Advanced life support (ALS) is a set of emergency medical interventions used to treat cardiac arrest, severe breathing failure, and other immediately life-threatening conditions. It goes beyond basic CPR and defibrillation by adding medications, advanced airway devices, cardiac monitoring, and real-time interpretation of heart rhythms. In most settings, the term is used interchangeably with Advanced Cardiovascular Life Support (ACLS), which is the specific certification and protocol system maintained by the American Heart Association.
How ALS Differs From Basic Life Support
Basic life support (BLS) covers the fundamentals: chest compressions, rescue breathing, use of an automated defibrillator, bleeding control, and splinting. These are non-invasive techniques that bystanders and first responders can perform with relatively brief training. ALS builds on every one of those skills but adds invasive procedures that require clinical training and equipment typically found in ambulances or hospitals.
The key additions in ALS include placing a tube into the airway to secure breathing, starting an IV line to deliver fluids and medications directly into the bloodstream, reading and interpreting heart rhythms on a cardiac monitor, and delivering precisely timed electrical shocks (synchronized cardioversion) based on what those rhythms show. In short, BLS keeps blood and oxygen moving until help arrives. ALS attempts to identify and fix the underlying cause of the emergency while keeping that circulation going.
Airway Management in ALS
One of the biggest distinctions between basic and advanced life support is how the airway is managed. In BLS, rescuers use a simple head-tilt or jaw-thrust to open the airway and a bag-mask device to push air into the lungs, pausing compressions every 30 pushes to deliver 2 breaths.
ALS providers have two main tools beyond that. The first is an extraglottic airway device, a flexible tube inserted into the throat that sits above the vocal cords and creates a seal for ventilation. It requires less training than full intubation and works well in chaotic field conditions where lighting is poor and patient positioning is difficult. The second is endotracheal intubation, where a tube is passed through the vocal cords directly into the windpipe. The European Resuscitation Council considers this the gold standard for airway control, though it demands a skilled practitioner to perform safely.
Once either advanced airway is in place, the rescue changes significantly. Rescuers no longer need to pause compressions to give breaths. Instead, chest compressions continue without interruption while a breath is delivered every 6 seconds (about 10 breaths per minute). This uninterrupted compression strategy improves blood flow to the brain and heart during resuscitation.
Medications Used During ALS
Drug therapy is a core component of ALS that has no equivalent in basic life support. The medications serve two main purposes: restarting and stabilizing the heart’s electrical activity, and maintaining blood pressure so organs receive oxygen.
Epinephrine (adrenaline) is the primary drug in cardiac arrest. It constricts blood vessels and stimulates the heart, improving the chances that defibrillation will restore a normal rhythm. The standard protocol calls for a dose every 3 to 5 minutes throughout the resuscitation effort.
For certain dangerous heart rhythms that don’t respond to defibrillation alone, providers use antiarrhythmic drugs. The first-line option is given as a larger initial dose followed by a smaller second dose if needed. A second antiarrhythmic serves as an alternative. These medications work by stabilizing the heart’s electrical signaling so it can return to a coordinated rhythm.
Identifying Reversible Causes
ALS isn’t just about performing procedures. A major part of the training focuses on diagnostic reasoning during the arrest itself. Providers are taught to systematically consider twelve reversible conditions, commonly called the “H’s and T’s,” that could be causing or worsening the cardiac arrest. Identifying the right one can mean the difference between a failed resuscitation and a save.
- Hypovolemia: severe blood or fluid loss
- Hypoxia: dangerously low oxygen levels
- Hydrogen ion excess (acidosis): the blood becomes too acidic, often from prolonged oxygen deprivation
- Hyperkalemia or hypokalemia: potassium levels too high or too low, both of which disrupt heart rhythm
- Hypothermia: core body temperature drops low enough to cause the heart to stop
- Toxins: drug overdoses or poisonings
- Tamponade: fluid compressing the heart from outside, preventing it from filling
- Tension pneumothorax: air trapped in the chest cavity, collapsing a lung and compressing the heart
- Thrombosis: a blood clot blocking a coronary artery (heart attack) or pulmonary artery (pulmonary embolism)
Each of these has a specific treatment. A tension pneumothorax, for instance, requires releasing the trapped air with a needle. Hyperkalemia can be treated with IV calcium and other agents that shift potassium back into cells. Without identifying and treating the root cause, even flawless CPR and medications may not bring someone back.
What Happens After the Heart Restarts
Getting a pulse back is not the end of ALS care. Post-resuscitation management is a critical phase because the body sustains significant injury during cardiac arrest, and the hours that follow carry a high risk of the heart stopping again or the brain suffering permanent damage.
Oxygen levels are carefully controlled, targeting a blood oxygen saturation between 90% and 98%. Both too little and too much oxygen can harm recovering tissues, so providers avoid leaving someone on maximum oxygen once they can measure levels accurately. Blood pressure is maintained at a minimum threshold to ensure the brain and other organs receive adequate blood flow.
Temperature control is another pillar of post-arrest care. For patients who remain unconscious after resuscitation, current guidelines recommend actively managing body temperature for at least 36 hours. The goal is to prevent fever, which worsens brain injury. Research has not conclusively shown that cooling to a specific lower target is better than simply preventing the temperature from rising, but none of the major trials found that cooler targets caused harm either.
Who Gets Trained in ALS
ALS certification is required for a broad range of healthcare professionals, though the specific requirements vary by hospital and role. Emergency physicians, cardiologists, anesthesiologists, and hospitalists typically maintain ACLS certification. Nurse anesthetists, physician assistants in emergency departments and hospital medicine, and advanced practice providers with sedation privileges are also generally required to be ACLS-certified.
Paramedics are the primary ALS providers outside the hospital. Their scope of practice includes most ALS interventions, from advanced airway placement to cardiac medications, performed in the back of an ambulance or at the scene of an emergency. Emergency medical technicians (EMTs), by contrast, operate at the BLS level. This distinction shapes how ambulance systems are designed: many communities staff ambulances with both a paramedic (ALS) and an EMT (BLS) working as a team.
ACLS certification courses typically last one to two days and must be renewed every two years. The training emphasizes team-based resuscitation, real-time rhythm interpretation, and structured decision-making under pressure, all practiced through simulated cardiac arrest scenarios.