What are the different types of shock and their management?

Types of Shock and Their Management

Shock is classified into four major categories based on pathophysiology: hypovolemic, distributive, cardiogenic, and obstructive shock, each requiring specific management approaches tailored to the underlying mechanism. 1, 2

Classification of Shock Types

1. Hypovolemic Shock

• Definition: Results from intravascular volume loss
• Causes: Hemorrhage (most common in trauma), severe dehydration, excessive diuresis, vomiting, diarrhea
• Clinical Features:
  • Tachycardia
  • Weak pulses
  • Capillary refill time >2 seconds (when combined with decreased urine output, absent tears, dry mucous membranes) 1
  • Cold extremities
  • Decreased urine output (<30 mL/hr)

2. Distributive Shock

• Definition: State of relative hypovolemia from pathological redistribution of intravascular volume 2
• Types:
  • Septic shock: Most common form of distributive shock
  • Anaphylactic shock: Severe allergic reaction
  • Neurogenic shock: Disruption of sympathetic nervous system
  • Adrenal crisis: Acute adrenal insufficiency
• Clinical Features:
  • Warm, flushed skin (early)
  • Bounding pulses (early)
  • Hypotension
  • Tachycardia
  • In septic shock: fever, altered mental status, source of infection

3. Cardiogenic Shock

• Definition: Inadequate cardiac output due to primary cardiac dysfunction 1, 3
• Causes: Myocardial infarction (most common), heart failure, valvular disease, arrhythmias, cardiomyopathy
• Clinical Features:
  • Hypotension (SBP <90 mmHg for >30 minutes)
  • Evidence of end-organ hypoperfusion
  • Elevated lactate (>2 mmol/L)
  • Pulmonary congestion
  • Cardiac index <1.8-2.2 L/min/m²
  • Pulmonary capillary wedge pressure >15 mmHg 1, 3

4. Obstructive Shock

• Definition: Mechanical obstruction to blood flow causing decreased cardiac output 2
• Causes: Pulmonary embolism, tension pneumothorax, cardiac tamponade, constrictive pericarditis
• Clinical Features:
  • Hypotension
  • Elevated jugular venous pressure
  • Muffled heart sounds (tamponade)
  • Unilateral decreased breath sounds (tension pneumothorax)
  • Pulsus paradoxus (tamponade)

Management Approaches

1. Hypovolemic Shock Management

• First-line: Fluid resuscitation with balanced crystalloids 2
• Approach:
  • Establish adequate IV access (two large-bore IVs)
  • Rapid infusion of crystalloids (20 mL/kg boluses in pediatrics) 1
  • Control bleeding source if hemorrhagic
  • Blood product transfusion for hemorrhagic shock
  • Monitor response: vital signs, urine output, lactate clearance

2. Distributive Shock Management

• First-line: Combination of vasopressors and fluid replacement 2
• Septic Shock Protocol:
  • Early fluid resuscitation
  • Norepinephrine as first-line vasopressor after adequate fluid resuscitation 1
  • Source control (antibiotics, drainage of infected collections)
  • Consider vasopressin (up to 0.03 UI/min) if persistent hypotension 1
  • Add dobutamine for myocardial depression with decreased perfusion 1

3. Cardiogenic Shock Management

• First-line: Inotropic support and addressing underlying cause 3
• Approach:
  • Dobutamine as first-line inotrope (2-20 μg/kg/min) for acute heart failure 1, 3
  • Norepinephrine for persistently hypotensive cardiogenic shock with tachycardia 1
  • Dopamine may be considered in patients with bradycardia 1
  • For myocardial infarction: immediate coronary revascularization 1, 3
  • Consider mechanical circulatory support for refractory cases:
    • Left ventricular failure: Impella devices, IABP, TandemHeart
    • Right ventricular failure: Impella RP or TandemHeart Protek-Duo
    • Biventricular failure: Bilateral Impella pumps or VA-ECMO with LV venting 3

4. Obstructive Shock Management

• First-line: Immediate life-saving intervention to relieve obstruction 2
• Specific interventions:
  • Tension pneumothorax: Needle decompression followed by chest tube
  • Cardiac tamponade: Pericardiocentesis
  • Pulmonary embolism: Anticoagulation, consider thrombolysis or embolectomy
  • Constrictive pericarditis: Pericardial window or pericardiectomy

Monitoring Parameters for All Shock States

• Target parameters 3:
  • Cardiac index ≥2.2 L/min/m²
  • Mixed venous oxygen saturation ≥70%
  • Mean arterial pressure ≥70 mmHg
  • Urine output >30 mL/h
  • Lactate clearance

Common Pitfalls and Caveats

1. Delayed recognition: Shock can progress rapidly; early identification is critical for improved outcomes.

2. Misclassification: Shock states can overlap or convert from one type to another; continuous reassessment is essential 4.

3. Overaggressive fluid resuscitation: Can worsen cardiogenic and some forms of obstructive shock.

4. Underresuscitation: Inadequate fluid replacement in hypovolemic and distributive shock leads to persistent tissue hypoperfusion.

5. Failure to address underlying cause: Treating only the hemodynamic abnormalities without addressing the root cause (e.g., sepsis source, bleeding, cardiac pathology) will lead to poor outcomes.

6. Ventilation considerations: Consider early endotracheal intubation in severe shock to reduce work of breathing and improve oxygenation 3.

7. Delayed escalation of care: Failure to involve specialists or initiate mechanical support when indicated can worsen outcomes.