Intravenous
Intravenous refers to the administration of liquids directly into a vein (be it a nutrient solvent, an anesthetic or a street drug such as cocaine or heroin).
In the context of body modification, use of injectable anesthetics is almost never intravenous (although doctors will sometimes administer a Valium or Versed/Demerol drip to calm the client during a procedure). Injections are usually limited to subcutaneous injection of local anesthetic or a nerve block.
The only case in which anesthetic might be injected intravenously is in a DIY amputation in which the body part being removed can be exsanguinated and the blood vessels are filled with a standard injectable anesthetic such as lidocaine.
Those anesthetics administered intravenously should only be used under the supervision of medical professionals.