Sepsis and Bacteremia
Introduction
Introduction to sepsis and bacteremia Sepsis is a general term for systemic inflammatory response, such as body temperature, respiratory, and circulatory changes. It is the endotoxin, exotoxin produced by pathogens, and the absorption of various inflammatory mediators they mediate. The damage caused, when sepsis combined with organ perfusion insufficiency, such as lactic acidosis, oliguria, acute mental changes, etc., is called pyemia syndrome (pyemiasyndrome). If bacteria invade the blood circulation and blood culture is positive, it is called bacteremia. Sepsis and bacteremia are often secondary to infections after severe trauma and various purulent infections. The pathogens are complicated and the number of bacteria. More, more toxic. Generally, the onset is rapid, the condition is heavy, the change is fast, and the organ is often insufficiently perfused. Clinically, we must give positive and comprehensive treatment. At the same time of anti-infection, we should pay attention to correct electrolyte imbalance and acid-base imbalance, and timely grasp the involvement of important organs such as heart, lung, liver and kidney and actively deal with it. basic knowledge The proportion of illness: 0.08% Susceptible people: no special people Mode of infection: non-infectious Complications: osteomyelitis myocarditis gastrointestinal bleeding septic shock
Cause
Causes of sepsis and bacteremia
(1) Causes of the disease
Often secondary to large-area burn wound infections, open fractures with infection, sputum, diffuse peritonitis, biliary or urinary tract infections, acute obstructive suppurative cholangitis, etc., due to incomplete localization of infection lesions, making a large number of virulence The pathogens constantly or frequently invade the blood circulation, or the inflammatory mediators produced by local infections enter the blood in large quantities, triggering systemic inflammatory reactions and causing sepsis.
Common predisposing factors
(1) weakening of human body resistance: such as chronic diseases, old age, young children, malnutrition, anemia, hypoproteinemia, etc.
(2) long-term use of glucocorticoids, immunosuppressive agents, anticancer drugs, etc., leading to normal immune function changes, or the use of broad-spectrum antibiotics to change the state of the original symbiotic bacteria, non-pathogenic bacteria or conditional pathogens can be multiplied, Initiating infections for pathogenic bacteria, such as systemic fungal infections.
(3) improper treatment of local lesions: abscess failed to drain in time, debridement is not complete, wounds contain foreign bodies, dead space, poor drainage and so on.
(4) Long-term indwelling intravenous catheters, etc., help the pathogens to multiply and directly invade the blood, and stimulate the systemic inflammatory response.
2. Common pathogens cause a wide variety of pathogenic bacteria in sepsis. Common pathogens are:
(1) Gram-negative bacilli: Gram-negative bacilli infection in modern surgical infections has exceeded Gram-positive cocci, commonly known as Escherichia coli, Bacteroides, Pseudomonas aeruginosa, Proteus, followed by Klebsiella, intestine Bacillus, etc., due to the results of antibiotic screening, and the necrotic tissue caused by trauma is beneficial to the growth of such bacteria. The main toxin of Gram-negative bacilli is endotoxin, which is a lipopolysaccharide (LPS), which causes death in bacteria. After release from the cell wall, acting on phagocytic cells causes cytokine release, thereby triggering a series of chain reactions, abdominal infections, infections of adjacent parts such as the genitourinary system and perineum are often difficult to avoid contamination.
The sepsis caused by Gram-negative bacilli is generally serious, and there may be three low phenomena (low body temperature, low white blood cells, low blood pressure), and more septic shock.
(2) Gram-positive cocci: its main virulence is exotoxin, such as enterotoxin, toxic shock syndrome toxin-1 (TSST-1), etc., the more common pathogens are:
1 Staphylococcus aureus: due to the emergence of multi-drug resistant strains in recent years, including resistance to -lactams and aminoglycosides, these strains also tend to spread blood, which can form metastatic abscesses in the body, some strains Local infections can also cause high fever, rashes, and even shock.
