A numbing medicine turned a woman's blood blue - CNN

Good morning all,

We recently described human blood in lecture, noting that it is red in color (of course!), and that its color comes from the hemoglobin pigment inside of our red blood cells.

How about a person whose whole blood is blue?

In the news this week is a report about a woman who used excessive amounts of a common over-the-counter analgesic (benzocaine) which rendered her hemoglobin blue in color:

https://www.cnn.com/2019/09/19/health/blue-blood-trnd/index.html

Persons of low blood oxygen levels are considered to be 'cyanotic', and often have a pale or bluish cast to their skin.  If their hemoglobin has been poisoned, it can impair oxygen transport/delivery, at worst, to a fatal degree.

In this case, the blue color was not physiologically problematic.  This woman's blood was still relatively high in oxygen content, but contained more cyanomethemoglobin (which causes the blue color) than is normal (few percent).  Luckily for this woman, her problem was cosmetic only, and the antidote (ironically, doses of methylene blue) was both simple and effective.

Interestingly, blue blood is perfectly normal in crustaceans (such as crabs and lobsters), because they employ hemocyanin (rather than hemoglobin) for oxygen transport.  Their blood is of such great medical utility for testing of toxins and contamination that a large (and controversial) industry is devoted to its collection:

https://www.theatlantic.com/science/archive/2018/05/blood-in-the-water/559229/

And, there is a known genetic disorder than causes cyanosis to run in (a small number of) families, including the famous 'blue Fugates of Kentucky':

https://www.iflscience.com/health-and-medicine/the-science-behind-the-mysterious-blue-people-of-kentucky/all/

So, the next time you hear the term "blue bloods", you might wonder if it is genetic, pharmaceutical, or crustacean in its basis...

Have a great weekend -
Dr. Nealen