Shock

Neurogenic shock

• Etiology & Mechanism:
  • Disruption of descending sympathetic pathways from acute spinal cord injury (SCI $\ge$ T6), epidural hematoma, or high spinal anesthesia.
  • Unopposed parasympathetic (vagal) tone $\to$ massive peripheral vasodilation + loss of cardiac accelerator reflex.
• Hemodynamics & Clinical Findings:
  • Classic Triad: Hypotension, paradoxical bradycardia, and warm, dry, flushed extremities (early).
  • Hemodynamic Profile: ↓ SVR (primary driver), ↓ CVP / PCWP (venous pooling), ↓ or normal CO.
  • Other Signs: Poikilothermia (loss of thermoregulation), flaccid paralysis/areflexia below lesion level (spinal shock).

Management

• Immediate Step: ABCs + 2 large-bore IV access + aggressive fluid resuscitation (usually 30 mL/kg crystalloid bolus). c
  • A single peripheral IV is insufficient to handle the high-volume fluid and blood resuscitation.
• Hypovolemic: Isotonic crystalloid. If severe hemorrhage (Hgb < 7 or symptomatic), administer PRBCs/MTP (Massive Transfusion Protocol).
  • Massive Transfusion Protocol (MTP):
    • Indicated for severe shock (ABC score ≥ 2: penetrating trauma, SBP ≤ 90, HR ≥ 120, (+) FAST).
    • Balanced Transfusion (1:1:1 Ratio): 1 unit pRBC : 1 unit FFP : 1 unit Platelets.
    • Uncrossmatched blood: O-negative (women of childbearing age) or O-positive (men and older women) until type-specific blood is available.
    • Limit Crystalloids: Avoid aggressive crystalloid infusion (limit to ≤1 L) to prevent hemodilution, hypothermia, and worsening of the “lethal triad.”
• Cardiogenic:
  • Caution with fluids (can worsen pulmonary edema).
  • Inotropes: Dobutamine (if normotensive), Norepinephrine (if hypotensive).
  • Revascularization (PCI/CABG) if MI.
• Distributive (Sepsis):
  • Aggressive IVF.
  • Vasopressor of choice: Norepinephrine (first-line).
  • Add Vasopressin if refractory.
• Distributive (Anaphylaxis):
  • First-line: IM Epinephrine (do not delay for IV).
  • Fluids, antihistamines, steroids (adjuncts).
• Obstructive:
  • PE: Anticoagulation/Thrombolytics/Embolectomy.
  • Tamponade: Pericardiocentesis.
  • Tension Pneumothorax: Needle decompression -> Chest tube.