[Lumbar epidural catheterization: estimation of the length of the inserted catheter]

A catheter in the epidural space can be the cause of various iatrogenic complications. In order to avoid leaving too great a length in the lumbar epidural space during epidural anaesthesia, graduated Tuohy needles can be used (Perifix), together with graduated epidural catheters. On the latter, a special marking shows that, when it reaches the needle hub, the catheter tip is at the needle bevel. Approximately 5 to 7 cm of catheter length are introduced into the epidural space. The needle is removed and placed upside down next to the catheter, with the hub in contact with the patient's skin. In this position, the distance between the special marking on the catheter and the graduation on the needle which marked the skin level is equivalent to the length of catheter in the epidural space. This distance, and therefore catheter length, can then be reduced to about 4 cm by carefully withdrawing the catheter. Some possible improvements of catheters and needles are discussed. Knowing exactly how much catheter is within the epidural space could be of particular importance whenever that space is uncommonly far from the patient's skin: obesity, oedema, use of the paramedian route or a very oblique angle of the needle in the sagittal plane.