Final answer:
A major burn assessed as a full-thickness burn involves damage to all layers of the skin along with the underlying muscle and bone, and is termed a fourth-degree burn. These burns require specialized medical interventions including possible amputation, skin grafts, and supportive care to address dehydration and prevent infection.
Step-by-step explanation:
A nurse would assess a major burn as a full-thickness burn if it involves not just the full thickness of the skin but also the underlying muscle and bone. A burn of such severity is known as a fourth-degree burn, which is the most extreme form of thermal injury. Unlike first-degree, second-degree, or even third-degree burns, which damage the epidermis and dermis to varying extents, a fourth-degree burn is characterized by the destruction of all layers of the skin, as well as damage to deeper tissues such as muscles and bones.
Given the extent of damage in a full-thickness burn, the nerve endings are often destroyed, which paradoxically can result in less pain than burns of lesser degrees. However, such burns cannot heal on their own due to the extensive tissue destruction and require medical interventions like excision (debridement), possible amputation, and skin grafting from an unaffected part of the body or from skin grown in tissue culture.
Burn victims with fourth-degree burns also face critical risks of dehydration, electrolyte imbalance, and infection due to the compromised integrity of the skin, hence requiring immediate and specialized medical treatment to manage these complications.