Septic shock is a potentially fatal medical condition that occurs when sepsis, which is organ injury or damage in response to infection, leads to dangerously low blood pressure and abnormalities in cellular metabolism.
Medicine is the science and practice of establishing the diagnosis, prognosis, treatment, and prevention of disease. Medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Contemporary medicine applies biomedical sciences, biomedical research, genetics, and medical technology to diagnose, treat, and prevent injury and disease, typically through pharmaceuticals or surgery, but also through therapies as diverse as psychotherapy, external splints and traction, medical devices, biologics, and ionizing radiation, amongst others.
Sepsis is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. Common signs and symptoms include fever, increased heart rate, increased breathing rate, and confusion. There may also 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 fluid replacement.
Infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. Infectious disease, also known as transmissible disease or communicable disease, is illness resulting from an infection.
The primary infection is most commonly caused by bacteria, but also may be by fungi, viruses or parasites. It may be located in any part of the body, but most commonly in the lungs, brain, urinary tract, skin or abdominal organs.It can cause multiple organ dysfunction syndrome (formerly known as multiple organ failure) and death.
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
Multiple organ dysfunction syndrome (MODS), also known as multiple organ failure (MOF), total organ failure (TOF) or multisystem organ failure (MSOF), is altered organ function in an acutely ill patient requiring medical intervention to achieve homeostasis.
Death is the permanent cessation of all biological functions that sustain a living organism. Phenomena which commonly bring about death include aging, predation, malnutrition, disease, suicide, homicide, starvation, dehydration, and accidents or major trauma resulting in terminal injury. In most cases, bodies of living organisms begin to decompose shortly after death.
Frequently, people with septic shock are cared for in intensive care units. It most commonly affects children, immunocompromised individuals, and the elderly, as their immune systems cannot deal with infection as effectively as those of healthy adults. The mortality rate from septic shock is approximately 25–50%.
Immunodeficiency is a state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") due to extrinsic factors that affect the patient's immune system. Examples of these extrinsic factors include HIV infection, extremes of age, and environmental factors, such as nutrition. In the clinical setting, the immunosuppression by some drugs, such as steroids, can be either an adverse effect or the intended purpose of the treatment. Examples of such use is in organ transplant surgery as an anti-rejection measure and in patients suffering from an overactive immune system, as in autoimmune diseases. Some people are born with intrinsic defects in their immune system, or primary immunodeficiency. A person who has an immunodeficiency of any kind is said to be immunocompromised. An immunocompromised person may be particularly vulnerable to opportunistic infections, in addition to normal infections that could affect everyone. Immunodeficiency also decreases cancer immunosurveillance, in which the immune system scans the body's cells and kills neoplastic ones.
The immune system is a host defense system comprising many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue. In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity. In humans, the blood–brain barrier, blood–cerebrospinal fluid barrier, and similar fluid–brain barriers separate the peripheral immune system from the neuroimmune system, which protects the brain.
Mortality rate, or death rate, is a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of deaths per 1,000 individuals per year; thus, a mortality rate of 9.5 in a population of 1,000 would mean 9.5 deaths per year in that entire population, or 0.95% out of the total. It is distinct from "morbidity", which is either the prevalence or incidence of a disease, and also from the incidence rate.
Septic shock is a result of a systemic response to infection or multiple infectious causes. Sepsis may be present, but septic shock may occur without it.The precipitating infections that may lead to septic shock if severe enough include but are not limited to appendicitis, pneumonia, bacteremia, diverticulitis, pyelonephritis, meningitis, pancreatitis, necrotizing fasciitis, MRSA and mesenteric ischemia.
Appendicitis is inflammation of the appendix. Symptoms commonly include right lower abdominal pain, nausea, vomiting, and decreased appetite. However, approximately 40% of people do not have these typical symptoms. Severe complications of a ruptured appendix include widespread, painful inflammation of the inner lining of the abdominal wall and sepsis.
Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Typically symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing. Severity is variable.
Bacteremia is the presence of bacteria in the blood. Blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal. It is distinct from sepsis, which is the host response to the bacteria.
Sepsis is a constellation of symptoms secondary to an infection that manifests as disruptions in heart rate, respiratory rate, temperature, and white blood cell count. If sepsis worsens to the point of end-organ dysfunction (kidney failure, liver dysfunction, altered mental status, or heart damage), then the condition is called severe sepsis. Once severe sepsis worsens to the point where blood pressure can no longer be maintained with intravenous fluids alone, then the criterion has been met for septic shock.
