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
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.