Because a gaping wound like this has a high risk of infection, proper first aid is essential. Note: For obvious reasons, this is a simulated injury.
Place absorbent gauze on the wound and apply direct pressure on top to stop the bleeding. Elevate the wound slightly above the heart.
When bleeding stops, clean the wound with a high-pressure stream of water from an irrigation syringe, hydration bladder, or plastic bag with a needle hole poked in it.
Gently press the edges of the wound together and hold them in place with wound closure strips. In a pinch, you can close a wound with thin strips of duct tape.
Apply a layer of antibiotic ointment to a sterile dressing.
Put the dressing over the wound, making sure to cover it completely, and tape it in place. Evacuate the patient to a doctor.