A 7-year-old patient presents with right elbow swelling and deformity after falling off of a trampoline. Figures A and B demonstrate the injury radiographs. In the emergency department, the patient has a warm pink hand with a strong radial pulse and intact AIN motor function. The patient is taken to the OR the next morning for closed reduction and percutaneous pinning. After the fracture is reduced and the pins are placed, the patient's hand appears pale and cool with absent radial pulses. What is the next appropriate step?