With poor peripheral perfusion due to shock, many cells in the body no longer receive enough oxygen and, therefore, are no longer able to produce energy by fully breaking down carbohydrates and fats. This failure of metabolism results in the formation and accumulation of lactic acid, which causes metabolic acidosis. Metabolic acidosis is made worse in diarrhoea by the loss of bicarbonate in the stool. The use of aspirin (salicylates) may also make the acidosis worse.
Children with a metabolic acidosis develop rapid sighing (deep) breathing. The clinical diagnosis of acidosis can be confirmed by blood gas analysis.
The blood gas analysis in an infant with a metabolic acidosis shows a low pH and low standard bicarbonate together with an increased base deficit. In an attempt to correct the acidosis, the child often hyperventilates which lowers the pCO2.