What Is Sepsis Infection?

Sepsis is a life-threatening condition that arises when the body’s response to infection injures its own tissues and organs. Common signs and symptoms include fever, increased heart rate, increased breathing rate, and confusion.

There also may be symptoms related to a specific infection, such as a cough with pneumonia, or painful urination with a kidney infection. In the very young, old, and people with a weakened immune system, there may be no symptoms of a specific infection and the body temperature may be low or normal, rather than high.

Severe sepsis is sepsis causing poor organ function or insufficient blood flow. Insufficient blood flow may be evident by low blood pressure, high blood lactate, or low urine output. Septic shock is low blood pressure due to sepsis that does not improve after reasonable amounts of intravenous fluids are given.

Sepsis Infection Symptoms

On top of the symptoms related to the underlying cause, sepsis frequently is associated with either fever, low body temperature, rapid breathing, elevated heart rate, confusion, and edema. Early signs are a rapid heart rate, decreased urination, and high blood sugar. Signs of established sepsis include confusion, metabolic acidosis (which may be accompanied by faster breathing and lead to a respiratory alkalosis), low blood pressure due to decreased systemic vascular resistance, higher cardiac output, and dysfunctions of blood coagulation (where clotting may lead to organ failure).

The drop in blood pressure seen in sepsis may lead to shock. This may result in light-headedness. Bruising or intense bleeding may occur.


Early diagnosis is necessary to properly manage sepsis infection, as initiation of early goal directed therapy is key to reducing mortality from severe sepsis.

Within the first three hours of suspected sepsis, diagnostic studies should include white blood cell counts, measuring serum lactate, and obtaining appropriate cultures before starting antibiotics, so long as this does not delay their use by more than 45 minutes. To identify the causative organism(s), at least two sets of blood cultures using bottles with media for aerobic and anaerobic organisms should be obtained, with at least one drawn through the skin and one drawn through each vascular access device (such as an IV catheter) in place more than 48 hours. even though bacteria are present in the blood in only about 30% of cases.

Another possible method of detection is by polymerase chain reaction. If other sources of infection are suspected, cultures of these sources, such as urine, cerebrospinal fluid, wounds, or respiratory secretions, also should be obtained, as long as this does not delay the use of antibiotics.

Within six hours, if blood pressure remains low despite initial fluid resuscitation of 30 ml/kg, or if initial lactate is ≥ 4 mmol/L (36 mg/dL), central venous pressure and central venous oxygen saturation should be measured. Lactate should be re-measured if the initial lactate was elevated.

Within twelve hours, it is essential to diagnose or exclude any source of infection that would require emergent source control, such as necrotizing soft tissue infection, infection causing inflammation of the abdominal cavity lining, infection of the bile duct, or intestinal infarction. A pierced internal organ (free air on abdominal x-ray or CT scan), an abnormal chest x-ray consistent with pneumonia (with focal opacification), or petechiae, purpura, or purpura fulminans may be evident of infection.

If the SIRS criteria are negative it is very unlikely the person has sepsis; if they are positive, there is just a moderate probability that the person has sepsis.


There are different levels of sepsis: sepsis, severe sepsis, and septic shock.

In 2016 screening by systemic inflammatory response syndrome (SIRS) was replaced with qSOFA, which is two of the following three: increased breathing rate, change in level of consciousness, and low blood pressure.

  • SIRS is the presence of two or more of the following: abnormal body temperature, heart rate, respiratory rate, or blood gas, and white blood cell count.
  • Sepsis is defined as SIRS in response to an infectious process.
  • Severe sepsis is defined as sepsis with sepsis-induced organ dysfunction or tissue hypoperfusion (manifesting as hypotension, elevated lactate, or decreased urine output).
  • Septic shock is severe sepsis plus persistently low blood pressure, despite the administration of intravenous fluids.

End-organ Dysfunction

Examples of end-organ dysfunction include the following:

  • Lungs: acute respiratory distress syndrome (ARDS) (PaO2/FiO2 < 300)
  • Brain: encephalopathy symptoms including agitation, confusion, coma; causes may include ischemia, hemorrhage, formation of blood clots in small blood vessels, microabscesses, multifocal necrotizing leukoencephalopathy
  • Liver: disruption of protein synthetic function manifests acutely as progressive disruption of blood clotting due to an inability to synthesize clotting factors and disruption of metabolic functions leads to impaired bilirubin metabolism, resulting in elevated unconjugated serum bilirubin levels
  • Kidney: low urine output or no urine output, electrolyte abnormalities, or volume overload
  • Heart: systolic and diastolic heart failure, likely due to chemical signals that depress myocyte function, cellular damage, manifest as a troponin leak (although not necessarily ischemic in nature)

More specific definitions of end-organ dysfunction exist for SIRS in pediatrics.

