eli5: how come when your organs are in your body, they need to be 98 degrees, but in an organ transplant the organ is cooled?
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You keep meat in the fridge to stop it going bad and prolong it’s use by date. Same thing with organs. Cold ischaemia (time without oxygenated blood getting to the muscle) is longer than warm ischemia time.
Imagine moving laptop from one location to another. Best would be to entirely power it down but if you can not do that putting it in to very low power use mode (aka sleep state) helps. Cold temperatures do that for living tissue because colder temperatures slow down chemical reactions. Most reactions that happen after an organ is removed are not desirable. Best would be to stop the chemical reactions entirely but for living tissue we have not yet figured out how to do that without irreversible damage.
So you’re comparing a state in which an organ needs to be actively working to a state where it should not be actively working.
So normally, organs have an ideal temperature that they “work” at. There’s a lot of reasons for this from enzymes, biochemical reactions, etc. to amount of blood required to deliver oxygen for these organs to continue functioning, all which are temperature sensitive.
When you are taking organs out of the body, you are depriving them of blood (and thus oxygen) to carry out all of these metabolic functions. The cells in these organs will slowly start to accumulate waste products, break down, and die as they try to continue these metabolic and chemical reactions without oxygen.
What freezing does is slows down these chemical reactions almost to a halt. Enzymes, proteins, reactions require energy (usually in the form of heat) to work. This reduces the requirement of oxygen and lets organs become viable for a lot longer outside of the body without a blood supply.
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Well the organ needs to be at that temp to function. When it isn’t inside you you don’t need the heart to pump blood. You need it to not break down and rot. Once it is back inside a persons chest is when you want it to start working again.
Your body has an immune system to fight infection, the cells get food and oxygen, and the organs need to be warm to do their job.
Outside of the body, the organs don’t need to their job, the cells aren’t getting food nor oxygen to stay alive, and there’s no immune system to fight off microorganisms. Cooling the organ slows the rate that the cells starving of oxygen and food die, and inhibits growth of microorganisms.
When I’m your body, your body is doing things to keep them alive and functioning. Outside your body, they don’t have that support and decay. Cold slows that decay so the body it’s transplanted into can still use it.
Cold cells use less oxygen, like cold hibernating bears use less energy.
Organs, outside the body, have no oxygen supply.
So you cool them so the cells use the lowest amount of oxygen possible while not dying.
Because your organs don’t need to be working when in a transplant icebox. The cold helps slow down the speed at which cells run. In the cold, they function slower, and die slower.
Your heart will stop pumping if it gets too cold. That doesn’t mean it’s broken or rotten. Just that it’s stopped, and needs to be reheated and likely restarted.
Glad this question was asked. I’ve never thought about it but it’s good to actually know. Thanks
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