Hydrodynamic behaviour of anti-reflux needle-free connectors during microinfusion with syringe pump: A bench-top study.

INTRODUCTION

Needle-free connectors (NFCs) are routinely used in vascular access management to reduce catheter-related complications, such as blood reflux and infection. Although neutral displacement NFCs are widely adopted, the hydrodynamic behaviour of devices equipped with an internal anti-reflux valve during continuous microinfusion remains poorly investigated. Concerns persist regarding the possible interference of pressure-activated valves with flow regularity at very low infusion rates (0.1-10 mL/h).

METHODS

Bench-top study in a laboratory setting. An extracorporeal circuit was used to simulate cardiac output and a central venous haemodynamic environment. Three NFCs were tested: one neutral displacement connector without an anti-reflux valve and two neutral displacement connectors with anti-reflux technology. Continuous infusions were delivered inside the circuit using a syringe pump at three infusion rates: 0.5, 1, and 3 mL/h. The pressures upstream and downstream of the connector were recorded, and flow regularity was assessed by analysing the coefficient of variation derived from air-bubble displacement within the infusion line.

RESULTS

All tested NFCs maintained continuous and stable infusions at all flow rates. No bolus formation or flow interruptions were observed. Coefficient of variation values were low to moderate across the experimental conditions and were comparable between connectors with and without an anti-reflux valve. When applied to a simulated microinfusion of norepinephrine, the observed variability resulted in small estimated dose oscillations.

CONCLUSION

Neutral displacement NFCs equipped with anti-reflux valves did not show evidence of altered infusion regularity under the experimental conditions tested. The results of this study suggest that using anti-reflux NFCs for the continuous delivery of drugs with a narrow therapeutic range may be considered compatible with low-flow infusion under controlled experimental conditions. This study represents a preliminary step toward further investigations on anti-reflux NFCs during syringe pump infusion and changeover.