Burn infection

Introduction to burn infection After the burn, the skin is destroyed as a natural shield against microbial invasion, and the necrotic skin tissue is a good "medium" for microbial growth and reproduction. Therefore, burn wounds are highly susceptible to infection. In recent years, due to the improvement of the level of burn shock treatment, the mortality of shock has decreased significantly, and burn infection has become the main cause of death from severe burns. Prevention and treatment of burn infection is the key to burn treatment. basic knowledge The proportion of illness: 0.013% Susceptible people: no special people Mode of infection: non-infectious Complications: hypernatremia bacteremia

Causes of burn infection

Cause

After burn, the skin is destroyed as a natural barrier against microbial invasion, and bacterial infection occurs. Common bacteria are Staphylococcus aureus, Pseudomonas aeruginosa, Citrobacter freundii, nitrate-negative bacilli and other intestinal-negative bacilli, severe burns. Toxic bacteria, anaerobic bacteria and viral infections may also occur.

Burn infection prevention

When a local or systemic infection occurs, it is generally difficult to treat. The prevention of infection is more important. Reasonable preventive measures include the following:

1, debridement, aseptic operation and disinfection measures

Although the pathogenic bacteria of systemic infection are not completely from the wound surface, the bacteria in the wound have a certain relationship with the infection, so it is necessary to take measures to reduce the bacteria. The commonly used principles of debridement and aseptic operation are used in the early stage of admission. Under the premise of not resisting shock, the necessary debridement should be applied to remove the pollutants and rot on the wound surface, and the wound should be washed with 1 or 0.5% chlorhexidine, and finally the wound should be washed with normal saline at 20 ° C ~ 35 ° C. In order to reduce the number of bacteria in the wound, aseptic operation and disinfection cannot be ignored in the way to prevent infection, although it is not easy to place the patient in a sterile laminar flow room, which is not necessary in general, but will It is necessary to place the patient in a ward with disinfection and isolation conditions. All factors that may cause cross-infection (such as equipment in the ward, medical personnel, etc.) should be avoided. The principle of sterility is to prevent iatrogenic infection. key.

2, nutrition

Large-area burn patients usually have malnutrition, immune dysfunction and infection, and the three are causal. The study shows that the high-protein treatment group's conditioning index, serum total protein, transferrin in patients with severe burns. The C3 and IgG levels were higher than the control group. Strengthening nutrition and maintaining a positive nitrogen balance significantly reduced the incidence and mortality of invasive infections.

3, immunotherapy

Immunological research on burn infection is more immunotherapy of Pseudomonas aeruginosa infection. Immunotherapy is divided into active immunization and passive immunization. At present, active immunization for clinical application is mainly Pseudomonas aeruginosa vaccine, and passive immunization is Pseudomonas aeruginosa immunoglobulin. Or high-priced immune serum (or plasma).

(1) Active immunization: Pseudomonas aeruginosa vaccine can be divided into lipopolysaccharide antigen and endotoxin protein antigen according to antigen component, and 7-valent Pseudomonas aeruginosa vaccine and 16-valent Pseudomonas aeruginosa vaccine (PEV-01) belong to lipopolysaccharide antigen. The Pseudomonas aeruginosa vaccine (EP) developed in China is an endotoxin antigen, and the Pseudomonas aeruginosa vaccine has good immunogenicity. On the day of admission, the burn patients were inoculated with PEV-01 three times on the day of admission and 16 times. The antibody titer of the component increased from 1/4 to 1/32 on admission to 1/64 to 1/256, and remained for 4 weeks. The lectin and hemagglutination in the serum had a protective effect against the lethal attack of Pseudomonas aeruginosa. Patients who have not been injected with vaccines rarely have protective antibodies.

The inoculant level in the plasma of patients inoculated with bacterin is low. The endotoxin titer of patients infected with Pseudomonas aeruginosa without inoculation of bacterin is high, and the endotoxin consumes the C3 component of complement, which impairs the non-specific immune mechanism and increases the susceptibility of patients to infection. Inoculation with Pseudomonas aeruginosa vaccine reduces the level of endotoxin in the blood, and indirectly enhances the patient's resistance to the bacterial infection of the word.