Cardiovascular dysfunction (after fluid resuscitation with at least 40 ml/kg of crystalloid)

  • Hypotension with blood pressure < 5th percentile for age or systolic blood pressure < 2 standard deviations below normal for age, or vasopressor requirement, or two of the following criteria: unexplained metabolic acidosis with base deficit > 5 mEq/L, lactic acidosis: serum lactate 2 times the upper limit of normal, oliguria (urine output < 0.5 ml/kg/h), prolonged capillary refill > 5 seconds, core to peripheral temperature difference > 3 °C
  • Respiratory dysfunction (in the absence of cyanotic heart disease or known chronic lung disease): the ratio of the arterial partial-pressure of oxygen to the fraction of oxygen in the gases inspired (PaO2/FiO2) < 300 (the definition of acute lung injury), or arterial partial-pressure of carbon dioxide (PaCO2) > 65 torr (20 mmHg) over baseline PaCO2 (evidence of hypercapnic respiratory failure), or supplemental oxygen requirement of greater than FiO2 0.5 to maintain oxygen saturation ≥ 92%
  • Neurologic dysfunction: Glasgow Coma Score (GCS) ≤ 11, or altered mental status with drop in GCS of 3 or more points in a patient with developmental delay/intellectual disability
  • Hematologic dysfunction: platelet count < 80,000/mm3 or 50% drop from maximum in chronically thrombocytopenic patients, or international normalized ratio (INR) > 2, Disseminated intravascular coagulation
  • Kidney dysfunction: serum creatinine ≥ 2 times the upper limit of normal for age or 2-fold increase in baseline creatinine in patients with chronic kidney disease
  • Liver dysfunction (only applicable to infants > 1 month): total serum bilirubin ≥ 4 mg/dl, or alanine aminotransferase (ALT) ≥ 2 times the upper limit of normal

Consensus definitions, however, continue to evolve, with the latest expanding the list of signs and symptoms of sepsis to reflect clinical bedside experience.


A 2013 review concluded moderate-quality evidence exists to support use of the procalcitonin level as a method to distinguish sepsis from non-infectious causes of SIRS. The same review found the sensitivity of the test to be 77% and the specificity to be 79%. The authors suggested that procalcitonin may serve as a helpful diagnostic marker for sepsis, but cautioned that its level alone cannot definitively make the diagnosis.

A 2012 systematic review found that soluble urokinase-type plasminogen activator receptor (SuPAR) is a nonspecific marker of inflammation and does not accurately diagnose sepsis. This same review concluded, however, that SuPAR has prognostic value, as higher SuPAR levels are associated with an increased rate of death in those with sepsis.

Sepsis Treatment And Management

Early recognition and focused management may improve the outcomes in sepsis. Current professional recommendations include a number of actions (“bundles”) to be followed as soon as possible after diagnosis. Within the first three hours someone with sepsis should have received antibiotics and, intravenous fluids if there is evidence of either low blood pressure or other evidence for inadequate blood supply to organs (as evidenced by a raised level of lactate); blood cultures also should be obtained within this time period.

After six hours the blood pressure should be adequate, close monitoring of blood pressure and blood supply to organs should be in place, and the lactate should be measured again if initially, it was raised. A related bundle, the “Sepsis Six“, is in widespread use in the United Kingdom; this requires the administration of antibiotics within an hour of recognition, blood cultures, lactate and hemoglobin determination, urine output monitoring, high-flow oxygen, and intravenous fluids.

Apart from the timely administration of fluids and antibiotics, the management of sepsis also involves surgical drainage of infected fluid collections and appropriate support for organ dysfunction. This may include hemodialysis in kidney failure, mechanical ventilation in lung dysfunction, transfusion of blood products, and drug and fluid therapy for circulatory failure.

Ensuring adequate nutrition—preferably by enteral feeding, but if necessary, by parenteral nutrition—is important during prolonged illness. In those with high blood sugar levels, insulin to bring it down to 7.8-10 mmol/L (140–180 mg/dL) is recommended with lower levels potentially worsening outcomes. Medication to prevent deep vein thrombosis and gastric ulcers also may be used.


In severe sepsis and septic shock, broad-spectrum antibiotics (usually two, or a β-lactam antibiotic with broad coverage) are recommended. Some recommend they be given within one hour of making the diagnosis, stating that for every hour of delay in the administration of antibiotics, there is an associated 6% rise in mortality. Others did not find a benefit with early administration. Two sets of blood cultures should be obtained before starting antibiotics if this can be done without delaying the administration of antibiotics.

Several factors determine the most appropriate choice for the initial antibiotic regimen. These factors include local patterns of bacterial sensitivity to antibiotics, whether the infection is thought to be a hospital or community-acquired infection, and which organ systems are thought to be infected.

