80 year old man, tachypnoeic, borderline hypoxia with…

Mixed respiratory and metabolic alkalosis – expected CO2 for HCO3 of 28.6 would be 40

Normal A-a gradient

Mild hypokalaemia

High Hb

Normal Na, Cl, Glucose, lactate

Causes include:

dehydration

diuretics

RTA

Central and peripheral causes of Respiratory alkalosis

Normal A-a gradient implies no shunt or VQ mismatch

This patient had a pneumonia and his blood gas normalised after 1 litre of Normal Saline!!