Classic Signs of Sepsis
The classic signs of sepsis include fever (>38.3°C) or hypothermia (<36°C), tachycardia (>90 bpm), tachypnea (>20-30 breaths/min), and altered mental status, along with evidence of organ dysfunction or tissue hypoperfusion. 1, 2
General Clinical Parameters
The most recognizable signs that should trigger immediate sepsis consideration include:
- Fever with core temperature >38.3°C or hypothermia with core temperature <36°C 3, 1, 2
- Tachycardia defined as heart rate >90 beats per minute or >2 standard deviations above normal for age 3, 1, 2
- Tachypnea with respiratory rate >20-30 breaths per minute 3, 1, 2
- Altered mental status representing early organ dysfunction 3, 1
- Significant edema or positive fluid balance (>20 mL/kg over 24 hours) 3, 2
- Hyperglycemia (plasma glucose >110-140 mg/dL) in the absence of diabetes 3, 1, 2
Inflammatory Markers
Laboratory findings that support sepsis diagnosis include:
- Leukocytosis (WBC >12,000/μL) or leukopenia (WBC <4,000/μL) 1, 2, 4
- Normal WBC with >10% immature forms (bandemia) 1, 2
- Elevated C-reactive protein or procalcitonin (>2 standard deviations above normal) 3, 1, 2
Hemodynamic Abnormalities
Critical cardiovascular signs include:
- Arterial hypotension with systolic blood pressure <90 mmHg, mean arterial pressure <70 mmHg, or systolic blood pressure decrease >40 mmHg in adults 3, 1, 2
- Mixed venous oxygen saturation >70% 3, 1
- Cardiac index >3.5 L/min/m² 3, 1
Organ Dysfunction Parameters
Signs indicating progression to severe sepsis include:
- Arterial hypoxemia with PaO₂/FiO₂ ratio <300 3, 1, 2
- Acute oliguria with urine output <0.5 mL/kg/h for at least 2 hours despite adequate fluid resuscitation 3, 1, 2
- Creatinine increase ≥0.5 mg/dL 3, 1
- Coagulation abnormalities with INR >1.5 or aPTT >60 seconds 3, 1, 2
- Ileus with absent bowel sounds 3, 1, 2
- Thrombocytopenia with platelet count <100,000/μL 3, 1, 2
- Hyperbilirubinemia with plasma total bilirubin >4 mg/dL 3, 1
Tissue Perfusion Abnormalities
Signs of inadequate tissue perfusion that indicate severe disease:
- Hyperlactatemia (>1-3 mmol/L) 3, 1, 2
- Decreased capillary refill or skin mottling 3, 1, 2
- Peripheral cyanosis 1
Respiratory Manifestations
When sepsis affects the lungs, patients may present with:
- Severe dyspnea and unremitting hypoxemia 3
- Tachypnea with elevated minute ventilation 3
- Increased work of breathing due to ventilation-perfusion mismatching 3
Important Clinical Caveats
In neutropenic patients, white blood cell count cannot be used as a diagnostic criterion, making fever, tachycardia, tachypnea, and organ dysfunction the primary indicators 3. These patients may have attenuated inflammatory responses, requiring heightened clinical suspicion 3.
Elderly patients may present with fewer classic signs and attenuated inflammatory responses, necessitating lower thresholds for sepsis consideration 1.
The clinical presentation can range from flagrant to subtle, and early recognition based on these classic signs allows for prompt intervention that directly impacts mortality 4, 5. Approximately 45% of patients meeting clinical sepsis criteria will have positive blood cultures, with mortality rates around 30% 6.