Shock: Diagnosis and Management

Introduction

• Shock is a life-threatening medical emergency defined by inadequate tissue perfusion leading to cellular dysfunction and end-organ injury.
• Clinical features include hypotension, tachycardia, tachypnea, altered mental status, lactic acidosis, and end-organ dysfunction.¹
• Shock is divided into four major categories: hypovolemic, cardiogenic, distributive, and obstructive.
• Please see the OA summary on shock overview and classification for more details. Link
• Each category includes several distinct etiologies. Mixed shock states often carry a worse prognosis.¹

Diagnostic Approach to Shock

• Diagnosis and management occur simultaneously. Initial evaluation should include focused history, physical examination, and POCUS to clarify etiology and assess response to therapy.²

Clinical Manifestations

• Inadequate tissue perfusion
• Hypotension (often, but not universally present)
• Tachycardia (compensatory; may be absent in bradyarrhythmias or neurogenic shock)
• Tachypnea (compensation for metabolic acidosis)
• Metabolic acidosis, frequently lactic acidosis
• End-organ hypoperfusion: altered mental status, oliguria, prolonged capillary refill, cool or mottled extremities (early distributive shock may present with warm extremities)

Laboratory Evaluation

• Acid–base status
  • Elevated lactate levels (more than 2 mmol/L) and high–anion-gap metabolic acidosis reflect tissue hypoxia. Nonanion-gap metabolic acidosis may occur with diarrhea or large-volume normal saline administration.
• Basic metabolic panel
  • Identifies electrolyte abnormalities and renal dysfunction, including hypokalemia (from renin-angiotensin-aldosterone system activation) and hyperkalemia or hyperglycemia in diabetic ketoacidosis.
• Liver function tests
  • “Shock liver” presents with markedly elevated aspartate aminotransferase and alanine aminotransferase from hepatic hypoperfusion.
• Cardiac biomarkers
  • Troponin helps evaluate myocardial injury. Demand ischemia (type II myocardial infarction) is common in shock and usually requires no ischemia-directed workup unless there is active concern for acute coronary syndrome.
• Arterial blood gas
  • Evaluates oxygenation, ventilation, and pH.
• Coagulation profile
  • Assesses for coagulopathy in hemorrhagic shock or disseminated intravascular coagulation in septic shock.
• Complete blood count
  • Assesses anemia, leukocytosis, or leukopenia.

POCUS

POCUS is essential in evaluating undifferentiated shock and should be applied serially.^3,4

Cardiac Views

• Depressed left or right ventricular systolic function suggests cardiogenic shock.
• Right ventricular dilation and septal flattening (“D-sign”) indicate pulmonary embolism and obstructive shock.
• Pericardial effusion with right atrial or right ventricular diastolic collapse indicates tamponade.

Lung Views

• B-lines are consistent with pulmonary edema (commonly seen in cardiogenic shock).
• Absent lung sliding and a lung point are suggestive of pneumothorax.

Inferior Vena Cava (IVC) Assessment

• A plethoric, non-collapsible IVC suggests elevated central venous pressure (cardiogenic or obstructive shock).
• A small, collapsible IVC greater than 50% suggests low central venous pressure (hypovolemic or distributive shock).

Abdominal/Pelvic Views

• Free intraperitoneal fluid may indicate trauma-related hemorrhage, ruptured aneurysm, or perforated viscus.
• Free fluid in the pelvis in reproductive-age females should raise concern for ruptured ectopic pregnancy.

Extremities

• Evaluation of deep veins may reveal a deep vein thrombosis as the embolic source for pulmonary embolism.

Management of Shock

Shock requires immediate intervention with concurrent resuscitation and treatment of the underlying cause. Airway, breathing, and circulation priorities apply universally.

Hypovolemic Shock

• Hemorrhagic
  • Immediate bleeding control (surgical, endoscopic, interventional radiology, or obstetric).⁵
  • Crystalloid resuscitation should be initiated; in severe trauma or hemorrhage, balanced blood product transfusion guided by massive transfusion protocols is indicated.⁵
  • Permissive hypotension may be considered in select patients until hemostasis is achieved.²
• Nonhemorrhagic
  • Treat the underlying cause (e.g., antiemetics for vomiting, antidiarrheals for diarrhea).
  • Restore circulating volume with balanced crystalloids and correct electrolyte disturbances.²
• Cardiogenic Shock
  • Optimization of preload, afterload, contractility, heart rate, and rhythm, with early consideration of mechanical circulatory support, is central to the management of cardiogenic shock.⁶

