By Dr Ananya Mandal, MD
A cardiac arrest is a sudden failure of the heart to pump blood around the circulatory system to the vital organs. This is a serious medical emergency. For every minute that a person is in cardiac arrest before a defibrillator is available, the chances of survival are reduced by about 10%. Cardiopulmonary resuscitation along with defibrillation of the heart can start the heart's pumping rhythm again.
Cardiac arrest outside of hospital
Cardiac arrest that occurs outside of a hospital setting mostly follows a heart attack or a severely altered heart rhythm caused by ventricular fibrillation. In these cases, defibrillation is key to managing the arrest. Defibrillation equipment is available in most ambulances and needs to be administered as soon as possible.
Cardiac arrest inside hospital
Treatment of cardiac arrest that is given inside hospitals follows advanced life support protocols. In the United States, protocols are outlined by the Advanced Cardiac Life Support for adults, by the Pediatric Advanced Life Support for children and by the Neonatal Advanced Life Support for newborns.
All management of cardiac arrest begins with CPR or cardiopulmonary resuscitation and defibrillation. Hospitals' protocols for resuscitation are often initiated by a Code Blue which indicates the onset of cardiac arrest or respiratory failure. For adequate CPR, three things need to be ensured:
A = Airways are opened by tilting the head back and lifting the chin
B = Breathing is checked for by looking for and listening out for signs of breathing
C = Circulation is attempted with cardiac compression
In hospitals, the opening of airways can be secured with the use of an endotracheal tube. Intravenous fluids and medications that stimulate the heart and make it pump can also be used and ventilation can ensure that adequate oxygenation and circulation is maintained. Medications used to make the heart pump include adrenaline and dopamine or dobutamine.
Patients with ventricular fibrillation may have unstable or pulseless ventricular tachycardia that must be immediately treated with defibrillation. Medications such as amiodarone may also be administered. In the complete absence of any electrical activity of the heart, epinephrine and atropine are used to bring back the heart's pumping action.
Before cardiac activity is restored, some set-ups may induce hypothermia or cool the body. This is called therapeutic hypothermia and helps to decrease the likelihood of ischemic injury following a period of impaired blood flow.
Immediately after the cardiac arrest is managed, there is a risk of recurrence. Preventive management with medications and life support aims to reduce this risk.
Reviewed by Sally Robertson, BSc