Mechanical characteristics of plastic base Ports and impact on flushing efficacy

BACKGROUND: Three types of totally implantable venous access devices, Ports, are currently in use: titanium, plastic (polyoxymethylene, POM), and mixed (titanium base with a POM shell). Physics theory suggests that the interaction between a non-coring needle (NCN, made of stainless steel) and a plastic base would lead to the stronger material (steel) altering the more malleable material (plastic). OBJECTIVES: To investigate whether needle impacts can alter a plastic base’s surface, thus potentially reducing flushing efficacy. STUDY DESIGN AND METHODS: A Port made of POM was punctured 200 times with a 19-gauge NCN. Following the existing guidelines, the needle tip pricked the base with each puncture. The Port’s base was then examined using a two-dimensional optical instrument, and a bi-dimensional numerical simulation using COMSOL(®) was performed to investigate potential surface irregularities and their impact on fluid flow. RESULTS: Each needle impact created a hole (mean depth, 0.12 mm) with a small bump beside it (mean height, 0.02 mm) the Reynolds number Re(k)≈10. A numerical simulation of the one hole/bump set showed that the flushing efficacy was 60% that of flushing along a flat surface. DISCUSSION: In clinical practice, the number of times a Port is punctured depends on patient and treatment characteristics, but each needle impact on the plastic base may increase the risk of decreased flushing effectiveness. Therefore, the more a plastic Port is accessed, the greater the risk of microorganisms, blood products, and medication accumulation. CONCLUSIONS: Multiple needle impacts created an irregular surface on the Port’s base, which decreased flushing efficacy. Clinical investigation is needed to determine whether plastic base Ports are associated with an increased risk of Port infection and occlusion compared to titanium base Ports.