septic shock

Septic Shock 

Definition

Septic shock is a potentially lethal drop in blood pressure due to the presence of bacteria in the blood.

Description

Septic shock is a possible consequence of bacteremia, or bacteria in the bloodstream. Bacterial toxins, and the immune system response to them, cause a dramatic drop in blood pressure, preventing the delivery of blood to the organs. Septic shock can lead to multiple organ failure including respiratory failure, and may cause rapid death. Toxic shock syndrome is one type of septic shock.

Causes and symptoms

During an infection, certain types of bacteria can produce and release complex molecules, called endotoxins, that may provoke a dramatic response by the body's immune system. Released in the bloodstream, endotoxins are particularly dangerous, because they become widely dispersed and affect the blood vessels themselves. Arteries and the smaller arterioles open wider, increasing the total volume of the circulatory system. At the same time, the walls of the blood vessels become leaky, allowing fluid to seep out into the tissues, lowering the amount of fluid left in circulation. This combination of increased system volume and decreased fluid causes a dramatic decrease in blood pressure and reduces the blood flow to the organs. Other changes brought on by immune response may cause coagulation of the blood in the extremities, which can further decrease circulation through the organs.

Septic shock is seen most often in patients with suppressed immune systems, and is usually due to bacteria acquired during treatment at the hospital. The immune system is suppressed by drugs used to treat cancer, autoimmune disorders, organ transplants, and diseases of immune deficiency such as AIDS. Malnutrition, chronic drug abuse, and long-term illness increase the likelihood of succumbing to bacterial infection. Bacteremia is more likely with preexisting infections such as urinary or gastrointestinal tract infections, or skin ulcers. Bacteria may be introduced to the blood stream by surgical procedures, catheters, or intravenous equipment.

Toxic shock syndrome most often occurs in menstruating women using highly absorbent tampons. Left in place longer than other types, these tampons provide the breeding ground for Staphylococcus bacteria, which may then enter the bloodstream through small tears in the vaginal lining. The incidence of toxic shock syndrome has declined markedly since this type of tampon was withdrawn from the market.

Symptoms

Septic shock is usually preceded by bacteremia, which is marked by fever, malaise, chills, and nausea. The first sign of shock is often confusion and decreased consciousness. In this beginning stage, the extremities are usually warm. Later, they become cool, pale, and bluish. Fever may give way to lower than normal temperatures later on in sepsis.

Other symptoms include:

• rapid heartbeat
• shallow, rapid breathing
• decreased urination.
• reddish patches in the skin

Septic shock may progress to cause "adult respiratory distress syndrome," in which fluid collects in the lungs, and breathing becomes very shallow and labored. This condition may lead to ventilatory collapse, in which the patient can no longer breathe adequately without assistance.

Diagnosis

Diagnosis of septic shock is made by measuring blood pressure, heart rate, and respiration rate, as well as by a consideration of possible sources of infection. Blood pressure may be monitored with a catheter device inserted into the pulmonary artery supplying the lungs (Swan-Ganz catheter). Blood cultures are done to determine the type of bacteria responsible. The levels of oxygen, carbon dioxide, and acidity in the blood are also monitored to assess changes in respiratory function.

Treatment

Septic shock is treated initially with a combination of antibiotics and fluid replacement. The antibiotic is chosen based on the bacteria present, although two or more types of antibiotics may be used initially until the organism is identified. Intravenous fluids, either blood or protein solutions, replace the fluid lost by leakage. Coagulation and hemorrhage may be treated with transfusions of plasma or platelets. Dopamine may be given to increase blood pressure further if necessary.

Respiratory distress is treated with mechanical ventilation and supplemental oxygen, either using a nosepiece or a tube into the trachea through the throat.

Identification and treatment of the primary infection site is important to prevent ongoing proliferation of bacteria.

