Medical Marvel: Sulfhemoglobinemia (Green Blood)

Sulfhemoglobinemia is:

... a rare condition in which there is excess sulfhemoglobin (SulfHb) in the blood. The pigment is a greenish derivative of hemoglobin which cannot be converted back to normal, functional hemoglobin. It causes cyanosis even at low blood levels.

Sulfhemoglobinemia is usually drug induced. Drugs associated with sulfhemoglobinemia include acetanilid, phenacetin, nitrates, trinitrotoluene and sulfur compounds (mainly sulphonamides). Another possible cause is occupational exposure to sulfur compounds. The condition generally resolves itself with erythrocyte (red blood cell) turnover, although blood transfusions can be necessary in extreme cases.

A case report appeared in The Lancet last year, documenting one instance of this condition:

The man - a 42-year-old white Canadian - had developed a compartment syndrome (localised tissue/nerve damage due to restricted blood flow) in both lower legs after falling asleep in a sitting position. He was a smoker whose medical history included chronic shoulder pain and migraine, and was taking a number of regular medications, including sumatriptan to treat the migranes.

Doctors decided he needed urgent fasciotomies (a limb saving procedure in which tissue is cut into to relieve pressure) and he underwent emergency tests, which determined he was mildly tachycardic (rapid heart beat) but had normal blood pressure and his only initial abnormal blood result was an extremely high creatine kinase concentration.

In the operating theatre, multiple attempts to insert a radial arterial catheter yielded dark greenish-black blood, which was immediately sent away for analysis. Meanwhile the catheter was eventually fully inserted, and the man recovered well.

Sulfhaemoglobinaemia, rather than cyanosis, was diagnosed as the cause of the green-black blood.

Green blood! Who knew?


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