The pathophysiology of septic shock is not entirely understood, but it is known that a key role in the development of severe sepsis is played by an immune and coagulation response to an infection. Both pro-inflammatory and anti-inflammatory responses play a role in septic shock.Septic shock involves a widespread inflammatory response that produces a hypermetabolic effect. This is manifested by increased cellular respiration, protein catabolism, and metabolic acidosis with a compensatory respiratory alkalosis.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets along with deposition and maturation of fibrin. Disorders of coagulation are disease states which can result in bleeding or obstructive clotting (thrombosis).
Most cases of septic shock are caused by gram-positive bacteria,followed by endotoxin-producing gram-negative bacteria, although fungal infections are an increasingly prevalent cause of septic shock. Toxins produced by pathogens cause an immune response; in gram-negative bacteria these are endotoxins, which are bacterial membrane lipopolysaccharides (LPS).
Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.
Lipopolysaccharides (LPS), also known as lipoglycans and endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria.
In gram-positive bacteria, these are exotoxins or enterotoxins, which may vary depending on the species of bacteria. These are divided into three types. Type I, cell surface-active toxins, disrupt cells without entering, and include superantigens and heat-stable enterotoxins. Type II, membrane-damaging toxins, destroy cell membranes in order to enter and include hemolysins and phospholipases. Type III, intracellular toxins or A/B toxins interfere with internal cell function and include shiga toxin, cholera toxin, and anthrax lethal toxin.
In gram-negative sepsis, free LPS attaches to a circulating LPS-binding protein, and the complex then binds to the CD14 receptor on monocytes, macrophages, and neutrophils. Engagement of CD14 (even at doses as minute as 10 pg/mL) results in intracellular signaling via an associated "Toll-like receptor" protein 4 (TLR-4). This signaling results in the activation of nuclear factor kappaB (NF-κB), which leads to transcription of a number of genes that trigger a proinflammatory response. It was the result of significant activation of mononuclear cells and synthesis of effector cytokines. It also results in profound activation of mononuclear cells and the production of potent effector cytokines such as IL-1, IL-6, and TNF-α. TLR-mediated activation helps to trigger the innate immune system to efficiently eradicate invading microbes, but the cytokines they produce also act on endothelial cells. There, they have a variety of effects, including reduced synthesis of anticoagulation factors such as tissue factor pathway inhibitor and thrombomodulin. The effects of the cytokines may be amplified by TLR-4 engagement on endothelial cells.
In response to inflammation, a compensatory reaction of production of anti-inflammatory substances such as IL-4, IL-10 antagonists, IL-1 receptor, and cortisol occurs. This is called compensatory anti-inflammatory response syndrome (CARS).Both the inflammatory and anti-inflammatory reactions are responsible for the course of sepsis and are described as MARS (Mixed Antagonist Response Syndrome). The aim of these processes is to keep inflammation at an appropriate level. CARS often leads to suppression of the immune system, which leaves patients vulnerable to secondary infection. It was once thought that SIRS or CARS could predominate in a septic individual, and it was proposed that CARS follows SIRS in a two-wave process. It is now believed that the systemic inflammatory response and the compensatory anti-inflammatory response occur simultaneously.
At high levels of LPS, the syndrome of septic shock supervenes; the same cytokine and secondary mediators, now at high levels, result in systemic vasodilation (hypotension), diminished myocardial contractility, widespread endothelial injury, activation causing systemic leukocyte adhesion and diffuse alveolar capillary damage in the lung, and activation of the coagulation system culminating in disseminated intravascular coagulation (DIC).
The hypoperfusion from the combined effects of widespread vasodilation, myocardial pump failure, and DIC causes multiorgan system failure that affects the liver, kidneys, and central nervous system, among other organ systems. Recently, severe damage to liver ultrastructure has been noticed from treatment with cell-free toxins of Salmonella.Unless the underlying infection (and LPS overload) is rapidly brought under control, the patient usually dies.
