Pain at the site of rocuronium injection is a common side-effect in pediatric patients. This prospective, randomized, double-blind study evaluated the efficacy of a combination of nitrous oxide and lidocaine pretreatment on withdrawal response during rocuronium injection in children.

Sixty six pediatric patients, ages 5 to 12 years, were randomly assigned to two groups. The oxygen group received 100% oxygen, and the nitrous oxide group received 50% N₂O in oxygen over 2 min. After anesthesia was induced with 2.5% thiopental sodium 5 mg/kg and manual occlusion of the forearm was performed, 1% lidocaine 1 mg/kg was injected over 15 sec. After the occlusion was released, 0.1% rocuronium 0.6 mg/kg was injected over 5 sec. Patient response to rocuronium injection was graded using a 4-point scale.

Overall incidence of withdrawal movements was significantly lower in the nitrous oxide group (1 patients; 3.1%) than in the oxygen group (8 patients; 25.8%) (P = 0.013). No patient in the nitrous oxide group displayed arm or generalized movement (grade 3 or 4) associated with rocuronium injection.

This study demonstrated that a combination of inhaled 50% N₂O in O₂ and 1 mg/kg lidocaine pretreatment significantly reduced the incidence of rocuronium-induced withdrawal movements in pediatric patients compared with lidocaine pretreatment alone.