While advanced trauma life support has traditionally emphasized the “ABC” (airway, breathing, and circulation) approach for all trauma patients, a more nuanced approach is required in order to avoid catastrophic outcomes in the early resuscitation of the polytrauma patient.

First Priorities in Trauma Resuscitation

Focus should be on physiologic priorities.¹ The most severe, life-threatening injuries should be temporized first. The two categories of immediate life threats in trauma include massive external hemorrhage, temporized by local pressure and/or tourniquet, and critical airway compromise. Critical airway compromise can be further divided into critical/refractory hypoxia, which is less than 90 percent oxygen saturation despite optimized noninvasive ventilation; and dynamic airway, which is evolving disruption of the airway anatomy and/or head and neck injuries that are expected to worsen over the next few minutes.

Second Priorities: “C” Before “A”

After the immediate life threats of massive external hemorrhage and critical airway compromise have been addressed, resuscitation should then focus on hemodynamic optimization before definitive airway management. Endotracheal intubation causes an increase in intrathoracic pressure, resulting in a decrease in right atrial pressure, which negatively impacts both hemorrhagic and obstructive shock. Pre-intubation hypotension is a significant risk factor for post-intubation cardiac arrest.²  Hence, the adage, “Resuscitate before you intubate” in volume-depleted patients. Procedures to relieve obstructive shock, such as bilateral finger thoracostomies and thoracotomy, should be considered prior to endotracheal intubation. A similar “CABC” (circulation, airway, breathing, and circulation) approach has been adapted in the cardiac arrest literature.

Step-wise Approach to Identify Occult Shock

The patient who rolls into your resuscitation room after a worrisome mechanism and with a mean arterial pressure of 30 is in an obvious shock state. However, many trauma patients present in occult shock. Under-recognition of occult shock in trauma is associated with poor patient outcomes.³ The following step-wise approach will minimize your chances of missing occult shock.

1. Calculate the shock index (heart rate divided by systolic blood pressure [SBP]) and/or delta shock index.^4,5 If the shock index is >1 or the delta shock index  ≥0.1, assume occult shock is present.
2. Assess the lowest blood pressure (BP) measured and trend the BP over time; if isolated or persistent SBP <110, assume occult shock.⁶ A single low BP either in the field or in the emergency department has been shown to predict poor outcomes in trauma patients.
3. Positive focused assessment with sonography in trauma (FAST) with flat inferior vena cava (IVC)? Assume occult shock.
4. Consider a volume challenge to assess for active occult hemorrhage by administering 250 mL of crystalloid under pressure followed by assessment for signs of perfusion. If a patient transiently responds to 250 mL of crystalloid, you may assume active occult hemorrhage.

A shock index of >1 or a delta shock index of ≥0.1 is a sign of occult shock and is predictive of post-intubation hypotension, transfusion requirements, injury severity, and mortality.^4,5 A practical tip to help identify occult shock is to ask EMS not only what the most recent BP was, but what the lowest BP they recorded was. A single drop in BP in the field or in the emergency department is predictive of the need for surgical intervention and mortality.⁷ One common pitfall in diagnosing shock is ignoring pre-hospital hypotension that normalizes without intervention. An isolated decrease in SBP <105 mmHg is associated with a 12-fold increase in the need for immediate therapeutic intervention.⁸

The shock index is unreliable in patients with altered physiologic compensation such as elderly patients, undertreated hypertension, and patients taking medications that lower the heart rate, such as beta-blockers.⁹ In these patients, consider the delta shock index, which may be a more reliable indicator of occult shock.⁵