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 C0.5), for inguinal hernia repair 1 ml/kg (group C1.0), and for orchiopexy 1.25 ml/kg (group C1.25). 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 C0.5, T12 [L1‐T8] in group C1.0, and T10 [L2‐T7] in group C1.25. Analysis by age distribution (infants: 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.