Determining an Appropriate To-Keep-Vein-Open (TKVO) Infusion Rate for Peripheral Intravenous Catheter Usage
Optimum TKVO rate for PIVC is unknown. We used computer models to simulate saline infusion through a 20-gauge PIVC in 2 veins. Low rates (10 mL/h) may not clear the PIVC tip and keep the device patent. Increase to >20 mL/h is effective, but 30–40 mL/h appears most effective. This additional fluid load must be considered based on the needs of each patient. Background: Evidence to support an optimum continuous to-keep-vein-open (TKVO) infusion rate for peripheral intravenous catheters (PIVCs) is lacking. The aim of this study was to simulate typical TKVO rates, in combination with flushing, to better understand TKVO in relation to PIVC patency. Methods: We simulated saline infusion through a 20-gauge PIVC in 2 forearm veins (3.3 and 2.2 mm) using computational fluid dynamics under various venous flow rates (velocities 3.7–22.1 cm/s), with a saline flush rate of 1 mL/s and TKVO infusion rates of 10, 20, and 40 mL/h. We determined TKVO efficacy using the stream of saline clearing the stasis region at the device tip and the shear stress acting on the vein. Results: At 10 mL/h TKVO rate, blood stasis occurs around the PIVC tip as saline is pulled into the faster-moving venous blood flow, creating the blood recirculation (stasis) zone at the device tip. When TKVO increases >20 mL/h, this stasis diminishes, and the likelihood of patency increases. Shear stress on the vein is negligible during TKVO but increases 10- to 19-fold when flushing the small and large veins investigated here. Conclusions: Low TKVO rates (10 mL/h) may not clear the PIVC tip and keep the device patent. Based on our simulations, we propose a TKVO rate of at least 20 mL/h could be used in practice; however, 30–40 mL/h appears most effective across different venous flow rates and peripheral vein sizes. However, this additional fluid load must be carefully considered based on the needs of each patient.Highlights
Abstract
(A) Computer-aided design of a hypothetical catheter body from a 20-gauge PIVC (actual device shown for illustration purposes only) and idealized vein, and (B) PIVC inserted into the vein and situated in the final position for all further simulations. Note: the model is not specific to a certain PIVC manufacturer but is instead created using the typical dimension of the catheter section of a 20-gauge PIVC. As shown in (A), the hub or port was not incorporated into the geometry or simulation, and instead the saline was infused directly into the catheter. Therefore, the hub or port has no influence on the simulation. The catheter was inserted into the vein at an angle of 20°.
Percentage of saline in each simulation. Insert shows region downstream to device tip. The effect of TKVO rate is apparent where, at a low infusion rate of 10 mL/h, the saline stream exiting the catheter cannot overcome the blood pool at the tip. This effect diminishes when the TKVO rate increases to 20 mL/h and above.
(A) Diffusion of saline into venous blood stream, (B) percentage blood stasis, and (C) the stasis rendered into 3 dimensions in the 2.2-mm vein (left) and 3.3-mm vein (right).
(A) Saline stream exiting a 20-gauge PIVC when inserted in a large (3.3 mm) vein with 20 mL/h TKVO at various venous flow rates. While effective at reduced and typical venous flow rates, this TKVO rate becomes ineffective with increased venous flow and blood recirculates at the device tip (white arrowhead). (B) Further demonstration of the ineffectiveness of low TKVO rates (10 mL/h) during increased venous flow (56 mL/min; 22.1 cm/s). The force of the saline exiting the device tip cannot overcome the force of the recirculating blood, and device blockage is the likely outcome.
Resulting saline stream width for each TKVO infusion rate, vein diameter and venous flow rate investigated, as well as velocity scalar plots for the 2.2-mm vein at the standard venous flow rate (8.4 mL/min; 7.3 cm/s). As can be seen in (C), once the TKVO velocity begins to match the venous velocity, the stream width and thus efficiency is greatly improved. A TKVO rate of 40 mL/h results in a minimum of 80% saline stream width (shaded zone) in all configurations.
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