Wound infiltration with different concentrations of bupivacaine for postoperative pain relief in children after hernioplasty

Wound instillation seems to be an easy and preferable way to achieve postoperative analgesia in pediatric hernioplasty. This prospective, randomized and double-blinded pilot-study was initiated to gain preliminary information in order to define the appropriate concentration of local anaesthetic for efficient posthernioplastic analgesia. Method: 29 children aged 3.1 to 13.7 (5.25 (3.8-8.2) years were randomly assigned to receive either 0.2 ml/kg bupivacaine 0.125% (n = 10), bupivacaine 0.25% (n = 10) or bupivacaine 0.5% (n = 9). The local anesthetic (LA) was instillated intraoperatively before wound closure above the external oblique muscle and below Scarpa's fascia. After entering the post-anesthetic care unit (PACU) pain was assessed by a trained nurse using the linear analogue pain scale (LAPS) in intervals of 15 min. Patients were observed in the PACU for 30-60 min. Pain was further evaluated for 5.5(3-6) h in the ward every hour. In day-only patients the parents were contacted 24 h postoperatively to obtain additional information. Results: From the beginning of the observation period the 0.5% group tended to have less pain than the others in the PACU. The 0.125% and 0.25% group required earlier supplementary analgetics. In addition, the 0.5% group needed once (1/9) supplementary analgesics, the 0.25% group five times (5/10) and the 0.125% group six times (6/10). None of these results is statistically significant,though they appear to he clinically relevant. Discussion: Wound instillation with 0.2 ml of bupivacaine 0.5% seems to be easy to perform, safe and efficient in controlling posthernioplastic pain. Because of the small numbers of patients included however, no statistically significant differences were observed between the groups. Neither in the LAPS an arrival and observation at the PACU nor in the need for supplementary analgesics. Despite lacking significance the clinical impression suggests a difference to be validated by larger studies. Our data implies that wound instillation with 0.2 ml/kg bupivacaine 0.5% should be regarded for routine usage.