Sepsis and septic shock: life-threatening infection emergency¶

Sepsis is the body's overwhelming, life-threatening response to an infection. It occurs when a localized infection you already have (such as pneumonia, a urinary tract infection, a skin wound, a dental abscess, or an abdominal infection) triggers an uncontrolled inflammatory chain reaction throughout your bloodstream and immune system.

Instead of targeting only the invading bacteria, virus, or fungus, your immune system begins damaging your own blood vessels, tissues, and major organs. Left untreated, sepsis progresses within hours to septic shock, widespread microscopic blood clotting, multi-organ failure, and death. Sepsis is a true medical emergency that requires the exact same speed and urgency as a heart attack or stroke.

Do this now¶

1. Call your local emergency number immediately. Dial 911 in the United States and Canada, 112 across the European Union, 999 in the United Kingdom, or 000 in Australia (see all emergency numbers).
2. Say the word "sepsis" to the dispatcher and paramedics. State clearly: "I suspect sepsis." Using that exact term triggers rapid pre-hospital sepsis triage protocols, point-of-care lactate testing, and priority emergency room notification.
3. Check the TIME warning signs and physical observations. Look for Temperature abnormalities (fever above 38.3 degrees Celsius / 101 degrees Fahrenheit or hypothermia below 36.0 degrees Celsius / 96.8 degrees Fahrenheit), Infection signs, Mental decline (new confusion, delirium, or difficulty waking), and Extreme illness (shortness of breath, shaking chills, or pale, mottled skin).
4. Position the person to support blood flow and breathing. If they feel faint, dizzy, or have low blood pressure, lay them flat on their back so blood can reach the brain; if they have severe pneumonia or struggle to breathe while flat, keep their head and shoulders propped at a 30-to-45-degree angle.
5. Keep them comfortable without overheating. Cover someone experiencing violent shaking chills (rigors) with a light blanket, but do not pack them in heavy layers or apply ice baths, which increase metabolic stress.
6. Give nothing by mouth and prepare a medication list. Do not offer food, water, or oral fever reducers, because sepsis frequently causes vomiting and reduced consciousness that lead to airway aspiration. Gather all current medications, recent surgical discharge papers, and the exact time symptoms started for arriving paramedics.

Emergency sepsis triage and recognition flow¶

flowchart TD
    Start["Suspected or Confirmed Infection<br/>Pneumonia, UTI, wound, post-partum, or viral illness"] --> Screen{"Check Red Flag Symptoms:<br/>Confusion, rapid breathing (>22/min),<br/>extreme shivering, mottled skin, or no urine?"}

    Screen -->|Yes, 1 or more present| Call911["Call Emergency Dispatch Immediately<br/>911 US/Canada, 112 EU, 999 UK<br/>State clearly: 'I suspect sepsis'"]
    Screen -->|No red flags yet| AgeCheck{"Is patient an infant (<1 yr), pregnant/postpartum,<br/>elderly (>65 yr), or on chemotherapy?"}

    AgeCheck -->|Yes, high-risk group| UrgentEval["Seek Same-Day Urgent Medical Evaluation<br/>High-risk patients often lack fever<br/>Monitor mental status and breathing hourly"]
    AgeCheck -->|No| Monitor["Treat Local Infection as Directed<br/>Check temperature and hydration every 4 hours<br/>Re-evaluate immediately if symptoms worsen"]

    Call911 --> FirstAid["Pre-Hospital Stabilization<br/>Keep patient lying down or semi-upright for breathing<br/>Give nothing by mouth; prepare medication list"]
    FirstAid --> HospitalBundle["Hospital Hour-1 Sepsis Bundle<br/>Blood lactate and blood cultures<br/>Immediate IV antibiotics and IV fluids"]

Pathophysiology: how a local infection becomes septic shock¶

Medical teams track the progression of systemic infection across distinct physiological stages as microvascular circulation breaks down:

1. Localized infection¶

Pathogens such as bacteria (Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae), viruses (influenza, SARS-CoV-2), or fungi multiply in a specific anatomical site. The most common starting points are the lungs (pneumonia, accounting for roughly half of all sepsis cases), the urinary tract and kidneys, the gastrointestinal tract (appendicitis, diverticulitis, gall bladder infection), and the skin or soft tissues (cellulitis, surgical incisions, pressure ulcers, or burns).

2. Systemic sepsis and endothelial leak¶

When microbial toxins and pathogen-associated molecular patterns enter the bloodstream, the immune system releases a massive surge of pro-inflammatory signaling proteins called cytokines. Instead of remaining localized, this cytokine surge attacks the endothelium (the delicate inner lining of blood vessels throughout the body). Blood vessels become abnormally porous, allowing intravascular fluid to leak out into surrounding tissues, while nitric oxide causes systemic vasodilation that drops arterial blood pressure.

