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

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

M.M., SHOWING CYANOSIS OF LIPS

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

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

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

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)

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

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

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

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

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

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

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

Blood on swab – note chocolate colour

What is the management of methaemoglobinaemia?

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

Blood samples, showing improvement after methylene blue therapy

Treatment - note rapid improvement

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

Further reading ??