Spontaneous movements associated with rocuronium: is pain on injection the cause?

Spontaneous movements are sometimes observed of the arm into which rocuronium is administered. In order to assess a possible relationship between these movements and pain, we injected in 10 awake, ASA I patients, in a double-blind manner, both rocuronium 1 ml (10 mg) and 0.9% NaCl 1 ml (placebo), with a 30-s interval in between. None of the patients receiving placebo complained of pain, but eight of 10 patients reported a strong burning pain during injection of rocuronium with brisk flexion of the elbow and wrist, similar to those observed in patients after induction of anaesthesia. A second injection of rocuronium did not produce such pain and no movements were observed. We conclude that injection of rocuronium is associated with severe, burning pain of short duration, responsible for the spontaneous movements in the arm observed after induction of anaesthesia.