The phagocytic activity of neutrophils increased after inoculation of bacterins, and the phagocytosis of neutrophils to latex particles, Aerogenes and S. variabilis was enhanced. In the presence of specific antibodies, neutrophils killed P. aeruginosa. The ability of bacilli is significantly enhanced.

The appropriate dose of the vaccine can produce the maximum antibody response level. The recommended dosage is generally 25 g/kg/time for the 7-valent vaccine, one adult dose (RHD) for the PEV-01, and 0.5RHD for the children under 12 years old. Intradermal and intramuscular combined or subcutaneous injection, usually 5 to 7 days to produce appropriate antibody levels, so the sooner the vaccine is inoculated, the first inoculation should be carried out within 6 days, because the patient's response to the vaccine is equivalent after 6 days. Poor, active immunization usually 5 to 7 days, the serum IgG antibody content can reach the level of protection, the maintenance time is relatively short, continuous immunization, 3 to 7 days of vaccination until the threat of Pseudomonas aeruginosa infection disappears.

After the injection of the vaccine, local redness may occur, and the body temperature may increase. When the reaction is serious, the dosage of the vaccine should be stopped or reduced.

(2) Passive immunization: Passive immunization is to inject Pseudomonas aeruginosa immunoglobulin or high-valent immune serum (or plasma) into the patient. The high-valent immune plasma is prepared by injecting vaccine into the volunteers, and separating the plasma when the antibody titer reaches 1:512. Freeze-dried preservation, adult dosage 250ml, children 125ml, usually injected within a week, Pseudomonas aeruginosa immunoglobulin started on the day of admission, for 3 consecutive days, 0.5ml for adults, 0.2ml for children.

Passive immunization can make up for the shortcomings of active immunization. For those with low immune function, it is generally recommended to inject multivalent Pseudomonas aeruginosa vaccine and high-priced Pseudomonas aeruginosa immunoglobulin or immune plasma immediately after burn.

4. Prophylactic antibiotics

The principle of prophylactic antibiotics is early, combined, adequate and sensitive. Although some scholars do not advocate prophylactic antibiotics, we believe that the rational use of antibiotics can reduce the incidence of invasive infections. Early refers to large areas and depth. Patients with burned or more polluted patients are treated with antibiotics to prevent infection after admission; combined means that the combination of two types of antibiotics inhibits the proliferation of bacteria on the wound and under the armpit, usually using cephalosporin plus amikacin.

5, active treatment of wounds

The necrotic tissue of the burn wound provides a good medium for the bacteria. The wound is the main source of infection, and the damage of the immune function after burn is also restored to normal after the wound is healed or covered by the cut skin graft. Therefore, the wound is actively treated (including Cutting the skin graft and local topical drugs to promote wound healing is the key to preventing infection.

Burn infection complications Complications hypernatremia bacteremia

It is prone to complications such as hypernatremia and bacteremia.

Symptoms of burn infection Common symptoms After nausea and vomiting burn burns burnt yellowish... Reduced urine volume after burns Pulse increase after burns Phosphorus burns combined with poisoning burn wounds sweet suffocation... Palm scar deformity burn wounds dark gray or... Burns Wound odor smell secretion nose flap

First, the local symptoms of wound infection

The observation of the wound surface is the main means to judge the local infection. The medical staff should be required to observe the wound changes at any time. The common symptoms of wound infection are:

1, the color of the wound secretion, the smell and the amount of change, different bacterial infections can produce different changes, Staphylococcus aureus infection is a pale yellow sticky secretion; hemolytic streptococcus infection is light brown thin secretion; green pus The bacillus infection is a green or blue-green viscous secretion with a sweet scent; the anaerobic infection can smell the fecal odor.

2. Dark gray or black necrotic spots appear on the wound surface, and necrotic spots often appear on the wounds infected by Gram-negative bacilli.

3, wound surface deepening or delayed wound healing, due to bacterial invasion of deep blood vessels leading to ischemic necrosis, wound surface deepening to delay the wound.

4, eschar in advance deliquescence, shedding, or insect bite-like changes, indicating local infections.

