When an animal is given an injection, whether intravenously (IV), intramuscularly (IM), subcutaneously or by any other parenteral route, intra-arterial (IA) injection may occur. Since arteries run parallel to many veins, the chances are greater when IV routes are used.
Nachreiner, Raymond F.
"Accidental Intra-Arterial Injection,"
Iowa State University Veterinarian: Vol. 28
, Article 6.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol28/iss1/6