How to make a finger survive

Seeing this very dramatic story, I came to think of what we see in movies, somebody looses a finger, and they put it on ice and rush to the Emergency room. I wondered if this was really the best way, and asked our old pal, Pascal MD. Quoths he:

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Reminds me precisely of Chapter 1 in my Emergencies course last year.
The problems with separated body parts are several. Globally, anything other than "internal organs" has a high tolerance to blood circulation deprivation, especially if the nerves were severed too and no muscle activity uses up their cell energy. (Otherwise, lactic acid build-up would soon cause great damage.) But they still need:
- Not to dry up. It destroys the cells.
- To remain cold. This slows the metabolism and hence the damage.
- Not to freeze. Frost creates sharp microscopic ice crystals that tear the cells apart. So far, real-life "deep freeze cryogeny for humans" is nothing but a scam.
- Acidity isn't the only problem. Fluid concentration also is. Pure water causes osmotic shock that destroys the cells. And cells destroyed equals dead tissue.

The ideal solution of course, is something akin to what that article mentions: the piece of skull that they had to temporarily remove was "grafted" elsewhere inside the person's body. With the blood vessels reconnected, the tissue can safely survive indefinitely. Whether it endures some modifications is another story. (For instance, muscle that doesn't "work" and contract regularly undergoes atrophy. Same with bones, as seen in astronauts.)

Now, the best option for a detached body part until you rush to the hospital, is to keep it very cool, but above ice temperature; moist, and not in pure water or concentrated liquids (sea water is too salty). Ideally, normal saline serum at a temperature of about 5 or 6° Celsius.
Often, one doesn't have that under hand. But it's easy to improvise, as I've taught my students!
Normal saline concentration is precisely NaCl at 9g/l. A perfectly flat large spoonful of table salt is precisely 4? grams. So, either two of these in a one-litre bottle of mineral water, or one flat spoonful of table salt in a half-litre bottle. Tap water is OK, it's very clean germ-wise. But mineral water bottles from a nearby store have the advantage of often being sold straight out of the cooler...
For larger amputations (a hand, an ear or nose) that don't easily pass through a bottleneck, just find a larger container such as a tupperware box, and prepare more "hand-made saline serum".
After that, the results still depend of course on how much time elapses before starting surgical repair.

Joke: a guy arrives at the hospital, with all his fingers missing.
The surgeon exclaims: "But you should've brought them! We could have reattached them for you."
The guy says: "Oh yeah? And how was I supposed to pick them up?"

Bear in mind that often, a knocked-down tooth is ALSO a body part that can be surgically reattached by a specialist.

A less ideal option that still work better than nothing, is to put "it" in a wet piece of cloth, and then inside some ice cubes. This way, it stays moist, and is cooled without freezing from direct contact with the ice. Hopefully.
Milk has been suggested. Cool, natural fresh milk MIGHT be okay as a make-do substitute. But anything sweetened, flavored, or prepared from powder is likely to be catastrophic, because osmolar concentrations (and added substances) will usually be all wrong.

So, in answer to your suggestion, about one normal ice cube to keep your half-litre of improvised normal saline moderately cold is okay. Think of it like a summer beverage: nicely cool, but NOT FREEZING. Estimating the temperature with your lips or (remaining) finger is quite reliable.
Then again, often the main problem is the exact opposite, with your precious cargo having to endure the heat on the road. Maybe keep a stock of ice cubes on the side, and add one whenever things get too warm. But watch out for the dilution effect on your saline serum.