Sepsis

Core definition and pathophysiology

Sepsis arises when an infection triggers an overwhelming or impaired whole-body immune response, leading to widespread inflammation, endothelial injury, leaky vasculature, microvascular thrombosis, and ultimately impaired organ perfusion and damage.
Bacterial infections are the most common cause, but viruses (e.g., influenza, COVID‑19), fungi (e.g., Candida), and, less often, parasites or even severe noninfectious insults can precipitate a septic response.

Common sources and pathogens

Frequent primary infection sites include lungs (pneumonia), abdomen (intra‑abdominal infections), urinary tract, skin/soft tissue, and less commonly CNS and other organs.​
Typical bacterial pathogens include gram‑positive organisms such as staphylococci and streptococci and gram‑negative organisms like E. coli, Klebsiella, and Pseudomonas, while Candida species dominate fungal sepsis.​

Clinical features and progression

Early manifestations often include fever or hypothermia, tachycardia, tachypnea, altered mental status, oliguria, hyperglycemia, and signs related to the primary infection focus (e.g., cough, dysuria, abdominal pain).
As sepsis progresses to severe sepsis and septic shock, patients develop objective organ dysfunction (e.g., respiratory failure, AKI, coagulopathy, liver dysfunction, encephalopathy), hypotension, elevated lactate, and a high risk of multiple organ dysfunction syndrome (MODS) and death.

Diagnosis and risk stratification

Diagnosis is clinical and hinges on suspected or confirmed infection plus evidence of a dysregulated host response and organ dysfunction, supported by vitals, labs (including lactate, WBC, creatinine, LFTs, coagulation parameters), cultures, and imaging to identify the source.
Risk is stratified using sepsis criteria and “bundles” that emphasize prompt identification of high‑risk patients and early interventions, often in a monitored or ICU setting for those with shock or evolving organ failure.

Early warning signs of sepsis are often subtle and can look like a “bad infection that’s suddenly worse than expected.” Key early features include:

• Fever, chills or feeling very cold (or sometimes an abnormally low temperature).

• Fast heart rate and/or rapid breathing, even at rest.

• Feeling very unwell, weak, or “something is wrong” out of proportion to a usual infection.

• New confusion, disorientation, extreme sleepiness, or not acting like their normal self.

• Shortness of breath or trouble breathing.

• New severe or unexplained pain or discomfort (for example, “worst ever” or all‑over body pain).

• Cold, clammy, or sweaty skin; sometimes mottled, pale, or bluish skin, lips, or nail beds.

Many public campaigns summarize adult red flags with the acronym TIME:

• T – Temperature (very high or very low).

• I – Infection (known or suspected).​

• M – Mental decline (confused, sleepy, difficult to rouse).

• E – Extremely ill (severe pain, shortness of breath, “I feel like I might die”).

If sepsis is suspected in anyone with an infection (or recent surgery/trauma), they need urgent medical assessment; guidelines advise seeking emergency care and explicitly stating concern for sepsis.

Management principles

Sepsis is time‑critical: recommended care bundles call for rapid administration of broad‑spectrum IV antibiotics, early and aggressive IV fluid resuscitation, early blood cultures and lactate measurement, and close hemodynamic and organ‑function monitoring, escalating to vasopressors, mechanical ventilation, and renal replacement therapy as needed.
Effective management also requires prompt source control—such as drainage of abscesses, debridement of necrotizing soft‑tissue infection, or surgery for perforated viscera—since ongoing infection drives continued inflammatory injury.