An Automated External Defibrillator (AED) is a portable device designed to deliver an electrical shock to the heart during sudden cardiac arrest. It analyzes the heart’s electrical activity and, if a shockable rhythm is detected, advises and delivers a controlled electrical current. The primary goal of an AED is to restore a normal heart rhythm, significantly increasing survival chances. Its presence in public places allows bystanders to provide immediate life-saving intervention before professional medical help arrives.
What “No Shock Advised” Means
When an AED states “no shock advised,” it signifies the device has completed its analysis of the person’s heart rhythm and determined an electrical shock would not be beneficial. It means the person’s specific cardiac rhythm is not one that responds to defibrillation.
This determination does not mean the person is not in cardiac arrest. Instead, it indicates their heart’s electrical activity, or lack thereof, falls into a category that defibrillation cannot correct. Understanding this distinction is important for rescuers to continue appropriate care.
Why an AED May Not Advise a Shock
An AED may advise against a shock for reasons related to the heart’s electrical activity or external factors. One common reason is the presence of non-shockable rhythms, such as Asystole. Asystole, often called a “flatline,” means there is no electrical activity in the heart to be reset by a defibrillation shock.
Pulseless Electrical Activity (PEA) is another non-shockable rhythm. In PEA, the heart shows organized electrical activity on an electrocardiogram, but this activity does not result in effective mechanical pumping action, meaning there is no pulse.
An AED will also not advise a shock if the person is conscious, responsive, or has a palpable pulse, indicating they are not in cardiac arrest. The device’s sensors detect the heart’s normal electrical signals or the presence of a circulating blood flow, correctly identifying that defibrillation is unnecessary or potentially harmful.
Excessive movement during the AED’s rhythm analysis can also lead to a “no shock advised” reading due to interference. Any significant patient movement, such as tremors or repositioning, can distort the electrical signals the AED is trying to analyze. This interference prevents the device from accurately detecting a true shockable rhythm, leading it to withhold a shock for safety reasons.
Next Steps After “No Shock Advised”
Upon receiving a “no shock advised” message from an AED, the rescuer must immediately continue high-quality chest compressions without interruption. For rhythms like Asystole and PEA, continuous chest compressions are the only way to maintain some blood flow to the brain and other vital organs. This consistent blood flow is important to sustaining life until advanced medical care arrives.
The AED should remain attached to the person throughout the resuscitation effort. The device will continue to analyze the heart rhythm approximately every two minutes, and it might advise a shock if the rhythm changes. Removing the pads or disconnecting the device would interrupt this ongoing monitoring and potential for future intervention.
It is important to ensure that emergency medical services (EMS) have been called and are en route to the location. Whether through a bystander calling 911 or the local emergency number, professional medical help provides advanced interventions beyond what an AED and basic CPR can offer. Their arrival brings specialized equipment and medications necessary for definitive care.