Yes, the needle can be reused as long as you did not contaminate, ie: touch the needle to your hands or other surfaces. But use a new needle the next time you give fluids again. The other vet's video offered good advice. The reason for the fluids not flowing is because the tip of the needle is probably upu agains muscle or fat. Therefore, the opening is blocked. Usually redirecting the needle or pulling it out just a small amount will start the flow again.