Sepsis
Critical Care / Infectious Disease
Illness script · Critical Care / Infectious Disease
Sepsis
Life-threatening organ dysfunction caused by a dysregulated host response to infection (SOFA ≥2 change from baseline).
This illness script for Sepsis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Extremes of age (elderly, neonates); immunocompromise (HIV, chemotherapy, steroids)
- Indwelling devices (central lines, urinary catheters, ventilators)
- Chronic illness: diabetes, CKD, cirrhosis, malignancy
- Recent surgery, trauma, or burns
- Common sources: pneumonia, UTI, abdominal/biliary, skin/soft tissue, bacteremia
02
Presentation
- Fever (>38.3°C) or hypothermia (<36°C); tachycardia; tachypnea
- Altered mental status (hallmark of occult or severe sepsis)
- Warm, flushed skin early ('warm shock'); cool, mottled skin late
- Septic shock: persistent hypotension (MAP <65 mmHg) despite adequate fluids + vasopressors needed
- Lactate ≥2 mmol/L indicates tissue hypoperfusion even without overt hypotension
03
Pathophysiology
- Pathogen (or its products: LPS, exotoxins) triggers massive innate immune activation
- Systemic cytokine storm (TNF-α, IL-1, IL-6) causes widespread endothelial injury
- Microvascular thrombosis + vasodilation → tissue hypoperfusion and oxygen debt
- Mitochondrial dysfunction → cellular metabolic failure → multi-organ dysfunction
04
Diagnostics
- Blood cultures × 2 (before antibiotics) — gold standard for pathogen ID
- Serum lactate: ≥2 = sepsis-associated hypoperfusion; ≥4 = septic shock regardless of BP
- CBC, BMP, LFTs, coagulation (assess organ dysfunction / DIC)
- Procalcitonin: supports bacterial etiology; useful for antibiotic de-escalation
- Source workup: UA/urine culture, CXR, CT abdomen/pelvis as clinically indicated
05
Management
- Hour-1 Bundle (Surviving Sepsis): draw cultures, start broad-spectrum antibiotics within 1 hour
- IV fluid resuscitation: 30 mL/kg crystalloid (LR preferred) for hypotension or lactate ≥4
- Vasopressors (norepinephrine first-line) if MAP <65 after fluids
- Source control: drain abscess, remove infected device, surgical intervention as needed
- Reassess fluid responsiveness; avoid over-resuscitation (use dynamic measures); steroid (hydrocortisone) for refractory septic shock
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Systemic Inflammatory Response Syndrome (SIRS)
SIRS lacks confirmed/suspected infection and organ dysfunction (SOFA criterion); sepsis requires both
Cardiogenic Shock
Cardiogenic shock: elevated JVP, pulmonary edema, low CO on echo — not fever/infection source
Anaphylaxis
Anaphylaxis: acute allergen exposure, urticaria, bronchospasm, angioedema — responds rapidly to epinephrine
Adrenal Crisis
Adrenal crisis: known steroid use or adrenal disease, hyponatremia/hyperkalemia, dramatic response to steroids
Keep reading
Full library- Seborrheic DermatitisChronic, relapsing inflammatory skin condition causing greasy, yellowish scales and erythema in sebaceous gland-rich areas.
- Septic ArthritisBacterial infection of a synovial joint causing acute inflammation; a surgical emergency requiring urgent drainage to prevent joint destruction.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.