Prognosis

Septic shock is most likely to develop in the hospital, since it follows infections which are likely to be the objects of treatment. Because of this, careful monitoring and early, aggressive therapy can minimize the likelihood of progression. Nonetheless, death occurs in at least 25% of all cases.

The likelihood of recovery from septic shock depends on may factors, including the degree of immunosuppression of the patient, underlying disease, promptness of treatment, and type of bacteria responsible. Mortality is highest in the very young and the elderly, those with persistent or recurrent infection, and those with compromised immune systems.

Prevention

The risk of developing septic shock can be minimized through treatment of underlying bacterial infections, and prompt attention to signs of bacteremia. In the hospital, scrupulous aseptic technique on the part of medical professionals lowers the risk of introducing bacteria into the bloodstream.

Resources

Other

The Merck Page. April 13, 1998. http://www.merck.com.

Key terms

Bacteremia — Invasion of the bloodstream by bacteria.

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shock (shok)

1. a sudden disturbance of mental equilibrium.

2. a profound hemodynamic and metabolic disturbance due to failure of the circulatory system to maintain adequate perfusion of vital organs.

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anaphylactic shock  see anaphylaxis.

cardiogenic shock  shock resulting from inadequate cardiac function, as from myocardial infarction or mechanical obstruction; characteristics include hypovolemia, hypotension, cold skin, weak pulse, and confusion.

endotoxin shock  septic shock due to release of endotoxins by gram-negative bacteria.

hypovolemic shock  shock due to insufficient blood volume, either from hemorrhage or other loss of fluid or from widespread vasodilation so that normal blood volume cannot maintain tissue perfusion; symptoms are like those of cardiogenic shock.

insulin shock  a hypoglycemic reaction to overdosage of insulin, a skipped meal, or strenuous exercise in an insulin-dependent diabetic, with tremor, dizziness, cool moist skin, hunger, and tachycardia, sometimes progressing to coma and convulsions.

septic shock  shock associated with overwhelming infection, most commonly infection with gram-negative bacteria, thought to result from the actions of endotoxins and other products of the infectious agent that cause sequestration of blood in the capillaries and veins.

serum shock  see anaphylaxis and see under sickness.

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septic shock

n.

1. Shock associated with sepsis, usually associated with abdominal and pelvic infection resulting from trauma or surgery.

2. Shock associated with septicemia caused by gram-negative bacteria.

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septic shock,

a form of shock that occurs in septicemia when endotoxins or exotoxins are released from certain bacteria in the bloodstream, occasionally caused by the presence of fungi or viruses in the blood. These toxins cause vasodilation, resulting in a dramatic fall in blood pressure. Fever, tachycardia, increased respiration rate, and confusion or coma also may occur. Septic shock is usually preceded by signs of severe infection, often of the genitourinary or GI system. The causative bacterium is most frequently gram-negative. Antibiotics, vasopressors, and IV fluids and volume expanders are usually given. In some cases, treatment with monoclonal antibodies may be considered. Kinds of septic shock include toxic shock syndrome and bacteremic shock. Compare hypovolemic shock. See also shock.

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septic

pertaining to sepsis.

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septic fever

is fever associated with infection either as local abscess or cellulitis or as a septicemia or bacteremia. The infective agent may be a bacteria, virus, fungus, protozoa or even algae.

septic mastitis

mastitis characterized by the presence of bacteria in the milk.

septic shock

see toxemic shock.

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shock

a condition of acute peripheral circulatory failure due to derangement of circulatory control or loss of circulating fluid. It is marked by hypotension, coldness of the skin and tachycardia.

