The “Chain of Survival” uses the metaphor of a chain to describe the sequential steps required to maximize the chance of survival following sudden cardiac arrest. For the average person witnessing an event outside of a medical facility, the traditional protocol involves five distinct links. Current international resuscitation guidelines, such as those from the American Heart Association, have since been updated to include a sixth link to encompass the full journey of a survivor. This standardized protocol ensures that a patient receives the right care at the right time, preventing delays that reduce survival rates.
The Five Essential Links of the Out-of-Hospital Chain
The standard sequence for an Out-of-Hospital Cardiac Arrest (OHCA) begins with the layperson’s immediate action: the Recognition and Activation of the Emergency Response System. Recognizing cardiac arrest, often indicated by sudden collapse and unresponsiveness, is the first step that must be taken without delay. Immediate activation involves calling 911 or the local emergency number to bring professional help to the scene.
The second link is Early Cardiopulmonary Resuscitation (CPR), a mechanical intervention that maintains blood flow to the brain and other vital organs until the heart can be restarted. High-quality chest compressions are emphasized, requiring a rescuer to push hard and fast at a rate of 100 to 120 compressions per minute. For an adult, compressions should reach a depth of at least 2 to 2.4 inches (5 to 6 centimeters), allowing the chest to fully recoil after each push.
The third link, Rapid Defibrillation, is the only action that can correct the chaotic electrical rhythm, known as ventricular fibrillation, which often causes sudden cardiac arrest. The chance of survival decreases by approximately 10% for every minute defibrillation is delayed. Using an Automated External Defibrillator (AED) as soon as it arrives is important, as the device is designed to be used by untrained bystanders to deliver an electrical shock.
The fourth link focuses on Effective Advanced Resuscitation, which commences once Emergency Medical Services (EMS) personnel arrive. Paramedics and advanced providers take over with specialized treatments, including antiarrhythmic medications, advanced airway management, and sophisticated monitoring.
This step transitions the patient from basic life support to a higher level of care, aiming to stabilize the heart rhythm and maintain circulation.
The final acute step is Integrated Post-Cardiac Arrest Care, delivered upon the patient’s arrival at the hospital. This involves a coordinated team effort to address the underlying cause of the cardiac arrest and mitigate secondary injury, particularly to the brain. Common interventions include targeted temperature management to protect neurological function and percutaneous coronary intervention (PCI) if the cause was a heart attack. This intensive care phase ensures the patient’s circulation and organ function are stabilized following the return of spontaneous circulation (ROSC).
Contextualizing the Chains: Different Steps for Different Settings
While the Out-of-Hospital Chain of Survival provides a standardized protocol, the sequence varies significantly when an event occurs within a medical facility. The In-Hospital Cardiac Arrest (IHCA) Chain of Survival reflects the controlled environment and the presence of trained medical staff. This distinction is necessary because the resources and speed of intervention are different in a hospital setting.
The IHCA chain begins with Surveillance and Prevention, recognizing that a patient’s condition often deteriorates hours before a full cardiac arrest. Medical staff utilize continuous monitoring and early warning systems to identify subtle changes in heart rate, blood pressure, or respiration that signal an impending crisis.
This proactive approach aims to prevent the arrest entirely, rather than just respond to it.
The second IHCA link is the Recognition and Activation of the Rapid Response Team (RRT), which differs from calling 911. The RRT is an internal hospital team of specialized clinicians trained to stabilize acutely ill patients outside of the intensive care unit. This in-house activation allows for a much faster response time, often within minutes, as advanced equipment and trained personnel are already present. Subsequent links, such as high-quality CPR and defibrillation, remain fundamentally the same, but are performed by highly trained professionals using immediately available hospital equipment.
The Critical Sixth Link: Post-Cardiac Arrest Recovery
The most recent addition to the modern Chain of Survival is the sixth link: Recovery. This step was formally incorporated to recognize that survival from cardiac arrest does not end upon discharge from the hospital. Recovery encompasses the long-term physical, cognitive, and emotional needs of the survivor and their caregivers.
This link emphasizes ongoing medical management and rehabilitation tailored to the specific impairments a patient may experience, such as physical weakness, neurological deficits, or memory issues. Beyond physical rehabilitation, the recovery phase addresses the psychological toll of the event, focusing on assessing and treating conditions like anxiety, depression, and post-traumatic stress disorder. The inclusion of this sixth link stresses a holistic, patient-centered approach that supports the survivor’s return to a functional life.