The aim of the present study was to use a quantitative fluorescence imaging technique to evaluate the invisible amount of residual lipid emulsion in port chambers flushed with various fundamental protocols. Chambers were filled with lipid emulsion containing indocyanine green and then flushed with 5–70 mL of normal saline. Chambers were flushed at various speeds (15–60 mL/min), with a time interval of 1 or 3 s between boluses, and with varying directions of flow. The slower the flushing speed, the more lipid emulsion that remained. Pulsatile flushing with either time interval did not decrease the residual amounts, and the areas well-cleansed after flushing were oriented to the bevel-opening direction. These findings suggest that to reduce the residual amount of lipid emulsion poured in a chamber, fast and furious flushing under continuous as opposed to pulsatile flushing is of paramount importance.

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Introduction: The aim of this study was to compare the efficacies of pulsatile and bolus flushing methods for removing residual parenteral nutrients in common shapes of central venous (CV) and peripheral venous (PV) catheters. Methods: Straight or looped tubes filled with parenteral nutrients containing indocyanine green (ICG) were flushed with 10 mL of saline at various speeds with several pulsatile intervals. Pseudomonas aeruginosa engineered with a luciferase gene was inoculated in the flushed CV catheters. The imaging technique detected the ICG remaining and the bacterial growth in the flushed catheters. Results: In the CV catheter, the residue was greater with pulsatile flushing with longer intervals than with bolus flushing at a relatively high flushing speed. In the PV catheter, the flushing speed with any pulsatile intervals did not affect the residue. A looped catheter showed less residue than the straight catheter regardless of the flushing condition. Bacterial growth occurred in the nutrient residue in the flushed tubes. Conclusion: Speed of flushing and the shape of catheters, but not pulsatile flow generation, are essential components for the efficacious removal of parenteral nutrients in the catheter. Moreover, the slight differences in remaining nutrients inside the catheter affected subsequent bacterial growth.