Final answer:
The primary problem for the patient in the emergent phase after suffering thermal burns to the entire posterior aspect of his body is maintaining intravascular volume.
Step-by-step explanation:
The primary problem of the patient in the emergent phase after suffering thermal burns to the entire posterior aspect of his body is likely to be maintaining intravascular volume.
Burns result in a massive loss of fluid, leading to dehydration and circulatory failure. Intravenous fluids are administered to offset dehydration and maintain blood volume. This is crucial in the emergent phase to support tissue perfusion and prevent shock.