Spread of extradural analgesia following caudal injection in children. A statistical study.

Data on the segmental spread of analgesia from three independent studies of caudal extradural blocks in children with three different local anaesthetic agents were examined with multiple regression techniques to find the effects of age on dose requirements. All three studies confirmed the existence of a linear relationship between the spread of analgesia and age. As there were no significant differences between the three regression lines a common regression line was calculated. This may be used as a guideline for predicting dose requirements in the daily routine of anaesthesia. By injecting a mixture of a radio-opaque substance and 4% lignocaine it was shown by comparison of the radiological spread of the solution and the distribution of clinical analgesia that the latter always exceeded the former by four to six segments. This may indicate the occurrence of diffusion.