BACKGROUND: Rocuronium administration is associated with a severe burning pain during injection in 50-80% patients. The purpose of this study was to evaluate mixtures of saline, lidocaine, sodium bicarbonate (NaHCO₃) and lidocaine-NaHCO₃ with rocuronium to reduce injection pain and withdrawal movement.

METHODS: One hundred and twenty patients were randomly assigned to one of four groups in a double blinded, prospective study; Group S (0.9% normal saline 5 ml mixed with rocuronium 50 mg/5 ml, n = 30), Group L (2% lidocaine 5 ml mixed with rocuronium 50 mg/5 ml, n = 30), Group B (8.4% NaHCO₃ 5 ml mixed with rocuronium 50 mg/5 ml, n = 30) and Group LB (4% lidocaine 2.5 ml and 8.4% NaHCO₃ 2.5 ml mixed with rocuronium 50 mg/5 ml, n = 30). After all patients had received an intubating dose (0.6 mg/kg) of premixed rocuronium over 5 seconds, we investigated the incidence and severity of pain and withdrawal movement. We measured the onset and duration of muscle relaxation using train-of-four (TOF) and the pH values and osmolalities of each mixture.

RESULTS: The incidence and severity of pain during injection were significantly reduced in Groups B and LB compared with Group S. The withdrawal movement was observed 8 patients (26.7%) in Group S, but in no patient in Groups B or LB. No significant difference in the incidence of pain or withdrawal response was observed between Groups S and L.

CONCLUSIONS: We conclude that premixed NaHCO₃ with rocuronium is effective at reducing injection pain and withdrawal movement whereas the addition of lidocaine has little effect.