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What is septic

Reading File
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Searching PubMed

"sepsis"[MeSH Terms] AND "definition"

Reading File
"Septic" most often means sepsis-related. It describes a body-wide, life-threatening reaction to infection. (If you meant a septic tank, tell me and I'll cover that.)
Definitions
  • Sepsis is an infectious syndrome with high morbidity and mortality and long-term effects in survivors. The word comes from the Greek sipsi, "to make rotten." Osler said the patient usually appears to die from the body's response to infection, not from the infection itself (Harrison's Principles of Internal Medicine 22E, Ch. 315).
  • Current definition (Sepsis-3, 2016): life-threatening organ dysfunction caused by a dysregulated host response to infection. In practice this is suspected infection plus an acute rise in SOFA score of 2 or more. The Harrison's excerpt I retrieved cut off just as it began describing Sepsis-3, so this part comes from my own knowledge.
  • Septic shock is sepsis with circulatory and cellular/metabolic failure. Clinically, the patient needs vasopressors to keep mean arterial pressure at 65 mmHg or higher and has a lactate above 2 mmol/L despite adequate fluids. This is also from my own knowledge.
  • Older definitions: the 1992 consensus defined sepsis as infection plus 2 or more SIRS criteria. These were temperature below 36°C or above 38°C, heart rate above 90, respiratory rate above 20, and WBC below 4,000 or above 12,000/μL. Sepsis-3 dropped the SIRS criteria (Harrison's, Ch. 315).
Causes and sources
  • About 88% of cases begin in the community, and about 12% begin in hospital.
  • About 53% of US cases are culture-positive for bacteria, split fairly evenly between gram-positive and gram-negative organisms. Viruses and fungi can also cause sepsis.
  • The most common gram-positive organisms are S. aureus, Streptococcus and Enterococcus. The most common gram-negative organisms are E. coli, Klebsiella and Pseudomonas.
  • The most common primary sites are the urinary tract (48.9%), respiratory tract (32.9%), abdomen (13.6%) and skin or soft tissue (10.3%).
Clinical picture and management (from my own knowledge)
  • Typical features are fever or low temperature, fast heart rate and breathing, confusion, low urine output, and low blood pressure.
  • Treatment is urgent. It includes early broad-spectrum antibiotics, blood cultures and lactate measurement, IV fluids, vasopressors (usually norepinephrine) if hypotension persists, and source control.
Recent evidence check: I searched PubMed for systematic reviews and meta-analyses from the last 2 years. None contradicts the definitions above. The results were a 2026 veterinary consensus definition of sepsis in dogs and cats and a meta-analysis of presepsin as a diagnostic marker (PMID 42321635).
I can go deeper on pathophysiology, SOFA/qSOFA, or treatment if you'd like.
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