People die on the ICU.
This is just a fact of life: we can’t save everybody. Bodies fall apart if enough bad things happen to them. Sometimes we can keep part of the body alive, but not the rest; sometimes we can support consciousness even when the body is doomed, although eventually even consciousness will fade. More often, we can keep the body running even while the brain is completely dead.
You’ll notice that, with other organ systems, we use different terms than with the brain. If your kidneys have some working tissue, but aren’t strong enough to get your blood really clean, you have renal failure. If your kidneys are so fucked up they shrivel into black raisins and you never pee again and you depend on a dialysis machine to clear out all your nitrogen waste products forever, we call it end stage renal failure, not renal death.
If your liver is a huge lumpy pile of scar tissue and blood can’t flow through it at all, you aren’t experiencing liver death (although you will soon die unless you get a new liver), you’re in end stage liver failure. If your lungs are full of gross shit and require mechanical assistance to get oxygen and carbon dioxide in and out of your blood, you are in respiratory failure; if your lungs are filled with scar tissue and nodules and all the cilia are burned out and every breath uses up more oxygen than it gains, you are in end stage respiratory failure. All of these things lead directly to death, although we’ve learned to cheat them a little better over time, but they are not death.
We also talk about heart failure, in which the heart can’t move blood well enough to maintain equilibrium without medical help. We even talk about end stage heart failure sometimes, although this mostly means this person is about to be dead. The true end stage of heart failure is cardiac death.
We call it death, because for a very long time, the lack of a pulse was death. There was no way to get it back. Once you crossed that line, you were gone.
But we’ve learned to cheat even that death, sometimes, if we’re lucky. We can, if we’re willing to break ribs and insert tubes and flood the body with toxins, restart the heart. We can even support a fatally wrecked heart for a while with ventricular assist devices. What was once death is now closer to failure.
So if we’ve blurred the line between life and death, what’s left? Is there anything that can be so damaged that we can’t compensate for it? Is there anything that truly goes beyond failure into death?