6.2 Cardiogenic Shock

Pump Failure: Defining Cardiogenic Shock

Cardiogenic shock is inadequate tissue perfusion caused by primary cardiac pump failure. Stroke volume and cardiac output fall because the myocardium cannot contract effectively, because heart rate/rhythm is critically abnormal, or because structural heart disease prevents effective forward flow. Unlike pure hypovolemic shock, preload is often normal or high; giving large fluid volumes can worsen pulmonary edema and right-heart failure. Unlike pure distributive shock, the core problem is not primarily vasodilation—it is inadequate cardiac output.

PALS expects you to recognize cardiogenic features quickly so you do not automatically apply the same 20 mL/kg × multiple boluses pattern used for uncomplicated hypovolemia. Misclassification is a classic exam and real-world trap: the child with myocarditis can look "septic" (tachycardic, poorly perfused, sometimes febrile) until hepatomegaly, rales, and a gallop declare pump failure.

Major pediatric causes

Any cause of prolonged hypoxia, acidosis, or coronary underperfusion can convert another shock type into a mixed picture with cardiogenic features—another reason continuous reassessment matters.

Recognition: Signs That Point to the Pump

Use the evaluate–identify–intervene loop. On the Pediatric Assessment Triangle, appearance is often abnormal (irritable, lethargic, or anxious), work of breathing may be increased from pulmonary edema or compensatory tachypnea, and circulation to skin is typically cool and mottled with delayed capillary refill.

Exam-critical findings

What cardiogenic shock is not

• Isolated mild dehydration without congestion signs after gastroenteritis is hypovolemic until proven otherwise.
• Warm, bounding, flash-refill septic physiology without congestion is distributive until myocardial dysfunction appears.
• Equal breath sounds with sudden unilateral absence after trauma lean toward tension pneumothorax (obstructive), not primary myocarditis.

Compensated vs hypotensive cardiogenic shock

Children maintain blood pressure with intense tachycardia and vasoconstriction until late. Normal blood pressure does not exclude cardiogenic shock. Hypotension for age, altered mentation, and progressive bradycardia signal decompensation and imminent arrest risk. Treat perfusion, not the blood-pressure number alone.

Management Priorities for Cardiogenic Shock

1. Support oxygenation and ventilation

Give oxygen to correct hypoxemia. Pulmonary edema may require careful positive-pressure support; expert airway management is often needed. Avoid prolonged hypoxia—it further depresses myocardial function. Likewise, avoid unnecessary hyperoxia once oxygenation is adequate in monitored settings, but do not withhold oxygen from the critically hypoxemic child while you debate targets.

2. Cautious fluids — 5–10 mL/kg with reassessment

If the child may be hypovolemic and cardiogenic features are uncertain, or if some preload is needed, give a smaller isotonic fluid challenge of about 5–10 mL/kg, then reassess heart rate, perfusion, lung sounds, liver size, and work of breathing. Stop further fluid if congestion worsens. This is the highest-yield contrast with hypovolemic shock management (10–20 mL/kg repeated boluses). Exam items frequently test whether you choose the smaller aliquot when hepatomegaly or rales are present.

3. Inotropes and vasoactive support

Children with cardiogenic shock usually need inotropic and/or vasoactive infusions (agent selection per PALS, institutional septic/cardiogenic pathways, and pediatric critical-care consultation). The therapeutic goal is improved cardiac output and end-organ perfusion—not simply a higher blood-pressure number from pure vasoconstriction that increases afterload excessively. Continuous ECG and blood-pressure monitoring, reliable IV/IO access, and ICU-level care are required.

4. Treat the rhythm

If tachyarrhythmia is causing shock (for example SVT with poor perfusion), follow the PALS tachycardia algorithms: synchronized cardioversion for unstable patients, adenosine pathway considerations when appropriate for stable-enough narrow-complex SVT (Chapter 9–10). If severe bradycardia with poor perfusion persists despite oxygenation and ventilation, follow the bradycardia algorithm (CPR if heart rate remains <60/min with poor perfusion despite support; epinephrine; treat causes). Restoring an effective rate and rhythm can reverse "cardiogenic" shock that is actually rate-related.

5. Avoid hypoxia and severe acidosis; seek expert/ICU support early

Hypoxia and profound acidosis impair catecholamine responsiveness and myocardial performance. Support ventilation and perfusion while preparing transfer to a pediatric ICU or involvement of cardiology/critical care. Mechanical support strategies and advanced heart-failure therapies are beyond basic PALS technical skills but are the destination of the referral pathway—your job is early recognition, safe initial stabilization, and escalation.

6. Medications to handle carefully

Do not routinely push large fluid volumes, and do not assume every poorly perfused child needs the hypovolemic fluid recipe. Avoid agents or interventions that markedly increase myocardial oxygen demand without improving output unless directed by experts. Correct hypoglycemia and critical electrolyte abnormalities that worsen arrhythmias and contractility.

Differentiating at the Bedside (Exam Synthesis)

Ask three questions on every shock vignette:

1. Volume loss history? Diarrhea, vomiting, bleeding, burns → hypovolemic likely.
2. Infection + vasodilation signs? Fever, warm shock features → distributive/septic pathway.
3. Congestion + pump clues? Hepatomegaly, rales, gallop, cardiomegaly, known heart disease, arrhythmia → cardiogenic strategy.

Mixed shock is real (septic myocardial depression, cardiogenic shock with relative hypovolemia). When mixed, reassess after every small intervention and escalate early.

Clinical scenario

A 14-month-old has 3 days of viral symptoms, now with lethargy, heart rate 190/min, cool mottled skin, delayed capillary refill, enlarged liver, and rales at both bases. Blood pressure is low-normal for age. This is cardiogenic shock until proven otherwise (myocarditis/cardiomyopathy pattern). Priorities: oxygen, monitors, careful 5–10 mL/kg fluid only if indicated with immediate reassessment, early vasoactive/inotropic support, ECG to exclude arrhythmia, avoid repeated large boluses, and urgent critical-care/cardiology involvement. Choosing repeated 20 mL/kg boluses without reassessment would be the dangerous wrong answer.

Chapter 6.3 covers obstructive causes that can mimic pump failure until the obstruction is relieved.