A 32-year-old man is brought to the emergency department following a motor vehicle collision with severe blunt abdominal trauma. Clinical examination reveals hypotension (BP 85/50 mmHg), tachycardia (HR 128/min), cold extremities, and altered mental status. After securing two large-bore IV lines and initiating rapid crystalloid infusion, the patient remains in hemorrhagic shock. What is the drug of choice for immediate hemodynamic support while awaiting definitive surgical intervention?

Explanation

## Vasopressor Selection in Hemorrhagic Shock **Key Point:** Noradrenaline (norepinephrine) is the first-line vasopressor in hemorrhagic shock because it provides both α-adrenergic vasoconstriction (restores perfusion pressure) and β-adrenergic inotropic support (maintains cardiac output). ### Mechanism in Hemorrhagic Shock **High-Yield:** In Class III–IV hemorrhagic shock, the primary goal is to restore mean arterial pressure (MAP ≥ 65 mmHg) and tissue perfusion while awaiting hemorrhage control. Noradrenaline achieves this through: - **α-effects:** Peripheral vasoconstriction → increased systemic vascular resistance (SVR) and MAP - **β-effects:** Increased heart rate and contractility → improved cardiac output ### Comparative Pharmacology | Agent | α-Effect | β-Effect | Use in Shock | Rationale | |-------|----------|----------|--------------|----------| | **Noradrenaline** | +++++ | ++ | First-line | Balanced α/β; restores perfusion + maintains CO | | Dobutamine | + | +++++ | Cardiogenic shock | Pure inotrope; causes vasodilation—worsens hypotension in hemorrhagic shock | | Hydralazine | Vasodilator | — | Hypertensive emergency | Contraindicated; reduces SVR in shock | | Esmolol | — | β-blocker | Tachyarrhythmia control | Negative inotrope; worsens shock | **Clinical Pearl:** Dobutamine and other pure inotropes are avoided in hemorrhagic shock because they cause peripheral vasodilation, which exacerbates hypotension. Noradrenaline's dual action is essential when fluid resuscitation alone is insufficient. ### ATLS Principle **Warning:** The sequence is **Fluids → Vasopressors → Definitive Control**. Vasopressors are a bridge to surgery, not a substitute for hemorrhage control. Early surgical consultation is mandatory. [cite:ATLS 10e]