Methaemoglobinaemia
physiology
MetHb = Hb containing Fe3+
Suggests exposure to oxidative stress
homeostasis usually via reductive mecahnisms including cytochrome b5 reductase
| Headline | |
|---|---|
| Etiology | ➥ Clinical state - anything to cause prolonged oxidative stress? e.g. sepsisssss ➥ Toxins: nitrites (e.g. amyl nitrite/poppers); local anaesthetics, methylene blue (!! in high doses...), metoclopramide, aniline dyes... ➥ PMH: Inborn errors of metabolism |
| Clinical presentation | Non-specific, but mainly hypoxic symptoms. Cyanosis, 'happy hypoxia' |
| Diagnostic investigations | ABG, or specifically request from lab - Use to calculate saturation gap = SaO2 - SpO2 - >5% implies abnormal hb |
| Differentials | |
| Immediate management | A/B: FiO2 100% (maximise functional Hb) IV glucose? (physiologically sound. maybe, maybe not.) Methylene blue (...hmm) Consider exchange transfusion Toxbase it, as always |
| Ongoing management |