Cardiac arrest

A cardiac arrest is the cessation of normal circulation of the blood due to failure of the ventricles of the heart to contract effectively during systole. The resulting lack of blood supply results in cell death from oxygen starvation. Cerebral hypoxia, or lack of oxygen supply to the brain, causes victims to lose consciousness and stop breathing. more...

Cardiac arrest is a medical emergency that, if left untreated, invariably leads to death within seconds to minutes. The primary first-aid treatment for cardiac arrest is cardiopulmonary resuscitation (commonly known as CPR).

Etiology

Coronary heart disease (commonly known as coronary artery disease, or CAD) is the predominant disease process associated with sudden cardiac death in the United States. The incidence of CAD in individuals who suffer sudden cardiac death is between 64 and 90%. Other causes of cardiac arrest include electrocution and near-drowning, as well as other cardiac conditions such as the cardiomyopathies.

In children, cardiac arrest is typically caused by hypoxia from other causes such as near-drowning. With prompt treatment survival rates are high.

Every fatal injury or illness ultimately terminates in cardiac arrest, which is a natural part of the processes of death.

Treatable causes

There are 8 reversible causes of cardiac arrest, known as the "4Hs and 4Ts". They are looked for and treated by ambulance technicians/paramedics or by medical staff at the hospital while undertaking advanced life support, protocols for which will be used alongside any specific treatments for each of the causes. Lay rescuers performing basic life support can generally neither identify or treat them (with the exception of hypovolemia due to external bleeding), and so can offer only supportive treatment pending the arrival of emergency medical services.

4 Hs:-

• Hypoxia - A lack of oxygen to the brain and other vital organs. This is treated by providing the patient with oxygen, either through a bag-valve-mask device, or by inserting an endotracheal tube (intubation)

• Hypovolemia - A lack of circulating body fluids, principally blood. This is usually (though not exclusively) caused by some form of bleeding. Peri-arrest treatment includes giving IV Fluids and blood transfusions, and controlling the source of any bleeding - direct pressure for external bleeding, or emergency surgery (usually an immediate emergency thoracotamy on the ward, to clamp off the descending aorta and achieve haemostasis, the bleed is then repaired properly once the patient has regained circulation) for internal bleeding

• Hypo/Hyper-metabolic disorders - An abnormally high or low level of electrolytes such as potassium and calcium circulating the body. An arterial blood gas and blood electrolyte test are performed to find the problem, then IV crystalloids are given to correct it.

• Hypothermia - A low core body temperature, defined clinically as a temperature of less than 35 degrees celsius. The patient is re-warmed either by using a cardiac bypass or by irrigation of the body cavities (such as thorax, peritoneum, bladder) with warm fluids; or warmed IV fluids. CPR only is given until the core body temperature reached 30 degrees celsius, as defibrillation is ineffective at lower temperatures. Patients have been known to be successfully resuscitated after periods of hours in hypothermia and cardiac arrest, and this has given rise to the often quoted medical truism "You're not dead until you're warm and dead"

4 Ts:-

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