4 Types of Shock

April 3rd, 2025

Shock can be broadly categorized into four main types: hypovolemic, cardiogenic, distributive, and obstructive. Each type has distinct pathophysiological mechanisms, clinical presentations, and management strategies. This article provides an in-depth analysis of each shock type to aid clinicians in timely diagnosis and treatment.

1. Hypovolemic shock

Hypovolemic shock occurs from a substantial loss of intravascular volume, resulting in decreased cardiac output and tissue hypoperfusion. It is most commonly caused by hemorrhage (trauma, gastrointestinal bleeding) or non-hemorrhagic fluid loss (vomiting, diarrhea, burns, or excessive diuresis).

Pathophysiology

Loss of intravascular volume results in decreased venous return to the heart, reducing preload, stroke volume, and cardiac output. The body compensates through vasoconstriction, tachycardia, and activation of the renin-angiotensin-aldosterone system (RAAS) to sustain blood pressure. However, if fluid loss exceeds compensatory mechanisms, tissue perfusion declines, leading to metabolic acidosis and organ dysfunction.

Clinical features

• Hypotension

• Tachycardia

• Cold, clammy skin

• Decreased urine output

• Altered mental status

Management

• Volume resuscitation:
  • Crystalloids (normal saline, lactated Ringer’s)
  • Blood transfusion if hemorrhagic shock

• Identify and treat the cause:
  • Control bleeding
  • Address underlying fluid loss

• Hemodynamic monitoring:
  • Central venous pressure (CVP), lactate levels, urine output

2. Cardiogenic shock

Cardiogenic shock is caused by the heart’s inability to pump sufficient blood, leading to inadequate perfusion. Common causes include myocardial infarction (MI), severe heart failure, valvular disease, and arrhythmias.

Pathophysiology

A decrease in myocardial contractility leads to reduced stroke volume and cardiac output. The compensatory response includes increased systemic vascular resistance (SVR), but this worsens myocardial oxygen demand, perpetuating a cycle of ischemia and dysfunction.

Clinical features

• Hypotension

• Tachycardia or bradycardia (depending on the cause)

• Pulmonary edema (dyspnea, rales)

• Cool extremities, cyanosis

• Jugular venous distension (JVD)

Management

• Cardiac support
  • Inotropes (dobutamine)
  • Correct unstable tachyarrhythmias or bradyarrhythmias
  • Vasopressors (norepinephrine)
• Revascularization in MI
  • Percutaneous coronary intervention (PCI)
  • Coronary artery bypass grafting (CABG)

• Mechanical support
  • Intra-aortic balloon pump (IABP)
  • Ventricular assist devices (VADs)

3. Distributive shock

Distributive shock results from inappropriate vasodilation, leading to relative hypovolemia. The most common subtype is septic shock, but anaphylactic, neurogenic, and endocrine shock also fall under this category.

Septic shock

Septic shock is caused by a systemic inflammatory response to infection, leading to vasodilation, capillary leakage, and mitochondrial dysfunction.

Clinical features

• Fever or hypothermia

• Hypotension despite adequate fluid resuscitation

• Tachycardia

• Warm extremities (early), cool extremities (late)

Management

1. Early broad-spectrum antibiotics
2. Fluid resuscitation (30 mL/kg crystalloid)
3. Vasopressors (norepinephrine, vasopressin)
4. Source control (e.g., draining abscesses or removing infected catheters)

Anaphylactic shock

Anaphylactic shock results from severe allergic reactions leading to massive histamine release, resulting in vasodilation, increased vascular permeability, and airway edema.

Clinical features

• Urticaria, angioedema

• Hypotension

• Wheezing, stridor

• Gastrointestinal symptoms (nausea, vomiting)

Management

1. Epinephrine (IM, 0.3–0.5 mg)
2. Antihistamines (diphenhydramine, ranitidine)
3. Steroids (methylprednisolone)
4. Airway management if severe

Neurogenic shock

Neurogenic shock occurs due to injury to the spinal cord, disrupting sympathetic outflow and causing unopposed parasympathetic activity.

Clinical features

• Hypotension with bradycardia

• Warm, flushed skin (due to vasodilation)

Management

1. Fluid resuscitation
2. Vasopressors (norepinephrine, phenylephrine)
3. Spinal stabilization and supportive care

4. Obstructive shock

Obstructive shock results from mechanical obstruction of blood flow, impairing cardiac output. Common causes include pulmonary embolism (PE), tension pneumothorax, and cardiac tamponade.

Pulmonary embolism

Pathophysiology: PE obstructs pulmonary circulation, increasing right ventricular afterload and reducing left ventricular preload.

Clinical features

• Sudden dyspnea

• Tachycardia

• Pleuritic chest pain

• Hypotension if massive PE

Management

1. Anticoagulation (heparin, DOACs)
2. Thrombolysis if massive PE
3. Surgical embolectomy if necessary

Tension pneumothorax

Air trapping in the pleural space leads to lung collapse and mediastinal shift, compressing major vessels.

Clinical features

• Sudden respiratory distress

• Tracheal deviation away from the affected side

• Absent breath sounds

• Hypotension

Management

• Immediate needle decompression (2nd intercostal space, midclavicular line)

• Chest tube placement

Cardiac tamponade

Pericardial fluid accumulation impairs ventricular filling, decreasing cardiac output.

Clinical features (Beck’s Triad)

• Hypotension

• Muffled heart sounds

• JVD

Management

• Pericardiocentesis

• Pericardial window if appropriate

Shock is a complex and multifactorial syndrome that requires rapid identification and targeted intervention. Understanding the various types — hypovolemic, cardiogenic, distributive, and obstructive — is crucial for effective clinical management.

Each type necessitates specific treatment strategies to restore perfusion, prevent organ failure, and improve patient outcomes. Clinicians must remain vigilant in diagnosing and managing shock promptly, as early intervention significantly impacts prognosis.