What are the guidelines to define sepsis in a post-operative patient?

Defining Sepsis in Post-Operative Patients

In post-operative patients, sepsis diagnosis requires different criteria depending on timing: within the first 48 hours post-operatively, sepsis requires PROVEN infection (bacteremia, fungemia, or UTI) plus SIRS criteria, whereas after 48 hours, sepsis can be diagnosed with SUSPECTED or proven infection plus SIRS criteria. 1

Time-Based Diagnostic Approach

First 48 Hours Post-Operatively (More Stringent Criteria)

Sepsis requires ALL of the following:

• Proven infection (documented bacteremia, fungemia, or urinary tract infection) 1
• SIRS criteria (at least 2 of the following):
  • Hypo- or hyperthermia (>38.5°C or <36.0°C) 1
  • Tachycardia or bradycardia 1
  • Tachypnea 1
  • Leukocytosis or leukopenia 1
  • Thrombocytopenia 1

Rationale: The ACC/AHA guidelines emphasize that SIRS may result from surgical stress and/or cardiopulmonary bypass during the first 48 hours, making clinical criteria more stringent to avoid false-positive diagnoses. 1

After 48 Hours Post-Operatively (Standard Criteria)

Sepsis requires:

• Suspected OR proven infection 1
• SIRS criteria (same as above - at least 2 criteria) 1

Additional Diagnostic Considerations

Organ Dysfunction Assessment

For severe sepsis or septic shock, assess for:

• Sepsis-induced hypotension: SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg 1, 2
• Elevated lactate: >1 mmol/L indicates tissue hypoperfusion 2
• Acute oliguria: Urine output <0.5 mL/kg/h for at least 2 hours despite adequate fluid resuscitation 2
• Acute lung injury: PaO₂/FiO₂ <250 (without pneumonia) or <200 (with pneumonia) 2
• Creatinine elevation: ≥0.5 mg/dL increase or >2.0 mg/dL for severe sepsis 2
• Coagulation abnormalities: INR >1.5 or aPTT >60 seconds 2
• Thrombocytopenia: Platelet count <100,000/μL 2
• Hyperbilirubinemia: Total bilirubin >2 mg/dL for severe sepsis 2

Contemporary Sepsis-3 Definition Context

While the Sepsis-3 consensus defines sepsis as life-threatening organ dysfunction (SOFA score increase ≥2 points) caused by dysregulated host response to infection 1, the ACC/AHA guidelines provide specific post-operative criteria that account for the unique physiologic stress of surgery. 1

Critical Pitfalls to Avoid

Do not diagnose sepsis in the first 48 hours post-operatively based on SIRS criteria alone - this is the most common error, as fever, tachycardia, and leukocytosis are expected physiologic responses to surgery. 1

Do not wait for positive cultures after 48 hours - clinical suspicion with SIRS is sufficient to initiate sepsis protocols after this timeframe. 1

In post-operative intra-abdominal infections, recognize that tertiary/persistent peritonitis (>48 hours after initial source control) carries higher mortality and often involves multidrug-resistant organisms. 1

Immediate Management Priorities

Once sepsis is diagnosed:

• Administer IV antimicrobials within 1 hour of recognition 2
• Give at least 30 mL/kg IV crystalloid within 3 hours for sepsis-induced hypoperfusion 2
• Target MAP ≥65 mmHg with vasopressors if needed 2
• Normalize lactate as a resuscitation endpoint 2
• Obtain blood cultures (at least 2 sets) before antibiotics when possible 2