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allergic shock

see anaphylactic shock.

shock bodies

hyaline globules composed of fibrin degradation products which act as microthrombi and cause hemorrhage and necrosis.

burn shock

the loss and redistribution of fluid, electrolytes and plasma protein, increased blood viscosity and increased peripheral resistance that follow a severe burn contribute to shock.

cardiogenic shock

classically associated with acute myocardial infarction in humans; in animals may be caused by intrinsic congestive heart failure, cardiac depression caused by anesthetic overdosage or other drugs with negative inotropism, rarely, thromboembolism.

colloidoclastic shock

shock due to breakdown of the physical equilibrium of the body colloids. Thought to cause anaphylactic shock due to the absorption of the colloids into the bloodstream.

distributive shock

see vasogenic shock (below).

electric shock

see electrical injuries.

electroplectic shock

electric shock. See also electrical stunning.

endotoxic shock

caused by endotoxins, especially Escherichia coli. See also toxemic shock.

shock gut

animals in shock develop changes in the gut including congestion and hemorrhage into the lumen.

hypovolemic shock

shock due to reduced blood volume as a result of water deprivation, fluid loss due to diarrhea, vomiting, extensive burns, intestinal obstruction, whole blood loss.

insulin shock

a condition of circulatory insufficiency resulting from overdosage with insulin, which causes too sudden reduction of blood sugar. It is marked by tremor, weakness, convulsions and collapse.

irreversible shock

shock which has reached the stage where irreparable damage has been done to tissues, e.g. liver, kidneys and treatment will not salvage the patient although it might prolong life for a long time.

shock lung

animals in shock due to massive burns, septicemia, disseminated intravascular coagulation (DIC), acute viral or bacterial pneumonias or trauma develop an acute respiratory distress syndrome. The pulmonary lesion is a nonspecific acute or subacute interstitial pneumonia.

nervous shock

a temporary cessation of function in nervous tissue caused by an acute insult such as trauma without the part having been directly or detectably damaged. The loss of function is only temporary, usually for a few minutes but it may last for several hours. There may be residual signs due to direct damage when the shock passes. Stunning by a lightning stroke is an example.

shock organs

those organs, specific to each animal species, which respond to allergens circulating in the blood.

septic shock

see toxemic shock.

spinal shock

flaccid paralysis up and down the body from the site of the spinal cord lesion. Accompanied by a fall in skin temperature, vasodilatation and sweating. Signs disappear within an hour or two. There may be residual signs due to physical injury to tissue.

toxic shock

see toxemic shock.

vasogenic shock, vasculogenic shock

shock exists because of the severe reduction in effective circulating blood volume caused by sequestration of blood and other fluids in the vascular system and their withdrawal from the circulating blood. Is the classical shock of traumatic injury, burns, uterine prolapse, extensive surgery.

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septic shock

Bacteremic shock Infectious disease A condition identical to the sepsis syndrome with an added component of hypotension–systolic BP < 90 mm Hg or loss in the baseline systolic BP of > 40 mm Hg; SS has been formally defined by clinical parameters as 'Sepsis-induced hypotension despite fluid resuscitation plus hypoperfusion abnormalities…', which include lactic acidosis, oliguria, or an acute alteration in mental status; SS is end-stage of a continuum of a biologic inflammatory response to infection Etiology Gram-negative bacilli–eg, E coli, Klebsiella spp, gram-positive cocci–eg, Staphylococcus spp; viruses, fungi rarely cause SS Epidemiology SS kills 100k to 175k people/yr–US, 13^th major cause of death in US Risk factors Underlying disease–DM; hematologic CA; GI, GU, hepatobiliary disease, recent infection, prolonged antibiotics, recent surgery Clinical Either reflect response to infection–ie, tachycardia, tachypnea, changes in temperature, leukocytosis, or the organ system(s) involved–eg, cardiovascular, hematologic, hepatic, renal, pulmonary; SS is severe if there is hypoperfusion, lactic acidosis, hypotension, or altered mental status Mediators Bacterial endotoxin evokes a vehement response by the complement system, kinin system, and plasma phospholipases and release of various cytokines–eg, TNF-a, IL-1, IL-6, β-endophins, PAF, PGs, leukotrienes. See Sepsis, Sepsis syndrome, Severe sepsis, SIRS.