Antibiotic regimens should be reassessed daily and narrowed if appropriate. Treatment duration is typically 7–10 days with the type of antibiotic used directed by the results of cultures. Giving antibiotics continuously may be better than giving them intermittently.

Intravenous fluids

Intravenous fluids are titrated (measured and adjusted) in response to heart rate, blood pressure, and urine output; restoring large fluid deficits can require 6 to 10 liters of crystalloids in adults. In children an initial amount of 20mL/Kg is reasonable in shock. In cases of severe sepsis and septic shock where a central venous catheter is used to measure blood pressures dynamically, fluids should be administered until the central venous pressure (CVP) reaches 8–12mmHg.

Once these goals are met, the central venous oxygen saturation (ScvO2), i.e., the oxygen saturation of venous blood as it returns to the heart as measured at the vena cava, is optimized. If the ScvO2 is less than 70%, blood may be given to reach a hemoglobin of 10 g/dL and then inotropes are added until the ScvO2 is optimized.[30] In those with acute respiratory distress syndrome (ARDS) and sufficient tissue blood fluid, more fluids should be given carefully.

Crystalloid solutions are recommended initially. Crystalloid solutions and albumin are better than other fluids (such as hydroxyethyl starch) in terms of risk of death. Starches also carry an increased risk of acute kidney injury, and need for blood transfusion. Various colloid solutions (such as modified gelatin) carry no advantage over crystalloid.

Albumin also appears to be of no benefit over crystalloids. Packed red blood cells are recommended to keep the hemoglobin levels between 70 and 90 g/L. A 2014 trial however, found no difference between a target hemoglobin of 70 or 90 g/L.[54]


The use of steroids in sepsis is controversial. Studies do not give a clear picture as to whether and when glucocorticoids should be used. The 2012 Surviving Sepsis Campaign recommends against their use in those with septic shock if intravenous fluids and vasopressors stabilize the person’s cardiovascular function. While a 2015 Cochrane review found low quality evidence of benefit.

During critical illness, a state of adrenal insufficiency and tissue resistance to corticosteroids may occur. This has been termed critical illness–related corticosteroid insufficiency. Treatment with corticosteroids might be most beneficial in those with septic shock and early severe ARDS, whereas its role in others such as those with pancreatitis or severe pneumonia is unclear.

However, the exact way of determining corticosteroid insufficiency remains problematic. It should be suspected in those poorly responding to resuscitation with fluids and vasopressors. ACTH stimulation testing is not recommended to confirm the diagnosis. The method of stopping glucocorticoid drugs is variable, and it is unclear whether they should be slowly decreased or simply abruptly stopped.

Early Goal Directed Therapy

Early goal directed therapy (EGDT) is an approach to the management of severe sepsis during the initial 6 hours after diagnosis. It is a step-wise approach, with the physiologic goal of optimizing cardiac preload, afterload, and contractility. It includes giving early antibiotics.

It involves monitoring of hemodynamic parameters and specific interventions to achieve key resuscitation targets which include maintaining a central venous pressure between 8-12 mmHg, a mean arterial pressure of between 65-90 mmHg, a central venous oxygen saturation (ScvO2) greater than 70% and a urine output of greater than 0.5 ml/kg/hour. The goal is to optimize oxygen delivery to tissues and achieve a balance between systemic oxygen delivery and demand.[61] An appropriate decrease in serum lactate may be equivalent to ScvO2 and easier to obtain.

In the original trial, early goal directed therapy was found to reduce mortality from 46.5% to 30.5% in those with sepsis, and the Surviving Sepsis Campaign has been recommending its use. However, three more recent large randomized control trials (ProCESS, ARISE, and ProMISe), did not demonstrate a 90-day mortality benefit of early goal directed therapy versus the standard therapy in severe sepsis. It is likely that some parts of EGDT are more important than others. Following these trials the use of EGDT is still considered reasonable.


Approximately 20–35% of people with severe sepsis and 30–70% of people with septic shock die. Lactate is a useful method of determining prognosis with those who have a level greater than 4 mmol/L having a mortality of 40% and those with a level of less than 2 mmol/L have a mortality of less than 15%.

There are a number of prognostic stratification systems such as APACHE II and Mortality in Emergency Department Sepsis. APACHE II factors in the person’s age, underlying condition, and various physiologic variables to yield estimates of the risk of dying of severe sepsis. Of the individual covariates, the severity of underlying disease most strongly influences the risk of death.

Septic shock is also a strong predictor of short- and long-term mortality. Case-fatality rates are similar for culture-positive and culture-negative severe sepsis. The Mortality in Emergency Department Sepsis (MEDS) score is simpler and useful in the emergency department environment.

Some people may experience severe long-term cognitive decline following an episode of severe sepsis, but the absence of baseline neuropsychological data in most sepsis patients makes the incidence of this difficult to quantify or to study.