What is the recommended basic life support algorithm for an unresponsive adult without a pulse?

Basic Life Support for Unresponsive Adult Without Pulse

For an unresponsive adult without a pulse, immediately begin high-quality chest compressions at 100-120 compressions per minute with a depth of 5-6 cm, using a 30:2 compression-to-ventilation ratio, and apply the AED as soon as available. 1

Initial Assessment and Scene Safety

• Verify scene safety first before approaching to avoid becoming a second victim 2, 3
• Check for responsiveness by shouting and tapping the victim 1
• Simultaneously assess breathing and pulse within 10 seconds—look for no breathing or only gasping while checking for a pulse 1, 2
• If no pulse is detected within 10 seconds, immediately begin CPR without delay 2, 3

Activation of Emergency Response

• Activate the emergency response system immediately and retrieve the AED/defibrillator 1, 2
• If alone, activate emergency services first via mobile device if available, then begin CPR 4
• If multiple rescuers are present, one rescuer stays with the patient while another activates emergency services and retrieves equipment 2, 3

High-Quality CPR Technique

Chest compressions are the absolute priority and must be started immediately rather than beginning with ventilation 2:

• Compression depth: 5-6 cm (at least 2 inches) in adults 1, 2
• Compression rate: 100-120 compressions per minute 1, 2
• Hand position: Center of the chest on the lower half of the sternum with arms extended, elbows locked, and shoulders vertically above the patient's chest 2, 5
• Allow complete chest recoil between compressions—incomplete recoil prevents cardiac refilling and is a critical error 1, 2
• Minimize interruptions: Keep pauses less than 10 seconds 1, 2
• Compression-to-ventilation ratio: 30 compressions followed by 2 breaths for both single and two-rescuer scenarios in adults 1, 2
• Each ventilation should be delivered quickly (1 second per breath) with sufficient volume to produce visible chest rise 2
• Change compressor every 2 minutes or sooner if fatigued to maintain quality 1

Early Defibrillation Protocol

• Use the AED as soon as it becomes available—do not delay CPR to retrieve it, but apply immediately once present 1, 2
• After 2 minutes of CPR, check rhythm to determine if shockable (ventricular fibrillation or pulseless ventricular tachycardia) 1, 2
• If shockable rhythm: Deliver one shock immediately, then resume CPR for 2 minutes before reassessing rhythm 1, 2
• If non-shockable rhythm: Resume CPR immediately for 2 minutes without shock 1, 2
• Continue this cycle of 2 minutes of CPR followed by rhythm check until advanced life support providers arrive or the victim shows signs of movement 1

Advanced Life Support Considerations

Once advanced providers arrive or if you are trained in advanced life support:

• Establish IV/IO access as soon as feasible without interrupting compressions 2
• Administer epinephrine 1 mg IV/IO every 3-5 minutes for all cardiac arrest rhythms 1, 2
• For refractory ventricular fibrillation or pulseless ventricular tachycardia, consider amiodarone 300 mg bolus (second dose 150 mg) or lidocaine 1-1.5 mg/kg 1, 2
• Manage airway with bag-mask ventilation initially, then consider advanced airway (endotracheal intubation or supraglottic device) 1
• Once advanced airway is placed, provide continuous compressions with 1 breath every 6 seconds (10 breaths per minute) 1

Special Circumstances

• For suspected opioid overdose: Administer naloxone if available while continuing CPR 1, 2
• For compression-only CPR: Untrained rescuers or those unable/unwilling to provide ventilations should perform continuous chest compressions without breaths 2, 4, 5

Critical Pitfalls to Avoid

• Do not delay CPR to obtain history—immediate chest compressions are the priority 2, 3
• Do not perform prolonged pulse checks—if uncertain after 10 seconds, start CPR immediately 2, 3
• Do not provide inadequate compression depth or rate—compressions must be hard (5-6 cm) and fast (100-120/min) to be effective 2, 3, 4
• Do not lean on the chest between compressions—this prevents adequate cardiac refilling 2, 3, 4
• Do not interrupt compressions for prolonged periods—keep all pauses under 10 seconds 1, 2
• Do not hyperventilate—excessive ventilation is harmful and should be avoided 1