Sepsis and septic shock !

Sepsis is a life-threatening reaction to an infection that damages the body's own organs; septic shock is its most severe form, with failing circulation.

Updated 2026-10-30

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In biochemistry

Microorganisms that cause it

In immunology

In the clinical exam

In physiology

Why it happens

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What it is

Life-threatening organ dysfunction caused by a dysregulated host response to infection. Septic shock is the subset with circulatory and cellular failure severe enough to markedly raise mortality.

Who gets it

A leading cause of death in hospitals worldwide, including Latin America; most cases start in the community. Among 2,510 adults with severe sepsis or septic shock in emergency departments of three hospitals in Medellín, Colombia, urinary (27.8%) and lung (27.5%) infections were the commonest sources and in-hospital mortality was 11.5%.

Causes

Pneumonia, the most common source
Intra-abdominal infection (peritonitis, cholangitis, appendicitis, abscess)
Urinary tract infection and pyelonephritis
Skin and soft tissue infection; infected catheters and devices
Bacteria (gram-negative and gram-positive) most often; also fungi and viruses

Risk factors

Extremes of age (infants and older adults)
Immunosuppression: cancer, chemotherapy, HIV, steroids, transplant
Diabetes, chronic kidney or liver disease, alcohol use disorder
Recent surgery, invasive devices or hospital stay
Pregnancy and the postpartum period

Pathophysiology

Microbial products trigger an excessive inflammatory and clotting response together with immune suppression. Vasodilation, capillary leak and microvascular thrombosis reduce tissue perfusion and oxygen use, causing lactate rise and dysfunction of the lungs, kidneys, liver, brain, heart and coagulation system.

Classification

Sepsis (Sepsis-3): infection plus an acute increase of 2 or more points in the SOFA score
Septic shock: sepsis needing vasopressors to keep mean arterial pressure at or above 65 mmHg, with lactate above 2 mmol/L despite adequate fluids
By source: respiratory, abdominal, urinary, skin, device-related or unknown

Symptoms and signs

Fever or hypothermia, chills
Fast heart rate and fast breathing
Low blood pressure, cold mottled skin and slow capillary refill
Confusion, agitation or drowsiness
Reduced urine output
Symptoms of the source: cough, abdominal pain, painful urination, a red hot skin area

Diagnosis

Clinical: Suspected infection plus signs of organ dysfunction. qSOFA (respiratory rate ≥22, altered mentation, systolic pressure ≤100 mmHg) is a bedside prompt for risk, not a diagnostic test; SOFA scores dysfunction of six organ systems. Early warning scores are also used.
Tests: Blood cultures (ideally before antibiotics) and cultures from the suspected source, lactate, full blood count, creatinine, bilirubin, coagulation tests, blood gas and glucose; procalcitonin in some settings.
Imaging: Chest X-ray for pneumonia; ultrasound or CT of the abdomen to find a source needing drainage; bedside ultrasound to assess the heart and fluid status.

Differential diagnosis

Hypovolaemic shock (bleeding, dehydration)
Cardiogenic shock (myocardial infarction, myocarditis)
Anaphylaxis
Pulmonary embolism
Acute pancreatitis or other non-infectious systemic inflammation
Severe dengue or other tropical infections

Goal of treatment

Recognise sepsis early, restore tissue perfusion, start effective antimicrobials quickly and control the source of infection, while supporting failing organs.

Treatment

Acute: Early broad-spectrum antibiotics, ideally within the first hour when shock or sepsis is likely, after taking cultures without delaying treatment; later narrowed to the organism found.
Acute: Intravenous crystalloid fluids for hypoperfusion, guided by repeated assessment of response; vasopressors (noradrenaline first-line) if hypotension persists.
Procedure: Source control: drainage of abscesses or empyema, removal of infected devices, surgery for peritonitis or necrotising infection, relief of obstructed bile or urine.
Follow-up: Intensive care monitoring of blood pressure, urine output, lactate and organ function; oxygen, ventilation, dialysis or corticosteroids in refractory shock as needed.

Drugs for this condition

Complications

Acute respiratory distress syndrome (ARDS)
Acute kidney injury
Disseminated intravascular coagulation
Septic cardiomyopathy and arrhythmias
Liver dysfunction and delirium
Multiple organ failure and death
Long-term weakness, cognitive problems and post-intensive care syndrome

Prognosis

Mortality rises with the number of failing organs and is highest in septic shock. Early recognition and prompt antibiotics, fluids and source control improve survival. Survivors often have lasting physical, cognitive or psychological effects.

Prevention

Vaccination (influenza, pneumococcus and others)
Hand hygiene and infection control in hospitals
Prompt treatment of common infections and careful care of catheters and devices

Test yourself

Think of the answer, then tap the question to see it.

How does the Sepsis-3 consensus define sepsis?

Life-threatening organ dysfunction caused by a dysregulated host response to infection, shown by an acute rise of 2 or more points in the SOFA score.

What are the three qSOFA criteria?

Respiratory rate of 22 or more, altered mentation and systolic blood pressure of 100 mmHg or less.

How is septic shock defined?

Sepsis needing vasopressors to keep mean arterial pressure at or above 65 mmHg, with lactate above 2 mmol/L despite adequate fluid resuscitation.

What are the key principles of early sepsis management?

Cultures, early broad-spectrum antibiotics, intravenous fluids for hypoperfusion, vasopressors if needed, lactate measurement and source control.

What is the most common source of sepsis?

Pneumonia, followed by abdominal and urinary tract infections.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Bacterial Sepsis (StatPearls (NCBI Bookshelf), 2023); Association between site of infection and in-hospital mortality in patients with sepsis admitted to emergency departments of tertiary hospitals in Medellin, Colombia (Revista Brasileira de terapia intensiva, 2019) · adapted, CC BY 4.0.

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Right lower lobe highlighted on the Durgical 3D model