1. Is spinach really good for you?
A case of
Methaemoglobinaemia
Jonathan Mervis

2. Case Study M.M. is a 3 month old female infant
diarrhoea and vomiting for 3 days
herbal medications given (oral and enema)
increasing irritability, dyspnoea, poor feeding, depressed level of consciousness
Family have running water, electricity, sewage

3. M.M., SHOWING CYANOSIS OF LIPS

4. What are possible causes of M.M.’s cyanosis?

5. Causes of cyanosis in children
Inadequate O2 of haemoglobin (common)
Pulmonary disorders
R-L shunts
Congestive heart failure
Cardiovascular collapse

6. Causes of cyanosis in children, continued
2. Methaemoglobinaemia (rare)
Congenital:
Cytochrome B5 reductase deficiency
cytochrome B5 deficiency
haemoglobin M
Acquired:
Toxins
Drugs

7. Normal Physiology 100 % SaO2 Ph 50 CO2 Temp 2,3 DPG 2 6 12 PaO2 ( Kpa)
ADD EXPLANATION
Temp
2,3 DPG 2 6 12
PaO2
( Kpa)

8. Methaemoglobin Oxidation= Loosing an electron
Reduction=gaining an electron
Fe(2+) Ferrous ion = good
SHORT NOTE
Fe(3+) Ferric ion = bad

9. Methaemoglobin
Fe(3+)
Fe(2+) e-
Cytochrome B5 Reductase
Cytochrome B5

10. Methaemoglobinaemia 20% acute increase = fatigue
30% acute increase = raised heart rate
50% acute increase = weak/ dyspnoeic/ confused
70%-80% acute increase= coma and death

11. Toxin induced MetHb Dependant on toxin, dose and duration of exposure
Neonates and infants are more susceptible

12. Common toxins producing MetH
Water from wells
Drugs (over-the-counter meds, metoclopramide, nitrites, anti-malarials)
Vegetables (SPINACH!)
Diarrhoea

13. Case Study, continued M.M. was profoundly acidotic, shocked
initial blood gas
Ph= 6.75/ CO2 =1.53/ O2 =26.4 unrecordable
Poor perfusion, cyanosed, but good air entry and easy to ventilate
Blood gas in ICU
Ph=6.78/ CO2=2.41/O2=57.2/ -27/ 3.4

14. Case Study, continued
Central venous access yielded chocolate brown blood
Lactate 17.6
throughout this time his O2 saturation remained 80%-83%
Hb= 7.8

15. Blood on swab – note chocolate colour

16. What is the management of methaemoglobinaemia?

17. Management Ascorbic acid (vitamin C) Methylene blue
reduces methaemoglobin directly
Methylene blue
acute levels >40%
IV 1-2mg/kg
repeat dose
G6PD deficiency
Dramatic response

18. Blood samples, showing improvement after methylene blue therapy

19. Treatment - note rapid improvement

21. Conclusion Consider methaemoglobinaemia when there is
Cyanosis with high PaO2 ,
Child is easy to ventilate and well-perfused

22. Further reading ??