Final answer:
The correct documentation for a red sacral area that does not blanch when tested is Erythema. This suggests capillary congestion possibly due to inflammation or infection and could indicate impending skin damage or a pressure ulcer.
Step-by-step explanation:
If the sacral area has remained red for 2 hours and does not blanch when tested, the best description for the nurse to document would be Erythema. Erythema refers to redness of the skin caused by the congestion of capillaries, which may indicate inflammation or infection. Since the redness does not disappear when pressure is applied (non-blanching), it suggests that the underlying capillaries are filled with blood and is potentially a sign of skin damage or pressure ulcer development.