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

Abstract

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. 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. 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. 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.