2 Staphylococcus epidermidis: has been classified as "non-pathogenic bacteria" for many years. Because it is easy to adhere to medical plastic products such as intravenous catheters, bacteria are embedded in the mucus, which can escape the defense of the body and the role of antibiotics. The infection rate in recent years obviously increase.
3 Enterococcus: It is a resident bacteria in the human intestine. It can participate in the infection of various parts of the bacteria. Some enterococcal sepsis is not easy to find the primary lesion.
(3) Non-spore anaerobic bacteria: no spore anaerobic bacteria can not be detected by ordinary bacterial culture, easy to be ignored, abdominal abscess, appendix abscess, anal abscess, empyema, brain abscess, aspiration pneumonia, oral and maxillofacial Necrotic inflammation, perineal infection and many other anaerobic bacteria, about 2 / 3 combined with aerobic bacteria infection in anaerobic infection, the two types of bacteria have synergistic effects, can increase necrotic tissue, easy to form abscess, pus There may be fecal odor, and common non-spore anaerobic bacteria are Bacteroides, Clostridium, Anaerobic Staphylococcus and Anaerobic Streptococcus.
(4) Fungi: Conditional pathogens, often occur in the continuous application of broad-spectrum antibiotics, bacteria are widely inhibited, so that fungi can be overgrowth, become a double infection after general bacterial infection; basic diseases are heavy, plus the application of immunosuppressants , hormones, etc., further weaken the immune function; long-term indwelling intravenous catheter.
Common pathogenic fungi in surgical fungal infections are Candida albicans, Aspergillus, Mucor, and Cryptococcus neoformans.
(two) pathogenesis
The body changes in sepsis, more local infection than the activation of inflammatory reactions, and the lack of specific targeted lesions in local reactions, the pathogens and their products escape local defense into the circulatory system, leading to activation of intravascular complement and clotting factors. Histamine and serotonin (5-HT) released by systemic activation of mast cells cause vasodilation and increased permeability. When local inflammation is severe, a large amount of pro-inflammatory signals such as TNF can be released, resulting in circulating macrophages. Cells, neutrophils are activated, and macrophages in distant parts, such as alveolar macrophages, and Kupffre cells in the liver are also activated, causing the activation of disseminated inflammatory cells, and inflammation at the systemic level is initiated, resulting in systemic blood vessels. Dilation, increased blood flow (high hemodynamic state) and systemic edema, chemokines produced by inflammatory reactions cause leukocytes, endothelial cells to interact and migrate, systemic proinflammatory cytokine chain reaction, stimulate neutrophil release of lysozyme Body enzymes, interleukin-1, interleukin-6, interleukin-8, and generate oxygen free radicals through respiratory bursts to kill engulfed bacteria Decomposes necrotic tissue and has the function of defending against bacteria, but it can also cause damage to the vascular endothelium and perivascular parts. The inflammatory injury of microcirculation causes platelet aggregation and vasoconstriction, eventually leading to microcirculation blockage and tissue destruction, and formation of necrotic tissue. It can also trigger a focal inflammatory response and spread to the whole body, thus forming a vicious circle. Tissue-specific destruction mediated by systemic inflammatory response is a direct mechanism for the development of multiple organ dysfunction.
Prevention
Sepsis and bacteremia prevention
Active treatment of primary infections, rational use of antibiotics; for long-term venous catheterization and urinary catheterization, etc. should strengthen local skin cleaning and disinfection, long-term use of glucocorticoids, immunosuppressants and anti-cancer drugs for patients The disease resistance is low. While strengthening nutrition and improving physical fitness, protective isolation should be done.
