When your patient turns blue after you’ve infiltrated lignocaine around their wound…think Methaemoglobinaemia 21 May, 201511 July, 2021 EMKF MetHb level (%) Signs and symptoms 1-3% (normal) None 3-15% Low pulse oximetry (<90%) Gray cutaneous coloration 15-20% Chocolate brown blood Cyanosis 20-50% Dizziness, syncope Dyspnea Weakness Headache 50-70% CNS depression, coma, seizure Dysrhythmias Tachypnea Metabolic acidosis >70% Death Hypoxic injury
