Protection of Dialysis Staff from COVID-19 Infection: Setting Up and Impact of Extended Blood Lines during Dialysis.

A novel coronavirus (COVID-19) has been rapidly spreading worldwide, and its transmission to medical staff is a critical issue. In particular, medical staff in dialysis facilities face a higher risk of COVID-19 infection because dialysis patients visit frequently and stay for a long time and staff work in close proximity to patients.1 We report a novel use of extension blood line (EBL) device that maintains an adequate distance between the patient and dialysis machine (DM), which can be used safely and effectively for COVID-19-positive patients undergoing hemodialysis. This modification of conventional dialysis technology may reduce exposure of dialysis staff to COVID-19. Methods A DBG-03 DM and the corresponding blood circuit (Nikkiso Co., Ltd., Tokyo, Japan) were used in each dialysis session. In addition, three-connected SAFEED EBLs (total length, 1.5 m; individual line length, 0.5 m; inner diameter, 3.1 mm; volume, 3.8 ml; Code No. SF-ET3825L, Terumo, Tokyo, Japan) or a single SureFlow N ET (length, 1.5 m; inner diameter, 3.3 mm; volume, 13 ml; NIPRO, Osaka, Japan) were used to maintain a distance of approximately 2.5 m between the patient and DM (Figure 1A and B). A partition with a curtain between the patient and DM was also used as direct defense against droplets (Figure 1A and C).2 A ceiling-mounted camera was used for monitoring from outside the room (Figure 1B). The additional priming volumes of the three-connected EBLs and single EBL were 23 and 26 ml, respectively. The room temperature was set at 25–28°C, and the dialysate temperature was set at 37.0°C (regular dialysate temperature, 36.0°C) to prevent hypothermia. We used these EBLs in two COVID-19-positive patients who were receiving maintenance hemodialysis (Table 1). Case 1 was a 50-year-old man with nephrosclerosis. A high-flow nasal cannula was used during the use of the EBL. Case 2 was a 49-year-old man with diabetic nephropathy. Written informed consent was obtained from the patients. The numbers of dialysis sessions with each configuration were as follows: three-connected EBL, n = 3 (case 1; n = 3); single EBL, n = 9 (case 1; n = 6, case 2; n = 3); no EBL, n = 5 (case 1; n = 3, case 2; n = 2). Table 1. - The Setting of Dialysis Case 1 Case 2 Dialysis mode Hemodialysis Hemodialysis Dialysate flow 500 ml/min 500 ml/min Filter type Polysulfone Cellulose triacetate Treatment duration (dialysis) 27 days (12 times) 48 days (9 times)* Number of dialysis per week 3 times 3 times Anticoagulant dose Nafamostat 120 or 160 mg Nafamostat 160 mg or heparin 5000 units Vascular access Arteriovenous fistula Arteriovenous fistula Needle size 16 G 16 G *This patient received continuous renal replacement therapy from day 3 to day 30 in the intensive care unit. Figure 1.: The novel use of extension blood line device for dialysis patients with COVID-19 infection. A: The addition of the extension blood line to a regular blood line maintains a distance of approximately 2.5 m between the patient and the dialysis machine. The use of a partition with a curtain between the patient and dialysis machine may also reduce the risk of infection, B: The view from the ceiling-mounted camera, C: The view from the room entrance. Dialysis staff can monitor the dialysis machine from the entrance window.Results There were no major problems during the priming or dialysis sessions. However, visible blood clots were observed at the needle tip and the EBL junction when using the three-connected EBLs in case 1. We therefore switched to a single EBL, after which no blood clots were observed. Figure 2 shows the venous return pressure (VRP) of each EBL in case 1. The VRP at a blood flow of 200 ml/min in the three-connected EBL was numerically higher in comparison to the single EBL. The VRP at a blood flow of 250 ml/min in the single EBL was significantly higher in comparison to dialysis without an EBL. The average VRP in all lines was <150 mm Hg. The body temperature (BT) did not decrease after dialysis sessions using the single EBL (before 36.6 ± 0.4°C vs. after 36.8 ± 0.3°C; p = 0.258); however, there