Sulphhaemoglobin (SHb)
Definition
A modified haemoglobin species in which one or more pyrrole rings is sulphonated by reaction with hydrogen sulphide. Produces green-brown blood and livor mortis; detectable by co-oximetry (absorption peak at 618 nm). Cannot be reversed by standard antidotes.
- Abbreviation
- SHb
- Cause
- Sulphonation of haemoglobin by hydrogen sulphide
- Visible effect
- Green-brown blood and livor mortis
- Detection
- Co-oximetry, absorption peak at 618 nm
- Reversibility
- Not reversed by standard antidotes
Common questions
Why can't standard cyanide or CO antidotes reverse sulphhaemoglobin?+
Sulphhaemoglobin forms through an irreversible chemical modification of the haemoglobin molecule itself, unlike carbon monoxide or cyanide poisoning where the toxic ligand can be competitively displaced or metabolised. Once the pyrrole ring is sulphonated, that haemoglobin molecule is permanently nonfunctional and must be replaced by new red cell production.
How does an examiner distinguish sulphhaemoglobin discolouration from ordinary decomposition?+
The distinctive green-brown colour of SHb can resemble putrefactive changes, so co-oximetry is used to confirm the diagnosis by its characteristic absorption peak near 618 nm rather than relying on colour alone. Scene history of hydrogen sulphide exposure, such as sewer or industrial settings, supports the interpretation.
Related terms
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- Carboxyhaemoglobin (COHb)
- The compound formed when carbon monoxide binds to haemoglobin at the oxygen-binding site, with an affinity 200-250 times greater than oxygen. Produces...
- Cherry-Red Livor Mortis
- Bright pink-red post-mortem lividity produced by the spectral absorption shift of carboxyhaemoglobin; also seen in cyanide poisoning and hypothermia. Distinguished from natural...
- Co-Oximetry
- Spectrophotometric analysis of blood that simultaneously quantifies oxyhaemoglobin, deoxyhaemoglobin, carboxyhaemoglobin, methaemoglobin, sulphhaemoglobin, and total haemoglobin by their distinct absorption wavelengths. The primary...
- Cytochrome C Oxidase (Complex IV)
- The terminal electron acceptor in the mitochondrial respiratory chain, inhibited by both cyanide and hydrogen sulphide. Inhibition prevents oxidative phosphorylation and ATP...
- GC-FID
- Gas chromatography with flame ionisation detection. The standard analytical method for quantifying cyanide and methanol in blood and tissue specimens. Provides both...
- Knockdown Pattern (H2S)
- The scene distribution of multiple H2S victims clustered at the entrance or access point of a confined space, as first responders and...