1 hour

This morning an old lady came as an emergency to our ward, reanimated, covered in blood and some other  nasty stuff. Everything was pretty stressful, she had no pulse, no blood pressure and we continued doing the CPR. My team leader was bagging her (Intensive ward slang for ventilating the lungs with an Ambug Bag, we don't do the mouth-to-mouth sort of thing, it's gross and highly unhygienic) and I hopped on the bed and started reanimating.
At first it was pretty exhausting, suddenly it turned easier. I think I broke a rib. Or two.
I looked at her face and seriously, it was distorted in agony.
We tortured her while trying to save her life.

The docs kept on discussing whether to continue or not.
Someone said: "Dude, she's 84.."
one of the Docs said: "I mean we are already reanimating for an hour straight or so.."
(45 minutes on the normal ward, 15 minutes at our ward)
When I heard that, I knew she was dead already.
Even if we would've managed to get a pulse and some blood pressure, her brain would've been damaged irreparably.
If this would've been one of my relatives I would've told the Docs to stop immediately and to fuck off.

Two minutes later she was declared dead, two hours later a colleague and I took her down to the cooling chamber.
She looked peaceful then.
I think it was the best way this story could've ended.