Needle visibility in different tissue models for ultrasound-guided regional anaesthesia

Models for ultrasound-guided regional anaesthesia (USGRA) are important for research and training. However, the limited data available show great differences in quality of needle and tissue visualisation with regard to the applied model. This study aims to compare common USGRA models and human tissue with regard to their influence on needle visibility.

We conducted this study using four models (embalmed human cadaver, turkey breast, pork, and synthetic gel models) and a volunteer (human control) as well as two different needles [Stimuplex A (StA), conventional needle; Stimuplex D Plus (StD+), needle with improved echogenicity]. We obtained ultrasound videos of needle advancement and withdrawal using the in-plane approach at a 45° angle in all four models and the volunteer. Fifteen test persons were prospectively enrolled. Ultrasound videos were presented in a randomised, blinded manner. The test persons were asked to rate the visibility of the needle shaft (VS) and tip (VT) on a four-point scale (0-3).

VS and VT were comparable between the human control and cadaver model for both needle types. The pork, turkey, and synthetic gel models had significantly higher visibility scores than the human control for both needle types. VS of StD+ was significantly higher than that of StA in the pork and turkey models, but not in the synthetic model, cadaver model, or human control.

In this pilot study, needle visibility in embalmed cadaver is comparable with that in human control. Needle visibility was significantly higher in other tissue models (turkey breast, pork, synthetic gel models) than in the human control, which may limit their value in training environments.