Intravenous (IV) access is indicated if the casualty is in hemorrhagic shock or at significant risk of shock or if the casualty needs medications but cannot take them by mouth. So not every casualty needs an IV, and some of them will be able to tolerate oral fluid replacement therapy, saving limited IV fluids and blood products for others.

A saline lock is preferred compared to a Direct Line, for several reasons:

- It is easier to move a casualty without an IV line and bag.
- The chance of having the catheter dislodged is less than with an attached IV line.
- IV fluids are conserved for those who really need them instead of being used to keep a line patent.
- Rapid IV access is still available, as needed.
- The amount of equipment the Combat Medic needs to carry and maintain is reduced.