Absent markings on an epidural catheter

We should like to report an inconvenient occurrence caused by absent epidural catheter markings. Our normal practice during insertion of an epidural is to thread the catheter through the Tuohy needle until the 15-cm marker has just disappeared into the hub. This ensures that there are 5 cm of catheter protruding from the end of the needle, allowing a margin of safety when removing the Tuohy. We then withdraw the catheter until 5 cm are left in the epidural space [1]. On this occasion, we were using a 16-gauge Tuohy needle (SIMS Portex Epidural minipack) in an obstetric patient. The depth of the epidural space was 6 cm. On withdrawing the Tuohy needle it was noted that the catheter had double bands 3 cm from the skin. This was taken to be the 10-cm marker and making the assumption that the catheter had been inadvertently withdrawn with the Tuohy, it was decided to remove the rest of the catheter and reinsert the epidural. On removing the rest of the catheter another double-band marker appeared. On closer inspection it could be seen that the first double band had in fact been the 15-cm marker, and that the third band had been poorly imprinted upon the catheter (see figure below). Subsequent epidural insertion into this patient proved difficult requiring a further three attempts before success was achieved.1 On further examination of a randomly selected set of epidural packs, another two catheters with a poorly imprinted 15-cm mark were found. This case shows that despite a high level of quality control, faults can occur during the manufacture of epidural catheters. Previous reports have described catheters with abnormally located side holes [2] and those with irregularities on the outside diameter [3, 4]. These have prevented the Tuohy needle from being withdrawn back over the catheter following its insertion. To avoid problems, we would recommend inspection of markings as part of the catheter pre-insertion check, as well as making sure that it is patent by flushing with saline and that it will pass freely through the Tuohy needle. I am writing to inform you that the investigation into the incident referred to by Dr Smith concerning the markings on our 16G epidural catheter has been completed and a summary of the findings is given below. Examination of the returned samples has confirmed the reported fault. The third ring at the 15-cm mark is very faint, making the mark easily confused with the double ring at the 10-cm mark. As a part of the manufacturing process, a 100% manual inspection is relied upon to identify any faults of this nature and to isolate and reject all affected products. Although it is clear that this has been ineffective in this instance, a review of our Complaints History files for this product range has confirmed this to be the first reported incident of this nature since at least January 1991. I can confirm that the details of the problem have been highlighted to relevant personnel emphasising the need for vigilance at all stages of manufacture. In addition, we are currently reviewing the possibility of installing an automated detection system to verify the presence and clarity of the rings on each catheter as it is manufactured. I apologise on behalf of SIMS Portex for any inconvenience caused by this incident and thank Dr Smith for bringing the matter to our attention. T. J. Andrews SIMS Portex Ltd, Hythe, Kent CT21 6JL, UK