The ability of TLR4 to respond to a distinct LPS species are clinically important. Pathogenic bacteria may employ LPS with low biological activity to evade proper recognition by the TLR4/MD-2 system, dampening the host immune response and increasing the risk of bacterial dissemination. On the other hand, such LPS would not be able to induce septic shock in susceptible patients, rendering septic complications more manageable. Yet, defining and understanding how even the smallest structural differences between the very similar LPS species may affect the activation of the immune response may provide the mechanism for the fine tuning of the latter and new insights to immunomodulatory processes.
According to current guidelines, requirements for diagnosis with sepsis are "the presence (probable or documented) of infection together with systemic manifestations of infection".These manifestations may include:
Documented evidence of infection, may include positive blood culture, signs of pneumonia on chest x-ray, or other radiologic or laboratory evidence of infection. Signs of end-organ dysfunction are present in septic shock, including kidney failure, liver dysfunction, changes in mental status, or elevated serum lactate.
Septic shock is diagnosed if there is low blood pressure (BP) that does not respond to treatment. This means that intravenous fluid administration alone is not enough to maintain a patient's BP. Diagnosis of septic shock is made when systolic blood pressure is less than 90mm Hg, a mean arterial pressure (MAP) is less than 70 mm Hg, or a systolic BP decreases 40 mm Hg or more without other causes for low BP.
Septic shock is a subclass of distributive shock, a condition in which abnormal distribution of blood flow in the smallest blood vessels results in inadequate blood supply to the body tissues, resulting in ischemia and organ dysfunction. Septic shock refers specifically to distributive shock due to sepsis as a result of infection.
Septic shock may be defined as sepsis-induced low blood pressure that persists despite treatment with intravenous fluids.Low blood pressure reduces tissue perfusion pressure, causing the tissue hypoxia that is characteristic of shock. Cytokines released in a large scale inflammatory response result in massive vasodilation, increased capillary permeability, decreased systemic vascular resistance, and low blood pressure. Finally, in an attempt to offset decreased blood pressure, ventricular dilatation and myocardial dysfunction occur.
Septic shock may be regarded as a stage of SIRS (Systemic Inflammatory Response Syndrome), in which sepsis, severe sepsis and multiple organ dysfunction syndrome (MODS) represent different stages of a pathophysiological process. If an organism cannot cope with an infection, it may lead to a systemic response - sepsis, which may further progress to severe sepsis, septic shock, organ failure, and eventually, result in death.
Treatment primarily consists of the following:
Because lowered blood pressure in septic shock contributes to poor perfusion, fluid resuscitation is an initial treatment to increase blood volume. Patients demonstrating sepsis-induced hypoperfusion should be initially resuscitated with at least 30 ml/kg of intravenous crystalloid within the first three hours.Crystalloids such as normal saline and lactated Ringer's solution are recommended as the initial fluid of choice, while the use of colloid solutions such as hydroxyethyl starch have not shown any advantage or decrease in mortality. When large quantities of fluids are given, administering albumin has shown some benefit.
Treatment guidelines call for the administration of broad-spectrum antibiotics within the first hour following recognition of septic shock. Prompt antimicrobial therapy is important, as risk of dying increases by approximately 10% for every hour of delay in receiving antibiotics.Time constraints do not allow the culture, identification, and testing for antibiotic sensitivity of the specific microorganism responsible for the infection. Therefore, combination antimicrobial therapy, which covers a wide range of potential causative organisms, is tied to better outcomes. Antibiotics should be continued for 7–10 days in most patients, though treatment duration may be shorter or longer depending on clinical response.
Among the choices for vasopressors, norepinephrine is superior to dopamine in septic shock. mm Hg. In 2017, the FDA approved angiotensin II injection for intravenous infusion to increase blood pressure in adults with septic or other distributive shock.Norepinephrine is the preferred vasopressor, while epinephrine may be added to norepinephrine when needed. Low-dose vasopressin also may be used as an addition to norepinephrine, but is not recommended as a first-line treatment. Dopamine may cause rapid heart rate and arrhythmias, and is only recommended in combination with norepinephrine in those with slow heart rate and low risk of arrhythmia. In the initial treatment of low blood pressure in septic shock, the goal of vasopressor treatment is a mean arterial pressure (MAP) of 65
Methylene blue has been found to be useful for this condition.Although use of methylene blue has mostly been in adults it has also been shown to work in children. Its mechanism of action is thought to be via the inhibition of the nitric oxide-cyclic guanosine monophosphate pathway. This pathway is excessively activated in septic shock. Methylene blue has been found to work in cases resistant to the usual agents. This effect was first reported in the early 1990s.
