..if you mean to put in intravenouse transfusion, then do what the others (Carole Kirby)had said, like tie the torniquet above where you want to put the catheter.....
...if you want to stop the bleeding , apply direct pressure to the site..
..but in some cases, i have noticed some doctors, applying pressure furthest from the body(below).. i have tried this before like applying a torniquet below the site where you want to put cannula, and it helps, because we know vein carried blood from the body to the heart and so if you apply pressure below the site, the bleeding will stop..if the vein is superficial, apply pressure below that vein and voila!!!!..
try that.... for confrimation