Cerebral ischaemia can be global (complete in cardiac arrest or incomplete in hypotension) or focal (as in cerebrovascular disease). In complete global ischaemia, waste products accumulate and the integrity of cell membranes breaks down, leaking potassium out of cells and allowing calcium into cells. Neurotransmitters accumulate and the chance of brain recovery is thought to be small after 4-5 minutes.
The widespread use of CPR often brings unrealistic expectations of recovery following cardiac arrest. Prognosis after cardiac arrest has been extensively investigated. A summary is as follows:
• In a Dutch study, survival to discharge of 8% for witnessed arrests at home and 18% outside the home was observed.
• In a German study, survival to discharge of 5-3-16-6% after out-of-hospital resuscitation was observed.
• A review of 26 000 in-hospital arrests showed 15 2% survival to discharge.
• Another study showed 8% survival to discharge after in-hospital cardiac arrest.
• 20-50% survivors have neurological or neuropsychological deficits.
These studies include all types of cardiorespiratory arrest, ranging from ventricular fibrillation on a Coronary Care Unit to cardiorespiratory arrest in multiple organ failure on the
ICU. The British Medical Association and UK Royal College of Nursing guidelines on "decisions related to cardiopulmonary resuscitation" make the following points and discuss in detail the principles surrounding communication, advance decisionmaking, and legal issues (see Further Reading below):
• Cardiorespiratory function ceases as part of dying, thus CPR can theoretically be attempted on every individual prior to death. So it is essential to identify patients in whom cardiorespiratory arrest is a terminal event in their illness and in whom CPR would be inappropriate
• It should be made clear that a "Do not attempt CPR" refers to CPR only. All other treatments will still be given unless specified to the contrary.
• In the UK, it is good practice to discuss with patients their wishes regarding CPR, if appropriate, but it is not mandatory.
• In cases of incapacity, the role of the next of kin in England and Wales is to communicate what the patient would have wanted in the circumstances. They have no legal jurisdiction and clinical decisions remain the responsibility of the specialist in charge of the patient's care.
• Good communication is the essential ingredient in decision-making on CPR.
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