Various formulae have been proposed for calculation of volume of local anaesthetic drugs to achieve specific dermatomal level of caudal epidural analgesia, but their comparisons are rare. We compared spinal height based Spiegel (modified for T10 level block) with weight based Takasaki formulae in achieving sensory blockade upto T10level during caudal block in paediatric patients.

All children aged between 1-10 year, ASA I who undergwent an infra-umbilical surgery were eligible for enrolment. After informed consent, each patient was randomly allocated to receive caudal block with 0.25% bupivacaine using volume calculated by either Spiegel formula (group I) or Takasaki formula (group II). Level of sensory blockade was assessed using pin-prick method. The patient and investigator, who measured the level of blockade, were blinded in this study. Institute Ethics Committee reviewed and approved the study protocol.

Fifty patients (25 in each group) completed the study. The two groups were comparable to each other with respect to age, sex, weight, spinal height, type of surgery, duration of surgery and post-operative sedation score. Sensory blockade corresponding to T10 segment were achieved in all patients. However, the highest level of spinal segment blockade achieved and the mean volume used in patients in group I was significantly lower than that achieved in group II reflecting greater accuracy of height based formula (p<0.000).

This study shows that spinal height based modified Spiegel formula is more accurate than weight based Takasaki formula for calculation of 0.25% bupivacaine volume for caudal epidural analgesia to achieve T10 sensory blockade.