Background: The physics of ideal fluid flow is well characterized. However, the effect of catheter size, tubing types, injection port adjuncts, and viscosity on flow is not well described. We used a simulated environment to determine how various permutations of common elements affect fluid flow.
Study design and methods: We tested 16 peripheral and central venous catheters to assess flow through several standard infusion sets and a rapid infuser set; tested flow through standard and blood infusion sets with the addition of intravenous extension tubing, stopcocks, and a needleless connector; and compared the relative viscosity of commonly used blood products and colloids to that of normal saline.
Results: The maximal flow rate was 200 mL/min for the standard infusion set but 800 mL/min for the rapid infusion set. Choice of infusion tubing was the rate-limiting component for many larger catheters. A 14-gauge, single-lumen central venous catheter (CVC) and 18-gauge peripheral intravenous catheter (PIV) had equivalent flow rates with all infusion sets. A 16-gauge single-lumen CVC allowed a flow rate that was slower than that of a 20-gauge PIV, and faster than that of a 22-gauge PIV. The addition of adjuncts slowed flow rate. Needleless connectors had the greatest impact, reducing flow by 75% for the blood infusion set. Packed red blood cells had a viscosity 4.5 times that of normal saline and thereby reduced flow.
Conclusion: Catheter and tubing choice, adjuncts, and fluid viscosity influence flow rates. Our results will help inform adequate vascular access planning in the perioperative environment.
Berman, D. J., Schiavi, A., Frank, S. M., Duarte, S., Schwengel, D. A. and Miller, C. R. (2020) Factors that influence flow through intravascular catheters: the clinical relevance of Poiseuille’s law. Transfusion. July 8th. https://doi.org/10.1111/trf.15898 (epub ahead of print).