1, burn wound path
Because there are a lot of necrotic tissues in burn wounds, bacterial colonization is inevitable. When bacteria are confined to surface exudates or liquefied necrotic tissues, it has little effect on the whole body, but if bacteria invade adjacent living tissues and reach a certain amount, systemic symptoms will appear, which are generally called "invasive infection of burn wounds" or "burn wound sepsis". Debridement can reduce the number of bacteria on the wound surface, and local use of sensitive topical drugs can also control the invasion of bacteria on the wound surface, leading to invasive infection.
2. Enterogenous infection
The strains of early sepsis are sometimes different from the strains of wounds at that time, and they are all resident bacteria in the intestine. Therefore, the route of enterogenous infection has long been proposed, and this hypothesis has been confirmed recently.
3, purulent phlebitis
Due to long-term intravenous infusion, patients with extensive burns occasionally have phlebitis, and purulent thrombophlebitis often becomes the focus of systemic infection. Because the infection focus is hidden, bacteria enter the blood without being found. The importance of phlebitis as the source of infection after burn should be paid attention to. Autopsy showed that venous thrombosis or pus often appeared in the vein of indwelling catheter after phlebotomy, but it was not detected before death.
4, deep muscle tissue necrosis
Muscle necrosis caused by various reasons is easy to induce infection, and sometimes even gas gangrene threatens the life of patients. The common causes of deep muscle necrosis are: ① muscle necrosis caused by third-degree burns; ② Annular eschar causes progressive muscle ischemic necrosis; ③ Electrical burns often lead to deep muscle necrosis; ④ Burn combined with crush injury; ⑤ Muscle necrosis secondary to vascular embolism.
5, respiratory tract infection
Inhalation injury causes respiratory congestion, edema, necrosis and shedding of tracheal intima in different degrees, which leads to respiratory infection and diffusion and becomes the source of infection. In addition, due to the limitation of chest eschar, long-term bed rest and sputum accumulation cause respiratory tract infection, especially for children and elderly patients.
6. Iatrogenic infection
Infected people caused by improper medical operation can not be ignored. Common ones are: ① blood transfusion and blood transfusion pollution; ② Infection caused by improper management of respiratory tract after tracheotomy; ③ Retrograde infection caused by indwelling catheter; ④ Respiratory tract infection caused by feeding and vomiting.
Second, the classification of infection
According to the pathogenic bacteria of burn infection, burn infection can be divided into the following three categories:
1, bacterial infection
Bacterial infection is the most common cause of burn infection. Gram-positive bacterial infection with the emergence of sensitive antibiotics, although the incidence has declined, but sometimes there will be staphylococcus aureus infection and hemolytic streptococcus infection. The infections caused by Pseudomonas aeruginosa, Escherichia coli, Edwardsiella, Klebsiella, Proteus (including Indole-negative Proteus) and Serratia among Gram-positive bacteria are increasing gradually. With the development of anaerobic culture technology, the discovery rate of anaerobic infection has also increased in recent years. Common infections are caused by black stomach bacteria and digestive cocci produced by anaerobic bacteria with or without spores.
2. Mold infection
Fungal infections are increasing due to the extensive or long-term use of a variety of antibiotics. There are common herpesvirus moniliforme, cytomegalovirus and varicella herpesvirus. It is more common in superficial burn wounds of children.
According to the location and depth of invasion, burn infection can be divided into the following categories:
1, wound contamination
Bacteria grow on the surface of the wound, but they do not invade the burned tissue, and there are no local and systemic symptoms.
2. Wound infection
There is a certain amount of bacteria in the burn tissue, but it does not invade the normal tissue around the wound, and only local symptoms appear.
3. Invasive infection
That is, systemic infection is that normal tissues reach a certain amount of bacteria, resulting in systemic symptoms. Sepsis includes burn wound sepsis. Teplitz first put forward the concept of burn wound sepsis. He pointed out that the number of bacteria in each gram of necrotic tissue under the eschar exceeded 105, which was called burn wound sepsis for intruders adjacent to unburned tissue.
clinical picture
First, the local symptoms of wound infection
Observation of wound surface is the main means to judge local infection, which requires medical staff to observe the changes of visible wound surface at any time. Common symptoms of wound infection are:
1. Changes in color, smell and quantity of wound exudate. Different bacterial infections will produce different changes. Staphylococcus aureus infection is a yellowish viscous secretion; Streptococcus hemolyticus infection is light brown with thin secretion; Pseudomonas aeruginosa infection is green or blue-green viscous secretion with sweet smell; Anaerobic bacteria infection can smell feces.
2. Dark gray or black necrotic spots appear on the wound surface. Necrosis spots often appear on wounds infected by gram-negative bacilli.
