Sepsis
System: Bloodstream and Sepsis · Parent MOC: MOC - Diseases by System
One-Sentence Definition
Life-threatening organ dysfunction caused by a dysregulated host response to infection (Sepsis-3) — a clinical syndrome, not a single pathogen.
Clinical Presentation
- Suspected infection + acute organ dysfunction (SOFA rise): respiration, coagulation, liver, CV, CNS, renal
- Septic shock: profound circulatory/cellular failure (vasopressors + lactate criteria per definitions)
- Source may be occult — check every system hub
Pathogens
| Source examples | Organisms | System notes |
|---|---|---|
| Lung | Pneumococcus, Klebsiella, Pseudomonas, S. aureus | Community-Acquired Pneumonia · Hospital-Acquired Pneumonia |
| Urine | Escherichia coli, Klebsiella pneumoniae | Acute Pyelonephritis |
| Skin | Streptococcus pyogenes, Staphylococcus aureus | Necrotizing Soft Tissue Infection |
| Abdomen | Polymicrobial Enterobacterales / anaerobes | Gastrointestinal Infections |
| Line | Staph, Candida, GNRs | CLABSI |
Pathogenesis
- Pathogen molecules (e.g., LPS — Bacterial Cell Wall) + host immunity → cytokine storm, endothelial leak, DIC, shock
- Overlap Pathology and MOC - Immunology
Diagnosis
| Step | Test | Note |
|---|---|---|
| Clinical | qSOFA/SOFA + infection suspicion | Definitions evolve — know local protocol |
| Micro | Blood cultures ×2 before abx if no delay | Also culture likely source |
| Labs | Lactate, CBC, CMP, coags | Trend organ injury |
| Source imaging | Directed by exam |
Treatment Principles (Hour-1 / bundle thinking)
- Resuscitate (fluids, O₂, pressors as needed)
- Cultures then rapid empiric antibiotics covering likely source + local MDR
- Source control (drain, remove line, OR)
- Narrow with results; stewardship after stabilization
Prevention
- Vaccination, infection control, device bundles, stewardship
Differential / Pitfalls
- Pancreatitis, adrenal crisis, PE, anaphylaxis, noninfectious SIRS mimics
- Empiric abx without cultures when cultures were feasible
Learning Aids
Diagrams
Clinical Example
Example
Case: Hypotension, lactate 4.5, fever; cloudy urine; no meningismus.
Question: Immediate micro steps and likely source disease?
Answer: Blood + urine cultures → broad empiric abx → think Acute Pyelonephritis / urinary sepsis; image if obstructed; narrow with AST (Escherichia coli common).
Related
- Bloodstream and Sepsis · CLABSI · Infective Endocarditis
- MOC - Antimicrobials · MOC - Antimicrobial Resistance (AMR)
Active Recall
- Sepsis vs septic shock (conceptual)?
- Order of cultures vs antibiotics when both possible?
- Why source control matters as much as drugs?