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I got this wrong but best I could come up with was this was about Bradford Hill Criteria for establishing causality. And of the 9 included, F has the most that are actually included in the information given to us. I chose D but I think since we don't know about other study results, we can't include it as directly answering the question about *this* study.
Someone double check me here:
A: biologic plausibility is a weak point in the criteria, according to the wiki. Also probably not true in regards to this study.
B: Sensitivity is not part of the criteria
C: " "
D: We don't know about consistency
E: " B "
Found this ... still confused about why A and D are wrong though... https://stats.stackexchange.com/questions/534/under-what-conditions-does-correlation-imply-causation
The three criteria for causality are: 1) empirical association (i.e. strength of association; a change in independent variable correlates or is associated with a change in dependent variable), 2) time order (i.e. temporal relationship; the independent variable must come before change in the dependent variable, or plainly stated, cause must come before effect). and 3) nonspuriousness (i.e. dose-response gradient; the relationship between 2 variables is due to a direct relationship between the two, not because of the actions of changes in a third variable... this can be evinced by a dose-dependent response).
I don't think so. I know that K+ levels decrease with laxative use, due to dehydration, which activates the RAAS, which increased aldosterone, which cause Na+ re-absorption and K+ wasting. Aldosterone also causes the alpha intercalated cells to secrete more H+ into the urine, which causes a serum alkalosis. Therefore, in order to correct that, bicarb re-absorption decreases in the kidneys, which brings the pH closer to normal. As far as Chloride, I guess that must be re-absorbed with Na+ due to it being negatively charged (?). That's the one thing I'm not sure about.
I think what they are getting at is that it is Diarrhea--> Non-anion gap metabolic acidosis (HARDASS). This would mean that HCO3- would be low and chloride would be high (in non-anion gap acidosis the chloride increases and that's why you don't have a gap).
Normally, stool's electrolyte content primarily consists of bicarb, potassium, and sodium. Since the colon reclaims sodium in exchange for potassium, the potassium content of stool is usually double that of sodium. Most of our bicarb loss in stool actually occurs through the loss of organic acid anions, i.e. bicarb that's been titrated by the organic acids formed by bacterial fermentation in the colon (e.g. lactic acid).
*Bottom line: our stool is alkaline, with mostly bicarb and potassium.*
Diarrhea is a cause of *NON-anion gap metabolic acidosis* due to bicarb loss in the stool. We aren't adding any acids to the mix -- we're simply losing anions -- which is why our anion gap remains normal. Potassium goes along for the ride and we end up with *hypokalemic* metabolic acidosis. And because we're losing anions, we want to compensate by *increasing retention of Cl-*.
**Anion gap = Na+ - [Cl- + HCO3-]**
another observation to support this: The patient's RR is 30/min, which demonstrates a compensatory respiratory alkalosis, in response to the non-anion gap metabolic acidosis