What are the types of shock and how are they assessed using the look, listen, feel approach?

Types of Shock: Assessment Using Look, Listen, Feel Approach

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

Classification of Shock Types

1. Hypovolemic Shock

• Definition: Results from intravascular volume loss
• Causes: Hemorrhage, severe dehydration, excessive diuresis, vomiting, diarrhea 1
• Look:
  • Tachycardia
  • Weak pulses
  • Cold, pale extremities
  • Decreased skin turgor
  • Dry mucous membranes
• Listen:
  • Rapid, thready pulse
  • Clear lung fields
• Feel:
  • Capillary refill time >2 seconds
  • Cool skin
  • Weak peripheral pulses

2. Distributive Shock

• Definition: State of relative hypovolemia from pathological redistribution of intravascular volume
• Types: Septic shock, anaphylactic shock, neurogenic shock, adrenal crisis 1
• Look:
  • Warm, flushed skin (early septic shock)
  • Urticaria/angioedema (anaphylactic)
  • Hypotension
  • Altered mental status
• Listen:
  • Bounding pulses
  • Possible wheezing (anaphylactic)
  • Possible crackles (septic)
• Feel:
  • Warm peripheries (early)
  • Fever (septic)
  • Rapid pulse

3. Cardiogenic Shock

• Definition: Inadequate cardiac output due to primary cardiac dysfunction
• Causes: Myocardial infarction, heart failure, valvular disease, arrhythmias, cardiomyopathy 1
• Look:
  • Hypotension (SBP <90 mmHg for >30 minutes)
  • Jugular venous distention
  • Peripheral edema
  • Cyanosis
• Listen:
  • S3 gallop
  • Pulmonary crackles
  • Murmurs (valvular causes)
• Feel:
  • Cold, clammy skin
  • Weak pulses
  • Pulmonary edema

4. Obstructive Shock

• Definition: Mechanical obstruction to blood flow causing decreased cardiac output
• Causes: Pulmonary embolism, tension pneumothorax, cardiac tamponade, constrictive pericarditis 1
• Look:
  • Hypotension
  • Elevated jugular venous pressure
  • Unilateral chest expansion (tension pneumothorax)
  • Cyanosis
• Listen:
  • Muffled heart sounds (tamponade)
  • Unilateral decreased breath sounds (pneumothorax)
  • Tracheal deviation (tension pneumothorax)
• Feel:
  • Pulsus paradoxus (tamponade)
  • Tracheal deviation (tension pneumothorax)
  • Subcutaneous emphysema (pneumothorax)

Diagnostic Assessment

Vital Signs Assessment

• Blood pressure: Hypotension (SBP <90 mmHg) is common to all shock types 1
• Heart rate: Typically elevated (except in neurogenic shock)
• Respiratory rate: Usually increased
• Temperature: Elevated in septic shock, may be decreased in late shock states
• Oxygen saturation: Often decreased

Hemodynamic Parameters

• Cardiac index: Target ≥2.2 L/min/m² 1
• Mixed venous oxygen saturation: Target ≥70% 1
• Mean arterial pressure: Target ≥70 mmHg 1
• Urine output: Target >30 mL/h 1

Laboratory Assessment

• Lactate levels: Elevated (>2 mmol/L) indicates tissue hypoperfusion 1
• Complete blood count: May show anemia (hypovolemic) or leukocytosis (septic)
• Coagulation studies: May reveal DIC in septic shock
• Cardiac biomarkers: Elevated in cardiogenic shock
• Blood cultures: For suspected septic shock

Management Approach Based on Shock Type

Hypovolemic Shock

• Fluid resuscitation with balanced crystalloids as first-line treatment 1
• Blood products for hemorrhagic shock
• Address underlying cause (control bleeding, replace fluid losses)

Distributive Shock

• Combination of vasopressors and fluid replacement 1
• Norepinephrine as first-line vasopressor after adequate fluid resuscitation
• Specific treatments for underlying cause (antibiotics for sepsis, epinephrine for anaphylaxis)

Cardiogenic Shock

• Inotropic support and addressing underlying cause 1
• Dobutamine as first-line inotrope (2-20 μg/kg/min) for acute heart failure
• Consider mechanical circulatory support based on failure pattern:
  • Left ventricular failure: Impella devices, IABP, or TandemHeart
  • Right ventricular failure: Impella RP or TandemHeart Protek-Duo
  • Biventricular failure: Bilateral Impella pumps or VA-ECMO with LV venting 1

Obstructive Shock

• Immediate life-saving intervention to relieve obstruction 1
  • Needle decompression for tension pneumothorax
  • Pericardiocentesis for cardiac tamponade
  • Anticoagulation, thrombolysis, or embolectomy for pulmonary embolism

Special Considerations

Ventilatory Support

• Consider early endotracheal intubation and mechanical ventilation to reduce work of breathing and improve oxygenation 1
• Non-invasive positive pressure ventilation may be considered for respiratory distress in non-intubated patients 1

Multidisciplinary Care

• A multidisciplinary shock team approach has been associated with improved 30-day all-cause mortality (HR, 0.61; 95% CI, 0.41–0.93) in patients with cardiogenic shock 1

Common Pitfalls and Caveats

1. Misdiagnosis of shock type: Incorrect identification can lead to inappropriate treatment. Use the look, listen, feel approach systematically.

2. Delayed recognition of pre-shock: Patients with compensatory vasoconstriction may maintain near-normal systolic blood pressure despite malperfusion, which can be falsely reassuring 2

3. Failure to recognize mixed shock states: Patients may present with features of multiple shock types simultaneously.

4. Over-reliance on single parameters: Integrate clinical, laboratory, and hemodynamic data for accurate diagnosis.

5. Inadequate monitoring: Continuous reassessment is essential as shock states can evolve rapidly.

6. Delayed intervention: Prompt recognition and treatment are crucial for improving outcomes.