It has to do with observed laws of averages... a patient such as the one you described probably had a period of prolonged brain anoxia and if, after taking sedation off, this patient has not exibited any signs of spontaneous improvement in level of consciousness or even improvements in being able to breathe on her own, all within about 5 days or so, the odds are she never would! An EEG would be done to rule out any higher brain wave functions and finding none, discussions would be initiated to end life support. Sometimes though, even after ending ventilator support, a patient’s brainstem and medulla are still quite functional and the patient may remain breathing with a healthy heart beat for a time...it depends on the damage to the brain. Thus you have a potential Terri Schiavo situation, especially if over time (longer than 5 days) the patient does begin to exhibit increased responsiveness though not in ways that give any hope of return to independent life!
It sounds like you have a medical background. One word you used piqued my interest: sedation.
The woman I have written about was deliberately cooled to 91 degrees, I think as an attempt to prevent brain damage. This is apparently very painful, so she was also sedated.
After a day in the hospital, she was warmed up, and they tried to take her off the sedatives. But, each time they did this, her body would tremor so badly, they couldn’t accurately monitor vital signs.
I don’t think they ever took her off the sedatives. Could the presence of sedatives affect the ability to monitor brain function?
I certainly hope "independent life" isn't the standard by which we're allowed to let patients die. They are plenty of people who can't live independently, newborn babies for one thing, and they still have the right to life.