2 ms·

Not a dumb question. What you've just described is an ECMO machine ("extracorporeal membrane oxygenation", related to the surgical machines oft known as a heart

Not a dumb question. What you've just described is an ECMO machine ("extracorporeal membrane oxygenation", related to the surgical machines oft known as a heart-and-lung machine). The act of putting the patient on it is called putting them "on bypass" and involves cutting through some of the most major blood vessels in the body, administration of large doses of heparin as a blood thinner, and a team of about ten to twenty people to ensure that they don't die. It's a major operation. After a while the mechanical stress of the pump causes blood cells to be sheared and lyse, causing haemolysis, which would otherwise be fatal if not replaced.

darkerside 4y ago
Is the heart that much better of a pump than the ECMO? I didn't realize there was mechanical stress on the blood itself from the ECMO machine.
- azalemeth 4y ago
  "Yes", is the short answer. Every ECMO machine I've ever seen uses a [1] peristaltic pump and, despite the use of tubes coated with anticoagulants and with various proprietary bits of chemistry [2] to reduce the size of the inviscid layer and hence shear stresses, the maximum length of time you can spend on them is limited. It's always a downhill battle and typically a "metric shitton" of heparin is infused in order to reduce the risk of thrombus, despite the hemorrhagic risk [3]. All of these things are fine balancing acts but you do not want to be on ECMO for a long time. Similar technologies, such as cardiac LVADs are only licensed in the UK as a bridge to transplant, for example, where a well-defined end-date already exists before putting the patient on them. [1] https://en.wikipedia.org/wiki/Peristaltic_pump https://en.wikipedia.org/wiki/Peristaltic_pump [2] https://www.terumo-europe.com/en-emea/products/tubing-set-perfusion-circuit https://www.terumo-europe.com/en-emea/products/tubing-set-pe... [3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457945/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457945/

darkerside 4y ago

Is the heart that much better of a pump than the ECMO? I didn't realize there was mechanical stress on the blood itself from the ECMO machine.

azalemeth 4y ago
"Yes", is the short answer. Every ECMO machine I've ever seen uses a [1] peristaltic pump and, despite the use of tubes coated with anticoagulants and with various proprietary bits of chemistry [2] to reduce the size of the inviscid layer and hence shear stresses, the maximum length of time you can spend on them is limited. It's always a downhill battle and typically a "metric shitton" of heparin is infused in order to reduce the risk of thrombus, despite the hemorrhagic risk [3]. All of these things are fine balancing acts but you do not want to be on ECMO for a long time. Similar technologies, such as cardiac LVADs are only licensed in the UK as a bridge to transplant, for example, where a well-defined end-date already exists before putting the patient on them. [1] https://en.wikipedia.org/wiki/Peristaltic_pump https://en.wikipedia.org/wiki/Peristaltic_pump [2] https://www.terumo-europe.com/en-emea/products/tubing-set-perfusion-circuit https://www.terumo-europe.com/en-emea/products/tubing-set-pe... [3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457945/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457945/