Anything can happen while you are away -- and you need to be able to deal with it because your cat depends on you. During thirty years of traveling with my cats, I have rarely had a medical emergency.  But they can and do happen.  Make sure you  have your cat's health records with you so that you can give them to any vet you need to go to while you are away.  You should also have your vet's phone number with you so that s/he can be contacted to discuss your cat's situation if necessary.  Ideally, you will also have the name of a vet that you can go to if you do have an emergency.  The last thing you want to be doing is hunting through the phone book trying to find a vet you can go to and trying to locate directions!

Diarrhea:  Use the medication prescribed by your vet.  If it continues, go to the emergency vet you have located.
Vomiting:  Use the medication prescribed by your vet.  If it continues, go to the emergency vet you have located.
Poisoning:  Despite all your best efforts, your cat finds a way to get hold of some poison.  Immediately stop your cat from licking its coat and paws and possibly ingesting more poison.  Create an Elizabethan collar -- use piece of cardboard or a Chinette plate, cut a hole just large enough to go over your cats head.  Now, take a damp wash cloth and wash the paws thoroughly.  Then wipe the coat with the damp cloth to remove as much of the poison as you can.  Call the emergency vet tell them what you have done, what the poison is (if you know), and see what they want you to do next.  Make sure you take the poison with you so the vet can identify it and get the correct antidote in place.
Small Cuts:  Wash the area gently and cut the fur away from the area.  Put on Polysporin antibiotic cream.  Repeat twice a day until the cut has healed.
Large Cuts:  Take your cat to the emergency vet you have located as a stitch may be required.