3, the wound deepened or delayed healing. Because bacteria invade deep blood vessels, it leads to ischemic necrosis, wound deepening and delayed healing.
4, eschar deliquescence, early shedding or insect bite changes, indicating the occurrence of local infection.
5. Most gray spots on scabbed skin or scabbed wounds indicate fungal infection. The spots quickly developed to the wound and merged into flaky villi, and the surface color gradually became obvious, showing gray, light green, light yellow or brown. A few days later, a thin layer of powder appeared on the wound.
6, pus or abscess appears under the scab. When Staphylococcus aureus is infected, an abscess will appear under the scab. If the scab is green pus with a sweet fishy smell, it is mostly infected by Pseudomonas aeruginosa.
7, granulation tissue edema, redness or necrosis. Staphylococcus aureus or fungal infection can lead to granulation tissue necrosis. However, necrotic spots can regenerate on granulation wounds infected by green bacteria.
8. There is redness, bleeding or necrosis around the wound. The wound edge infected by hemolytic streptococcus has obvious inflammatory reaction.
Second, the performance of systemic infection after burns
Despite the continuous application of new antibiotics in clinic, the treatment measures have been improved several times, and the supplement of nutrition and immune enhancers has also increased greatly, but the main cause of death of patients with extensive burns is burn sepsis or wound sepsis. According to statistics at home and abroad, 66.7% ~ 75% of the dead patients are related to infection.
(1) Types and clinical significance of systemic infection after burns
1, septicemia and bacteremia
⑴ Septicemia: Cells (or other microorganisms) invade the blood stream, reproduce and grow in blood or organs and tissues, and at the same time produce a large number of mycin and its products, causing systemic clinical symptoms, accompanied by changes in fluid dynamics and metabolism. -It's called sepsis. If septic shock occurs, the prognosis is poor. Generally, positive blood culture is used as the diagnostic basis of septicemia. The bacteria that cause septicemia may come from burns, venous catheter infection, visceral infection or enterogenous infection. Sepsis is the late manifestation of wound poisoning.
⑵ bacteremia: The brief appearance of living bacteria in blood circulation is called bacteremia. It often occurs in the process of escharectomy or escharectomy of burn wounds, with mild clinical symptoms and no hemodynamic and biochemical changes.
2, burn wound sepsis and endomycin.
⑴ Burn wound sepsis: Telplitz( 1964) first discovered that Pseudomonas aeruginosa propagated in normal tissues around burn wounds, invaded lymphatic vessels and blood vessels or infiltrated blood vessels to form embolism. When a large amount of endomycin is released into the blood circulation, clinical symptoms of sepsis appear, and blood culture is often negative, which is called burn wound sepsis. Perivasculitis or vasculitis changes during biopsy of tissue around the wound. The amount of bacteria in the tissue around the wound is usually greater than 105/g tissue. However, this index is not an index to diagnose wound sepsis, and it should be judged by combining biopsy with systemic symptoms.
Bacteria causing wound sepsis include gram-negative bacterial infection, gram-positive bacterial infection, fungal infection and mixed infection.
⑵ Endomycin: Endomycin released from the inner layer of the cell wall of Gram-negative bacteria enters the blood, which leads to changes in hemodynamics and functions of major internal organs, resulting in sepsis symptoms, while blood culture is negative. The content of endomycin can be determined by serum limulus test.
According to clinical symptoms, burn endomycin can be divided into four types. First, mild and temporary hypotension, shortness of breath, slight decrease in blood gas analysis, and good prognosis. Second, respiratory endomycin shock, hypotension, breathing more than 40 times per minute, coma, oliguria and metabolic acidosis soon appeared, and most patients died of respiratory failure. The third type is DIC-type endomycin shock, which often occurs in scabbing and gossip of infected wounds, characterized by hemodynamic changes and dysfunction of coagulation system, punctate bleeding and microemboli in unburned skin. Pathological examination often found renal and skin deep vein embolism and punctate bleeding. The fourth type mostly occurs when antibiotics are injected to kill a large number of gram-negative bacilli, releasing endomycin, causing hypotension. The body temperature can be as high as 465438 0 degrees, showing bimodal fever, coma, vomiting and diarrhea.
The symptoms of endomycin are similar to septic shock caused by gram-negative bacteria. The treatment is not only the systemic application of effective antibiotics and comprehensive treatment, but also the choice of drugs to resist or neutralize endomycin: ① glucocorticoid. Has the functions of directly antagonizing or neutralizing lipopolysaccharide of Escherichia coli and stabilizing complement. ② Disodium crotonate (DSCG). The application of disodium cromoglycate can stabilize mast cells and neutrophils to release histamine, serotonin and slow-response allergic substances, thus blocking the influence of these transmitters on the whole body. ③ Polymyxin B and its antibiotics. Literature shows that polymyxin B can neutralize endomycin, and carbenicillin can also neutralize endomycin in Escherichia coli.
