MO787: Effects of the End Structure of Temporary Indwelling Catheters on Blood Recirculation under Varying Blood Flow Rates of a Dialysis Machine and Diameters of a Mock Blood Vessel
Authors: Sato Yukihiro , Yanagizawa Katsuya , Kurihara Yoshitaka , Kobayashi Kozue , Kokubo Kenichi 
Published: May 2022

Abstract

BACKGROUND AND AIMS
The performance of temporary indwelling catheters allowing higher recirculation during hemodialysis may result in reduced clearance and inadequate dialysis and consequently, reduced patient survival. In actual clinical practice, it is often necessary to use a reverse connection to recover the blood flow rate for dialysis when there is inadequate blood removal during the treatment. The aim of the present study was to determine the effects of the end-structure of catheters used for hemodialysis on blood recirculation under varying blood flow rates of a dialysis machine and diameters of a mock blood vessel in a well-defined in vitro experimental system, focusing on the reverse connection.

METHOD
Pig blood was circulated by a roller pump through a mock vessel made of silicon tubes with an inner diameter of 15 mm or 20 mm. The tip of the inserted catheter was fixed at the center of a silicone tube. We connected the catheter to a dialysis machine, a blood circuit and a dialyzer. The blood flow rate of the dialysis machine was set at 100, 150, or 200 mL/min and the recirculation rates were determined. The recirculation rate was measured three times under each condition, and the average value was determined. Five types of catheters were used; Argyle TM 12 Fr × 25 cm (catheter A), Gentle Cath TM (Hardness gradient type) 12 Fr × 13 cm (catheter B), Gentle Cath TM 12 Fr × 24 cm (catheter C), Niagara TM 13.5 Fr × 24 cm (catheter D), Power-Trialysis® 13 Fr × 24 cm (catheter E). Catheters A, B, C and D have asymmetric structures with a side hole, while E has a symmetric structure.

RESULTS
The recirculation in the sequential connection was very low for all catheters. The recirculation rates in the reverse connection for catheters A, B, C, D and E were 40%, 25%, 17%, 25% and 10%, respectively. The recirculation rates were the lowest when the blood flow rate of the dialysis machine was set at 200 mL/min and the inner diameter of the mock blood vessel was 20 mm.

DISCUSSION
Recirculation was most likely to occur for catheter A. The distance from the end hole to the side hole was longer in catheters B, C and D than in catheter A, which could explain the lower recirculation rates. Among the catheters, catheter C had the largest side hole, and the blood spread widely into the vessel, leading to a lower recirculation rate. Therefore, the distance between the end hole and the side hole and the size of the end hole was deduced as being essential factors for reducing the recirculation in the case of reverse connection. For catheter E, the blood flow line in the mock vessel coming from the dialysis machine through the blood returning hole (side hole) was helical, and little blood existed near the blood withdrawal hole (the other side hole), which could be responsible for the reduced recirculation rate.

CONCLUSION
The least recirculation in the reverse connection was observed with symmetrical catheters, where the blood streamlines were spiral and did not intersect with the blood streamline between the blood withdrawal hole and the blood returning hole.