5, gray spots appear on the surface of the suede or eschar, mostly indicating fungal infection, spots develop rapidly to the wound surface, fused into flakes, the surface color is gradually obvious, grayish white, light green, light yellow or Brown, a thin layer of powder appeared on the wound surface after a few days.

6, pus or abscess appear under the armpit, when the Staphylococcus aureus infection, under the armpits can occur abscess, if the underarm is green and has a sweet scent pus, mostly Pseudomonas aeruginosa infection.

7, granulation tissue edema, redness or necrosis, Staphylococcus aureus or fungal infection can make granulation tissue necrosis, and green bacillus infection granulation wound surface can reproduce necrotic plaque.

8. Redness, bleeding spots or necrotic spots appear around the wound surface, and there are obvious inflammatory reactions at the edge of the wound wound by hemolytic streptococcus.

Second, the performance of systemic infection after burns

Although new antibiotics continue to be used in clinical practice, treatment measures have been improved, and the supplement of nutrition and immune enhancers has increased significantly. However, the main cause of death in large-area burn patients is still burn sepsis or wound sepsis. According to statistics at home and abroad, death 66.7% to 75% of patients are associated with infection.

(1) Types and clinical significance of systemic infection after burn

1, sepsis and bacteremia

(1) sepsis: cells (or other microorganisms) invade the bloodstream and grow in blood or organs and tissues, and produce a large amount ofmycin and products, causing systemic clinical symptoms, accompanied by changes in kinetics and metabolism, For sepsis, if septic shock occurs, the prognosis is poor. Generally, blood culture positive is used as the diagnosis basis for sepsis. The bacteria causing sepsis can come from burn wounds, venous catheter infection, visceral infection, or intestinal infection. Septicemia is wound poisoning. Late manifestations of the disease.

(2) bacteremia: live bacteria appear in the blood circulation, called bacteremia, often occurs in the process of burn wounds cutting or dislocation, the clinical symptoms are light, do not cause hemodynamics and blood biochemical changes.

2, burn wounds sepsis and endomycinemia

(1) Burn wounds sepsis: Telplitz (1964) first discovered that P. aeruginosa in normal tissues around burn wounds propagated, invaded lymphatic vessels and blood vessel walls or penetrated into blood vessels to form embolism, releasing a large amount of endomycin into the blood circulation. The clinical symptoms of sepsis, blood culture is often negative, called burn wound sepsis, there is a change in perivascular inflammation or vasculitis in the tissue biopsy around the wound, the amount of bacteria around the wound is generally greater than 105 / g tissue, but this The indicator is not an indicator of the diagnosis of sepsis in the wound. It should be judged by combining biopsy and systemic symptoms.

Bacteria that cause wound sepsis include Gram-negative bacterial infections, Gram-positive bacterial infections, fungal infections, and mixed infections.

(2) Endomycinemia: Gram-negative bacterial cell wall release endomycin into the blood, resulting in hemodynamics and functional changes of major viscera, sepsis symptoms, and blood culture negative, can be determined by serum sputum test The content ofmycin.

According to clinical signs, burn endotoxin can be divided into four types, one is mild, temporary hypotension, respiratory urgency, blood gas analysis shows that PCO2 and PO2 are mildly decreased, the prognosis is good, and the second is respiratory endomycin. Shock, hypotension, breathing more than 40 times per minute, soon coma, oliguria, metabolic acidosis, patients died of respiratory failure, the third is DIC endomycin shock, often occurs in infected wounds , showing hemodynamic changes and clotting system dysfunction, unburned skin with a little bit of bleeding and microemboli, pathological examination often found deep vein thrombosis, kidney and skin punctiform hemorrhage, the fourth most occurred in the injection of antibiotics to kill a large number Gram-negative bacilli release endomycin, causing hypotension, body temperature can be as high as 41 degrees, showing bimodal fever, coma, vomiting, and diarrhea.

