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 consi dered responsible for the electrostatic charge build-up in some oxygenators with a plastic heat exchanger. During use of such an oxygenator, an electr ical shock can be felt when touching the device. In the absence of a provok ed discharge, a spontaneous discharge may occur. The construction of the he at exchanger and the use of nonconductive materials enable some devices to function as a capacitor. if the voltage difference across the fibre wail is too high, an electrostatic discharge may occur. In 1997, four blood-to-wat er leaks in Maxima Forte oxygenators were reported on a worldwide basis. Af ter thorough research by Medtronic Cardiac Surgery (Cardiopulmonary Divisio n), the cause of the leaks was found to be an electrothermal event across t he 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 Administrat ion-approved and patient-safe solutions to prevent this electrostatic charg e build-up. We studied the electrostatic phenomenon in order to clarify the clinical as pects. The in vitro part of the study is related to the behaviour of the Me dtronic Biopump and the Stockert Shiley roller pump - in combination with t he 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 occl usion settings on the roller pump. Furthermore, we tried to capture the ele ctrical charge generated by the roller pumps in a capacitor and in some oxy genators with different types of heat exchanger. Finally we tested the exte rnal CELTM (Charge Equalization Line) and the internal 'Gold Wire' charge e qualization systems, both patented by Medtronic. In the in vivo part of the study. 15 patients were divided into three group s of five patients each. In the first group a roller pump with a PVC pumphe ader 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 Forte oxygenator with the external CEL protection was used . Owing to the fact that, at the time, the Maxima Forte 'Gold Wire' oxygena tor was not available for clinical use, only the external CEL could be eval uated.