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Reply To: VNCert EEC Exam Question: Blood Gas

Sara Jackson

My understanding is that bicarb buffers acids to compensate for a metabolic acidosis hence the decrease in bicarb, and hyperventilation is also a buffer by blowing off CO2, therefore this also decreases

Here I would say:
pH = acidosis
Co2 is the wrong direction for it to be respiratory acidosis therefore likely metabolic metabolic acidosis with correct respiratory compensation.
Bicarb will decrease because it’s buffering the metabolic acid.
The hyperlacteraemia would indicate a cause of the acidosis.

Where I would disagree with Annette (sorry Annette!) is that the lacteraemia is due to lactic acidosis OR poor tissue perfusion. We know we have an acidosis here, wholly or partly due to hyperlacteraemia. Poor tissue perfusion is one cause of hyperlacteraemia.

Lactate production may be higher than this indicates if severely dehydrated and may only be noted as such on our bloods once fluids are given and the lactate leaves the capillary beds to enter the venous circulation. Many vomiting patients are alkalaemic, due to acid loss, until hypoperfused/hypovolaemic secondary to severe dehydration or third spacing.

What underlying disease could cause an acidosis in a vomiting patient which is not related to lactate?