Ethical considerations for post-cardiotomy extracorporeal membrane oxygenation

Significant advances have been made in extracorporeal life support, which has resulted in the increased use of post-cardiotomy extracorporeal membrane oxygenation. Retrospective studies have contributed to the ongoing evolution of selection criteria for post-cardiotomy extracorporeal membrane oxygenation. Current indications include failure to wean from cardiopulmonary bypass, haemodynamic collapse, pulmonary hypertension, post-repair of hypoplastic left heart syndrome, or need for bridge to transplantation. Short- and mid-term results are improving. Ethical concerns still attend the process, however. Moral risks related to post-cardiotomy extracorporeal membrane oxygenation may be encountered before, during, and after the open heart procedure. At each stage of the decision-making process, moral risks are encountered by many factors that may result in decisions that may be contrary to the best interests of the patient, parents, or use of shared societal resources. These moral risks centre around the selection process, informed consent, decision making in the operating room, and post-operative maintenance of extracorporeal membrane oxygenation. Consideration of such risks is affected by questions of haemodynamic stability, haematologic compromise, neurologic status, and family concerns. We conclude that thorough understanding of the relevant scientific literature, heightened awareness of moral risks, and incorporation of ethical tenets in clinical deliberation will guide the clinician to do the right thing.

Inflammatory mediator removal by zero-balance ultrafiltration during cardiopulmonary bypass

The abnormal conditions to which blood is subjected during cardiopulmonary bypass (CPB) trigger an activation of the inflammatory response in all patients to varying degrees. Both complement activation and the release of cytokines characterize this response. Most inflammatory mediators have a molecular weight that is below the membrane pore size of commonly used ultrafilters, which should allow them to be freely filtered. However, some mediators have been shown to fail to cross through the membrane even though they are small enough to cross. The purpose of the present study was to determine whether certain inflammatory mediators could be removed by ultrafiltration when performed during the rewarming phase of CPB. Thirty adult patients undergoing a single, open-heart procedure were randomized to either control (no ultrafiltration) or to the zero-balance ultrafiltration (ZBUF) group. ZBUF was performed by removing 3 l/m2 blood using a 65-kDa ultrafilter with 1.3-m2 surface area. A volume of a balanced salt crystalloid solution (Plasmalyte) equal to the filtered blood volume was given to replace the fluid removed. Patient data was taken before CPB (T1), immediately following CPB (T2), and 12 h following the procedure (T3). The average volume of filtrate removed during ZBUF was 6405 ml, which was analyzed for the presence of interleukin (IL)-1, IL-6, tumor necrosis factor-alpha (TNF-α), C3a, and C5a. The average concentrations of the mediators measured in the effluent were: IL-1, 0.17 pg/ml; IL-6, 0.64 pg/ml; TNF-α, 1.25 ng/ml; C3a, 782.6 ng/ml; C5a, 25.6 ng/ml. In every case except for IL-1, the amounts of mediators removed were significantly greater than zero. This study demonstrates that ultrafiltration is a strategy that can be used during CPB in the adult to remove significant amounts of inflammatory mediators.