What are the diagnostic criteria and treatment options for different types of shock?

Diagnosing Shock Types

Shock diagnosis requires both hypotension (SBP <90 mm Hg or MAP <60 mm Hg for >30 minutes) AND evidence of end-organ hypoperfusion (decreased mentation, cold extremities, urine output <30 mL/h, or lactate >2 mmol/L), then differentiate the type using hemodynamic parameters and clinical context. 1

Initial Diagnostic Criteria for Any Shock State

All shock states require BOTH of the following 1:

Blood Pressure Criteria

• SBP <90 mm Hg for >30 minutes 1
• OR mean BP <60 mm Hg for >30 minutes 1
• OR vasopressor requirement to maintain SBP ≥90 mm Hg or MAP ≥60 mm Hg 1

Hypoperfusion Evidence (at least one required)

• Decreased mentation 1
• Cold extremities or livedo reticularis 1
• Urine output <30 mL/h 1
• Lactate >2 mmol/L 1

Common pitfall: Hypotension alone is insufficient for shock diagnosis—you must document end-organ hypoperfusion. 1

Differentiating Shock Types by Hemodynamics

Once shock is confirmed, use cardiac index (CI), systemic vascular resistance (SVR), and filling pressures to categorize 1:

Cardiogenic Shock

Hemodynamic profile: Low CI + High filling pressures + Variable SVR 1

• Cardiac index <2.2 L/min/m² (or <2.0 L/min/m² with SBP <90 mm Hg) 1
• Pulmonary capillary wedge pressure (PCWP) >15 mm Hg 1
• Cardiac power output <0.6 W 1
• Shock index (HR/SBP) >1.0 1

Clinical findings: Elevated venous pressure, cold/ashen extremities, weak pulses, respiratory distress, elevated BNP 1

Right ventricular shock variant 1:

• Pulmonary artery pulse index [(PASP-PADP)/CVP] <1.0 1
• CVP >15 mm Hg 1
• CVP-PCWP ratio >0.6 1

Emergency echocardiography is recommended to rapidly identify left or right ventricular dysfunction, acute valvular dysfunction, pericardial effusion, and guide differential diagnosis. 1

Distributive Shock (Septic/Vasodilatory)

Two hemodynamic patterns exist 1:

Pattern 1: High CI + Low SVR (Warm Shock)

• Cardiac index >3.5-4.0 L/min/m² 1
• Low systemic vascular resistance 1
• Warm extremities, bounding pulses initially 1
• Hypotension despite high cardiac output 1

Pattern 2: Low CI + Low SVR (Cold Shock)

• Cardiac index <2.2 L/min/m² 1
• Low systemic vascular resistance 1
• Cold extremities, weak pulses 1
• More common in pediatric septic shock 1

Newborn septic shock specific findings: Tachycardia, respiratory distress, poor feeding, poor tone, poor color, tachypnea, diarrhea, reduced perfusion, especially with maternal chorioamnionitis or prolonged rupture of membranes. 1

Critical distinction: Must differentiate newborn septic shock from cardiogenic shock due to ductal-dependent congenital heart disease—look for hepatomegaly, cyanosis, cardiac murmur, or differential upper/lower extremity blood pressures. 1

Hypovolemic Shock

Hemodynamic profile: Low CI + Low filling pressures + High SVR 2, 3, 4

• Low cardiac index 2, 3, 4
• Low central venous pressure (<8 mm Hg) 2, 3, 4
• Low PCWP 2, 3, 4
• Elevated SVR (compensatory vasoconstriction) 2, 3, 4

Clinical findings: Flat neck veins, dry mucous membranes, poor skin turgor, history of fluid losses (bleeding, vomiting, diarrhea, burns) 3, 4

Obstructive Shock

Hemodynamic profile: Low CI + Variable filling pressures + High SVR 2, 3, 4

Specific causes to identify 1, 2, 3, 4:

• Cardiac tamponade: Elevated and equalized diastolic pressures, pulsus paradoxus, distended neck veins—echocardiography is diagnostic 1
• Massive pulmonary embolism: Right ventricular dysfunction on echo, elevated CVP, low PCWP 1
• Tension pneumothorax: Unilateral absent breath sounds, tracheal deviation, hyperresonance 1

Emergency echocardiography is strongly recommended for rapid identification of pericardial effusion/tamponade, right ventricular dysfunction from PE, and to guide pericardiocentesis. 1

Staged Assessment for Cardiogenic Shock (SCAI Classification)

The American College of Cardiology endorses the SCAI staging system for cardiogenic shock severity 1:

• Stage A (At risk): Normal perfusion, normotensive, no hypoperfusion markers 1
• Stage B (Beginning shock): SBP <90 mm Hg or MAP <60 mm Hg, but preserved perfusion and normal lactate 1
• Stage C (Classic shock): Hypotension with hypoperfusion (cold extremities, altered mentation, oliguria), elevated lactate, impaired renal function 1
• Stage D (Deteriorating): Worsening hypotension/hypoperfusion despite escalating pressors or mechanical support 1
• Stage E (Extremis): Cardiac arrest, refractory hypotension, CPR, recurrent VT/VF 1

Refractory Shock: Occult Causes to Exclude

When shock persists despite appropriate therapy, systematically evaluate for 1:

• Pericardial effusion (requires pericardiocentesis) 1
• Pneumothorax (requires thoracentesis) 1
• Hypoadrenalism (requires hydrocortisone replacement) 1
• Hypothyroidism (requires triiodothyronine replacement) 1
• Ongoing blood loss (requires hemostasis and transfusion) 1
• Increased intra-abdominal pressure (requires decompression) 1
• Inadequate source control of infection (requires surgical intervention and appropriate antibiotics with MIC <1) 1

Practical Diagnostic Algorithm

1. Confirm shock diagnosis: Hypotension + hypoperfusion markers 1
2. Obtain immediate echocardiography for rapid differentiation of cardiac vs. non-cardiac causes 1
3. Measure hemodynamics (CI, CVP, PCWP if available) to categorize shock type 1
4. Assess clinical context: History (trauma, infection, cardiac disease), physical exam (warm vs. cold, JVD, breath sounds) 3, 4
5. Monitor lactate and ScvO2 to assess adequacy of resuscitation 1
6. If refractory, systematically exclude occult reversible causes 1

Key nuance: Shock states can overlap or transition—distributive shock can develop myocardial depression (becoming mixed distributive-cardiogenic), and cardiogenic shock can trigger inflammatory responses. Continuous reassessment is essential. 5