Arterial lines are used to monitor blood pressure during an operation; any blood that flows when the line is inserted into the artery should be vivid red, the sign it has been oxygenated.
But in this case, which occurred in October 2005, it was not.
"During insertion, we normally see arterial blood come out. That's how we know we're in the right place. And normally that blood is bright red, as you would expect in an artery," Flexman said in an interview Thursday.
"But in his case, the blood kept coming back as dark green instead of bright red.
The next day, the lab reported it had detected sulfhemoglobin, a condition thought to be triggered by some medications.
"It's so rare that we don't have a perfect understanding how it happens, but some drug donates a sulphur group that binds to the hemoglobin molecule and prevents it from binding to oxygen," Flexman explains. "And that gives it the green colour."
Oh. Eminently logical.