Evaluating needle-free connectors associated backflow in Midline and peripherally inserted central catheters: A top bench study

Background: Needle-free connectors (NFCs) are closure systems for vascular catheters largely used because effectively reduce needlestick incidents. They are classified based on their impact on the fluid column within the catheter as positive (fluid displacement into the vein), negative (fluid displacement back from the vein into the catheter), neutral (minimal displacement), or anti-reflux (equipped with additional anti-reflux valve). Each category has specific usage and clamping procedures. This study aimed to evaluate the backflow volume (BV) when different NFC categories and clamping sequences are used with a peripherally inserted central catheter (PICC) and a Midline catheter (MC). Methods: In this bench study, four types of NFCs with different flow displacement behavior were studied. Each NFC was evaluated using two different catheters: a 4 Fr × 60 cm single-lumen catheter (PICC), and a 4 Fr × 25 cm single-lumen catheter (MC). The experimental model simulated the physiological blood pressure of the superior vena cava. Three operators performed specific sealing sequences for each combination of NFC and catheter. After that, the BV (mm3) inside the catheter for every NFC was assessed. Results: None of the four NFCs was able to avoid the BV into the catheter. Positive NFC showed a lower BV as compared to the other three NFCs when tested with PICC: 0.83 [0.76–0.95] mm3 versus 1.14 [0.95–1.53] mm3 of Q-SYTE, versus 1.27 [1.02–1.59] mm3 of Neutron, versus 1.24 [0.95–1.84] mm3 of Bionector, whereas no differences were observed when tested with Midline. No differences were observed between different clamping sequences when used with neutral and anti-reflux NFCs. Conclusion: This study examined the performance of various NFC technologies with PICC and Midline. While no device eliminates BV, positive displacement NFCs showed lower flow reflux compared to the others when used with PICC. No difference between clamping sequences was observed for neutral and anti-reflux NFCs. © The Author(s) 2025.