How is sepsis defined and what are the diagnostic criteria and first‑hour management steps for an adult patient with suspected infection?

Sepsis: Definition, Diagnostic Criteria, and First-Hour Management

Definition

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection—not simply infection with inflammation, but infection that triggers harmful organ damage. 1, 2

The critical distinction is that sepsis requires both documented or suspected infection and evidence of organ dysfunction, not just fever or elevated white blood cell count. 1, 2

Diagnostic Criteria

Primary Diagnostic Framework: SOFA Score

The gold standard for diagnosing sepsis requires an increase in the Sequential Organ Failure Assessment (SOFA) score of ≥2 points from baseline, which correlates with in-hospital mortality >10%. 2

The SOFA score assesses six organ systems:

• Respiratory: PaO₂/FiO₂ ratio <300 or SpO₂ ≤90% 2
• Cardiovascular: Hypotension (SBP <90 mmHg or MAP <70 mmHg) or vasopressor requirement 2
• Renal: Creatinine >2.0 mg/dL or urine output <0.5 mL/kg/hr for ≥2 hours 2
• Hepatic: Bilirubin >2 mg/dL 2
• Coagulation: Platelets <100,000/μL or INR >1.5 2
• Neurological: Altered mental status or decreased Glasgow Coma Scale 2

Bedside Risk Stratification: NEWS2 and qSOFA

For initial risk assessment in acute hospital settings, calculate the National Early Warning Score 2 (NEWS2) to determine urgency of intervention and antibiotic timing. 1

The quick SOFA (qSOFA) identifies high-risk patients outside ICU settings when ≥2 of the following are present:

• Systolic blood pressure ≤100 mmHg 3
• Respiratory rate ≥22/min 3
• Altered mental status 3

Important caveat: The Sepsis-3 consensus explicitly discontinued SIRS criteria for sepsis classification, though SIRS may still serve as an early screening tool. 2

Septic Shock Criteria

Septic shock is diagnosed when sepsis criteria are met PLUS persistent hypotension after adequate fluid resuscitation (MAP <65 mmHg) OR lactate >4 mmol/L. 2

First-Hour Management Bundle

Immediate Actions (Within 60 Minutes)

1. Obtain Blood Cultures Before Antibiotics

Draw at least two sets of aerobic and anaerobic blood cultures from separate sites before administering antimicrobials. 4, 2

2. Administer Broad-Spectrum Antibiotics

Give empiric intravenous antibiotics within 60 minutes of sepsis recognition—every hour of delay increases mortality. 4

• Standard empiric regimen: Ceftriaxone 2g IV or cefotaxime 2g IV 4
• Adjust based on suspected source and local resistance patterns 4

3. Measure Serum Lactate

Obtain initial lactate level; values >2 mmol/L indicate tissue hypoperfusion and mandate aggressive resuscitation. 4, 2

4. Begin Rapid Crystalloid Resuscitation

Start intravenous isotonic crystalloid bolus immediately to restore intravascular volume. 4

5. Maintain Mean Arterial Pressure ≥65 mmHg

Target MAP ≥65 mmHg to protect cerebral perfusion and prevent end-organ damage; initiate vasopressors if hypotension persists after fluid resuscitation. 4, 2

Essential Laboratory Workup

• Complete blood count: Leukocytosis >12,000/μL or leukopenia <4,000/μL supports sepsis diagnosis 4
• Comprehensive metabolic panel: Monitor creatinine, bilirubin, and glucose for organ dysfunction 4
• Procalcitonin and CRP: PCT ≥1.5 ng/mL has 100% sensitivity for sepsis; CRP ≥50 mg/L has 98.5% sensitivity 2

Source Identification Imaging

The timing and modality of imaging depends on the suspected source:

• Suspected urosepsis: Begin with abdominal ultrasound for portability and speed; if negative or equivocal, proceed immediately to CT abdomen/pelvis with IV contrast (PPV 81.82% for septic foci) 2
• Respiratory symptoms (cough, dyspnea, chest pain): CT chest with IV contrast is preferred over plain radiography, which has only 58% sensitivity for pneumonia in septic patients 2
• Severe abdominal pain with peritoneal signs: Obtain contrast-enhanced CT abdomen to identify surgically drainable sources requiring source control within 24 hours 4

Critical Pitfalls to Avoid

Do not wait for confirmatory tests to initiate treatment—sepsis management is time-critical, and antibiotics must be given within the first hour even if cultures are pending. 4

Do not rely on fever or SIRS criteria alone—up to 10-15% of septic patients present with hypothermia <36°C rather than fever, and the absence of SIRS does not exclude sepsis. 4, 2

Do not use chest X-ray as the sole imaging modality for suspected pneumonia in septic patients—sensitivity is only 58%, and CT chest with contrast should be obtained when clinical suspicion is high. 2

Recognize atypical presentations in high-risk populations: Elderly patients may lack fever and present only with altered mental status; immunocompromised patients require a lower threshold for emergency evaluation. 4