While there is tentative evidence for β-Blocker therapy to help control heart rate, evidence is not significant enough for its routine use.There is tentative evidence that steroids may be useful in improving outcomes.
Tentative evidence exists that Polymyxin B-immobilized fiber column hemoperfusion may be beneficial in treatment of septic shock.Trials are ongoing and it is currently being used in Japan and Western Europe.
Recombinant activated protein C (drotrecogin alpha) in a 2011 Cochrane review was found not to decrease mortality and to increase bleeding, and thus, was not recommended for use.Drotrecogin alfa (Xigris), was withdrawn from the market in October 2011.
Sepsis has a worldwide incidence of more than 20 million cases a year, with mortality due to septic shock reaching up to 50 percent even in industrialized countries.
According to the U.S. Centers for Disease Control, septic shock is the thirteenth leading cause of death in the United States and the most frequent cause of deaths in intensive care units. There has been an increase in the rate of septic shock deaths in recent decades, which is attributed to an increase in invasive medical devices and procedures, increases in immunocompromised patients, and an overall increase in elderly patients.
Tertiary care centers (such as hospice care facilities) have 2-4 times the rate of bacteremia than primary care centers, 75% of which are hospital-acquired infections.
The process of infection by bacteria or fungi may result in systemic signs and symptoms that are variously described. Approximately 70% of septic shock cases were once traceable to gram-negative bacteria that produce endotoxins, however, with the emergence of MRSA and the increased use of arterial and venous catheters, gram-positive bacteria are implicated approximately as commonly as bacilli. In rough order of increasing severity these are, bacteremia or fungemia; sepsis, severe sepsis or sepsis syndrome; septic shock, refractory septic shock, multiple organ dysfunction syndrome, and death.
35% of septic shock cases derive from urinary tract infections, 15% from the respiratory tract, 15% from skin catheters (such as IVs), and more than 30% of all cases are idiopathic in origin.
The mortality rate from sepsis is approximately 40% in adults and 25% in children. It is significantly greater when sepsis is left untreated for more than seven days.
Inflammation is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecular mediators. The function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells and tissues damaged from the original insult and the inflammatory process, and initiate tissue repair.
Lemierre's syndrome refers to infectious thrombophlebitis of the internal jugular vein. It most often develops as a complication of a bacterial sore throat infection in young, otherwise healthy adults. The thrombophlebitis is a serious condition and may lead to further systemic complications such as bacteria in the blood or septic emboli.
Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts of the body. As clotting factors and platelets are used up, bleeding may occur. This may include blood in the urine, blood in the stool, or bleeding into the skin. Complications may include organ failure.
Cytokine release syndrome is a form of systemic inflammatory response syndrome that arises as a complication of some diseases or infections, and is also an adverse effect of some monoclonal antibody drugs, as well as adoptive T-cell therapies. Severe cases have been called cytokine storms.
Hemolytic-uremic syndrome (HUS) is a group of blood disorders characterized by low red blood cells, acute kidney failure, and low platelets. Initial symptoms typically include bloody diarrhea, fever, vomiting, and weakness. Kidney problems and low platelets then occur as the diarrhea is improving. While children are more commonly affected adults may have worse outcomes. Complications may include neurological problems and heart failure.
Systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult. Although the definition of SIRS refers to it as an "inflammatory" response, it actually has pro- and anti-inflammatory components.
Superantigens (SAgs) are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some pathogenic viruses and bacteria most likely as a defense mechanism against the immune system. Compared to a normal antigen-induced T-cell response where 0.0001-0.001% of the body’s T-cells are activated, these SAgs are capable of activating up to 20% of the body’s T-cells. Furthermore, Anti-CD3 and Anti-CD28 Antibodies (CD28-SuperMAB) have also shown to be highly potent superantigens.
Toxic megacolon is an acute form of colonic distension. It is characterized by a very dilated colon (megacolon), accompanied by abdominal distension (bloating), and sometimes fever, abdominal pain, or shock.
