Table 1

Clinical effects of methaemoglobinaemia

% MetHbClinical effects
0–15Clinical effects unlikely
15–30Mild: Cyanosis (tongue, lips, earlobe), fatigue, dizziness, headache
30–50Moderate: Weakness tachycardia, tachypnoea, mild dyspnoea
50–70Severe: Stupor, coma, convulsions, respiratory depression, cardiac dysrhythmias, acidosis
>70Potentially fatal