Complication
Sepsis and bacteremia complications Complications osteomyelitis myocarditis gastrointestinal bleeding septic shock
1. Osteomyelitis is prone to occur in children, and Gram-positive bacteria are more common.
2. Myocardial infection Gram-positive bacteria, bacterial toxins can invade myocardial tissue, causing myocarditis.
3. Gastrointestinal bleeding caused by fungal infections sepsis is easy to develop gastrointestinal bleeding.
4. Infectious shock Gram-negative bacilli are prone to septic shock.
Symptom
Symptoms of sepsis and bacteremia Common symptoms Relaxation of heat, hypotension, blood pressure, decreased blood pressure, apathy, no urine, high fever, facial flushing, redness, diarrhea
Mainly due to systemic inflammatory response and organ perfusion and dysfunction, the performance varies depending on the pathogenic strain.
1. Gram-positive bacterial sepsis may or may not have chills, fever is reserved for heat or relaxation, the patient's face is flushed, the limbs are warm, dry, mostly sputum and coma, often rash, diarrhea, vomiting, may occur Sexual abscess, such as subcutaneous abscess, spleenitis, liver and kidney abscess, etc., prone to myocarditis, the time of shock occurs later, blood pressure is also slower.
2. Gram-negative bacilli sepsis usually starts with a sudden chill, fever can be intermittent, when the temperature does not rise or lower than normal, the patient's limbs are cold, cyanosis, oliguria or anuria, sometimes the white blood cell count is not obvious or The counter-reduction is reduced, the shock occurs early, and the duration is long.
3. Fungal sepsis is similar to Gram-negative bacillus sepsis. The patient suddenly has a chill, high fever (39.5 ~ 40 ° C), the general situation deteriorates rapidly, there is apathy, lethargy, blood pressure drop and shock, a few patients still have digestion Hemorrhage, peripheral blood can often be a leukemia-like reaction, the emergence of late granulocytes and mesangial cells, white blood cell count up to 25 × 10 9 / L.
Examine
Examination of sepsis and bacteremia
1. The white blood cell count is obviously increased, generally up to (20 ~ 30) × 10 9 / L or more, or decreased, the left side of the nuclear shift, the childish type increases, and toxic particles appear.
2. Bacterial culture (aerobic and anaerobic bacteria)
(1) Blood bacterial culture.
(2) Pus bacterial culture.
If the two bacteria obtained are the same, the diagnosis of bacteremia is established, but many patients have been treated with antibiotics before bacteremia occurs, so that it is difficult to obtain a positive result in one culture, so blood should be drawn several times in a day. For bacterial culture, the best time to draw blood is to predict the occurrence of chills. Before fever, the positive rate can be increased.
3. Bone marrow bacterial culture blood culture is negative, and when bacteremia is highly suspected, bone marrow bacterial culture is feasible.
4. Fungal culture suspected fungal bacteremia, can be used for urine and blood fungi examination and culture.
5. Blood biochemical sepsis patients may have azotemia.
6. Blood gas analysis Patients with sepsis may have varying degrees of acidosis.
7. Renal function test When sepsis patients with renal dysfunction, protein, blood cells, ketone bodies, etc. may appear in the urine.
8. Immunological detection is a reference index for judging prognosis. Activated complement, leukotriene, thromboxane and TNF-1 have a large increase in inflammatory mediators, and the duration is long, the condition is serious and the prognosis is poor.
Ophthalmoscopy: fungal bacteremia, often small, white shiny round bulges on the retina and choroid of the fundus.
Diagnosis
Diagnosis and diagnosis of sepsis and bacteremia
1. The clinical manifestations of typical sepsis appear on the basis of the primary infection.
2. According to the nature of the primary infection and its pus traits, combined with the characteristic clinical manifestations and laboratory results, the pathogenic bacteria can be roughly distinguished as Gram-positive cocci or negative bacilli.
3. Patients with primary infections with concealed lesions or atypical clinical manifestations, such as chills, fever, rapid pulse rate, low blood pressure, abdominal distension, mucosal skin ecchymosis or altered consciousness, cannot be explained by primary infection. Also, be vigilant, close observation and further examination to avoid misdiagnosis and missed diagnosis (Table 1).
Sepsis is a systemic response caused by a primary infection and is not difficult to diagnose.
