The field of medicine has seen significant advances in the ability to support or replace native organ function over the last several decades. Renal hemodialysis, in existence since the 1940s [1], has become standard treatment for patients suffering from end-stage kidney disease and is often used in the outpatient setting as a bridge to transplantation or as a destination therapy, where it permanently replaces organ function [2]. Likewise, continuous venovenous hemodialysis (CVVHD) may be used in the critical care setting for potentially reversible kidney injury, among other indications [3]. Ventricular assist devices (VADs) may partially or completely replace cardiac function; a total artificial heart (TAH) completely replaces it [4], and either one may be used as a bridge to heart transplantation or a destination therapy [5,6]. Liver replacement alternatives, which include the extracorporeal liver assist device (ELAD) and the molecular adsorbent recirculating system (MARS), replaces the detoxification function of a failing liver [7].Extracorporeal membrane oxygenation (ECMO) uses a pump to withdraw deoxygenated blood from a central vein, provide oxygen and remove carbon dioxide via diffusion across a semipermeable membrane, and return oxygenated blood into a central vein or artery, essentially functioning as an external artificial lung, heart, or both [8]. In cases of respiratory failure, ECMO is being used with increased frequency as a supplement to, or occasionally in place of, invasive mechanical ventilation [9][10][11][12]. While this technology has the ability to replace a patient's native lung function, its use, like use of liver replacement therapies and CVVHD, requires ongoing attention in an intensive care unit (ICU). ECMO can serve as a bridge to recovery from reversible illnesses or as a bridge to transplantation for select patients, but not currently as a destination therapy.As organ replacement technologies become increasingly sophisticated and more readily available, we will have the ability to prolong organ function for longer, which raises significant questions about their appropriate use.
Appropriate Use of Organ-Replacement Interventions in Individual CasesThe fact that we have the ability to sustain organ function does not mean that it is always medically or ethically appropriate to do so. It is reasonable to base assessment of the medical appropriateness of a technology on the likelihood of its achieving reasonable goals. In the case of these sophisticated organ-replacement technologies, reasonable goals are not only replacing the failing organ but also