Final answer:
Fever > 104 and muscle rigidity on post op day one can be caused by an anesthesia reaction, surgical complications, or an infection.
Step-by-step explanation:
A possible cause of fever > 104 and muscle rigidity on post op day one would be an anesthesia reaction. An anesthesia reaction can occur as a result of a person's sensitivity to the anesthesia drugs used during surgery. This reaction can lead to fever, muscle rigidity, and other symptoms.
Surgical complications can also cause fever and muscle rigidity. Examples of surgical complications that can cause these symptoms include infections at the surgical site or damage to nerves or blood vessels during the procedure.
Infections are another possible cause. Viral or bacterial infections can lead to high fever and muscle rigidity as the body's immune system responds to the infection.