Why is it that if a dialysis patient has a ruptured fistula and is haemorrhaging, you shouldn't place a torniquet proximal to the haemorrhage?

Direct pressure: Hold direct pressure over the leak try to control without clotting the entire fistula or graft, so that it may be salvaged. Tourniquet may stop the bleeding if high enough pressure but may clot the fistula and require more extensive repair. Call 911 and get help and transport.

Tourniquets: Hemorrhage should always be controlled with direct pressure over the bleeding site when possible. Tourniquets are not such a good idea because application of one may stop bleeding, but will also cause a complete interruption of blood flow to an organ (hand in this case). If direct pressure does not stop the hemorrhage, then tourniquet is next step. Call 911 immediately!