I know when I had arm surgery they asked me to remove all my nail polish. They checked the circulation in my finger tips by pressing on them. I am guessing with the toes maybe they check circulation in that area as well even though I don't recall them doing that. Unless they did it while I was still under anaesthesia.
Actually I just found an answer to this, lol.
Source: The Sydney Morning Herald
Why do you have to remove nail polish before surgery?
Possibly the most important monitoring device that helps make modern anaesthesia so safe is the pulse oximeter. This measures the level of oxygen in the blood and works by passing red light through tissue, most commonly a finger tip, and computing the absorption of the light, which varies depending on the oxygenation. Nail polish may reduce the effectiveness of this monitor. The nail bed is one of the best places to detect cyanosis caused by low oxygen levels.
Good luck with your surgery! Please keep us updated.
Since i'm a surgery TA - let me explain (put the teacher's hat
It's because of the pulse oximeter and because it's very easy to check if you're lacking oxygen on your lips and underneath your nails (foot and hand fingers) - you turn blue. That's why you can't wear lipstick or nail polish - although the fingers can be misleading, since your fingers can turn blue because of cold.
As far as I was always told, it had to do with monitoring your oxygen flow with that finger-thingy *yes, I called it that*! Polish can supposedly "tamper" with the readings... As Lia just basically said...
I never knew why either, that does make a good deal of sense though. And here we keep thinking hospitals and doctors are just making this stuff up lately!