Interpret and act on an out-of-range vancomycin level — OSCE

A seven-year-old boy on intravenous vancomycin for a complicated methicillin-resistant Staphylococcus aureus bacteraemia is 48 hours into therapy. The ward nurse calls because his trough level has returned at 9 mg/L. He has improved clinically. The nurse asks whether to give the next dose and what to do about the level. You have eight minutes to interpret the result, exclude sampling error, state the target and sampling principle, defend a dose-adjustment plan, and explain the plan to the nurse and to the family.