Drotrecogin alfa (activated) is a recombinant form of human activated protein C that has anti-thrombotic, anti-inflammatory, and profibrinolytic properties. Drotrecogin alpha (activated) belongs to the class of serine proteases. Drotrecogin alfa has not been found to improve outcomes in people with severe sepsis. The manufacturer's aggressive strategies in marketing its use in severe sepsis have been criticized. On October 25, 2011, Eli Lilly & Co. withdrew Xigris from the market after a major study showed no efficacy for the treatment of sepsis.
Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane. While its toxic effects can be damaging, the sensing of lipid A by the human immune system may also be critical for the onset of immune responses to gram-negative infection, and for the subsequent successful fight against the infection.
Distributive shock is a medical condition in which abnormal distribution of blood flow in the smallest blood vessels results in inadequate supply of blood to the body's tissues and organs. It is one of four categories of shock, a condition where there is not enough oxygen-carrying blood to meet the metabolic needs of the cells which make up the body's tissues and organs. Distributive shock is different from the other three categories of shock in that it occurs even though the output of the heart is at or above a normal level. The most common cause is sepsis leading to type of distributive shock called septic shock, a condition that can be fatal.
C5a is a protein fragment released from cleavage of complement component C5 by protease C5-convertase into C5a and C5b fragments. C5b is important in late events of the complement cascade, an orderly series of reactions which coordinates several basic defense mechanisms, including formation of the Membrane Attack Complex (MAC), one of the most basic weapons of the innate immune system, formed as an automatic response to intrusions from foreign particles and microbial invaders. It essentially pokes microscopic pinholes in these foreign objects, causing loss of water and sometimes death. C5a, the other cleavage product of C5, acts as a highly inflammatory peptide, encouraging complement activation, formation of the MAC, attraction of innate immune cells, and histamine release involved in allergic responses. The origin of C5 is in the hepatocyte, but its synthesis can also be found in macrophages, where it may cause local increase of C5a. C5a is a chemotactic agent and an anaphylatoxin; it is essential in the innate immunity but it is also linked with the adaptive immunity. The increased production of C5a is connected with a number of inflammatory diseases.
A Jarisch–Herxheimer reaction is a reaction to endotoxin-like products released by the death of harmful microorganisms within the body during antibiotic treatment. Efficacious antimicrobial therapy results in lysis (destruction) of bacterial cell membranes, and in the consequent release into the bloodstream of bacterial toxins, resulting in a systemic inflammatory response.
Capillary leak syndrome is characterized by the escape of blood plasma through capillary walls, from the blood circulatory system to surrounding tissues, muscle compartments, organs or body cavities. It is a phenomenon most commonly witnessed in sepsis, and less frequently in autoimmune diseases, differentiation syndrome, engraftment syndrome, hemophagocytic lymphohistiocytosis, the ovarian hyperstimulation syndrome, viral hemorrhagic fevers, and snakebite and ricin poisoning. Pharmaceuticals, including the chemotherapy medications gemcitabine and tagraxofusp, as well as certain interleukins and monoclonal antibodies, can also cause capillary leaks. These conditions and factors are sources of secondary capillary leak syndrome.
Eritoran is an investigational drug for the treatment of severe sepsis, an excessive inflammatory response to an infection.
Murine caspase-11, and its human homologs caspase-4 and caspase-5, are mammalian intracellular receptor proteases activated by TLR4 and TLR3 signaling during the innate immune response. Caspase-11, also termed the non-canonical inflammasome, is activated by TLR3/TLR4-TRIF signaling and directly binds cytosolic lipopolysaccharide (LPS), a major structural element of Gram-negative bacterial cell walls. Activation of caspase-11 by LPS is known to cause the activation of other caspase proteins, leading to septic shock, pyroptosis, and often organismal death.
Vasodilatory shock, vasogenic shock, or vasoplegic shock is a medical emergency belonging to shock along with cardiogenic shock, septic shock, allergen-induced shock and hypovolemic shock. When the blood vessels suddenly relax, it results in vasodilation. In vasodilatory shock, the blood vessels are too relaxed leading to extreme vasodilation and blood pressure drops and blood flow becomes very low. Without enough blood pressure, blood and oxygen don’t be pushed to reach the body’s organs. If vasodilatory shock lasts more than a few minutes, the lack of oxygen starts to damage the body’s organs. Vasodilatory shock like other types of shock should be treated quickly, otherwise it can cause permanent organ damage or death as a result of multiple organ dysfunction.