Page last updated at 11:28 GMT, Monday, 9 January 2006

Sharon's medically induced coma

Ariel Sharon
Ariel Sharon suffered a massive cerebral haemorrhage

Ariel Sharon has been kept in a medically induced coma since Thursday last week - the day after he suffered a major stroke.

Here heavy sedation is used to give the body time to recover from the trauma of the stroke and, in Mr Sharon's case, three rounds of surgery to stop the bleeding in his brain.

The drug-induced coma keeps him in place and stops him writhing around and accidentally pulling out his tubes.

And while in intensive care, doctors are able to monitor the Israeli prime minister's vital signs.

The blood in the brain will resolve itself, its like having a bruise in the vault of the skull
Dr Pankaj Sharma
Head of stroke at Hammersmith Hospitals NHS Trust

Heavy sedation can also bring about a reduction in the pressure on the brain within the vault of the skull, says head of stroke at Hammersmith Hospitals NHS Trust Dr Pankaj Sharma.

He explains the damage caused to Mr Sharon's brain is as a result of blood from the major cerebral haemorrhage that caused the stroke clotting in his brain.

"The blood in the brain will resolve itself, its like having a bruise in the vault of the skull.

"The problem is the damage being caused around it," Dr Sharma added.

Blood that has escaped from the vascular system, the blood vessels, will naturally clot.

This clotting will prevent the cerebrospinal fluid, which keeps the brain hydrated and lubricated, from moving around naturally.

Mobility tests

As tiny holes in the skull get increasingly blocked, the fluid, which is still being produced, has nowhere to go and pressure builds up.

It is this, not the blood, which will be pushing on the brain, and which doctors hope the sedation will help to relieve.

Dr Sharma says there are not any major risks associated with bringing Mr Sharon out of sedation, in fact it is more risky to keep him sedated for longer.

"Sometimes it becomes difficult to get people off sedation because the brain becomes accustomed to it," he says.

The body becomes used to machines, like respirators, breathing for it, so the doctors will be monitoring the process of reducing sedation very closely.

'Fraction of the man'

As his brain takes over responsibility for breathing and maintaining blood pressure the coma will gradually lift.

Once Mr Sharon is fully conscious, a full assessment of how much damage the stroke has caused can be made.

He will undergo tests on his ability to move his legs and arms and how his speech has been affected.

Dr Sharma says the extent of the damage will be clear within 24 to 48 hours.

He stressed that even if Mr Sharon survived this "major assault" he was likely to have suffered great physical damage.

However, many people who have suffered less severe strokes are able to make a full recovery.

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