Dear Editor,

After reading the article of Nagathan et al,¹ which describes the delayed recognition of paraplegia following thoracic epidural block, we felt pity for the mishap. The catheter was placed 4 cm inside the epidural space and fixed on the skin at the 8 cm mark, suggesting that the depth from skin to epidural space could be 4 cm. The authors did say that the epidural catheter was secured along the midline of the spine but did not mention whether the insertion was performed via the median or paramedian approach. According to the scale on their Figure 3, the midline shortest distance from skin to epidural space is 3.14 cm in the sufferer. Although the skin-to-epidural space distance would be longer in paramedian approach, from our experience² the skin to epidural space could be around 4.65 cm at the T12-L1 level via the paramedian approach for an average 60 kg person; with each 10 kg of increase in body weight, the increase in depth would be 0.39 cm. Extrapolating our results, if applicable, the estimated depth from skin to epidural space for this victim would be around 3.7 cm if the paramedian approach was chosen. If we can estimate the distance from skin to epidural space beforehand, we will have a guide for epidural needle manipulation. This will help us to avoid inserting the needle farther, thus preventing inadvertent complications in epidural anesthesia.