Final answer:
A nurse should recognize an elevated erythrocyte sedimentation rate (ESR) as a potential sign of a complication post-fracture repair, whereas the mentioned WBC count, CRP level, and RBC count are within normal ranges and do not indicate complications.
Step-by-step explanation:
A nurse reviewing the laboratory results of a school-age child who is 1 week postoperative following an open fracture repair should identify an elevated erythrocyte sedimentation rate (ESR) as an indication of a potential complication. In this case, an ESR of 18 mm/hr is a potential sign of inflammation or infection, which can be common complications following a surgical procedure like an open fracture repair. Normal ESR values for children vary but are generally lower; thus, any elevated ESR can be significant. It is not specified as elevated in the options provided, and the clinical context is key, as mild elevations are sometimes seen postoperatively without infection.
White blood cell (WBC) count can also indicate infection or inflammation when increased, and in this case a WBC of 6,200/mm3 is within the normal range. Similarly, a C-reactive protein (CRP) level of 1.4 mg/L is normally a mark of inflammation, but it is not necessarily indicative of a complication if it is not significantly elevated from the normal range, which varies in different labs. Finally, a red blood cell (RBC) count of 4.7 x 10^6/µL is typically within the normal range for children and does not point towards a complication related to the surgery.