In an emergency, hospitals may be shut down, or overflowing with victims, in any case, you should be prepared with Wound Management and Sanitation.
Imagine trying to survive out in the woods, you have enough food, water, and shelter. But you get a cut and a day later, it is turning black. This is known as an infection, you must be prepared against this by having wound management supplies and sanitation. In this situation, you could leave your cut alone, and slowly let the infection kill you, or you can smother it with hydrogen peroxide and seal it to prevent the infection in the first place.