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SCMP Reporter

THE death on Monday of canto-pop star Danny Chan Pak-keung has highlighted the issue of brain stem death - something which some people still find confusing, doctors say.

  Yet it is an issue which they are increasingly likely to face in the modern technological world of medicine.

  Chan died after spending the last 17 months on an artificial respirator, in a coma, at Queen Mary Hospital.

  He was admitted on May 18 last year, after collapsing at his home. The cause of his death was brain stem failure.

  Today's highly sophisticated machines and highly potent drugs mean doctors can keep seriously ill patients like Chan alive for longer than ever before.

  So what is brain stem death and can we be sure that when a doctor says a person is brain stem dead, he really is - even if we can still see his heart beating?   The term brain stem death is used to describe irreversible brain damage.

  Essentially, it means that the brain cannot perform the vital functions necessary to sustain life.

  ''This concept is a valid one,'' said Dr Yu Yuk-ling, chief neurologist at Queen Mary Hospital. ''It is accepted by the medical profession and is used worldwide.''   Dr Yu said the concept of brain stem death came about because of dramatic advances in technology in the last three decades.

  In the past, a person was considered dead when their heart stopped beating, their blood stopped circulating and they stopped breathing.

  Nowadays, machines can keep the pulse beat going, can force blood around the body and can pump air into the lungs - even when the brain, ''the seat of control'' for these functions, has suffered irreversible damage.

  This made it necessary to find another way to define whether someone really was dead, Dr Yu said: ''You don't want to ventilate a dead person.''   Another spur for the adoption of the brain stem death concept was the ever increasing demand for organ donation, he said.

  The problem with harvesting organs from a cadaver is that it must be done as soon as possible.

  This is the main root of people's fear concerning brain stem death, according to Dr Michael Tsang Tse-shu, consultant physician at Queen Mary Hospital, and Chan's doctor.

  ''There are people who panic that it may be over-used,'' he said.

  Dr Tsang said doctors were very careful to ensure death really had occurred before harvesting organs.

  He said people should realise that while patients in a persistent vegetative state - ie, those in a coma but who still have some brain functioning and are therefore still alive - could be kept on a respirator indefinitely, this was not true of those whose brain cells had died.

  ''If the brain stem is really dead, even if we can keep the breathing by artificial ventilation, the vital signs will collapse,'' he said.

  This is what happened to Chan, whose ventilator was not switched off until his heart had stopped beating.

  Both Dr Yu and Dr Tsang say stringent tests are used to determine whether a person has suffered brain stem death.

  Queen Mary Hospital uses the British criteria, which Dr Yu said have been shown to be foolproof if rigorously applied.

  The prerequisite is that patients must be deeply comatose, unable to breathe spontaneously and have irremediable structural damage, such as a serious head injury.

 After certain conditions like drug overdose and hypothermia, have been excluded, doctors carry out a series of tests - checking breathing, circulation, pulse and corneal reflex, for example.

  These are repeated 12 or 24 hours later. Only then, is a patient pronounced brain stem dead.

  The public should be confident in this judgment, Dr Fu said: ''No one who has been certified properly as brain dead has come back to life.'' 



Brain death: the medical checks