3. Disseminated microvascular clotting and organ dysfunction¶

Simultaneously, the inflammatory cascade activates the blood coagulation system, forming thousands of microscopic fibrin clots inside tiny capillary beds (a process that can escalate into Disseminated Intravascular Coagulation, or DIC). These micro-clots block oxygen-rich blood from reaching organs, while consuming the body's platelets and clotting factors until spontaneous bleeding and purple skin blotches (purpura) appear:

• Lungs: Capillary leakage floods the pulmonary air sacs (alveoli) with protein-rich fluid, causing Acute Respiratory Distress Syndrome (ARDS) and severe hypoxemia.
• Kidneys: Falling renal perfusion pressure causes Acute Kidney Injury (AKI), halting urine production (oliguria or anuria) and allowing urea and potassium to build up in the blood.
• Brain: Septic encephalopathy impairs cerebral blood flow and blood-brain barrier integrity, presenting as acute delirium, agitation, slurred speech, or coma.
• Heart and liver: Myocardial depression reduces cardiac output, while impaired liver clearance elevates bilirubin and prevents normal glucose regulation.

4. Septic shock¶

Septic shock is the most lethal phase of sepsis. It is clinically defined as sepsis accompanied by profound circulatory and cellular metabolic abnormalities in which systolic blood pressure remains dangerously low (below 90 mmHg, or a Mean Arterial Pressure below 65 mmHg) despite aggressive intravenous fluid resuscitation, accompanied by a serum blood lactate level above 2 mmol/L. At this stage, body cells can no longer extract or use oxygen (cytopathic hypoxia), leading to rapid cardiovascular collapse.

Comparing localized infection versus systemic sepsis¶

Use this clinical comparison table to distinguish a routine fever response from a life-threatening sepsis emergency.

Recognizing atypical sepsis across high-risk age groups¶

One of the greatest dangers of sepsis is that vulnerable populations rarely display a classic high fever. Waiting for a thermometer to read high in an infant, an older adult, or a cancer patient can cost their life.

Neonatal and pediatric sepsis (infants and children)¶

Infants under 12 months (and especially newborns in the first 28 days of life) have immature immune systems that allow localized bacterial infections (such as Group B Streptococcus, E. coli, or respiratory syncytial virus complications) to enter the bloodstream and meninges rapidly. Seek immediate emergency care if a baby or child displays:

• Abnormal temperature regulation: A rectal temperature of 38.0 degrees Celsius (100.4 degrees Fahrenheit) or higher in any infant under 3 months old is an automatic medical emergency, as is an abnormally cold body temperature below 36.0 degrees Celsius (96.8 degrees Fahrenheit).
• Lethargy and altered tone: A baby who is floppy, limp, difficult to wake for feeds, or refuses two consecutive feedings.
• High-pitched or weak crying: A continuous, inconsolable high-pitched moan or a weak, whimpering cry that sounds completely different from normal crying.
• Respiratory distress: Nasal flaring, rhythmic grunting noises with every exhale, chest retractions (skin sucking in sharply around the ribs and breastbone), or pauses in breathing (apnea) lasting more than 15 seconds.
• Perfusion and fontanelle signs: Pale, mottled, or blue-tinged skin around the lips, cold hands and feet despite a warm room, a bulging or sunken soft spot (fontanelle) on top of the head, or a non-blanching purple rash that does not fade when you press the side of a clear drinking glass firmly against the skin.

Maternal and postpartum sepsis (pregnancy and up to 6 weeks after birth)¶

Pregnancy and childbirth alter immune responses and create anatomical pathways for infection following vaginal delivery, cesarean section, miscarriage, or amniocentesis. Normal physiological changes of pregnancy (faster heart rate and faster breathing) frequently mask early sepsis signs. Watch closely during pregnancy and for 42 days postpartum for:

• Lower abdominal, pelvic, or uterine pain and tenderness accompanied by foul-smelling vaginal discharge (lochia).
• Redness, pus, swelling, or separating edges along a cesarean section incision or perineal tear.
• Severe breast redness and flu-like body aches (mastitis) that suddenly worsen with confusion, dizziness, or rapid breathing.
• Sudden hypothermia, persistent tachycardia over 100 beats per minute, or severe generalized muscle pain (a classic early hallmark of invasive Group A Streptococcal puerperal sepsis).

Older adults (atypical afebrile delirium presentation)¶

Adults aged 65 and older account for more than 60 percent of all sepsis hospitalizations, yet up to 30 to 40 percent of older sepsis patients never develop a fever. Instead of mounting a high temperature, an aging immune system often responds with hypothermia or a normal temperature alongside sudden neurological and functional decline:

• Acute delirium and confusion: An older adult with an unrecognized urinary tract infection or early pneumonia may suddenly fail to recognize family members, become uncharacteristically agitated, hallucinate, or become non-verbal over a matter of hours.
• Unexplained falls and sudden immobility: A sudden inability to get out of a chair, new incontinence, or an unexplained fall on the floor is frequently the very first visible sign of sepsis in a frail older adult.