was a mild but significant decrease in BT after dialysis sessions using the three-connected EBLs (before 37.2 ± 0.6°C vs. after 36.9 ± 0.7°C; p = 0.029). The systolic blood pressure (BP) did not change to a statistically significant extent after dialysis sessions using a single EBL (before 148 ± 21 mm Hg vs. after 142 ± 20 mm Hg; p = 0.182); however, the systolic BP significantly increased after dialysis using the three-connected EBLs (before 127 ± 30 mm Hg vs. after 140 ± 29 mm Hg; p = 0.009).Figure 2.: The venous return pressures of each extension blood line in case 1. The venous return pressure at a blood flow of 200 ml/min was numerically higher when three-connected extension blood line was used in comparison to when a single extension blood line was used. The venous return pressure at a blood flow of 250 ml/min in the single extension blood line was significantly higher in comparison to when no extension blood line was used. The average venous return pressure was <150 mm Hg in all groups. *p < 0.05 vs. no extension blood line. Values are expressed as the mean ± standard deviation. No extension blood line, n = 13 (number of dialysis sessions = 3). Single extension blood line, n = 23 (number of dialysis sessions = 6). Three-connected extension blood lines, n = 8 (number of dialysis sessions = 3). n = total number of measurements per hour.Discussion Several approaches to protect dialysis staff from COVID-19 infection have been recommended, including the appropriate use of personal protection equipment, reemphasis of universal precautions, and less frequent dialysis schedules.3,4 However, none of these strategies involve securing a sufficient distance between the patient and DM. COVID-19 is transmitted through direct contact or droplets5; thus, social distancing, staying at least 2 m from other people, is recommended as infection control.6 In addition, the use of a high-flow nasal cannula, which was used in case 1, is associated with a higher risk of COVID-19 transmission, because it spreads cough-generated droplets beyond 2 m.7 In a conventional dialysis circuit, the distance between the patient and DM is approximately 0.5 m; however, the use of an EBL maintains a distance of >2 m from the infected patient when dialysis staff operate the DM. Thus, the EBL device may be useful for protecting dialysis staff from COVID-19 infection. The predictable concerns of this line extension method were the increased VRP, hypothermia, and clotting. The average VRP at blood flows of 200–250 ml/min was <150 mm Hg with both the single EBL and the three-connected EBL. According to the Hagen–Poiseuille law,8 the circuit pressure (P) is determined by the circuit length (L), circuit diameter (r), blood flow (Q), blood viscosity (μ), and dialyzer resistance: P = (Q·8 μL)/(πr4). Thus, the longer circuit when using an EBL increases the circuit pressure.8 Actually, the VRP in the single EBL configuration was significantly higher than when no EBL was used. In addition, a mild increase in VRP in the three-connected EBL was observed in comparison to the single EBL; this may be due to differences in the circuit diameter and/or blood viscosity.8 Nevertheless, the VRPs in the single and three-connected EBL configurations were both acceptable for actual use. However, the single EBL may have advantages in comparison to the three-connected EBL, for the following reasons. First, blood clots were not observed in the single EBL, while blood clots appeared in the three-connected EBLs, in which blood retention and turbulent flow at a total of six connection points might cause clots.9 Second, the BT and BP were not significantly changed by the single EBL, while they were significantly decreased and increased, respectively, by the three-connected EBLs. In conclusion, the connection of an EBL to the regular circuit is a safe and useful strategy for maintaining a sufficient distance between a COVID-19 patient and DM. In particular, a single EBL may be superior to multiple connected EBLs, in terms of the prevention of blood clots and stabilization of BT and BP. This novel method may contribute to protecting dialysis staff from COVID-19 infection during dialysis sessions.