(2) Clinical characteristics of systemic infection after burn.
1, systemic infection attack
Systemic infection can be divided into early and late stages according to the onset period, and their characteristics and influencing factors are different.
⑴ Early infection: Early infection occurred 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%. Patients with acute onset, especially those in shock stage, are often confused with burn shock, such as rapid pulse, shortness of breath and decreased blood pressure, so we should pay attention to differential diagnosis. It is difficult to treat early infection and the mortality rate of patients is high.
The high incidence of early burn infection is related to the following factors: first, the immune function of the body is obviously disordered within two weeks after burn, and second, there are many early complications in burn patients, such as shock, renal function injury and lung function injury. Patients who have experienced imbalance in shock stage have a high incidence of sepsis. In addition, early edema affects local blood circulation, granulation tissue is not formed, local defense barrier is not perfect, and invasive infection is easy to occur.
Early infection is mostly manifested as hypothermia, leukopenia, depression and other low reaction States.
⑵ Late infection: The infection after two weeks of burn belongs to late infection, and the incidence rate is lower than that at the early stage, which is mainly related to improper wound treatment and unreasonable application of antibiotics. The key to prevent infection is to actively treat the wound and cut scabs and skin grafts to cover the wound as soon as possible. If a large area of granulation tissue is exposed after escharectomy, it is most likely to induce invasive infection. Improper use of antibiotics can lead to opportunistic infections. In addition, improper whole-body nutrition support therapy and insufficient intake of protein and calories lead to long-term exhaustion of the body, which is also the main cause of late infection. Late infection is characterized by high body temperature, high white blood cells and high spirits.
2. Symptoms of invasive infection
The clinical manifestations of invasive infection are complex, which can be roughly divided into two types: high reaction type and low reaction type. Main performance:
⑴ Mental state: Patients with high reactivity may have high excitement, delirium, hallucinations, hallucinations, and even mania in severe cases. Low-response patients are in a state of inhibition, showing silence, lethargy and even coma.
⑵ Body temperature: Body temperature is characterized by high fever or low body temperature. Due to high metabolism, the body temperature of severely burned patients is often maintained at about 37℃ ~ 38.5℃, which does not necessarily mean that invasive infection has occurred. If the body temperature is as high as 39℃ or drops below 36℃, we should pay attention to whether infection occurs.
⑶ Pulse: The acceleration can reach more than 150 beats/min, and a slow pulse in the critical period indicates a poor prognosis.
⑷ Breathing: Breathing change is an important feature, manifested as dyspnea symptoms, such as shortness of breath or shallow shortness of breath or tangy smell.
5. Gastrointestinal function: loss of appetite is a common symptom, and some patients show nausea, vomiting and diarrhea. If intestinal paralysis leads to abdominal distension, it is a specific feature.
[6] Blood pressure: The decrease of blood pressure is mostly septic shock, indicating that the condition is critical, but the blood pressure of some patients has not changed significantly.
⑺ Changes of wound surface: Combined with the changes of wound surface, it can be diagnosed as invasive infection, which is characterized by increased secretion, special smell, deliquescence and shedding of eschar, edema and ulceration of granulation, accumulation under eschar, etc.
(8) Necrosis spots: Hemorrhage spots and necrosis spots may appear on the wound surface and normal skin, which are dark red or grayish black. Necrosis can be caused by bacteria or fungi, which is an indication of poor prognosis.
⑼ Laboratory examination: The sudden increase of white blood cells to 20× 109/ L or below 4× 109/ L is a more specific indication for the diagnosis of infection. The sudden drop of platelets to a low level has high diagnostic value, especially when DIC is combined. Invasive infection leads to corresponding manifestations of organ damage, such as elevated blood sugar, elevated serum bilirubin, and elevated serum creatinine.
Third, the clinical manifestations of systemic fungal infection
1, medical history
There are many reasons for systemic fungal infection, and the common ones are:
The wound is wet, and fungi are easy to multiply on it, which is mostly caused by the humid climate and improper treatment of the wound.
The condition is serious, the burn area is large and the course of disease is long. Due to long-term consumption, the body's resistance is weakened and its immune function is low, which is prone to systemic fungal infection. It usually occurs in about three weeks, but it also occurs within one week.
Large doses of antibiotics or silver sulfadiazine around the wound may lead to double infection of drug-resistant strains and fungi. With the application of broad-spectrum antibiotics, the incidence of fungal infection has increased, which also illustrates this point.
Improper wound treatment, such as necrotic tissue not removed in time, is prone to serious fungal infection, leading to sepsis.
Other factors, such as glucocorticoid therapy, total parenteral nutrition, fungal phlebitis caused by venous catheter, bacterial septicemia, etc., are the inducement of systemic fungal infection.
