What are the diagnostic guidelines for sepsis?

Diagnostic Guidelines for Sepsis

Sepsis should be diagnosed using a combination of clinical criteria for infection plus evidence of organ dysfunction, with specific laboratory and clinical parameters outlined in the Surviving Sepsis Campaign guidelines. 1

Definition and Diagnostic Criteria

Sepsis Definition

• Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection 2
• This represents a shift from earlier definitions that focused primarily on inflammatory response 1

Diagnostic Criteria for Sepsis

• Suspected or documented infection plus some of the following criteria 1:

General Variables

• Fever (>38.3°C) or hypothermia (core temperature <36°C) 1
• Heart rate >90 min-1 or more than two standard deviations above normal for age 1
• Tachypnea 1
• Altered mental status 1
• Significant edema or positive fluid balance (>20 mL/kg over 24h) 1
• Hyperglycemia (plasma glucose >140 mg/dL or 7.7 mmol/L) in the absence of diabetes 1

Inflammatory Variables

• Leukocytosis (WBC count >12,000 μL-1) 1
• Leukopenia (WBC count <4,000 μL-1) 1
• Normal WBC count with >10% immature forms 1
• Plasma C-reactive protein more than two standard deviations above normal 1, 3
• Plasma procalcitonin more than two standard deviations above normal 1, 4

Hemodynamic Variables

• Arterial hypotension (SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg in adults) 1

Organ Dysfunction Variables

• Arterial hypoxemia (PaO2/FiO2 <300) 1
• Acute oliguria (urine output <0.5 mL/kg/h for at least 2h despite adequate fluid resuscitation) 1
• Creatinine increase >0.5 mg/dL or 44.2 μmol/L 1
• Coagulation abnormalities (INR >1.5 or aPTT prolonged) 1
• Ileus (absent bowel sounds) 1
• Thrombocytopenia (platelet count <100,000 μL-1) 1
• Hyperbilirubinemia (plasma total bilirubin >4 mg/dL or 70 μmol/L) 1

Tissue Perfusion Variables

• Hyperlactatemia (>1 mmol/L) 1, 3
• Decreased capillary refill or mottling 1

Severe Sepsis Definition

• Severe sepsis is defined as sepsis-induced tissue hypoperfusion or organ dysfunction with any of the following 1:
  • Sepsis-induced hypotension 1
  • Lactate above upper limits of laboratory normal 1
  • Urine output <0.5 mL/kg/h for more than 2h despite adequate fluid resuscitation 1
  • PaO2/FiO2 <250 in the absence of pneumonia as infection source 1
  • Acute lung injury with PaO2/FiO2 <200 in the presence of pneumonia as infection source 1
  • Creatinine >2.0 mg/dL (176.8 μmol/L) 1
  • Bilirubin >2 mg/dL (34.2 μmol/L) 1
  • Platelet count <100,000 μL 1
  • Coagulopathy (INR >1.5) 1

Diagnostic Approach

Screening and Early Recognition

• Hospitals should implement sepsis screening programs for acutely ill, high-risk patients 1
• Early recognition is crucial as delayed diagnosis significantly increases mortality 5, 6

Microbiological Diagnosis

• Obtain appropriate routine microbiologic cultures before starting antimicrobial therapy if doing so results in no substantial delay (>45 min) in antimicrobial administration 1
• Always include at least two sets of blood cultures (both aerobic and anaerobic bottles) 1
• One blood culture should be drawn percutaneously and one through each vascular access device (unless recently inserted <48h) 1

Biomarkers

• While no single biomarker can definitively diagnose sepsis, several can aid in diagnosis 3:
  • Lactate: Elevated levels (>1 mmol/L) suggest tissue hypoperfusion; serial measurements help monitor treatment efficacy 1, 4
  • Procalcitonin: More specific for bacterial infections than other inflammatory markers; useful for antimicrobial de-escalation 4, 3
  • C-reactive protein: Indicates inflammation but lacks specificity for infection 4, 3

Imaging Studies

• Perform prompt imaging studies to confirm potential sources of infection 1
• Selection of imaging modality should be based on suspected source 6
• Common sources include pulmonary, urinary tract, abdominal, and skin/soft tissue infections 6

Management Implications of Diagnosis

Antimicrobial Therapy

• Administer effective IV antimicrobials within the first hour of recognition of sepsis or septic shock 1, 7
• Use broad-spectrum agents active against all likely pathogens 1
• Reassess antimicrobial regimen daily for potential de-escalation 1

Source Control

• Identify specific anatomic diagnosis of infection requiring source control as rapidly as possible 1, 7
• Implement source control measures within 12 hours of diagnosis when feasible 1, 7
• Use the least invasive approach for source control 1, 5

Fluid Resuscitation

• Administer at least 30 mL/kg of IV crystalloid fluid within the first 3 hours for patients with sepsis-induced hypoperfusion 1
• Guide additional fluid administration by frequent reassessment of hemodynamic status 1
• Target mean arterial pressure of 65 mmHg in patients with septic shock requiring vasopressors 1

Common Pitfalls in Sepsis Diagnosis

• Relying on a single biomarker to diagnose or exclude sepsis 8, 3
• Delaying antimicrobial therapy while waiting for definitive diagnosis 7, 5
• Failing to obtain appropriate cultures before starting antimicrobials 7, 5
• Not recognizing sepsis in patients with atypical presentations (elderly, immunocompromised) 6, 8
• Overlooking less common sources of infection (endocarditis, meningitis, osteomyelitis) 6
• Confusing sepsis with non-infectious causes of systemic inflammatory response 2, 8