Cherry-Pink Lividity
Definition
The bright pink discolouration of dependent tissues seen in CO and cyanide deaths. In CO the colour comes from COHb itself, in cyanide it comes from oxygenated venous blood because tissue cannot extract the oxygen.
- Seen in
- Carbon monoxide and cyanide deaths
- CO cause
- Colour of carboxyhaemoglobin itself
- Cyanide cause
- Oxygenated venous blood, oxygen unextracted by tissue
- Confirmation
- Co-oximetry, toxicology
Common questions
Why does cyanide poisoning produce pink lividity if cyanide is not itself coloured?+
Cyanide blocks cytochrome oxidase so tissues cannot use the oxygen delivered to them, so venous blood stays as bright red as arterial blood instead of turning the usual dark bluish colour, and that oxygenated venous blood is what produces the pink dependent staining.
Can cherry-pink lividity alone distinguish CO poisoning from cyanide poisoning?+
No, both produce a visually similar pink-red colour at the scene, so co-oximetry or toxicological analysis of blood carboxyhaemoglobin and cyanide levels is required to tell the two apart and confirm which agent was involved.
Related terms
- Anion Gap
- Sodium minus the sum of chloride and bicarbonate in serum. A widened anion gap (above 16) in a comatose patient with unexplained...
- 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...
- Conway Microdiffusion
- A two-chamber glass cell in which an acid in the outer ring liberates HCN from the sample and the gas diffuses into...
- Headspace GC
- Gas chromatography in which the sample (blood, urine, vitreous) is sealed in a vial, equilibrated at a fixed temperature, and a portion...
- Saturation Kinetics
- Enzyme behaviour at substrate concentrations above the Km, where the rate of metabolism is constant rather than proportional to concentration. Ethanol saturates...