Spread of ropivacaine by a weight-based formula in a pediatric caudal block: a fluoroscopic examination

Background Caudal block is the most common regional technique to provide post-operative analgesia in pediatric infra-umbilical surgery. This study was designed to define how many spinal segments would be covered by the weight-based dosage of caudally administered 0.2% ropivacaine in children using the fluoroscopic method. Methods After an approval from the institutional human research review board, in 83 ASA I boys undergoing day-case urological surgery, the distribution of ropivacaine mixed with a radioactive dye in relation to the volume injected caudally was studied. Three groups were studied: for perineal surgery 0.5 ml/kg (group C-0.5), for inguinal hernia repair 1 ml/kg (group C-1.0), and for orchiopexy 1.25 ml/kg (group C-1.25). The dose of 0.2% ropivacaine containing radiopaque dye at a ratio of 1 : 4 was injected at a rate of 1 ml 3 s-1. Fluoroscopic examination was performed immediately to define the level of the drug spread within the extradural space. Results The highest spinal levels [median with ranges] of spread were L2 [L4-T12] in group C-0.5, T12 [L1-T8] in group C-1.0, and T10 [L2-T7] in group C-1.25. Analysis by age distribution (infants: < 12 months; toddlers: 12-36 months; and children: > 36 months) revealed a larger spread in younger patients. Conclusions Based on the fluoroscopic findings, the weight-based doses for caudally administered 0.2% bupivacaine suggested by Armitage are also useful for ropivacaine to block the spinal level required for the different types of surgeries studied.