Shock: Types, Pathophysiology, Clinical Presentation, and Emergency Management

Shock is acute circulatory failure with inadequate tissue perfusion → cellular hypoxia → organ dysfunction → death if uncorrected.

Four Main Types (Hinshaw Classification)

Type	Primary Defect	Examples	Hemodynamics
Hypovolemic	Low preload	Hemorrhage, dehydration, burns	↓CO, ↑SVR, ↓PCWP
Cardiogenic	Pump failure	MI, cardiomyopathy, arrhythmia, valve rupture	↓CO, ↑SVR, ↑PCWP
Distributive	Low SVR	Septic, anaphylactic, neurogenic	↑/↓CO, ↓↓SVR, ↓PCWP
Obstructive	Flow obstruction	PE, tamponade, tension pneumothorax	↓CO, ↑SVR, ↑PCWP (tamponade)

Compensatory Responses (Early Shock)

• Sympathetic surge: ↑HR, ↑contractility, vasoconstriction (skin, splanchnic, renal)
• RAAS activation: Na⁺/H₂O retention, vasoconstriction
• ADH release: Water retention
• Cortisol: Metabolic support

Clinical Stages

1. Compensated: Normal BP, tachycardia, cool extremities, oliguria, anxiety
2. Decompensated: Hypotension, altered mental status, mottling, lactic acidosis
3. Irreversible: Multiorgan failure, refractory hypotension, death

Emergency Management (General Principles)

1. ABCs: Airway, Breathing, Circulation – intubate if needed
2. IV access (large bore ×2) / IO
3. Fluid resuscitation: Crystalloid 30 mL/kg bolus (hypovolemic, distributive); cautious in cardiogenic
4. Vasopressors: Norepinephrine first-line (septic, distributive); dobutamine (cardiogenic)
5. Source control: Antibiotics (sepsis), surgery (hemorrhage, obstruction), antidotes (anaphylaxis)
6. Monitor: MAP ≥65, lactate clearance, ScvO₂, urine output, echocardiography

Prevention

• Hydration, bleeding control, chronic disease management, allergy avoidance, VTE prophylaxis
• Early recognition of sepsis (qSOFA, SIRS)