Study objective: To compare the analgesic and anxiolytic effects of nitrous oxide (N2O) when inhaled by face mask with those of a cutaneous application of a eutectic mixture of local anesthetics (EMLA) cream with lidocaine and prilocaine during pre-operative venous cannulation in children.
Design: Prospective, randomized study.
Setting: Outpatient presurgical area and operating rooms of a freestanding children's hospital.
Patients: 50 unpremedicated ASA status I and II outpatients, aged 6 to 12 years, undergoing an elective surgical procedure.
Interventions: Each patient received either 70% N2O in 30% oxygen (O2) administered by face mask for 120 seconds or an application of 2.5 g of EMLA cream under an occlusive dressing for a minimum of 60 minutes. All patients then underwent a single attempt at venous cannulation in the dorsum of the hand with a 22-gauge intravenous catheter.
Measurements and main results: A visual analog scale (VAS) pain score (0 to 100) was generated by the investigator and subsequently obtained from each patient immediately after the venous cannulation was completed. The pain scores generated by the investigator were significantly lower in the N2O group than the EMLA cream group (p = 0.001). When compared with the patients in the EMLA cream group, the patients in the N2O group also self-reported significantly lower VAS pain scores (p = 0.006).
Conclusions: N2O administered by face mask appears to provide greater anxiolysis and attendant superior analgesia for pediatric venous cannulation than a cutaneous application of EMLA cream.