Why Is Cold Solution Used for Open Heart Surgery?

[Cheman]

According to sources I've read, the heart can be stopped by flooding it with "a cold solution containing potassium ions" - why must it be cold?

Thanks in advance.

 

[quetzalcoatl9]

during open heart surgery, the heart must be kept alive...by keeping the heart cold, the metabolism of the heart cells will be slowed down long enough that they can survive for awhile even under low-oxygen conditions. at room temp this is a few minutes; while cold, it can be much longer.

the potassium ions interfer with the ion channels of the nerve cells, thus stopping the heart from beating. potassium chloride is also administered to animals during euthanasia (after first being sedating with sodium thiopental) for the same purpose.

they also use heparin, btw, in the heart-lung machine to prevent the blood from clotting.

 

[Cheman]

Cool. Why does cooling the heart slow down its metabolism?

Thanks in advance.

 

[quetzalcoatl9]

metabolism can be boiled down to chemical reactions taking place within the cell. thermodynamically, chemical reactions can be slowed by lowering the temperature.

 

[Cheman]

But why do you want to run in on "low-oxygen consumption"?

Also, surely if you cool the heart you will slow down the rate of respiration (which is a chemical reaction and relies on thermodynamics too) so the cell will be supplying itself with less energy anyway, as well as not needing as much due to the slowing down of its metabolism. Therefore if you reduce the oxygen supply to the heart, like you said, you will be reducing concentration which will reduce the rate of respiration EVEN further, and therefore the cel will not be able to supply itself with suffivient energy?

Thanks in advance.

 

[quetzalcoatl9]

But why do you want to run in on "low-oxygen consumption"?

wouldn't cutting out someones heart make for "low-oxygen consumption"? i think that it would.

Also, surely if you cool the heart you will slow down the rate of respiration (which is a chemical reaction and relies on thermodynamics too) so the cell will be supplying itself with less energy anyway, as well as not needing as much due to the slowing down of its metabolism. Therefore if you reduce the oxygen supply to the heart, like you said, you will be reducing concentration which will reduce the rate of respiration EVEN further, and therefore the cel will not be able to supply itself with suffivient energy?

your argument doesn't make much sense to me, cheman...imagine you have only 1 liter of gasoline in your car. assume once you run out of gas, the car is dead. will it last longer at full throttle, or if you drive slow?

the energy needs of the cell will generally be much less at lower temperature.

in theory, if you could completely slow down the metabolism of a cell (think freezing) then the state of that cell could be preserved indefinately since all of the chemical reactions going on would be halted (well, mostly).

 

[Cheman]

Actually, i had more in mind during valve replacement surgary - why is there gona be oxygen reduction then?

And surely what i said did make sense - if all the reactions slow down then surely the reactions of cellular respiration will also slow down? Therefore, the energy source being made will be lower anyway without the need to reduce oxygen supply? So by lowering it even more surely that will mean the cells won't have enough energy?

Thanks in advance.

 

[quetzalcoatl9]

Actually, i had more in mind during valve replacement surgary - why is there gona be oxygen reduction then?

And surely what i said did make sense - if all the reactions slow down then surely the reactions of cellular respiration will also slow down? Therefore, the energy source being made will be lower anyway without the need to reduce oxygen supply? So by lowering it even more surely that will mean the cells won't have enough energy?

surely the heart will have less oxygen available during some major surgery like a valve replacement.

and second, yes the energy generating ability will be reduced, but so will the energy expenditure. therefore, the whole system has been slowed down.