The effect of volume of local anesthetic on the anatomic spread of caudal block in children aged 1-7 years

Abstract

To examine the anatomic spread of caudal local anesthetic solution in children aged 1-7 years. To determine whether incremental increases in the volume of caudal injections of 0.5, 0.75, and 1.0 ml·kg(-1) result in reliable (>90%) and potentially clinically significant increases in the number of vertebral segments reached. Caudal block is one of the most frequently performed pediatric regional analgesic techniques. Traditional formulae suggest that changes in the volume of caudal injectate in the range 0.5-1.0 ml·kg(-1) would have clinically useful effects. In a single blind design, 45 children aged 1-7 years undergoing caudal block received one of the three predetermined volumes (0.5, 0.75, and 1 ml·kg(-1) ) of local anesthetic solution containing radio-opaque contrast under controlled conditions. Following X-ray examination, the anatomic spread of the block was reported by a radiologist blinded to the volume of solution received. There were 15 children in each group, and they were similar in terms of age, height, and weight. Spread was observed between the 5th lumbar (L5) and 12th thoracic (T12) vertebral levels. A volume of 1 ml·kg(-1) results in a small but significantly greater spread of solution than 0.5 ml·kg(-1) (P < 0.05), but there was no difference between 0.5 and 0.75 ml or between 0.75 and 1.0 ml. No volume reliably reached a level higher than the second lumbar vertebra (L2). Incrementally increasing the volume of injectate between 0.5 and 1.0 results in a modest increase in the spread of the caudal solution. It is unlikely that volumes of <1 ml will reliably reach a vertebral level that is higher than L2.