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NBME 20 Answers
A 1-month-old male newborn is brought to the ...
Na+: 132; K+: 3.2; Cl−: 90; HCO3−: 37
decreased K+ (from increased RAAS due to volume loss) and decreased Cl- (loss of HCl from the stomach), Alkalosis from loss of HCl and thus high bicarb.
For this reason high to mid range K is wrong
Wouldn't increased RAAS lead to increased Na+? The answer shows decreased Na+.
Also, remember Bulimia Nervosa is associated with hypokalemia.
so the range they gave for K is 3-6? so 3.2 is WNL then?
or are we just operating on "it is on the lower end of normal in peds"
sodium levels in pyloric stenosis vary, nothing really classic, can be high as in this case simply due to hydration, can low in other cases if aldosterone managed to reverse that to the other extreme
K+ shouldn't increase. It's moving into cells due to metabolic alkalosis.
In the parietal cell of the stomach
Hydrogen ions are formed from the dissociation of carbonic acid. Water is a very minor source of hydrogen ions in comparison to carbonic acid. Carbonic acid is formed from carbon dioxide and water by carbonic anhydrase.
The bicarbonate ion (HCO3−) is exchanged for a chloride ion (Cl−) on the basal side of the cell and the bicarbonate diffuses into the venous blood, leading to an alkaline tide phenomenon.
RAAS increases from volume loss, and thus more aldosterone leads to low K+
Three reasons for hypokalemia.
First, some K+ is lost in gastric fluids.
Second, H+ shifts out of cells and K+ shifts into cells in metabolic alkalosis.
Third, ECF volume contraction has caused increased secretion of aldosterone.
Nevermind, I think I got it. Beta intercalated cells cannot function and excrete bicarb because we don't have chloride. Yea apparently I was exhausted.