What are the signs and symptoms of shock?

Signs and Symptoms of Shock

Shock is characterized by decreased perfusion manifested by altered mental status, capillary refill >2 seconds (cold shock) or flash capillary refill (warm shock), diminished (cold shock) or bounding (warm shock) peripheral pulses, mottled cool extremities (cold shock), and decreased urine output <1 mL/kg/h. 1

Clinical Manifestations by System

Neurological Signs

• Altered or decreased mental status - ranging from irritability and confusion to lethargy and becoming unarousable 1
• Inappropriate crying (in pediatric patients) 1
• Poor interaction with parents (in pediatric patients) 1

Cardiovascular Signs

• Tachycardia - an early compensatory mechanism to maintain cardiac output 1
• Abnormal pulse quality:
  • Weak pulses in hypovolemic and cardiogenic shock 1
  • Bounding peripheral pulses in warm/distributive shock 1
  • Differential between peripheral and central pulses in cold shock 1
• Blood pressure changes:
  • Normal blood pressure initially (compensated shock) 1
  • Hypotension (decompensated shock) - a late and ominous sign 2
  • Narrow pulse pressure in high systemic vascular resistance states 1
  • Wide pulse pressure in low systemic vascular resistance states 1

Skin Findings

• Prolonged capillary refill time >2 seconds in cold shock 1
• Flash (very rapid) capillary refill in warm shock 1
• Mottled, cool extremities in cold shock 1
• Warm skin in distributive/warm shock 1
• Cyanotic skin in advanced shock 1

Renal Signs

• Decreased urine output (<1 mL/kg/h) - a sensitive indicator of inadequate perfusion 1

Respiratory Signs

• Tachypnea - an early sign of shock 2
• Respiratory alkalosis from centrally mediated hyperventilation in early sepsis 1
• Respiratory acidosis in late shock due to muscle fatigue and altered mental status 1

Types of Shock and Specific Findings

Hypovolemic Shock

• Venoconstriction 1
• Low jugular venous pressure 1
• Poor tissue perfusion 1
• Tachycardia 1
• Cold extremities 1

Cardiogenic Shock

• Signs of heart failure (pulmonary rales, third heart sound) 1
• Elevated jugular venous pressure 1
• Weak peripheral pulses 1
• Cool extremities 1
• Systolic pressure <90 mmHg and central filling pressure >20 mmHg 1
• Cardiac index <1.8 L/min/m² 1

Distributive Shock (including septic shock)

• Warm extremities initially 1
• Bounding peripheral pulses 1
• Wide pulse pressure 1
• Flash capillary refill 1

Obstructive Shock

• Signs specific to underlying cause (tension pneumothorax, cardiac tamponade, pulmonary embolism) 3
• Elevated central venous pressure 3
• Pulsus paradoxus (in cardiac tamponade) 4

Laboratory and Monitoring Findings

• Elevated serum lactate levels 5
• Metabolic acidosis (late finding) 2
• Decreased mixed venous oxygen saturation (ScvO2 <70%) 1
• Decreased superior vena cava flow (<40 mL/kg/min in neonates) 1
• Abnormal arterial blood gases 1
• Elevated urine osmolarity 2
• Decreased urine sodium concentration 2

Progression of Shock

• Compensated shock: Tachycardia, increased systemic vascular resistance, normal blood pressure 1
• Decompensated shock: Failure of compensatory mechanisms resulting in hypotension 1
• Refractory shock: Persistent shock despite goal-directed use of inotropic agents, vasopressors, vasodilators, and maintenance of metabolic and hormonal homeostasis 1

Important Caveats

• Hypotension is a late sign of shock in children and indicates decompensation 1, 2
• Capillary refill time is influenced by ambient temperature, site, age, and lighting conditions 1
• Tachycardia may result from other causes such as pain, anxiety, and fever 1
• Systolic hypotension, oliguria, metabolic acidosis, and cold clammy skin are late signs of shock 2
• Early recognition of shock signs before hypotension develops is critical for improved outcomes 2, 4