A 29 year old man with fever, jaundice and RUQ tenderness has Haemolytic anaemia – (requires LDH, unconjugated bilirubin, Coombs test, haptoglobin and reticulocyte count) – patients LDH was 969 (120-250), unconjugated bilirubin 104  (<21) with normal platelets and Creatinine

MetHbaemia (normal<1.5) which also explains the discrepancy between the sats probe O2 and the ABG O2

likely to be due to Favasm (G6PD deficiency which causes haemolytic anaemia triggered by eating Fava beans). Exclude other causes of haemolytic anaemia. Other causes – liver disorder, Haemolytic Uraemic syndrome (E Coli / Shigella toxin) – both of which are less likely.

No acid base disorder, normal MCV/MCH/MCHC and platelets

Elevated WCC, his urine showed nitrites

The patient admitted to eating broad beans recently, which may have triggered the haemolysis due to his possible underlying G6PD deficiency.

The patient father was from Burma, mother from England

Methylene blue indications:

• methylene blue (1-2mg/kg over 5 minutes) provides an artificial electron acceptor to facilitate the reduction of MetHb via the NADPH-dependent pathway; give if:
  — symptomatic
  — consider if asymptomatic with >20% MetHb, or >10% if risk factors such as anaemia or ischemic heart disease
• repeat methylene blue at 30-60 min if inadequate response
• alternatives to methylene blue:
  —ascorbic acid (if methylene blue contra-indicated, e.g. G6PD deficiency)
  — exchange transfusion
  — hyperbaric oxygen

REASONS FOR FAILURE OF METHYLENE BLUE

Consider the following if MetHb levels do not fall with methylene blue:

• massive ongoing exposure to an oxidising agent
• sulfhaemoglobinemia (e.g. dapson, sulfonamides)
• G6PD deficiency
• methaemoglobin reductase deficiency
• abnormal haemoglobin
• excessive methylene blue (paradoxical effect in high doses)

Causes of acquired MetHbaemia:

• aniline dyes
• benzene derivatives
• chloroquine
• dapsone
• prilocaine
• metoclopramide
• nitrites (nitroglycerin, NO, sodium nitroprusside)
• sulphonamides