2. Clinical manifestations
⑴ Mental state: mostly excited state, sometimes hallucination, delirium, indifference or trance. Sometimes it is completely normal and conscious, which constitutes the performance of "if it is dark", and in severe cases it can be unconscious at last.
⑵ Body temperature: mostly missed fever or flabby fever, reaching a peak at about one o'clock at night, with slight chills before fever. Hypothermia may occur in the late stage or before death.
⑶ The pulse and heart rate increase rapidly, which is adapted to the fluctuation of body temperature, sometimes reaching 65438 040 beats/min, leading to late heart failure or cardiac arrest.
(4) Breathing is obviously accelerated (40-50 beats/min), and even dyspnea occurs. When fungi invade the lungs, dry and wet rales can be heard, and X-ray examination shows that the lung texture is thickened or there is a cotton ball-like shadow.
5. Gastrointestinal manifestations: Most patients have loss of appetite, nausea, dysphagia, watery diarrhea, mucus-like stool or tarry stool. There is inflammation, ulcer or false membrane in oral mucosa, and fungi can be seen in smear and culture. The phlegm is thick and jelly-like.
[6] Blood pressure: Blood pressure gradually drops before death.
(7) Wound changes: Fungi can form brown or black patches on the wound, which are round or irregular. Normal skin may have small bleeding spots or diffuse erythema nodules, and fungi can be seen in biopsy.
3. Laboratory inspection
⑴ Blood test: The increase of white blood cells can reach more than 20000 /mm3. Leukemia-like reaction was found in white blood cells, and late myeloid cells or myeloid cells were found in peripheral blood slides. Platelet count was normal, red blood cell count and hemoglobin content decreased.
⑵ Urine culture and microscopic examination: To take urine for fungal examination, it is necessary to collect samples with fresh urinary catheter or adopt aseptic operation method to collect middle urine, otherwise the positive result of urine pollution is of little significance. Generally, the positive time of urine culture is 2 ~ 3 days earlier than that of blood culture.
Other body fluid cultures can also be used as a reference for the diagnosis of systemic fungal infection, such as feces, sputum, wounds and secretions.
⑶ Blood culture: The positive rate of arterial blood culture is high. Whenever blood culture is positive once, the wound is extremely positive, which can be used as a diagnostic argument.
(4) Biopsy: Pay attention to aseptic operation when doing wound biopsy to prevent pollution. Invasive fungal infection can be diagnosed if fungal growth is found under eschar and adjacent biopsy tissue.
Fourth, the clinical manifestations of anaerobic infection
1, tetanus infection
The wound of burn patients is seriously polluted, and deep tissue necrosis often occurs, which is prone to tetanus. In order to prevent tetanus, besides active debridement and wound treatment, TAT 1500μ was injected routinely after injury, and the patients with extensive burns were injected again one week after injury.
If tetanus occurs, large doses of TAT, sedatives and antibiotics should be given for treatment.
2. Gas gangrene
Due to the loss of body fluids or shock, the deep tissue of the wound is necrotic, and Clostridium is easy to grow and reproduce, leading to gas gangrene. The clinical manifestations are that the affected area is heavy, there is a sense of wrapping, the limbs are obviously swollen, the pronunciation is distorted, gas can be seen on local X-ray, and gram-positive bacilli can be seen on secretion smear microscopy.
The key to prevent gas gangrene is thorough debridement, deep tissue necrosis is washed with 3% hydrogen peroxide and penicillin is used preventively. Once the gas gangrene is diagnosed, the necrotic tissue should be removed immediately by surgery, amputation if necessary, systemic application of penicillin or erythromycin, and systemic support treatment.
3. No infection of spore anaerobic bacteria.
Anaerobic bacteria infection mainly comes from patients themselves, especially the intestines. The anaerobic bacteria isolated from infected people mainly include Bacteroides fragilis, Bacteroides melanogenesis, Fusobacterium and digestive cocci. Anaerobic bacteria infection often coexists with aerobic bacteria infection, and the diagnosis depends on the typical fecal odor of secretions and the positive secretion or blood culture.
Clinical manifestations of viral infection of verb (abbreviation of verb)
With the improvement of virus detection technology, reports of virus infection are increasing. The common viral infection of burn patients is herpes simplex virus infection, which first manifests as vesicular herpes or hemorrhagic herpes, and then festers and necrosis. It usually occurs on deep second-degree wounds and can also be seen on normal skin. Mild people can recover on their own, and severe people form invasive infection, which invades internal organs and leads to death. Biopsy can find nuclear inclusion bodies and isolate viruses. Neutralizing antibody and complement binding antibody can be found in vascular examination.
Virus infection is mostly secondary to systemic bacterial infection or fungal infection. Diagnosis is difficult and there is no specific treatment.