A.M.
my son does this.... he is an explosive ball of energy(all the time!!) :) his pediatrician told me a little "little" salt is ok.. but when he gets that bad or i see it comming to give him gatoraid or pedalyte(sp). expecialy in summer when he works up a sweat 5 min after getting out of bed and then all day long. His ped also told me to make sure he's getting enough water too.
hope your doc can help.
A.