What is the definition of shock in pediatrics?

Definition of Shock in Pediatrics

Shock in pediatrics is defined as a state of inadequate blood flow and oxygen delivery to meet tissue metabolic demands, resulting in energy failure and organ dysfunction. 1

Clinical Diagnosis of Shock

Shock should be clinically diagnosed before hypotension occurs, as hypotension is a late and often terminal sign in pediatric patients. The American College of Critical Care Medicine provides clear criteria for recognizing shock in children:

Key Diagnostic Criteria

1. Suspected infection (manifested by hypothermia or hyperthermia)
2. Clinical signs of inadequate tissue perfusion including any of the following:
   • Decreased or altered mental status (irritability, inappropriate crying, drowsiness, confusion, poor interaction with parents, lethargy, or becoming unarousable)
   • Prolonged capillary refill >2 seconds (cold shock)
   • Diminished pulses (cold shock)
   • Mottled cool extremities (cold shock)
   • Flash capillary refill (warm shock)
   • Bounding peripheral pulses and wide pulse pressure (warm shock)
   • Decreased urine output <1 mL/kg/h 1

Important Clinical Considerations

• Hypotension is not necessary for the clinical diagnosis of shock but confirms the diagnosis when present with suspected infection 1
• Shock progresses along a continuum from compensated to decompensated states 1
• In compensated shock, tachycardia and increased systemic vascular resistance (vasoconstriction) maintain cardiac output and perfusion pressure
• Decompensation occurs when these mechanisms fail, resulting in hypotensive shock 1

Types of Shock in Pediatrics

Shock can be categorized into four main types:

1. Hypovolemic shock: Most common type in children, including shock due to hemorrhage 1
2. Distributive shock: Includes septic, anaphylactic, and neurogenic shock
3. Cardiogenic shock: Due to primary cardiac dysfunction
4. Obstructive shock: Due to obstruction of blood flow 2

Hemodynamic Patterns in Pediatric Shock

Children with shock may present with different hemodynamic patterns:

• Cold shock: Characterized by vasoconstriction, prolonged capillary refill, diminished pulses, and mottled cool extremities
• Warm shock: Characterized by vasodilation, flash capillary refill, bounding pulses, and wide pulse pressure 1

Monitoring Parameters

Effective monitoring of pediatric shock includes:

• Pulse oximetry
• Continuous electrocardiography
• Blood pressure and pulse pressure
• Temperature
• Urine output (target >1 mL/kg/h)
• Glucose and ionized calcium levels 1
• Mental status assessment
• Capillary refill time (target ≤2 seconds)
• Quality of peripheral and central pulses 1

Early Warning Signs

Threshold heart rates associated with increased mortality in critically ill infants and children:

• Infants: HR <90 or >160 beats per minute
• Children: HR <70 or >150 beats per minute 1

Common Pitfalls in Diagnosis

1. Waiting for hypotension: Hypotension is a late and often terminal sign in pediatric shock
2. Relying solely on biochemical tests: Clinical examination remains the cornerstone of early recognition 1
3. Misinterpreting capillary refill time: While useful, it can be influenced by ambient temperature, site, age, and lighting conditions 1
4. Attributing tachycardia to other causes: Tachycardia is a common sign of shock but can also result from pain, anxiety, and fever 1
5. Delaying treatment while waiting for confirmatory tests: This can worsen outcomes; treatment should begin based on clinical suspicion 1

Conclusion

The definition of shock in pediatrics focuses on inadequate tissue perfusion leading to energy failure and organ dysfunction. Early recognition through clinical signs before hypotension develops is crucial for improving outcomes. While various monitoring tools and laboratory tests can assist in diagnosis, the clinical examination remains the most important tool for timely identification and intervention.