Initial assessment – bedside tests

Bedside tests also provide useful information.

1) Chocolate Blood: In methaemoglobinaemia, arterial blood is chocolate coloured and it does not oxidise or turn redder on exposure to air

“Normal” blood sample on left compared to “chocolate blood” on right

2) Brown / black urine: Urine can also be discoloured

3) A low SpO2 on pulse oximetry which does not improve with supplemental oxygen. SpO2 as measured by pulse oximetry usually does not fall lower than 85%, so significantly lower readings suggest an alternative or additional cause of hypoxia.