(G-264) A Preliminary In Vitro Study of Pediatric Central Venous Catheter Related Thrombosis: Varying Catheter to Vein Ratios

Introduction:: Central venous catheters (CVCs) are essential cardiovascular devices that provide long term venous access for blood draws, medication administrations, and fluid infusions, and are commonly inserted in the jugular, subclavian, and femoral veins^1,2. However, CVCs are associated with complications such as infections and catheter related thrombosis (CRT), which can be fatal. The pediatric cohort is of particular interest in CVC research due to smaller vein sizes and lower venous flow rates allowing greater flow obstruction with CVC insertion. CRT occurs in children at an incidence of anywhere from 5-35%, likely due to under-reporting asymptomatic clots and accounts for 50-80% of deep vein thromboses in children^1,3. The metric of interest in the present study is the catheter-to-vein ratio (CVR), equivalent to the inner diameter of a patient’s vein divided by the outer diameter of a CVC. The CVR is not well-defined in the pediatric space: values of 0.33-0.45 are recommended, but it is not clear if a lower value could be of benefit to pediatric patients to lower CRT risk and increase overall CVC patency⁴. This study quantifies how CVR for CVCs in pediatric flows affects CVC-induced thrombosis through in vitro flow loop experiments.


Materials and Methods:: An in vitro flow loop was developed to assess CVC related thrombosis across two CVRs (0.20 and 0.33). A 5 French (1.67 mm diameter) Teleflex® Arrow dual lumen CVC was fixed in a 3D printed photo resin-based channel to model a CVC in the superior vena cava (SVC). The channel allowed precise control over CVC location during experiments; the CVC was fixed in the centerline of the channel for all experiments. The inside of the flow loop was soaked in bovine serum albumin (Sigma-Aldrich) prior to experiments. Human blood was collected (Institutional Review Board approved) in 3.2% sodium citrate (J.T. Baker®), reconstituted to 40% hematocrit and 214x10⁶ platelets/mL, and recalcified with 20 mM CaCl₂ (Sigma-Aldrich). Blood was driven in a closed loop by a peristaltic flow pump (Cole-Parmer®) for 1 hour at a Reynolds number (Re) of 890, corresponding to flow in the pediatric SVC (vein diameter of 11.35 ± 1.3 mm; flow rate of 1.5 ± 0.3 L/min). At the end of the 1-hour experiment, blood clots that formed on the device were analyzed by measuring clot size, mass, and location. Statistical methods were performed on clot mass, area, and location data via two sample unpaired t-tests.


Results, Conclusions, and Discussions:: Results include clot mass, surface area, and location on the CVC across two CVRs (n=4 for each; Figure 1). Results in Figure 1 show a higher mean clot mass and area at CVR = 0.33 compared to CVR = 0.20. This suggests that a lower CVR can result in less thrombosis in pediatric patients, though this was not a significant result (p > 0.05 in all cases). Data also revealed that areas prone to thrombosis on the CVC are the side hole and tip regions, which is where the majority of all clots in the study formed. An explanation of the results may be that the CVC location is idealized and positioned centrally within the tube in this study. However, implanted CVCs generally do not stay in one location for the duration of their use and may disturb the flow. Additional experiments altering the CVC location and orientation in the channel will be performed to understand local fluid mechanic changes leading to device-induced thrombosis. In conclusion, this study presents preliminary data investigating the CVR for pediatric SVC flows. Data suggest that a CVR of 0.20 may benefit such patients, though more work is required to support this hypothesis.


Acknowledgements (Optional): : This work was supported by the National Center for Advancing Translational Sciences, National Institutes of Health (Grant UL1 TR002014). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.


References (Optional): : 1. Citla Sridhar, D., et al. Thromb. Res. 187: 103–112 (2020).
2. Wiegering, V., et al. BMC Hematol. 14: 1–10 (2014).
3. Van Rooden, C. J., et al. J. Thromb. Haemost. 3: 2409–2419 (2005).
4. Sharp, R., et al. BMJ Open 11 (2021).