Tuesday, April 12, 2011

What causes cardiac arrest? and Treatment for cardiac arrest

Introduction to sudden cardiac arrest:
A natural disaster hits, the power goes off and the lights go out. It's a common scene that plays out during hurricane and tornado seasons, and it's very similar in trying to explain sudden cardiac arrest. The heart sustains an insult, the electricity is short circuited, the heart can't pump, and the body dies.

              The heart is an electrical pump, where the electricity is generated in special pacemaker cells in the upper chamber, or atrium, of the heart. This electrical spark is carried through pathways in the heart so that all the muscle cells contract at once and produce a heart beat. This pumps blood through the heart valves and into all the organs of the body so that they can do their work.

            This mechanism can break down in a variety of ways, but the final pathway in sudden death is the same: the electrical system is irritated and fails to produce electrical activity that causes the heart to beat. The heart muscle can't supply blood to the body, particularly the brain, and the body dies. Ventricular fibrillation (V Fib) is the most common reason for sudden death in patients. Without a coordinated electrical signal, the bottom chambers of the heart (ventricles) stop beating and instead, jiggle like Jello. Ventricular Fibrillation is treated with electrical shock, but for it to be effective, the shock usually needs to happen within less than four to six minutes, not only for it to be effective, but also to minimize brain damage from lack of blood and oxygen supply. Automatic external defibrillators (AEDs) are commonly available in public places to allow almost anybody to treat sudden death.

What is cardiac arrest?
Cardiac arrest is the sudden, abrupt loss of heart function. The victim may or may not have diagnosed heart disease. It's also called sudden cardiac arrest or unexpected cardiac arrest. Sudden death (also called sudden cardiac death) occurs within minutes after symptoms appear.A cardiac arrest is different from (but may be caused by) a heart attack, where blood flow to the muscle of the heart is impaired.

                Arrested blood circulation prevents delivery of oxygen to the body. Lack of oxygen to the brain causes loss of consciousness, which then results in abnormal or absent breathing. Brain injury is likely if cardiac arrest goes untreated for more than five minutes.For the best chance of survival and neurological recovery, immediate and decisive treatment is imperative.

What causes cardiac arrest?
The most common underlying reason for patients to die suddenly from cardiac arrest is coronary heart disease. Most cardiac arrests that lead to sudden death occur when the electrical impulses in the diseased heart become rapid (ventricular tachycardia) or chaotic (ventricular fibrillation) or both. This irregular heart rhythm (arrhythmia) causes the heart to suddenly stop beating. Some cardiac arrests are due to extreme slowing of the heart. This is called bradycardia.

Other factors besides heart disease and heart attack can cause cardiac arrest. They include respiratory arrest, electrocution, drowning, choking and trauma. Cardiac arrest can also occur without any known cause.

What Are the Symptoms of Sudden Cardiac Arrest?
Some people may experience symptoms of sudden cardiac arrest, such as a racing heartbeat or they may feel dizzy, alerting them that a potentially dangerous heart rhythm problem has started. In over half of the cases, however, sudden cardiac arrest occurs without prior symptoms.
However, due to inadequate cerebral perfusion, the patient will be unconscious and will have stopped breathing. The main diagnostic criterion to diagnose a cardiac arrest, (as opposed to respiratory arrest which shares many of the same features), is lack of circulation, however there are a number of ways of determining this.

Cardiac arrest is synonymous with clinical death.A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse is the gold standard for diagnosing cardiac arrest, but lack of a pulse (particularly in the peripheral pulses) may be a result of other conditions (e.g. shock), or simply an error on the part of the rescuer. Studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals or lay persons.
                 Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. The Resuscitation Council (UK), in line with the ERC's recommendations and those of the American Heart Association,have suggested that the technique should be used only by healthcare professionals with specific training and expertise, and even then that it should be viewed in conjunction with other indicators such as agonal respiration.

With positive outcomes following cardiac arrest unlikely, an effort has been spent in finding effective strategies to prevent cardiac arrest. With the prime causes of cardiac arrest being ischemic heart disease, efforts to promote a healthy diet, exercise, and smoking cessation are important. For people at risk of heart disease, measures such as blood pressure control, cholesterol lowering, and other medico-therapeutic interventions are used.

What is the treatment for sudden cardiac arrest?
The vast majority of people whose heart stops beating unexpectedly have ventricular fibrillation. The definitive treatment for this is defibrillation using electricity to shock the heart back into a regular rhythm. With technological advances, AEDs are now a routine sight wherever people congregate.

              Communities which institute public CPR education, use of AEDs, and rapid activation of 911 emergency medical services have dramatically increased survival rates from sudden cardiac arrest. Unfortunately, because the brain is so sensitive to the lack of oxygen and blood flow, unless treatment occurs within four to six minutes, there is a high risk of some permanent brain damage.

           Should the patient survive to be transported to the hospital, the reason for collapse and sudden death will need to be diagnosed. Regardless, the ABCs of resuscitation will be re-evaluated. Airway, Breathing, and Circulation (heart beat and blood pressure) will be supported, and admission to an intensive care unit is most likely.

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