A randomised study comparing the extent of block produced by spinal column height and body weight-based formulae for paediatric caudal analgesia

BACKGROUND AND AIMS: Height and weight-based formulae are used for calculation of dose of medications for caudal analgesia but these have not been compared. We compared spinal column height-based Spiegel and weight-based Takasaki and Armitage formulae for achieving maximum height of sensory neuraxial block after caudal epidural analgesia in paediatric patients. METHODS: In this double-blind randomised study, children aged between 1 and 6 years and planned for infra-umbilical surgery were randomly allocated to receive caudal epidural block (targeting T(10)level block) with 0.25% bupivacaine, using a volume calculated by modified Spiegel formula (group I), Takasaki formula (group II), and Armitage formula (group III). The Institute ethics committee reviewed and approved the study protocol. The primary endpoint of the study was the difference in the number of spinal segments blocked as assessed by pinprick method. The secondary endpoint was the difference in volume of 0.25% bupivacaine used among the groups. The groups were compared using one-way ANOVA. RESULTS: Seventy-five patients (25 in each group) completed the study as per protocol. The mean number of spinal segments blocked was significantly different among groups (P < 0.001) with patients in group I (13.8 ± 0.83) showing significantly lower number of spinal segments blocked as compared to that in group II (15.8 ± 1.06; P < 0.001), and group III (16.8 ± 1.28; P < 0.001). The mean volume of 0.25% bupivacaine used in group I was significantly lower (P < 0.001) than that in group II and group III. CONCLUSION: Dose calculation in caudal epidural analgesia as per spinal column height-based modified Spiegel formula was more precise than bodyweight-based Takasaki and Armitage formulae.