Blood lines conduct leakage current during haemodialysis: a potential safety risk during first failure, especially for patients with central dialysis catheter as access

Abstract

Haemodialysis (HD) machines are IEC-classified as I type B. When central dialysis catheters (CDCs) are used for access, there will be close electrical contact with the heart. To investigate the risk for HD patients, the leakage of current through the tubing set was measured during in vitro dialysis performed according to the IEC 60601-1 standard for class I cardiac floating (CF) devices. A series of eight measurements were made with Gambro GFS+12 dialysers, first with saline and then with blood in the blood lines. The leakage current exceeded the CF limit (50 μA) at the top of the CDC using the test ‘mains on applied part’ for saline (median 1008 μA, range 720–1241 μA), for blood (median 610 μA, range 449–772μA) and also for a ‘single fault condition’ using saline (median 68 μA, range 35–118 μA) or blood (47 μA, range 4–128 μA). In the single fault condition, the highest leakage current at the CDC (128 μA) almost exceeded the earth leakage current in normal conditions. A safety risk can appear if a single fault arises in the dialysis machine or another device connected to the same patient, or during ‘mains contact to the patient’. Then the current flow may be high enough to induce arrhythmias in the patient, especially when a CDC is used. These data and the use of CDCs as access for dialysis indicate that HD machines should be classified as cardiac floating rather than body (B) devices.