generally, the pulmonary and renal systems compensate for each other to return the body's pH to normal.
In a SINGLE acid/base disorder, the system NOT causing the problem will try to compensate by returning the ratio of bicarbonate to carbonic acid to teh normal 20:1.
The lungs compensate for metabolic disturbances by changing CO2 excretion. The kidneys compensate for respiratory disturbances by altering bicarbonate retention and H+ secretion.
What seems to be going on here is as you stated.. acute or chronic metabolic acidosis (or base bicarbonate deficit). It gets pretty deep... look up your anions and the anion gap...or I should say, your DOC should be looking these up !!! An anion gap greater than 16mEq suggests excessive accumulation of of umeasured anions. Low bicarb levels and low pH suggest metabolic acidosis... you need to know whether it is acute or chronic.
I'm concerned that the babe's doc is not investigating more thouroghly...
S/S of metabolic acidosis of course vary with the severity of the acidosis.. H/A, confusion, drowsiness, N/V, increased resp. rate and depth. cold, clammy skin, dysrythmias, shock.
CHRONIC metab.acidosis is usually seen with chronic renal failure.
The bicarb and pH decrease slowly.. and the patient is often asymptomatic until the bicarb is approx. 15 or less. But the cardinal feature of metab. acidosis is a decrease in the serum bicarb level.. often accompanied by hyperkalemia as a result of the shift of potassium out of the cells.
I work in dialysis, and we have to adjust the bicarb settings for our patients according to their lab results. What are the child's calcium levels? Are they low, too?
I would be asking a LOT of questions if I were you... refresh yourknowledge on acid/base and electrolytes, ABGs, etc. Then start asking questions and expecting some answers ! The child is exposed to a high acid concentration from SOMEWHERE which is being buffered by HCO3, causing the bicarbonate concentration to fall.
I hope you get to the bottom of this... I can only give you what little I know here... and certainly advise to go back to the docs and not settle for anything less than a thorough investigation and explanation !
Hugs to you, and please keep us posted.