Remember, we are not veterinarians. Consult your vet if you suspect gastric stasis or gas in your rabbit.
Keep simethicone on hand. Liquid simethicone is the ingredient in Baby or Infant gas drops, which is available over the counter in drugstores and many supermarkets. We administer between .5 and 1cc of liquid simethicone orally, using a syringe with no needle. Liquid simethicone is like Tums for people, and we have never experienced a rabbit having an adverse reaction to it. We administer a dose and wait for 30-45 minutes, while also trying other methods (below). If the first dose doesn't work, we don't hesitate to administer another. If your bunny is in too much pain please call your vet right away.
Keep your bunny moving.This can be difficult when your bunny doesn't feel well, but moving around can help your bunny get his or her gut moving again.
Keep your bunny warm. Pain can cause bunnies to go into shock, which can be deadly. Help to avoid shock by keeping your bunny warm. If your bunny is cold, put a dry towel into the dryer to heat it up and wrap your bunny in the warm towel. You can also use your own body heat and a blanket or towel to keep your bunny warm, or consider purchasing a Snuggle Safe, which you can heat to a safe temperature in the microwave and place under your bunny's bed.
Gently massage your bunny's tummy. Be careful, because bunnies are delicate inside and out. Your goal is to encourage the gas to move through the bunny's gut and out. Note that bunnies can't burp, so the only exit is through...the back end. This video below has some bunny tummy massage technique.
Keep your eye on hydration. You can use a small syringe to gently give your bunny a bit of water. Be careful to go very slowly and let your bunny process the water. You can also ask your vet about subcutaneous (sub-q) fluids. These are injected under the skin on the back of the neck out of a bag of fluids that looks like the IV fluids that are given to humans. Your vet will administer sub-q fluids, and can teach you how to do so and provide the supplies to take home if necessary.
Keep recovery foods on hand. We always have canned pumpkin and squash baby food on hand for recovering bunnies. You can offer this on its own or mix it with a few pellets that you have soaked in water. You can also use Critical Care. Be sure to keep open packages of Critical Care in the fridge, and respect the expiration date on the package after it is opened.