Final answer:
The most appropriate treatment for the patient with multiple traumas is to immobilize her using a backboard and ensure rapid transport, prioritizing the stabilization of her condition during transit.
Step-by-step explanation:
When managing a 19-year-old female with multiple trauma, bilateral humeral deformities, and a left midshaft femur deformity presenting with diaphoretic skin and a rapid, weak pulse, the treatment should prioritize transport and stabilization of injuries. The most appropriate treatment for this patient includes immobilizing her to the backboard and rapidly transporting her to an emergency facility.
The femur injury may require a traction splint; however, fast transport is imperative due to possible life-threatening injuries patients with multiple traumas might face, such as compromised circulation and potential fat embolism from the femur fracture, especially with the described vital signs.