PMC

A. Fr.6 Polyurethane catheter: Larger inner diameter and lesser wall thickness. More residual space after inserting a 0.035-inch Terumo wire during cannulation, which leads to less friction between wire and catheter. B. Fr.7 Silicone catheter: Smaller inner diameter and greater wall thickness. Small inner diameter after inserting a 0.035-inch Terumo wire during cannulation, which leads to more friction between wire and catheter. C. Three potential structure weakness points were identified during port revisions. D. Pinch-off syndrome related catheter fracture. It was caused by repetitive compressive forces exerted on the catheter result in catheter fracture related to material fatigue. E. Catheter fracture at junction site between locking nut and proximal catheter. It was caused by compressive forces that generated by surrounding soft tissue focused on unction site between locking nut and proximal catheter. F. Catheter stretched over the protruding stud of the connecting tube. Longitudinal fracture was identified at the point where the catheter overlies the protruding stud of the connecting tube.

(A) Main components of the collinear catheter before assembly. (B) Assembled IVPA catheter probe. (C) Zoom-in view of the catheter tip with illustration of collinear overlap between optical and ultrasonic waves. (D) Photograph of the fabricated catheter probe with a diameter of 1.6 mm, and the detailed structure of the catheter tip (inset).

Pigtail assisted tracking (PAT) for overcoming the “razor-blade” effect. (a) Guide catheter loaded over 0.035″ guidewire. Note the wide free space between the inner lumen of guide catheter and guidewire. Sharp edge at guide catheter tip works like a “razor blade” (inset picture). (b) Pigtail catheter fills this wide free space and abolishes the “razor-blade” effect. Additionally, it works like the dilator of EBU guide catheter and helps in navigating the complex forearm vasculature. (c) “Pigtail catheter-EBU guide catheter assembly”; 5 Fr pigtail catheter inside the 6 Fr EBU guide catheter with both ends of pigtail catheter outside the guide catheter. This assembly resembles and works like any single guide catheter.

Insertion of SMC. (A) CFNB. The catheter was placed with its orifices brought 0.2 cm from the femoral nerve under ultrasound guidance. The catheter proximal and distal ends are visualized. Importantly, the catheter may be repositioned by pulling at the latter. (B) The catheter placed for CFNB. The distance between the femoral nerve and catheter orifice was 0.2 cm. (C) CFNB catheter after 24 h. The distance between the catheter and orifice was 0.7 cm. No spread of ropivacaine bolus towards the femoral nerve was visualized. There was no reduction in pain intensity following bolus administration. The catheter was then pulled and the catheter orifice placed near the femoral nerve. (D) CFTB. The catheter was placed according to the same procedure, using catheter set with a suture-needle with the curvature radius of 7.5 cm. The catheter orifices were placed 2 mm from the saphenous nerve. (E) Ultrasound scan of CFTB after catheter insertion. A catheter orifice was placed near the saphenous nerve. The distance between the saphenous nerve and orifice was 0.2 cm. (F) Ultrasound scan of CFTB after 24 h. The distance between the saphenous nerve and catheter orifice was 0.4 cm. A bolus of ropivacaine is seen spreading towards the nerve. Arrow indicates the site of punction. Abbreviations: SAR—sartorius muscle; FA—femoral artery; SFA—superficial femoral artery.