A 48-year-old female patient with rheumatoid arthritis (on chronic corticosteroids) is undergoing elective hip arthroplasty. After induction with propofol and remifentanil, rocuronium 0.6 mg/kg IV is given for intubation. Intubation is achieved easily. At the end of surgery (120 minutes later), train-of-four (TOF) monitoring shows 2 out of 4 twitches. The anaesthetist plans to reverse the neuromuscular blockade. Which agent is most appropriate and why?