[Comparative evaluation of the microstructure of combined samples made on the basis of acrylic plastic]. / Sravnitel'naya otsenka mikrostruktury kombinirovannykh obraztsov, izgotovlennykh na osnove akrilovoi plastmassy.

THE RELEVANCE OF THE STUDY: Is dictated by the insufficient strength of the bases of removable plate prostheses made of acrylic plastic masses. The literature data confirm the high prevalence of strips of removable plate prostheses made of acrylic plastics, regardless of the complexity of the clinical situation, but in great dependence on the time of use of prostheses. The search for new approaches to reduce the risks of structural failures, regardless of the operating time, led to the emergence of a metal mesh and a composite frame. THE PURPOSE OF THE WORK: Is a comparative analysis of the resistance of structures to moisture and heat, in accordance with GOST R 57695-2017, aimed at modeling the aging of samples from acrylic polymers reinforced with a metal mesh and a composite frame based on fiberglass. MATERIALS AND METHODS: The whole experiment was carried out in accordance with GOST R 57695-2017 and was aimed at modeling the aging of three types of samples of acrylic polymers and combinations: «acrylic polymer-metal mesh¼, «acrylic polymer-composite frame¼ of size 20×18×1, 8 mm for studying microstructure and morphology. The obtained profiles of samples with a simulated aging effect were evaluated using an Axiovert 40MT optical microscope (Carl Zeiss), with an increase of ×200, ×500. RESULTS: Analysis of the microstructure data showed that profiles of 3 types of samples before exposure to aging factors have a homogeneous structure with a rough surface. With an increase of ×500 in four samples with a metal mesh, both before and after exposure to moisture and heat, the presence of voids between the base material and the metal reinforcing component is noted. In samples reinforced with composite material, its pronounced integration with acrylic plastic is preserved, which is due to the presence of a chemical bond. During the experiment, it was found that the conditions modeled according to GOST R 57695-2017 do not significantly affect the structure of the samples, and the morphology analysis revealed a close fit between the components of the materials in the combined samples and the absence of changes at the interface. CONCLUSIONS: The proposed option of reinforcing the base of a removable laminar denture, due to the introduction of a skeleton made of composite material based on fiberglass, is optimal for increasing the effectiveness of orthopedic treatment.

[CONTINUOUS HEMOGLOBIN MONITORING USING PULSE CO-OXIMETRY IN CARDIAC SURGERY.]

THE AIM: To assess the accuracy ofcontinuous hemoglobin monitoring using pulse co-oximetry and revealfactors affecting the results of the measurements during early postoperative period in cardiac surgery. MATERIALS AND METHODS: 27 patients undergoing off-pump CABG and 16patients after elective complex (repair or replacement of two or more valves) or combined (valve and coronary artery) cardiac surgery requiring CPB were enrolled into a prospective observational study. Both groups received continuous hemoglobin monitoring using pulse co-oximetry (SpHb). During early postoperative period SpHb was compared with hemoglobin concentration in the arterial blood (Hbart). RESULTS: Wefoundpositive correlation between SpHb and Hb in both groups (rho =0,29, p < 0,05 u rho=0,34; p<0.005 respectively). The Bland-Altman analysis showed a bias ? limits of agreement (?I.96 SD) between the continuously measured hemoglobin and reference arterial blood hemoglobin concentration of -6,0 ? 41,0 g/l in the off-pump group and 7,7 k 31,0 g/l in the CPB group. CONCLUSIONS: Hemoglobin measurement using pulse co-oximetry does not provide acceptable accuracy during early postoperative period in cardiac surgery. Applicability of this technology is influenced by vascular tone, systemic and regional tissue hypoperfusion.

Validation of cardiac output monitoring based on uncalibrated pulse contour analysis vs transpulmonary thermodilution during off-pump coronary artery bypass grafting.

BACKGROUND: Cardiac output monitoring, as a part of a goal-directed haemodynamic management, has been shown to improve perioperative outcome in high-risk patients undergoing major surgical interventions. However, thorough validation of cardiac output monitoring devices in different clinical conditions is warranted. The aim of our study was to compare the reliability of a novel system for cardiac index (CI) monitoring based on uncalibrated pulse contour analysis (UPCA) with transpulmonary thermodilution (TPTD) during off-pump coronary artery bypass grafting (OPCAB). METHODS: Twenty patients undergoing elective OPCAB were enrolled into the study. CI measured by means of UPCA (CIUPCA) was validated against CI determined with TPTD technique (CITPTD). Parallel measurements of CI were performed at nine stages during the surgery and after operation. We assessed the accuracy and the precision of individual values and the agreement of trends of changes in CI. RESULTS: Totally, 180 pairs of data were collected. There was a significant correlation between CIUPCA and CITPTD (ρ=0.836, P<0.01). According to a Bland-Altman analysis, the mean bias between the methods was -0.14 litre min(-1) m(-2) with limits of agreement of ±0.82 litre min(-1) m(-2) and a percentage error of 31%. A polar plot trend analysis revealed acceptable angular bias (-0.54°), increased radial limits of agreement (±52.7°), and decreased polar concordance rate (74%). CONCLUSIONS: In OPCAB, UPCA provides accurate and precise CI measurements compared with TPTD. However, the ability of this method to follow trends in cardiac output is poor. CLINICAL TRIAL REGISTRATION: NCT01773720 (ClinicalTrials.gov).

[Choice of optimal perfusion flow rate during surgical correction of combined acquired heart diseases].

