Modern treatment of sepsis. Effectiveness of empirical antibiotic treatment for severe sepsis

Antimicrobial agents are an essential component of complex therapy for sepsis. In recent years, there has been convincing evidence that early, adequate empiric antibiotic therapy for sepsis leads to a decrease in mortality and the incidence of complications (evidence category C). A series of retrospective studies also suggests that adequate antibiotic therapy reduces mortality in sepsis caused by gram-negative organisms (evidence category C), gram-positive microorganisms (evidence category D), and fungi (category C evidence). Given the data on improved outcomes of the disease with early adequate antibiotic therapy, antibiotics for sepsis should be prescribed urgently after the nosological diagnosis is clarified and before the results of bacteriological research are obtained (empirical therapy). After receiving the results of bacteriological research, the antibiotic therapy regimen can be changed taking into account the isolated microflora and its antibiotic sensitivity.

Etiological diagnosis of sepsis

Microbiological diagnosis of sepsis is decisive in the selection of adequate antibiotic therapy regimens. Antibiotic therapy directed at a known pathogen provides a significantly better clinical effect than empirical therapy aimed at a wide range of probable pathogens. That is why the microbiological diagnosis of sepsis should be given no less attention than the choice of the therapy regimen.

Microbiological diagnosis of sepsis involves examining the likely focus (s) of infection and peripheral blood. In the event that the same microorganism is released from the alleged focus of infection and from the peripheral blood, its etiological role in the development of sepsis should be considered proven.

When isolating various pathogens from the focus of infection and peripheral blood, it is necessary to assess the etiological significance of each of them. For example, in the case of sepsis, developing

against the background of late nosocomial pneumonia, with discharge from the respiratory tract P. aeruginosa in a high titer, and from peripheral blood - coagulase-negative staphylococcus, the latter, most likely, should be regarded as a contaminating microorganism.

The effectiveness of microbiological diagnostics depends entirely on the correct collection and transportation of pathological material. The main requirements for this are: the maximum approximation to the focus of infection, prevention of contamination of the material with extraneous microflora and the proliferation of microorganisms during transportation and storage prior to the start of microbiological research. The listed requirements can be met to the greatest extent when using specially designed devices of industrial production (special needles or systems for blood collection, compatible with transport media, containers, etc.).

The use of culture media for blood culture prepared in the laboratory, cotton swabs for taking material, as well as various kinds of improvised means (dishes from food products) should be excluded. Specific protocols for the collection and transportation of pathological material must be agreed with the microbiological service of the institution and strictly followed.

The study of peripheral blood is of particular importance in the diagnosis of sepsis. The best results are obtained when using commercial media (vials) in combination with automatic bacteria growth analyzers. However, it must be borne in mind that bacteremia  the presence of a microorganism in the systemic circulation is not a pathognomonic sign of sepsis. Detection of microorganisms even in the presence of risk factors, but without clinical and laboratory confirmation of the syndrome of systemic inflammatory response, should be regarded not as sepsis, but as transient bacteremia. Its occurrence is described after medical and diagnostic manipulations, such as broncho- and fibrogastroscopy, colonoscopy.

Subject to strict requirements for the correct sampling of material and the use of modern microbiological techniques, positive blood culture in sepsis is observed in more than 50% of cases. When isolating typical pathogens such as Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, mushrooms, for the diagnosis, as a rule, one positive result is enough. However, when isolating microorganisms that are skin saprophytes and can contaminate the sample ( Staphylococcus epidermidis, other coagulase-negative staphylococci, diphtheroids), two positive blood cultures are required to confirm true bacteremia. Modern automatic methods of blood culture research make it possible to record the growth of microorganisms within 6-8 hours of incubation (up to 24 hours), which makes it possible to obtain an accurate identification of the pathogen after another 24-48 hours.

To conduct an adequate microbiological blood test, the following rules should be strictly observed.

1. Blood for research must be taken before antibiotics are prescribed. If the patient is already receiving antibiotic therapy, then blood should be taken immediately before the next administration of the drug. A number of commercial blood test media contain sorbents of antibacterial drugs, which increases their sensitivity.

2. The standard for testing blood for sterility is the sampling of material from two peripheral veins with an interval of up to 30 minutes, while blood must be drawn from each vein into two vials (with media for the isolation of aerobes and anaerobes). Recently, however, the feasibility of research on anaerobes has been questioned due to the unsatisfactory cost-effectiveness ratio. With the high cost of consumables for research, the frequency of anaerobic excretion is extremely low. In practice, with limited financial resources, it is sufficient to confine oneself to blood sampling in one bottle for the study of aerobes. If there is suspicion of a fungal etiology, it is necessary to use special media for the isolation of fungi.

It has been shown that more samples have no advantages in terms of the frequency of detection of pathogens. Blood sampling at the height of fever does not increase the sensitivity of the method ( evidence category C). There are recommendations for taking blood two hours before the peak of fever is reached, but this is only feasible in those patients in whom the rise in temperature has a stable frequency.

3. Blood for research must be taken from a peripheral vein. The benefits of taking blood from an artery have not been shown ( evidence category C).

Blood sampling from the catheter is not allowed!The exception is cases of suspected catheter-associated sepsis. In this case, the purpose of the study is to assess the degree of microbial contamination of the inner surface of the catheter and blood sampling from the catheter is adequate to the set research goal. For this, a simultaneous quantitative bacteriological study of blood obtained from an intact peripheral vein and from a suspicious catheter should be carried out. If the same microorganism is isolated from both samples, and the quantitative ratio of contamination of samples from the catheter and vein is equal to or more than 5, then the catheter is most likely a source of sepsis. The sensitivity of this diagnostic method is more than 80%, and the specificity reaches 100%.

4. Blood sampling from a peripheral vein should be carried out with careful asepsis. The skin at the venipuncture site is treated twice with a solution of iodine or povidone-iodine with concentric movements from the center to the periphery for at least 1 minute. Immediately before the collection, the skin is treated with 70% alcohol. During venipuncture, the operator uses sterile gloves and a sterile dry syringe. Each sample (about 10 ml of blood or in the volume recommended by the manufacturer's instructions for the vials) is taken into a separate syringe. The cap of each vial with the medium is treated with alcohol before piercing with a needle to inoculate blood from a syringe. In some systems for seeding blood, special lines are used that allow blood to be taken from a vein without the help of a syringe - by gravity, under the suction action of a vacuum in a vial with a nutrient medium. These systems have the advantage of being eliminates one of the stages of manipulation, potentially increasing the likelihood of contamination - the use of a syringe.

Careful skin handling, vial caps, and the use of commercial blood collection adapter systems can reduce sample contamination to 3% or less)