Anesthésie et recherche clinique
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Fluoroscopy Study of Peripheral Nerve Block Catheter Tip Movement–Its Clinical Implication in Guiding Catheter Adjustment

Jiabin Liu, Lu Fan Cai and Nabil Elkassabany

Background: Continuous peripheral nerve block catheter has been widely used clinically.A small percentage of catheters usually need adjustment after placement.However, there is no study on how to adjust catheter in the literature. Methods: Twelve fresh pork legs were randomly allocated into one of two groups, perineural catheter advanced 5 cm or less beyond needle tip (N=6), or more than 5 cm beyond needle tip (N=6). For both groups, ultrasound guided sciatic nerve block was performed with the “in-plane” approach.The anatomic landmarks and the locations of the sciatic nerve block equate to the Labat approach in humans. Thirty milliliter of normal saline was used to dissect the epineuron space before threading 20G soft non-stimulating catheter. The catheter was pulled back in onecentimeter increments at the level of the skin while the location of the tip of the catheter was identified by fluoroscopy after each centimeter pull back. The main outcome was the catheter tip movement. Results: The catheter tips advanced either cephalic or caudally without dominance trend, while most catheter tips located superficially to the needle tip (11 out of 12). In T<5 cm group, the catheter tips movements were 0.46 ± 0.10 cm per centimeter pull back.In T>5 cm group, the catheter tip movement was initially 0.17 ± 0.11 cm per centimeter pull back, then increased to 0.25 ± 0.12 cm once the catheter tip was less than 5 cm beyond the initial depth of needle tip. Conclusions: We recommend that adjustment of the CPNC should base on the initial depth of the needle tip since the initial catheter tip movements among these over threaded catheters are very limited, and it would not be efficient in clinical practice to adjust peripheral nerve block catheter by pulling by centimeter increment.