Immunocompromised patients and neutropenic sepsis¶

Patients receiving cytotoxic chemotherapy for cancer, organ transplant recipients taking immunosuppressants, and people taking high-dose biologics or corticosteroids have severely depleted white blood cells (neutrophils).

• Neutropenic sepsis is a minute-by-minute emergency: In a chemotherapy patient, a single oral temperature reading of 38.3 degrees Celsius (101 degrees Fahrenheit), or a temperature of 38.0 degrees Celsius (100.4 degrees Fahrenheit) sustained for one hour, or shivering chills without a fever requires going straight to the emergency department for immediate intravenous antibiotics within 60 minutes (the "door-to-needle" target).
• Never give paracetamol (acetaminophen) or ibuprofen to mask a fever in a chemotherapy patient before calling their oncology emergency line or going to the hospital.

What happens at the hospital: the Hour-1 Sepsis Bundle¶

When you arrive at the emergency department and state that you suspect sepsis, clinicians use rapid screening tools such as qSOFA (quick Sequential Organ Failure Assessment: respiratory rate 22 or higher, altered mentation, and systolic blood pressure 100 mmHg or lower) or NEWS2 (National Early Warning Score 2 in the UK) and execute the Surviving Sepsis Campaign Hour-1 Bundle:

• Serum lactate measurement: A rapid blood draw measures lactic acid produced by oxygen-starved tissues; levels above 2 mmol/L indicate tissue hypoperfusion, and levels above 4 mmol/L indicate severe shock.
• Blood cultures before antibiotics: Two sets of blood cultures (aerobic and anaerobic) alongside urine, sputum, or wound cultures are drawn immediately so laboratories can identify the exact pathogen and its antibiotic sensitivity without delaying treatment.
• Broad-spectrum intravenous antibiotics: Powerful IV antimicrobials are infused within the first 60 minutes to halt bacterial replication immediately.
• Rapid crystalloid fluid resuscitation: For hypotension or lactate of 4 mmol/L or higher, nurses infuse 30 milliliters per kilogram of body weight of balanced crystalloid solution (such as Lactated Ringer's or normal saline) within the first 3 hours.
• Vasopressor support and source control: If blood pressure remains below a Mean Arterial Pressure of 65 mmHg despite fluids, intensive care teams start continuous norepinephrine infusions and arrange urgent surgical drainage of any abscess, infected kidney stone, or necrotic tissue.

Recovery and Post-Sepsis Syndrome (PSS)¶

Surviving sepsis is the beginning of a long rehabilitation journey. Up to 50 percent of sepsis survivors experience Post-Sepsis Syndrome (PSS), a combination of physical, cognitive, and psychological long-term effects that can last for months or years after hospital discharge:

• Physical complications: Profound muscle weakness and nerve damage (ICU-acquired weakness or critical illness polyneuropathy), persistent joint pain, breathlessness, hair loss, brittle nails, and chronic kidney or heart impairment.
• Cognitive and emotional effects: Memory deficits, difficulty concentrating ("brain fog"), insomnia, nightmares, clinical depression, and Post-Traumatic Stress Disorder (PTSD) triggered by delirium and intensive care stays.
• Heightened re-infection risk: The immune system remains dysregulated for months after severe sepsis, meaning survivors face a high risk of hospital readmission for secondary infections. Make sure survivors receive recommended pneumococcal, influenza, and COVID-19 vaccinations once cleared by their physician, and treat any new cut or urinary symptom promptly.

Frequently asked questions¶

Sources checked¶

• Surviving Sepsis Campaign (Society of Critical Care Medicine and European Society of Intensive Care Medicine): International Guidelines for Management of Sepsis and Septic Shock.
• World Health Organization (WHO): Global Report on the Epidemiology and Burden of Sepsis.
• US Centers for Disease Control and Prevention (CDC): About Sepsis and Get Ahead of Sepsis Clinical Guidelines.
• UK National Institute for Health and Care Excellence (NICE): Suspected Sepsis: Recognition, Diagnosis and Early Management (NG51) and UK Sepsis Trust Clinical Tools.
• Sepsis Alliance (United States): Sepsis TIME Recognition Protocol and Post-Sepsis Syndrome Guidance.

Related guides¶

• Recognizing and treating medical shock
• Severe allergic reactions and anaphylaxis
• Infected wounds, cuts, and scrapes
• Knocked-out tooth and dental abscesses
• Emergency numbers directory