The patient, a chemical plant worker, while working with an aggressive liquid, accidentally spilled it on his overalls, receiving a chemical burn on his right thigh and lower leg. After removing his clothes, the following was revealed: on the front inner surface of the right thigh and the front surface of the right lower leg with a transition to the dorsum of the foot, there are yellow-gray patches with fragments of epidermis in some places. The affected skin areas exhibit tactile and painful hypoesthesia. What emergency aid must be provided first in this case?