A color Doppler ultrasound-guided protocol for the precise placement of nerve catheters: an anatomical validation study in fresh and fixed cadavers.

Background: Continuous analgesia via peripheral nerve catheters (PNCs) is highly effective but prone to tip malposition. Direct ultrasound-guided localization of the PNC tip remains challenging, and no universal method is currently established. This cadaver-based study aimed to validate a color Doppler ultrasound-guided protocol for accurate PNC tip placement at the brachial plexus.

Methods: Eleven ultrasound-guided PNC placements were performed (5 fixed/6 fresh cadavers) according to our specific protocol. PNC tip positioning was repeatedly assessed by visualizing bolus injections via color Doppler ultrasound following 0.5 cm retraction if applicable. Good placement was defined as a color Doppler signal directly adjacent to the brachial plexus concomitant with hydrodissection within its fascial compartment. Verification was obtained through anatomical dissection of the PNC tip in situ and evaluation of the maximal staining site after dye injection via the PNC.

Results: The diagnostic agreement between the color Doppler signal and anatomical findings was 100%. In fixed cadavers, correct PNC tip placement was confirmed in 100% (5/5) of the specimens. Among the fresh cadavers, 83.3% (5/6) were correctly placed. One secondary malposition was detected by ultrasound and confirmed macroscopically. Qualitative analysis of dye staining revealed good localization in 81.8%, acceptable localization in 9.1%, and poor localization in 9.1% of the samples.

Conclusion: Our standardized color Doppler ultrasound-guided protocol reliably facilitates precise PNC tip placement in both fixed and fresh cadavers. Using this method, practitioners can accurately verify and adjust PNC tip position in cadavers. This universally applicable approach may translate to clinical practice but warrants further investigation.

Trial registration number: DRKS00005626 The present validation report was derived from an unpublished study. This study was registered with the German Clinical Trials Register under the clinical trial number DRKS00005626 in July 2015 [Weblink: https://drks.de/search/de/trial/DRKS00005626 ].