When my daughter had her nerve blocks, they always put a thermometer on her feet (one leg affected at a time so far) and there was always a significant difference in temp. Probably--trying to remember-- but a ten degree difference. After the block, a substantial temp increase--sometimes ten degrees warmer in the affected foot than the normal one. He always thought this was a good sign the blocks were working even if the pain didn't go away.

I know I am always warming her foot and leg and then finding ways to cool when needed. Mostly we use water but we generally have to warm it.