Question

you should apply ice or a cold pack to all suspected musculoskeletal injuries except when —
the victim is already in shock from his or her injury.
doing so would require you to put pressure on an open fracture.
a hot pack is available; then you should alternate cold and heat.

Explanation:

• For a victim in shock, the priority is to address shock (e.g., keeping them warm, elevating legs if no spinal injury suspected), not applying cold which can further constrict blood vessels and potentially worsen shock - related issues.
• Applying cold (ice or cold pack) to an open fracture (where bone is protruding through the skin) and putting pressure (as would be needed to hold the cold pack in place) can introduce more bacteria into the wound, increase risk of infection, and cause more damage to surrounding tissues.
• Alternating cold and heat is not the standard first - aid for suspected musculoskeletal injuries. Cold is typically used initially (for 48 - 72 hours in many cases) to reduce swelling, inflammation, and pain. Heat is used later (if at all, depending on the injury) to promote blood flow for healing. But having a hot pack available is not a valid reason to not use cold initially.

Answer:

The victim is already in shock from his or her injury.
Doing so would require you to put pressure on an open fracture.