hope this is what you wanted to know.
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| Moslem Doctor
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doc 179 this is what i asked for u ,u knew my Question well
what u said is the logic and this what i go with but if you return to kaplan u will find that when u add H ion or bicarbonate and it shift to left some co2 produced (so small amount cant be considerd) so actually there is no increase in co2! . so the hyperventilation here will be to make co2 less than normal just to help in shifting to left ,not to remove excess co2 in blood results from adding hydrogen ion
in kaplan they write
metabolic acidosis HCO3 decrease PCO2 no change
metabolic alkalosis HCO3 increase PCO2 no change
so what ever u add H , HCO3 ion actually no further increase in PCo2 (may this becuz normal respiration has the ability to wash even without hyperventilation?! i dont know thats was the Q) and this hyperventilation happend in metabolic acidosis not becuz there is primary increase in Pco2 but it low the normal level to push the reaction to left
iam sorry i keep repeating but just wanted to make Question clear and my view more near
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Say ye: "We believe in Allah, and the revelation given to us, and to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we bow to Allah (in Islam)." Holy Quran
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| Moslem Doctor
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add something in kaplan they write that this unchanged PCo2 occur when there is no respiratory compensation ,so this unchange PCo2 not result from our compensation ,it is already from first not changed
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Say ye: "We believe in Allah, and the revelation given to us, and to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we bow to Allah (in Islam)." Holy Quran
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