Which observation would prompt the nurse to intervene following a total hip replacement?

After a total hip replacement, one of the primary goals is to maintain proper alignment of the hip joint to prevent dislocation and ensure proper healing. The observation that the patient's heels are lying on the bed with their toes pointed upward indicates that the patient's legs may not be in the optimal position according to post-operative care guidelines.

In a post-operative setting, particularly after hip replacement surgery, it's crucial to avoid any positions that might lead to complications such as dislocation. Ideally, the legs should be positioned in a way that keeps the hips aligned and avoids internal rotation. When a patient's toes are pointed upward while their heels rest on the bed, it can suggest the potential for internal rotation of the hip, which is generally to be avoided.

The other scenarios presented fall within acceptable activities as part of the recovery process. Sitting up in bed and watching television is a normal activity that promotes gradual mobility. Using a walker indicates that the patient is progressing in their mobility and engaging in leg exercises as instructed is essential for rehabilitation. Thus, monitoring and ensuring proper positioning is critical, making the first observation the one that warrants nurse intervention.