A nurse is caring for a client who returns to the nursing unit from the recovery room after a sigmoid colon resection for adenocarcinoma. The client had an episode of intraoperative bleeding. The nurse notes: HR increased from 88 to 118/min over 1 hour, BP decreased from 124/78 to 98/60 mm Hg, urine output is 20 mL/hr, skin is cool and pale, and the client reports incisional pain 6/10. Which finding is the most concerning for hypovolemic shock?