The symptoms of endomycinemia are similar to the septic shock caused by Gram-negative bacteria. The treatment is in addition to systemic antibiotics and comprehensive treatment. It can be used to fight or neutralize endomycin: 1 glucocorticoid, there is direct Antagonizes or neutralizes the function of lipopolysaccharide and stabilizes complement of Escherichia coli, 2 gamma phenol disodium (DSCG), can stabilize mast cells with genterosodium disodium, neutrophils do not release histamine, serotonin and slow response Allergens, thereby blocking the effects of these transmitters on the whole body, 3 polymyxin B and its antibiotics, literature shows that polymucosin B has a neutralizing effect on endomycin, carbenicillin can also neutralize the large intestine Bacillus endomycin.

(B) the clinical characteristics of systemic infection after burn

1. The onset of systemic infection

Systemic infections can be divided into early and late stages according to the stage of onset, and the characteristics and influencing factors of the two are different.

(1) Early infection: The disease is caused by early infection within two weeks after burn. The incidence of invasive infection is high at this stage, which is the peak of systemic invasive infection, accounting for about 60%, and the incidence is urgent, especially in the shock stage. Its clinical manifestations are often confused with burn shock, such as pulse speed, shortness of breath, blood pressure, etc., should pay attention to differential diagnosis, early infection treatment is more difficult, patient mortality is higher.

The high incidence of early infection in burns is related to the following factors. Firstly, the immune function of the body is obviously disordered within two weeks after the burn. Secondly, the burn patients have many early complications, such as shock, renal function damage, lung function damage, etc., and the shock period is unbalanced. The incidence of sepsis is high in patients. In addition, early edema affects local blood circulation, granulation tissue is not formed, local defense barrier is not perfect, and invasive infection is prone to occur.

Early infections are often characterized by hypothermia, decreased white blood cells, and low-response states such as mental depression.

(2) Late infection: The infection that occurs after two weeks of burn is a late infection, and the incidence rate is lower than that of the early stage. It is mainly related to the improper treatment of wounds and the unreasonable application of antibiotics. Actively treating the wounds, and cutting the wounds as early as possible is the key to prevent infection. Large area granulation tissue exposure is most likely to induce invasive infection after dislocation. Improper use of antibiotics can cause opportunistic infections. In addition, systemic nutrition support therapy is inappropriate, protein and calorie intake are insufficient, resulting in long-term consumption of the body, which is also the main infection in the later stage. The reason is that late infections are characterized by high body temperature, high white blood cells, and high levels of mental hyperactivity.

2, the symptoms of invasive infection

The clinical manifestations of invasive infections are complex and can be roughly classified into two types: high-reactive and low-reactive.

(1) Mental state: High-response patients can be characterized by high levels of excitement, delirium, hallucinations, hallucinations, and arrogance in severe cases. Low-response patients are in a state of inhibition, manifesting as a few words, lethargy, and even coma.

(2) body temperature: body temperature shows high fever or body temperature decline, severe burn patients due to ultra-high metabolism, body temperature is often maintained at 37 ° C ~ 38.5 ° C, does not necessarily indicate that invasive infection is occurring, if the body temperature is as high as 39 ° C or below 36 ° C It should be noted whether an infection has occurred.

(3) Pulse: The performance is accelerated up to 150 beats/min. The pulse in the critical period is slow and the prognosis is poor.

(4) Respiratory: Respiratory changes are an important feature, manifested as dyspnea symptoms such as shortness of breath or shallow breathing or nose flapping.

(5) Gastrointestinal function: Loss of appetite is a common symptom. Some patients show nausea, vomiting, and diarrhea. If abdominal paralysis occurs, abdominal distension is a specific feature.

(6) Blood pressure: Most of the blood pressure drop is septic shock, indicating that the condition is more critical, but some patients have no significant changes in blood pressure.

(7) Wound changes: In combination with changes in wounds, invasive infections can be diagnosed, which are characterized by increased secretions and special odors, eschar stagnation, granulation, edema, ulceration, and squatting.

(8) Necrotic spot: The wound surface and normal skin may have necrotic spots at the bleeding point, which are dark red or grayish black. Necrotic spots may be caused by bacteria or fungi, which is an indication of poor prognosis.

Third, the clinical manifestations of systemic fungal infections

(1) Mental state: Mostly excited, sometimes hallucinations, embarrassment, indifference or sorrow, sometimes completely normal, conscious, constitutes "if there is darkness", serious people can finally coma.

