Methaemoglobinaemia

Question 1

what is Methaemoglobinaemia

Answer 1

describes haemoglobin which has been oxidised from Fe2+ to Fe3+.

This is normally regulated by NADH methaemoglobin reductase

Question 2

what is Methaemoglobinaemia

Answer 2

describes haemoglobin which has been oxidised from Fe2+ to Fe3+.

Question 3

Congenital causes of Methaemoglobinaemia

Answer 3

haemoglobin chain variants: HbM, HbH
NADH methaemoglobin reductase deficiency

Question 4

acquired causes for Methaemoglobinaemia

Answer 4

drugs: sulphonamides,
nitrates (including recreational nitrates e.g. amyl nitrite ‘poppers’),
dapsone,
sodium nitroprusside,
primaquine

chemicals: aniline dyes

Question 5

features of Methaemoglobinaemia

Answer 5

‘chocolate’ cyanosis

dyspnoea, anxiety, headache

normal pO2 but decreased oxygen saturation

Question 6

in severe Methaemoglobinaemia features

Answer 6

acidosis, arrhythmias, seizures, coma

Question 7

management of Methaemoglobinaemia?

Answer 7

NADH methaemoglobinaemia reductase deficiency: ascorbic acid

IV methylthioninium chloride (methylene blue) if acquired