Septic Shock Diagnosis
Septic shock is diagnosed when a patient with suspected or documented infection requires vasopressor therapy to maintain mean arterial pressure ≥65 mmHg AND has a serum lactate level >2 mmol/L (>18 mg/dL) despite adequate fluid resuscitation. 1, 2
Core Diagnostic Criteria
The diagnosis requires all three of the following components:
- Suspected or documented infection with evidence of systemic inflammatory response 1
- Persistent hypotension requiring vasopressors to maintain MAP ≥65 mmHg after adequate volume resuscitation 1, 2
- Elevated serum lactate >2 mmol/L in the absence of hypovolemia 1, 2
Clinical Presentation
Patients typically present with signs of inadequate tissue perfusion including:
- Altered mental status (irritability, confusion, drowsiness, lethargy, or unarousable state) 1
- Hypoperfusion signs: oliguria (<0.5 mL/kg/h), acute mental status changes, lactic acidosis 1
- Cold shock findings: prolonged capillary refill >2 seconds, diminished pulses, mottled cool extremities 1
- Warm shock findings: flash capillary refill, bounding peripheral pulses, wide pulse pressure 1
Diagnostic Algorithm
Step 1: Identify Suspected Infection
Look for clinical signs of infection with systemic inflammation:
- Temperature: >38.3°C or <36°C 3
- Heart rate: >90 beats per minute 1, 3
- Respiratory rate: >20 breaths per minute or PaCO₂ <32 mmHg 1, 3
- White blood cell count: >12,000/μL or <4,000/μL, or >10% immature forms 1, 3
Step 2: Assess for Organ Dysfunction
Evidence of organ dysfunction indicates progression from infection to sepsis:
- Cardiovascular: Hypotension (SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg) 1, 3
- Renal: Acute oliguria (<0.5 mL/kg/h for ≥2 hours despite fluids) or creatinine increase ≥0.5 mg/dL 3
- Respiratory: PaO₂/FiO₂ <300 3
- Hematologic: Platelets <100,000/μL, INR >1.5, or aPTT >60 seconds 3
- Hepatic: Bilirubin >4 mg/dL 3
- Neurologic: Altered mental status 1
Step 3: Confirm Septic Shock
After identifying sepsis (infection + organ dysfunction), septic shock is confirmed by:
- Persistent hypotension despite fluid challenge of 30 mL/kg crystalloid 2, 4
- Vasopressor requirement to maintain MAP ≥65 mmHg 1, 2
- Lactate >2 mmol/L measured immediately upon recognition 2, 3
Critical Pitfalls to Avoid
Do not wait for hypotension to diagnose septic shock if the patient is already on vasopressors—they may have normal blood pressure but still meet criteria if lactate is elevated and vasopressors are required 1, 2
Do not delay lactate measurement—it is essential for diagnosis and must be obtained immediately upon suspecting septic shock 2, 3
Do not confuse septic shock with other forms of distributive shock (anaphylaxis, neurogenic shock)—the presence of infection is mandatory 2
Do not continue excessive fluid administration while delaying vasopressor initiation—after the initial 30 mL/kg fluid challenge, start vasopressors if hypotension persists 2, 4
Do not fail to recognize perfusion abnormalities in patients receiving vasopressors who appear normotensive—elevated lactate, oliguria, or altered mental status indicate ongoing shock despite blood pressure support 1, 2
Pediatric Considerations
In children, septic shock is diagnosed clinically without requiring hypotension:
- Suspected infection with hypothermia or hyperthermia 1
- Signs of inadequate perfusion: decreased/altered mental status, prolonged capillary refill >2 seconds (cold shock), diminished pulses, mottled cool extremities, or flash capillary refill with bounding pulses (warm shock) 1
- Decreased urine output <1 mL/kg/h 1
- Hypotension, if present, is confirmatory but not required for diagnosis 1
Immediate Actions Upon Diagnosis
Once septic shock is diagnosed: