Topical wound anaesthesia in children--a temporary postoperative pain relief

BACKGROUND: Administration of local anaesthetics into the surgical wound may modulate pain at the peripheral level. A previous study in adults has shown good analgesic effects of topical lidocaine in wounds after herniorrhaphy. METHODS: Postoperative pain relief after topical administration of 10% lidocaine aerosol in the surgical wound was investigated in a randomised, double-blind study in children undergoing inguinal hernia repair. Forty-four patients aged between 9 months and 11 years were randomised into three groups. One group received active treatment with a lidocaine aerosol 2.5-4.7 mg kg-1, one group received a placebo aerosol and one control group was untreated. Postoperative pain was evaluated by nurse assessment, self-assessment and wound palpation 0, 1, 4 and 12 h after arrival in the recovery room. RESULTS: After 1 h the incidence of pain, as estimated by behavioural assessment and self-assessment, was significantly reduced in the lidocaine group in comparison to the placebo group, but not in comparison to the control group. The reaction on wound palpation was significantly reduced in the lidocaine group compared to both the placebo and control groups. At 0, 4 and 12 h no significant differences between the groups were observed. Plasma lidocaine concentrations were measured in six patients. Maximum individual concentrations were low, ranging from 0.17 to 0.86 microgram ml-1. CONCLUSION: A very short and clinically insignificant pain relief is obtained following the administration of a lidocaine aerosol in the surgical wound. A low pain level in this model may limit the possibility to detect an effect of lidocaine.