If, after splinting, the wrist begins to swell, turn pale, or look blue-ish, loosen the ties a bit. They may be too tight. The ties should be secure enough to stabilize the wrist, but you should always be able to feel a pulse.
You should also loosen the ties if there in continued or worsening pain. If these measures don’t help and the injured person is still experiencing pain, you should remove the splint altogether.
If the injured person is feeling faint and has short, rapid breath, they may be going into shock. Lay them down without affecting the injured wrist and elevate the feet slightly above the head. Keep the person warm until help arrives.