Final answer:
A tourniquet should not be left on for more than two hours as it can cause tissue damage beyond this time. Medical attention should be sought promptly for proper management.
Step-by-step explanation:
The maximum time a tourniquet can safely be left on to control bleeding without causing tissue damage is generally considered to be about two hours.
Even though the body initiates a vascular spasm response to injury, which involves the constriction of blood vessels and can last from 30 minutes up to several hours, continuous application of a tourniquet beyond two hours can result in nerve damage, tissue death, and other serious complications.
When applying a tourniquet to control bleeding and tie off a severed vessel, it is crucial to be aware of the duration it has been applied and seek medical attention as soon as possible so that it can be removed under proper medical supervision.