(2) Body temperature: mostly for heat retention or relaxation heat, peaking at around one night, mild chills before fever, and low body temperature before late or dying.

(3) Pulse, heart rate increases, and is compatible with body temperature fluctuations, sometimes up to 140 beats / min, late heart failure or cardiac arrest.

(4) The breathing is obviously accelerated (40-50 times/min) and even breathing difficulties. When the fungus invades the lungs, it can smell dry and wet rales. X-ray examination has thickened lung texture or cotton-like shadow.

(5) Digestive tract performance: Most patients have loss of appetite, nausea, difficulty swallowing, watery diarrhea, mucus-like stool or tar-like stool, inflammation of the oral mucosa, ulceration or formation of pseudo-membranes that are not easy to fall off, fungi can be found in smear and culture. The sputum is viscous and jelly-like.

(6) Blood pressure: The blood pressure gradually decreased before dying.

(7) Wound changes: Fungi can form brown or black plaque on the wound surface, which is round or irregular. There may be small bleeding spots or formation of diffuse erythema color nodules on normal skin. Fungi can be found on biopsy.

Fourth, the clinical manifestations of anaerobic infection

1, tetanus infection

Burn wounds are more serious in wounds, often with deep tissue necrosis, and easy to be combined with tetanus. In order to prevent the occurrence of tetanus, in addition to active debridement, treatment of wounds, routine injection of TAT1500 after injury, large-area burn patients strengthen injections one week after injury once.

In the event of tetanus, treatment should be given high doses of TAT, sedatives, and antibiotics.

2, gas gangrene

Electric burns or other concentrations of burns due to the loss or shock of body fluids, deep tissue necrosis of the wounds, Clostridium is easy to grow and breed, leading to gas gangrene, clinical manifestations of heavy parts, tight bandage, obvious swelling of the limbs, sputum pronunciation, Local X-ray showed gas, and smear microscopy revealed Gram-positive Bacillus.

The key to the prevention of gas gangrene is thorough debridement. Deep tissue necrosis is washed with 3% hydrogen peroxide. Prophylactic penicillin should be used. Once the gas gangrene is confirmed, the necrotic tissue should be removed immediately. If necessary, amputation should be performed. Systemic application of penicillin or red Mycin, systemic support therapy.

3, no spore anaerobic infection

Anaerobic infection mainly comes from the patient itself, especially the intestine. The anaerobic gas isolated from the infected person mainly includes fragile bacillus, melanin-producing bacteria, fusiform bacterium, digestive cocci, anaerobic infection and aerobic Bacterial infections are present at the same time, and the diagnosis is based on the typical fecal odor of the secretions, secretions or blood culture positive.

Fifth, the clinical manifestations of viral infection

With the improvement of virus detection technology, reports on viral infections have increased. The common viral infections in burn patients include herpes simplex virus infection. First, vesicular herpes is also present, which can also be hemorrhagic herpes, followed by ulceration and necrosis. In deep II degree wounds, it can also be seen in normal skin. Lighter can recover on its own. In severe cases, it can form invasive infection, invade internal organs, leading to death. Biopsy can find inclusions in the nucleus, and virus can also be isolated. Vascular examination can be performed. Neutralizing antibodies and complement-binding antibodies were found.

Viral infections are often secondary to systemic bacterial infections or fungal infections, which are difficult to diagnose and have no specific treatment.

Burn infection check

First, blood test.

Second, urine culture and microscopic examination.

Third, blood culture.

Fourth, biopsy: for wound biopsy should pay attention to aseptic operation to prevent pollution.

Diagnosis of burn infection

diagnosis

Diagnosis can be performed based on clinical manifestations and examinations.

Differential diagnosis

1, non-specific infection, also known as suppurative infection, general infection, pathogens are mostly purulent bacteria, but the same pathogenic bacteria can cause a variety of purulent infections, and different pathogenic bacteria can cause the same disease.

2, specific infection, specific bacteria, such as tuberculosis, tetanus and other infections, and non-specific infections, its clinical manifestations, changes in disease course and treatment principles and methods have distinct characteristics.

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