An air embolism, also called a gas embolism, is when an air bubble or air bubbles enter a vein or artery and block it. These air bubbles can travel to the brain, heart, or lungs and cause a seizures, blindness, ataxia or sudden death.
Air embolisms are caused by accidental injection of air into the horse's veins through a syringe, IV, or catheter. This is why it is extremely important horse owners do not give their horses intramuscular injections prior to being educated on the proper procedure by their veterinarian; it could have fatal consequences to the horse.