Final answer:
The nurse should observe for symptoms such as redness, warmth, and tenderness for phlebitis and swelling and pain for thrombus formation.
Step-by-step explanation:
To assess signs of phlebitis and thrombus formation, the nurse should observe for specific symptoms and physical findings. Signs of phlebitis may include redness, warmth, and tenderness along the affected vein. Signs of thrombus formation can include swelling and pain in the affected area.
For example, if a patient has a deep vein thrombosis (DVT) in their leg, they may experience swelling and pain in that leg. The leg may also feel warm to the touch and appear red or discolored.