Spread of radiopaque dye in the thoracic epidural space

A radiological study was performed in 23 patients to look for the position of thoracic epidural catheters and the spread of the contrast medium iohexol 300 mg/ml and 180 mg/ml when used in volumes of 3 and 8 ml. The dye was injected through the epidural catheter just after thoracic surgery. The spread of the dye showed no relation to the injected volume or the sensory spread after 2% lignocaine 3 ml. In three cases no contrast could be seen on the x-ray, and in two the radiopaque dye was found just outside the epidural space. No relationship between the spread of the dye and the sensory blockade was found, but the position of the epidural catheter should be checked radiographically when the epidural route is to be used for long-term pain relief.