Introduction: Despite the introduction of increasingly multifaceted diagnostic techniques and the general advances in emergency abdominal and vascular surgery, the outcome of treatment of patients with acute impaired intestinal circulation remains unsatisfactory. The non-invasive and high-resolution technique of optical coherence tomography (OCT) can be used intraoperatively to assess intestine viability and associated conditions that frequently emerge under conditions of impaired blood circulation. This study aims to demonstrate the effectiveness of multimodal (MM) OCT for intraoperative diagnostics of both the microstructure (cross—polarization OCT mode) and microcirculation (OCT angiography mode) of the small intestine wall in patients with acute mesenteric ischemia (AMI). Methods and Participants: A total of 18 patients were enrolled in the study. Nine of them suffered from AMI in segments II-III of the superior mesenteric artery (AMI group), whereby the ischemic segments of the intestine were examined. Nine others were operated on for adenocarcinoma of the colon (control group), thus allowing areas of their normal small intestine to be examined for comparison. Data on the microstructure and microcirculation in the walls of the small intestine were obtained intraoperatively from the side of the serous membrane using the MM OCT system (IAP RAS, Russia) before bowel resection. The MM OCT data were compared with the results of histological examination. Results: The study finds that MM OCT visualized the damage to serosa, muscularis externa, and blood vessels localized in these layers in 100% of AMI cases. It also visualized the submucosa in 33.3% of AMI cases. The MM OCT images of non-ischemic (control group), viable ischemic, and necrotic small intestines (AMI group) differed significantly across stratification of the distinguishable layers, the severity of intermuscular fluid accumulations, and the type and density of the vasculature. Conclusion: The MM OCT diagnostic procedure optimally meets the requirements of emergency surgery. Data on the microstructure and microcirculation of the intestinal wall can be obtained simultaneously in real time without requiring contrast agent injections. The depth of visualization of the intestinal wall from the side of the serous membrane is sufficient to assess the volume of the affected tissues. However, the methodology for obtaining MM OCT data needs to be improved to minimize the motion artefacts generated in actual clinical conditions.

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The problem of studying the oxygen status and biotissue microcirculation is of special interest for many directions in medical science since one of the causes of hypoxia development as a typical pathophysiological process is a microcirculatory "failure" associated with the impairment of normal anatomy of the capillary wall, changes in the rheological blood properties, acceleration or slowdown of the blood flow. Current imaging techniques enable the researchers to study the processes of biosystem vital activity at various levels: from organs and tissues to the substance molecular composition. Methods of functional bioimaging implemented into clinical practice provide the opportunity of watching online the processes of substance movement in the body, monitoring blood flow parameters, assessing hypoxia level, characterizing metabolism in greater detail, and, at the same time, correcting timely pathological conditions. The main advantages and disadvantages of bioimaging examination methods such as BOLD functional magnetic resonance tomography, positron emission tomography, optical imaging, laser Doppler flowmetry, and transcutaneous oximetry are considered in the present review. Special attention is paid to diffuse optical spectroscopy as a noninvasive method of lifetime study of substance content in biotissues. The principle of diffuse optical spectroscopy is based on the ability of tissue chromophores (oxyhemoglobin, deoxyhemoglobin, fatty acids, collagen) to absorb diffusely scattered light of a definite wavelength. Their concentrations are calculated with the allowance for the absorption coefficients of chromophores. Diffuse optical spectroscopy is being introduced in clinical practice to diagnose the degree of tumor malignization, evaluate vascularization in reconstructive operations, diagnose hypoxic tissue conditions, monitor intraoperatively blood flow parameters, measure hypoxia levels in diabetes mellitus. It provides the possibility to define and make clear indications to skin plastic surgery and, conceivably, to develop new methods of skin plasty.

AIM OF STUDY Was to compare the dynamics of engraftment of skin micrographs in a burn wound when using protectors from an allodermal graft and from a hydrogel coating.MATERIAL AND METHODS The experimental study was conducted on 18 rats with a scab formed 3 days after modeling a deep burn with an area of 20% of the body surface. Partial fascial necrectomy was performed: two rounded sections of the sling with a diameter of 25 mm were excised. 6 automicrographs of skin 4x4 mm, 0.3 mm thick, were applied to each surface freed from the scab. In each animal, micrographs on one of the wounds were covered with a hydrogel protector, on the other with an allodermotransplant from another animal of the group. A secondary aseptic dressing was applied to the protectors. On the 5th and 20th days after the operation, the state of micrographs was studied: blood circulation — according to laser Doppler flowmetry, microstructure in vivo — using optical coherence tomography, microstructure ex vivo — according to histological examination of biopsies.ReSUlTS Differences in the rate of restoration of blood circulation of micrographs in the early stages of the postoperative period were found. In the first 5 days, the perfusion of micrographs under an allodermal protector exceeded the indicator in micrographs under a hydrogel coating by 44 [21; 51] % (p=0.031) due to the contribution of endothelial and neurogenic mechanisms of blood flow modulation. Starting from day 10, the differences in perfusion were levelled, but there were signs of more active endothelial regulation of blood flow under the skin (p=0.028). Histologically, the appearance of full-blooded capillaries was revealed earlier in micrographs under the alloderm than when using a hydrogel protector. By 20 days, under the condition of regular change of hydrogel coatings, the area of wound healing under the studied coatings did not significantly differ. However, the structure of the integumentary tissue under the alloderm according to the optical coherence tomography data was closer to normal skin than when using a hydrogel protector.CONClUSIONS From the point of view of the physiology of the wound process, alloderm is the preferred option of an autograft protector in comparison with a hydrogel coating, which is probably due to the paracrine biological activity of the alloderm. However, hydrogel coatings can provide a comparable level of efficiency, provided they are regularly changed and, potentially, given the properties of cytokine activity.

Using bacteriophages to overcome the increasing resistance of microorganisms to antibiotics is a novel research venue of clinical importance. Among other challenges, this technique is expected to create and maintain an adequate local concentration of bacteriophages at the site of application. In addition, the possibility of combining the phage preparation with antioxidants and anesthetics may provide new options for stimulating the reparative process.The aim of the study was to assess the viability and lytic activity of bacteriophages incorporated into a hydrogel-based wound dressing that contains polyvinyl alcohol, phosphate buffer, with optional additions of succinic acid and lidocaine. Materials and Methods.A technique for incorporating bacteriophages into the complex hydrogel wound dressing ex tempore has been proposed. The bacteriolytic activity of phages inside the hydrogel was determined using standard microbiological techniques. Specifically, we used nutrient media with lawn cultures of Staphylococcus aureus added with the following antibacterial combinations: bacteriophages + succinic acid, bacteriophages + lidocaine, and bacteriophages + succinic acid + lidocaine. The lytic activity of bacteriophages was assessed within 1 to 7 days after the formation of the hydrogel.Results. In all samples containing bacteriophages, the presence of viable and lytically active phages was noted within 1 to 7 days, as evidenced by the "negative colonies" on the culture lawns. On days 1 to 3, no secondary growth was recorded in the phage-containing samples. In hydrogel samples containing phages, succinic acid, and lidocaine, secondary bacterial colonies were detected starting from day 4 indicating some reduction in the lytic activity. Conclusion.The results suggest that bacteriophages immobilized in the hydrogel maintain their viability and lytic activity, and this activity persists when the phages are combined with succinic acid and lidocaine.