Final answer:
The nurse should identify pain that increases with passive movement as a manifestation of compartment syndrome in a client with a short leg cast.
Step-by-step explanation:
When assessing for compartment syndrome in a client with a short leg cast, the nurse should be vigilant for specific clinical manifestations that indicate this potentially serious condition. Among the listed options, pain that increases with passive movement is a classical sign of compartment syndrome. This unique kind of pain arises because the pressure within the muscle compartments increases, causing decreased perfusion and ischemia. The other options such as a bounding pedal pulse, cap refill less than 2 seconds, and areas of warmth on the cast are not typical signs of compartment syndrome.