A 58-year-old female sustained a right femur fracture. She had a prior right total hip arthroplasty and will need a revision. Her past medical history includes hypertension, mild obstructive sleep apnea, hiatal hernia, and obesity. The patient is terrified of needles and states she had a bad experience with a prior cesarean section after multiple attempts at a spinal anesthetic. She is taken to the operating room and general anesthesia is induced with IV esmolol, lidocaine, fentanyl, propofol, and rocuronium. The tracheal intubation is uneventful. The femoral prosthesis with bone cement is placed. Two minutes later, you notice the end-tidal CO2 decrease to 25 mm Hg when it had been 35–40 mm Hg during the entire case. The minute ventilation has remained the same and you cycle the blood pressure cuff. The blood pressure is 78/45 mm Hg. A repeat blood pressure is 67/38 mm Hg and the end-tidal CO2 is now 12 mm Hg. What would you do next? What is your differential diagnosis?