A cat indwelling needle dropped into a blood vessel can lead to serious health problems. An indwelling needle is a medical device that is commonly used to administer fluids or inject medications to cats. If an indwelling needle accidentally falls into a cat's blood vessel, the needle can cause damage to the blood vessel, leading to bleeding or a blockage of the blood vessel. An indwelling needle can cause infection because it is a foreign object that can provide a breeding ground for bacteria. The needle can damage surrounding tissues or organs as it moves through the blood vessel, leading to pain and other complications. If a cat's indwelling needle falls into a blood vessel, seek veterinary help immediately. The veterinarian will take appropriate measures, such as using imaging techniques or surgery to locate and remove the needle to minimize potential health risks.