Final answer:
The most appropriate initial fluid for rapid volume expansion in this case would be normal saline solution.
Step-by-step explanation:
The most appropriate initial fluid for rapid volume expansion in this case would be normal saline solution.
In cases of multisystem trauma with signs of hypovolemic shock, such as rapid weak pulse, delayed capillary refill, and confusion, it is important to restore the volume of blood circulating in the body. Normal saline solution, which contains fluids and electrolytes similar to those of normal blood plasma, is commonly used for rapid volume expansion.
Other fluid options, such as blood products or colloids, may be considered depending on the specific situation and patient's needs.