Signs and Symptoms of Sepsis
Sepsis is defined by life-threatening organ dysfunction caused by a dysregulated host response to infection, and its recognition requires identifying both signs of infection and evidence of organ dysfunction. 1
Core Diagnostic Framework
The modern approach to sepsis recognition has evolved from the older SIRS criteria to focus on organ dysfunction. However, understanding both frameworks remains clinically useful 1:
General Signs of Infection and Inflammation
Temperature abnormalities:
Cardiovascular signs:
- Heart rate >90 beats per minute (or >2 standard deviations above normal for age) 1
- Tachycardia is one of the most consistent early findings 1
Respiratory signs:
- Respiratory rate >20 breaths per minute 1
- Tachypnea (increased respiratory rate) 1
- Partial pressure of CO2 <32 mmHg 1
Mental status changes:
- Altered mental status or confusion 1
- This is particularly important as it indicates brain dysfunction 1
Laboratory inflammatory markers:
- White blood cell count >12,000/μL or <4,000/μL 1
- >10% immature (band) forms 1
- Elevated C-reactive protein >2 SD above normal 1
- Elevated procalcitonin >2 SD above normal 1
Critical Signs of Organ Dysfunction (Severe Sepsis)
These findings differentiate sepsis from simple infection and indicate life-threatening disease 1:
Hemodynamic dysfunction:
- Arterial hypotension: systolic blood pressure <90 mmHg, mean arterial pressure <70 mmHg, or systolic blood pressure decrease >40 mmHg 1
- Septic shock specifically requires vasopressor therapy to maintain mean arterial pressure ≥65 mmHg 1, 2
Respiratory dysfunction:
- Arterial hypoxemia (PaO2/FiO2 <300) 1
- Acute lung injury with PaO2/FiO2 <250 without pneumonia as source 1
- Acute lung injury with PaO2/FiO2 <200 with pneumonia as source 1
Renal dysfunction:
- Acute oliguria: urine output <0.5 mL/kg/hr for at least 2 hours despite adequate fluid resuscitation 1
- Creatinine increase >0.5 mg/dL or creatinine >2.0 mg/dL 1
Hepatic dysfunction:
- Hyperbilirubinemia: total bilirubin >4 mg/dL or >2 mg/dL 1
Hematologic dysfunction:
- Thrombocytopenia: platelet count <100 × 10³/μL 1
- Coagulation abnormalities: INR >1.5 or aPTT >60 seconds 1
Gastrointestinal dysfunction:
- Ileus (absent bowel sounds) 1
Tissue perfusion abnormalities:
- Hyperlactatemia (lactate >1 mmol/L, and >2 mmol/L defines septic shock) 1, 2
- Decreased capillary refill or mottling 1
Metabolic signs:
- Significant edema or positive fluid balance (>20 mL/kg over 24 hours) 1
- Hyperglycemia (plasma glucose >140 mg/dL) in absence of diabetes 1
Clinical Recognition Patterns
The key distinction is that sepsis requires BOTH documented or suspected infection AND evidence of organ dysfunction 1. Simply having fever and tachycardia with infection is insufficient for a sepsis diagnosis under current definitions 1.
Septic shock represents the most severe presentation, characterized by profound circulatory dysfunction with vasodilation, requiring vasopressors to maintain adequate blood pressure AND having elevated lactate >2 mmol/L despite adequate fluid resuscitation 1, 2.
Common Pitfalls
Do not rely solely on vital sign abnormalities - the older SIRS criteria (fever, tachycardia, tachypnea, abnormal WBC) can identify inflammation but miss the critical element of organ dysfunction that defines true sepsis 1.
Patients on vasopressors may still have perfusion abnormalities despite normalized blood pressure - always assess lactate levels and other markers of tissue perfusion 2.
Young patients without comorbidities may be underestimated by scoring systems, as severe respiratory failure alone may not trigger high-risk categorization 1.
Mental status changes are easily overlooked but represent brain dysfunction and should prompt immediate sepsis evaluation 1.