In which situation is it essential to use a tourniquet?

Using a tourniquet is essential in situations of life-threatening bleeding because it is designed to quickly and effectively occlude blood flow to a limb in order to prevent severe blood loss that can lead to shock or death. When a traumatic injury results in uncontrolled arterial bleeding, traditional methods of direct pressure or elevation may not be sufficient to stop the flow of blood. In such cases, applying a tourniquet can be life-saving, as it creates a tight constriction around the limb to stop arterial blood flow, thereby stabilizing the patient until more advanced medical care can be provided.

In contrast, the other situations described do not warrant the use of a tourniquet because they involve less severe forms of injury where the bleeding can typically be managed through other means without risking further complications or harm to the patient.