9.1 Bradycardia with Poor Perfusion

Why Pediatric Bradycardia Is Different from Adult Bradycardia

In adult ACLS, symptomatic bradycardia is often a primary cardiac conduction or rate problem, and atropine is the usual first drug while pacing equipment is prepared. In pediatric PALS, the physiology and the algorithm reverse that priority. Children far more often develop bradycardia as a secondary response to hypoxia, respiratory failure, or shock than as a primary electrical disease. The most common pre-arrest rhythm in infants and children is bradycardia—typically hypoxic bradycardia—not ventricular fibrillation.

That single fact drives the entire algorithm:

1. Airway, oxygenation, and ventilation come first — always.
2. CPR is triggered by rate plus perfusion, not by "flatline only."
3. Epinephrine, not atropine, is the primary medication for symptomatic bradycardia with poor perfusion.

If you apply adult ACLS muscle memory ("give atropine first, worry about ventilation later") on a PALS exam or megacode, you will choose the wrong branch.

What "bradycardia" means clinically in PALS

Absolute heart-rate cutoffs for "too slow" vary by age (a newborn’s normal rate is much higher than a school-age child’s). For algorithm purposes, PALS focuses less on debating whether 70/min is "bradycardic for age" and more on this decision node:

Is the heart rate <60/min with signs of poor perfusion despite adequate oxygenation and ventilation?

If yes, the child is treated as a pre-arrest / arrest-pathway patient: start CPR and follow the bradycardia algorithm aggressively. If the rate is low for age but perfusion is acceptable and oxygenation/ventilation are optimizing, you still support ABCs, monitor closely, and treat causes—but you do not automatically launch full CPR solely because a monitor number looks low without the full clinical picture.

Signs of poor perfusion you must recognize

Bradycardia with poor perfusion is not a "watch and wait" rhythm in a collapsing child. It is the last compensatory window before asystole or PEA.

Algorithm Step 1: Support Airway, Oxygenate, Ventilate

Because hypoxia is the dominant cause of pediatric bradycardia, the first interventions are not chronotropic drugs. Open and maintain the airway. Provide high-concentration oxygen. If breathing is inadequate, assist ventilation with a bag-mask device using proper technique (seal, appropriate tidal volumes, avoid excessive rate and pressure). Correct hypoxemia and hypercarbia when possible—restoring oxygen delivery frequently improves heart rate without any medication.

Attach monitors (ECG, pulse oximetry, blood pressure as available). Establish IV or IO access while airway and ventilation are being optimized, but do not let difficult access delay oxygenation and CPR when those are indicated. Identify the rhythm (sinus bradycardia, junctional, heart block, etc.) while you treat the child, not instead of treating the child.

The critical branch: HR <60/min + poor perfusion despite support

After you have provided adequate oxygenation and ventilation, reassess heart rate and perfusion:

• If heart rate remains <60/min and poor perfusion persists, begin high-quality CPR immediately (chest compressions + coordinated ventilation per pediatric BLS ratios for the number of rescuers and presence/absence of an advanced airway).
• Do not delay compressions waiting for a drug to "kick in" if the child already meets this CPR trigger.
• Continue supporting oxygenation throughout—CPR without an airway plan is incomplete care in hypoxic bradycardia.

This threshold is one of the highest-yield PALS numbers on the written exam and megacode. Memorize it as a full phrase, not only "less than 60":

HR <60/min with poor perfusion despite adequate oxygenation and ventilation → start CPR.

Why "despite adequate oxygenation and ventilation" matters

If you have not yet oxygenated and ventilated, the correct first move is still ABC support. Many children improve when hypoxia is reversed. The CPR trigger assumes you are not skipping ventilation and jumping straight to compressions for a child who only needed a patent airway and oxygen. Conversely, once support is adequate and the child remains bradycardic and poorly perfused, further delay of CPR is harmful.

Medications: Epinephrine First, Atropine Selectively

Epinephrine — primary drug

For symptomatic bradycardia with poor perfusion in children, epinephrine is the primary pharmacologic agent. Standard PALS teaching dose:

• 0.01 mg/kg IV/IO (commonly expressed as 0.1 mL/kg of 1:10,000 concentration)
• Repeat approximately every 3–5 minutes while bradycardia with poor perfusion persists and CPR/algorithm care continues

Epinephrine increases heart rate and myocardial contractility and raises systemic vascular resistance, supporting coronary and cerebral perfusion pressure during low-output states. In pediatric practice it addresses both the rate problem and the perfusion problem more reliably than atropine when the driver is hypoxia, shock, or myocardial depression rather than pure excess vagal tone.

Atropine — not first-line like adult ACLS

Atropine is a muscarinic antagonist that reduces vagal effects on the SA and AV nodes. In PALS it is not the routine first drug for all symptomatic bradycardia. Reserve atropine when:

• Bradycardia is clearly related to increased vagal tone (e.g., during airway manipulation),
• Bradycardia is due to AV block where a vagolytic trial is reasonable while preparing definitive care, or
• Epinephrine is unavailable and a chronotropic/vagolytic agent is needed as a bridge.

The 2025 Pediatric Bradycardia With a Pulse Algorithm states the dose precisely: atropine 0.02 mg/kg IV/IO, may repeat once, minimum dose 0.1 mg, maximum single dose 0.5 mg. Both bounds are printed on the algorithm—know them as stated numbers, not approximations. It will not fix hypoxia, and it will not replace CPR when the HR <60 + poor perfusion trigger is met.

One nuance worth separating. The 2025 guidelines also address atropine as a premedication for emergency intubation, where a dose of 0.02 mg/kg with no minimum dose may be considered. The historical 0.1 mg floor traced back to a small 1971 surgical study, and later data in infants who received less than 0.1 mg found no paradoxical bradycardia. So the same drug carries two different framings: the bradycardia-with-a-pulse algorithm keeps the 0.1 mg minimum, while the intubation-premedication recommendation drops it. On an exam stem, read which situation you are in before you pick a bound.

Exam trap: adult vs pediatric first drug

Identify and Treat the Cause

Drugs and CPR buy time; cause treatment saves the child. Systematically consider:

Also consider hypoglycemia, severe electrolyte disturbances, and tension physiology or tamponade when the broader H’s and T’s apply. Bradycardia during intubation should prompt a check that oxygenation was optimized before and during the attempt and that vagal stimulation is recognized.

Clinical scenario (synthesis)

A 9-month-old with bronchiolitis becomes lethargic. Heart rate falls from 160 to 52/min; skin is mottled; pulses are weak. The team opens the airway, delivers high-flow oxygen, and begins assisted bag-mask ventilation. After effective ventilations, the rate remains 50/min with poor perfusion. Start CPR. Give epinephrine 0.01 mg/kg IV/IO, continue high-quality compressions and ventilation, reassess, and treat the respiratory failure driving the hypoxia. Choosing atropine as the first drug while delaying ventilation and CPR would be the classic wrong pathway.

Master this section and you own a large slice of the Pediatric Cardiac Arrest & Rhythms domain: pre-arrest recognition, the <60 CPR trigger, and the pediatric drug priority that differs from adult ACLS.