AssessmentsAdvanced cardiac life support (ACLS): Clinical practice
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 26-year-old man presents to the emergency department because of chest palpitations and lightheadedness. These symptoms began to appear one hour ago. The patient notes he does not take medications, has occasional beer on weekends, and does not smoke tobacco. He also denies any recreational drug use. Examination shows that the blood pressure is 112/66 mm Hg, pulse is 175/min, respirations are 16/min, and oxygen saturation is 98% on room air. Cardiac examination reveals S1 and S2 heart sounds without murmurs, and pulmonary exam is within normal limits. An ECG reading reveals a heart rate of 175/min with a QRS-complex of 95 milliseconds in regular rhythm. There are no discernable P-waves. A carotid sinus massage is performed, but has no effect on his symptoms or ECG. Which of the following is the most appropriate next step in management?
Advanced cardiac life support, or ACLS, is a structured way to respond to an unresponsive person with cardiac arrhythmias and cardiac arrest.
ACLS can be done by an individual or by a team that’s led by a team leader.
When we suspect a person may be in need of assistance, the first thing we need to do is determine their level of consciousness.
Talk loudly at them, rub their sternum, or apply pressure to their nail beds or ear lobes, while simultaneously checking for absent or abnormal breathing.
If they're not responsive, check their carotid pulse for about 10 seconds. If there's no pulse, first immediately activate the emergency response system to get more help and an AED or defibrillator. Then, move on to the ACLS algorithm.
The first thing to do is cardiopulmonary resuscitation or CPR, which combines chest compressions and artificial ventilation.
The big picture goal of CPR is to maintain blood flow to the brain while a patient is pulseless. Because the patient’s heart is not functioning, the team is mechanically squeezing the heart to ensure blood flows to the brain.
In a person over 8 years of age, chest compressions are done by placing the heel of one hand in the center of the chest, then placing the other hand on top, interlocking the fingers, and without flexing the elbows, pushing down on the chest to a depth of at least 5 centimeters or 2 inches - which is about the same size as a closed fist lengthwise.
Compressions are done at a rate of about 100 compressions per minute, which you can remember if you do them to the beat of “Staying alive” by the Bee Gees.
Additionally, the team attempts to artificially ventilate the patient so oxygen can enter the lungs and carbon dioxide can leave the lungs.
Artificial ventilation includes a variety of ways to assist respiration for a person who isn’t breathing or making sufficient respiratory effort on their own.
The options for ventilation usually involve a bag valve mask device to push air in.
A bag valve mask can be applied directly to the person’s mouth, or with an oral airway, a supraglottic airway like a laryngeal mask airway or LMA, or an endotracheal tube.
Directly applying the bag valve mask is the simplest option, since it’s just positioned over the nose and mouth of the patient, creating a tight seal so air does not escape around the sides of the mask.
If the bag valve mask is ineffective or difficult to perform, for instance due to an air leak because of an abnormally large face, then a supraglottic airway can be placed blindly into the airway through the mouth by pushing towards the throat.
This is generally prefered over endotracheal tube intubation because it’s faster to perform, and minimizes interruption of chest compressions.
Time and time again, researchers have shown that the most important part of ACLS is high-quality, uninterrupted chest compressions followed by defibrillation in those who need it.
That’s why intubation is done only if the patient can’t be ventilated by other means.
Continuous capnography should be performed in addition to clinical assessment for both confirming and monitoring correct tracheal tube placement, and for monitoring the quality of CPR and the return of spontaneous circulation.
Capnography is a recording of the amount of expired CO2 coming out of the tube.
When ventilating a patient in cardiac arrest, 100% oxygen should be used.
In a person over 8 years of age, the rate of compressions and breaths should be 30:2 for both single and 2 person CPR.
Finally, it’s important to have access with an intravenous - IV or intraosseous - IO - line in place as soon as possible, so that it’s ready in case you need to start giving medications.
Compressions and ventilation are started immediately on patients without a pulse.
However, as soon as an AED or cardiac monitor or defibrillator is available, using it becomes the most important step.
The ACLS team needs to troubleshoot the non-functioning heart by diagnosing the cardiac rhythm and defibrillating if indicated.
Chest compressions should be paused briefly to apply and use the AED or cardiac monitor to accurately assess the rhythm on the ECG and decide whether it’s a shockable rhythm like ventricular fibrillation or VFib and pulseless ventricular tachycardia or VT - or a non-shockable rhythm like asystole and pulseless electrical activity or PEA.
In ACLS, ECG interpretation is guided by three questions: is the rhythm fast or slow, are the QRS complexes wide or narrow, and is the rhythm regular or irregular.
Rhythms where a defibrillator can be used to shock a patient - shockable rhythms - are ones that are fast and have a wide QRS complex.
After that, VT is a regular rhythm, whereas VFib is an irregular rhythm.
If either VT or Vfib is found, defibrillation should be done as soon as possible.
Defibrillation with a synchronized shock is given when there’s a regular rhythm like in VT, whereas an unsynchronized shock is given when there’s no regular rhythm like in VFib.
The initial dose of energy that the defibrillator delivers typically ranges between 120 to 200 Joules, but a maximal dose can be used even on the first attempt.
Immediately after delivering the shock, chest compressions must be resumed right away without reassessing the rhythm.
After 2 minutes of chest compressions, there’s a new evaluation of the rhythm through ECG.