Arrhythmia Management

• Tachyarrhythmias: Unstable patients require immediate cardioversion or defibrillation, depending on the rhythm. Antiarrhythmic medications (e.g., amiodarone for ventricular tachycardia, procainamide for Wolff-Parkinson-White syndrome) should be considered based on the specific arrhythmia.²
• Bradyarrhythmias: Discontinue offending bradycardic medications; treat with atropine, dopamine, epinephrine, or isoproterenol in unstable patients. Temporary pacing may be required.²

Valvular Disease

• Acute severe mitral regurgitation often requires urgent surgical intervention; pulmonary edema may require oxygen therapy or mechanical ventilation.⁶
• Severe aortic stenosis with decompensation is managed with cautious hemodynamic support; definitive treatment is surgical or transcatheter aortic valve replacement.⁶
• Heart failure
  • Acute decompensated heart failure can be treated with diuretics, vasodilators, and inotropes to increase cardiac output. Mechanical circulatory support (intraaortic balloon pump, temporary left ventricular assist devices, or extracorporeal membrane oxygenation) may be required.⁶
• Acute myocardial infarction
  • Emergent reperfusion therapy (percutaneous coronary intervention or fibrinolysis) is indicated. Adjunctive therapies include aspirin, P2Y₁₂ inhibitors, heparin, beta-blockers, nitrates, and analgesia.⁶

Obstructive Shock

• Pulmonary embolism
  • Immediate anticoagulation is indicated. High-risk pulmonary embolism with hemodynamic instability may require systemic or catheter-directed thrombolysis, or surgical/catheter embolectomy. Intubation and mechanical ventilation may worsen right ventricular failure and should be undertaken cautiously. Temporary mechanical circulatory support may be needed in critically unstable patients.
• Cardiac tamponade
  • Emergent pericardiocentesis or surgical pericardial window is required to relieve cardiac compression.
• Tension pneumothorax
  • Immediate needle decompression followed by chest tube placement is indicated. Treatment should not be delayed for imaging.

Distributive Shock

• Septic shock
  • Broad-spectrum antibiotics should be administered promptly, within one hour of recognition.^7,8
  • Fluid resuscitation should balance rapid hemodynamic support with avoidance of fluid overload. While an initial bolus of balanced crystalloid (up to 30 mL/kg) has historically been recommended, emerging evidence supports a more individualized, dynamic approach, as many patients are not fluid-responsive and excess fluid may worsen outcomes.^7,8
  • Dynamic assessments, including passive leg raise, capillary refill time, stroke volume evaluation, and serial POCUS, should guide ongoing fluid therapy. Please see the OA summary on fluid responsiveness for more details. Link
  • Early vasopressor use is recommended for persistent hypotension, with norepinephrine classically as the first-line agent.² Vasopressin is commonly added for persistent vasoplegia.
  • Please see the OA summary on vasopressors and inotropes for more details. Link
  • Source control is crucial and may require drainage of abscesses, debridement of necrotic tissue, removal of infected foreign bodies or central lines, or surgical management of intra-abdominal pathology.⁹
• Neurogenic shock
  • Spinal stabilization, cautious IV fluid administration, and vasopressors are used to restore vascular tone and maintain perfusion.²
• Anaphylactic shock
  • Epinephrine is first-line, life-saving therapy; H₁/H₂ blockers and corticosteroids are used as adjunctive treatments.
  • Airway patency must be assessed immediately, with strong consideration for early intubation in patients with progressive edema or stridor.²

Mixed Shock

• Mixed shock is associated with worse outcomes and occurs when multiple shock etiologies coexist.^1,9 Notable combinations include:
  • Hemorrhagic + Obstructive: Trauma with hemorrhage plus tension pneumothorax or tamponade.
  • Hemorrhagic + Distributive: Traumatic spinal cord injury causing autonomic dysfunction.
  • Obstructive + Cardiogenic: Massive pulmonary embolism or tamponade leading to right ventricular failure.
  • Septic + Hypovolemic: Capillary leak and third spacing reduce intravascular volume; gastrointestinal fluid losses can exacerbate hypovolemia.
  • Septic + Cardiogenic: Septic cardiomyopathy due to toxin- and cytokine-mediated myocardial dysfunction.⁸

Summary

• Shock is a clinical manifestation of acute circulatory failure spanning hypovolemic, cardiogenic, obstructive, and distributive etiologies, frequently coexisting as mixed shock.
• Early recognition, rapid hemodynamic assessment, and prompt initiation of appropriate therapy are essential.
• A structured approach integrating clinical evaluation, laboratory assessment, and POCUS allows timely diagnosis and guides targeted interventions.^1,3,4,10
• Resuscitation should be individualized and focused on restoring effective tissue perfusion rather than achieving a single MAP target. Frequent reassessment and attention to microcirculatory endpoints are essential for optimizing outcomes.