Post Resuscitation Care
A cardiac arrest is defined when the heart stops beating, the person stops breathing and the brain shuts down due to a lack of blood flow. It has been estimated that there are over one million cardiac arrests events that take place in North America and the European Union per year. Cardiac arrest, which is synonymous with death from a clinical point of view is a potentially salvageable situation, and thus in the early stages when people have died it may be possible to restore the blood flow and restart the heart through medical intervention and thus bring the person back to life. Medical studies have shown that after attempts to restart the heart, it is possible to reactivate the heart in 20-50% of cases, however, sadly those people who have originally been revived still die due to various complications. Actual survival rates to discharge from hospital are much lower, and reflect the initial period of insult to the body from cardiac arrest. In the cases in which a cardiac arrest had taken place outside a hospital setting, the survival rates to discharge vary from 1 – 15% and in the cases of cardiac arrest that take place in a hospital setting discharge rates at best are about 25%.
Following the initial recovery of a heart beat after resuscitation attempts, which may take place in up to 50% of cases of cardiac arrest there is then significant damage that takes place to the vital organs of the body such that a majority of the people eventually die from complications. It is estimated that one third of cases die from brain and neurological damage, one third die from heart and myocardial damage and another third die from the various inflammatory processes that have taken place.
Cardiac arrest, is the most extreme type of bodily damage as by definition it is the first stage of death during which time there is total body ischaemia (lack of oxygen). In the brain it has been shown that the oxygen levels that are stored within the cells are rapidly depleted within about 2 minutes to reach a point in which they reach zero. Furthermore at the same time there is a rapid depletion of energy stores (ATP) and this leads to an accumulation of toxic materials that can no longer be cleared out of the cells. These include molecules such as lactate and acid. There is then massive cell damage and ultimately cell death as a consequence of these processes.
If the medical teams who are resuscitating the patient can restore the heart beat and thus restore blood flow into the brain there is then a danger of further damaging the brain. This is called reperfusion injury and mainly takes place due to high levels of oxygen free radicals which are a toxic form of oxygen that can actually cause cell injury and damage.
The latest medical guidelines published at the end of 2008 have set forward the means to try and limit the injury caused by reperfusion of the brain once the heart beat has been restored. The guidelines also make recommendations to limit the injury that is caused by damage to the heart and also the inflammatory process that ensues after a cardiac arrest.
Current guidelines strongly recommend that people who have recovered from a cardiac arrest should be cooled to approximately 34o which limits brain cell activity during the first 24 hours after recovery and hence limits the injury that is caused by reperfusion of the brain. It is also strongly recommended that complications that arise as a consequence of a cardiac arrest such as seizures or fevers as well as blood and glucose control should be optimized so as to limit the metabolism of brain cells and thus limit the amount of damage that takes place. New research is now focusing on attempts to try and cool the brain during the period of cardiac arrest (as opposed to after recovery from a cardiac arrest which is being carried out in most medical centres at this time) in which most of the damage is taking place so that patients who recover and whose heartbeat is restored will end up with less brain cell damage in the future. The results of such studies have not yet been published extensively.
Other significant recommendations include insuring that a patient’s blood pressure and breathing patterns on a life support machine are optimally managed and that in many cases patients should be evaluated for an early invasive test (cardiac catheterisation) which would assess whether there are blockages to the blood vessels that supply the heart, since many studies have shown that up to 80% of people who have a cardiac arrest have an underlying blockage of one of the blood vessels in the heart which leads to a heart attack.
The area of post resuscitation care is a very exciting development within the field of cardiac arrest, since one of the optimal goals for any physician or nurse taking care of patients who have suffered a cardiac arrest is to ensure that there will be as little brain damage and damage to other major organs as possible. There will be new guidelines published in 2010 that are likely to focus more on ways to limit damage after recovery from a cardiac arrest.