Study on causes and prevention of electrostatic charge build-up during extracorporeal circulation

For many years it has been known that roller pumps interfere regularly with the electrocardiogram (ECG) signal. This electrical activity is also considered responsible for the electrostatic charge build-up in some oxygenators with a plastic heat exchanger. During use of such an oxygenator, an electrical shock can be felt when touching the device. In the absence of a provoked discharge, a spontaneous discharge may occur. The construction of the heat exchanger and the use of nonconductive materials enable some devices to function as a capacitor. If the voltage difference across the fibre wall is too high, an electrostatic discharge may occur. In 1997, four blood-to-water leaks in Maxima Forté oxygenators were reported on a worldwide basis. After thorough research by Medtronic Cardiac Surgery (Cardiopulmonary Division), the cause of the leaks was found to be an electrothermal event across the fibre wall of one single fibre. No patient injuries were reported in any of the events. Medtronic patented a number of US Food and Drug Administration-approved and patient-safe solutions to prevent this electrostatic charge build-up. We studied the electrostatic phenomenon in order to clarify the clinical aspects. The in vitro part of the study is related to the behaviour of the Medtronic Biopump and the Stockert Shiley roller pump--in combination with the use of a PVC or silicone pumpheader. Subsequently, we have investigated the influence of the rotation or flow of both types of blood pumps and occlusion settings on the roller pump. Furthermore, we tried to capture the electrical charge generated by the roller pumps in a capacitor and in some oxygenators with different types of heat exchanger. Finally, we tested the external CEL (Charge Equalization Line) and the internal 'Gold Wire' charge equalization systems, both patented by Medtronic. In the in vivo part of the study, 15 patients were divided into three groups of five patients each. In the first group a roller pump with a PVC pumpheader was evaluated and, in the second group, a roller pump with a silicone pumpheader. The third group consisted of the Medtronic Biopump. In all the groups, a Maxima Forté oxygenator with the external CEL protection was used. Owing to the fact that, at the time, the Maxima Forté 'Gold Wire' oxygenator was not available for clinical use, only the external CEL could be evaluated.