Plasma leakage of oxygenators in ECMO depends on the type of oxygenator and on patient variables.

This study was conducted to identify the causes of plasma leakage of oxygenators in extra corporeal membrane oxygenation (ECMO). From 1996 through 2002, 91 oxygenators were used in 62 patients undergoing ECMO for respiratory and/or cardiac failure. Several types of oxygenators were used (Medtronic Maxima, Minima, PRF, Medos Hilite). Patient variables and variables related to the ECMO set-up were analysed for their relationship with oxygenator failure by a time related multiple regression analysis (Cox). Oxygenator failure occurred in 26% of the cases. The analysis identified the type of oxygenator (p=0.0016), younger patient age (p=0.04) and the number of oxygenators used (p=0.03) as the independent significant risk factors. The type of oxygenator used has the most overwhelming effect (significantly less leakage with the Medos Hilite). In conclusion, leakage of oxygenators is predominantly caused by the type of oxygenator used. Patient variables (younger age and the number of oxygenators used in one patient) are also significant and allude to an inflammatory process as underlying mechanism of plasma leakage.

A new pneumatic pump for extracorporeal circulation: TPP (true pulsatile pump). Experimental and first clinical results.

A pulsatile, membrane type pump, TPP, was developed for use in routine cardiac surgery. The artificial ventricle consists of a polycarbonate housing with an inlet and outlet polyurethane tricuspid valve. The membrane is actuated hydraulically. For pre-clinical studies, we designed a study in sheep. After a pump run of 6 hours the animals were allowed to recover and sacrificed after 72 hours. All clinical parameters returned to normal values (p > 0.05 vs. control values). During pump run we found elevated free plasma hemoglobine. However, these values returned to normal until the end of the observation period. Thereafter, the device was used in ten routine cardiac surgery procedures. All patients survived the procedure and were discharged from hospital. The postoperative course of lab parameters (kidney, liver and blood count) was no different to routine cardiac surgical procedures. This pulsatile pump system can thus be safely employed in cardiac surgery.

The use of a heparin removal device: a valid alternative to protamine.

PURPOSE: Experiments were carried out to test the efficacy and safety of the heparin removal device, a plasmapheresis filter that binds and eliminates heparin, in the context of extracorporeal circulation. PROCEDURES AND FINDINGS: Six dogs were put on cardiopulmonary bypass after heparinization. Upon weaning, additional heparin was administered to obtain an activated clotting time above 900s. The animals were connected to the heparin removal device and with flows of 500 ml/min, activated clotting time, activated partial thromboplastin time and plasma heparin concentrations were normalised to baseline after 30 min. Hemodynamic parameters remained unaffected. A slight decrease in red and white blood cell count and in platelets was observed which however recovered spontaneously two hours after the filter procedure. No damage to blood components could be observed. CONCLUSIONS: The use of a heparin removal device is as efficient as systemic administration of protamine to reverse the effects of heparinization. It may prevent the adverse reactions linked to protamine administration and therefore be indicated in certain subgroups of patients undergoing cardiopulmonary bypass.