Rat bite care

[Bogertophis]

I’ve seen trained professionals kill the rat instantly by whacking their head against the edge of the table and breaking the neck. It severs the spinal cord and they feel nothing.

The trouble is, most people are not up to doing that...& if you hesitate or otherwise blow it, you're going to cause pain & a mess. I can guarantee I'd never do that.
CO2 is the way to go.