Hemodynamic Instability: Definition and Clinical Criteria

Core Criteria for Hemodynamic Instability

The Advanced Trauma Life Support (ATLS) definition of hemodynamic instability is a systolic blood pressure <90 mmHg and heart rate >120 bpm, with evidence of skin vasoconstriction, altered level of consciousness and/or shortness of breath 1, 2, 3, 4
Systolic blood pressure <90 mmHg is a key criterion for hemodynamic instability, according to the Advanced Trauma Life Support (ATLS) definition 1, 3, 5
Heart rate >120 bpm is a key criterion for hemodynamic instability, according to the Advanced Trauma Life Support (ATLS) definition 1, 3
Evidence of skin vasoconstriction, such as cool, clammy skin with decreased capillary refill, is a key criterion for hemodynamic instability, according to the Advanced Trauma Life Support (ATLS) definition 1, 4
Altered level of consciousness is a key criterion for hemodynamic instability, according to the Advanced Trauma Life Support (ATLS) definition 1, 3
Shortness of breath is a key criterion for hemodynamic instability, according to the Advanced Trauma Life Support (ATLS) definition 1, 3

Requirement for bolus fluid infusions/transfusions to maintain blood pressure is a criterion for hemodynamic instability 1, 3
Need for vasopressor drugs to maintain adequate blood pressure is a criterion for hemodynamic instability 1, 4
Base deficit >5-6 mmol/L is a criterion for hemodynamic instability 1, 3
Shock index >1 (heart rate divided by systolic blood pressure) is a criterion for hemodynamic instability 1, 4
Transfusion requirement of at least 4-6 units of packed red blood cells within the first 24 hours is a criterion for hemodynamic instability 1, 3

Patients who show an initial response to adequate fluid resuscitation but then develop signs of ongoing blood loss and perfusion deficits are classified as "transient responders" and should be considered hemodynamically unstable 1, 3

Response to initial fluid resuscitation (transient vs. sustained improvement) is an important consideration when evaluating a potentially unstable patient 1, 3
Signs of end-organ hypoperfusion, such as altered mental status and decreased urine output, are important considerations when evaluating a potentially unstable patient 1, 4
Laboratory markers of tissue hypoperfusion, such as lactate and base deficit, are important considerations when evaluating a potentially unstable patient 3, 4

Relying solely on blood pressure as an indicator of hemodynamic stability can be misleading, as patients may maintain "normal" blood pressure despite significant ongoing blood loss through compensatory mechanisms 1, 3
Failing to recognize transient responders who initially stabilize with fluid resuscitation but later decompensate can lead to delayed intervention 1, 4
Delaying definitive intervention in unstable patients can lead to poor outcomes, as hemodynamic instability despite resuscitation suggests ongoing bleeding requiring immediate intervention 6

In pediatric patients, hemodynamic stability is considered a systolic blood pressure of 90 mmHg plus twice the child's age in years 7
An acceptable hemodynamic response in children is considered a positive response to fluid resuscitation after 3 boluses of 20 mL/kg of crystalloid 7
Trauma patients with hemodynamic instability require immediate intervention (surgery or angioembolization) if they show no or only transient response to resuscitation 6