Cardiac output during the use of cardiopulmonary bypass (CPB) is defined by perfusion flow rate, which is calculated by multiplying the perfusion index (PI) on the body surface area. To date, there is no clear definition of an optimal PI and flow rate of perfusion. 60 patients operated with CPB were enrolled in the prospective study to determine the relations between different modes of perfusion and oxygen transport during surgical correction of combined valvular heart disease. Calculation of the CPB flow rate was based on PI 2.5 and 3.0 l/min/m2. Results of the study demonstrate that perfusion based on PI 2.5 l/min/m2 provides more stable oxygen transport parameters and reduces the time of ICU stay in comparison with the flow rate based on PI 3.0 l/min/m2.

[Central venous blood oxygen saturation and venous to arterial PCO2 difference after combined heart valve surgery].

The aim of our study was to investigate the relationship between central venous oxygen saturation (ScvO2) and venous-to-arterial difference in PCO2 (Pv-aCO2) and their role in the assessment of balance between oxygen delivery and consumption after combined valve surgery. The prospective observation study included 38 adult patients with acquired valvular hear diseases, requiring surgical correction of two or more valves using cardiopulmonary bypass. All patients were divided into 2 groups according to the central value of central venous oxygen saturation (ScvO2): low ScvO2 (ScvO2 < 70%) and high ScvO2 (ScvO2 > 70%). In both groups blood gases, Pv-aCO2, lactate concentration, hemodynamic parameters, cardiac index, oxygen delivery and oxygen consumption were assessed. During the postoperative period there was a decrease of ScvO2 < 70% in 26% of patients which was accompanied by increased Pv-aCO2 > 5 mmHg and by risen oxygen consumption. We observed a moderate correlation between ScvO2 and Pv-aCO2 during the early postoperative period: at the end of surgery, 6 and 12 hours after it (rho = -0.53; -0.62 and -0.43 respectively, n = 38, p < 0.01). The changes in ScvO2 and Pv-aCO2 regressed after 24 hours in ICU. Thus, decreased ScvO2 and increased Pv-aCO2 after combined valve surgery are related and reflect the rise in oxygen consumption.

[Use of microstream capnography and alveolar recruitment during off-pump coronary artery bypass grafting].

The aim of the study was to investigate changes in EtCO2 and its correlation with PaCO2, and cardiac function during off-pump coronary artery bypass grafting (OPCAB) and to evaluate whether the recruitment maneuver was effective in improving gas exchange after OPCAB. Twenty adult patients scheduled for elective OPCAB were enrolled in a prospective randomized study. Anesthesia was maintained with midazolam, propofol, and fentanyl. After OPCAB the patients were randomized to a control group receiving conventional ventilation (n=10) or to a RM group (n=10) having ventilation and RM. RM was performed at min 15 after transfer to an ICU, by increasing airway pressure to 40 cm H2O for 40 sec subsequently adjusting PEEP to a level of 2 cm H2O above the lower inflection point of the pressure-volume curve. The measurements included hemodynamics, microstream capnography, respiratory parameters, and blood gasses. The baseline EtCO2 correlated with PaCO2 and cardiac index in both group (r = 0.7 and 0.81, respectively; p < 0.05). In the control group, OPCAB was followed by a rise in PaCO2 and worsening of arterial oxygenation (p < 0.05). After recruitment, EtCO, increased transiently whereas PaO2/FiO2 return to the baseline level. There was a moderate correlation between EtCO2 and PaCO2 before and after RM (r = 0.7 and 0.8, respectively; p < 0.05). The Bland-Altman analysis has shown that the difference between PaCO2 an EtCO2 was 1.9 +/- 11.4 mm Hg (M +/- 2SD). Thus, during OPCAB, EtCO2 measured by microstream capnography cor related well with PaCO2 and cardiac function. The use of RM after OPCAB increases CO2 elimination and improve arterial oxygenation.

Single transpulmonary thermodilution and continuous monitoring of central venous oxygen saturation during off-pump coronary surgery.

BACKGROUND: Off-pump coronary artery bypass grafting (OPCAB) requires thorough monitoring of hemodynamics and oxygen transport. Our aim was to find out whether therapeutic guidance during and after OPCAB, using an algorithm based on advanced monitoring, influences perioperative hemodynamic and fluid management as well as the length of post-operative ICU and hospital stay. METHODS: Patients were randomized into two groups of hemodynamic monitoring: the conventional monitoring (CM) group (n=20) and the advanced monitoring (AM) group (n=20). In the CM group, therapy was guided by central venous pressure, mean arterial pressure (MAP) and heart rate (HR), and in the AM group by the intrathoracic blood volume index, MAP, HR, central venous oxygen saturation (ScvO(2)) and cardiac index (CI). The measurements were performed before and during surgery, and at 2, 4 and 6 h post-operatively. RESULTS: In the AM group, colloids and dobutamine were given more frequently and were accompanied by increments in ScvO(2), CI and oxygen delivery compared with baseline. The percentage of ephedrine administration was higher in the CM group. The algorithm guided by AM decreased time until achieving the status of 'fit for ICU discharge' and post-operative hospital stay by 15% and 25%, respectively. CONCLUSIONS: A goal-directed algorithm based on advanced hemodynamic monitoring and continuous measurement of ScvO(2) facilitates early detection and correction of hemodynamic changes and influences the strategy for fluid therapy that can improve the course of post-operative period after coronary artery bypass grafting on the beating heart.

[Use of capnography during endoscopic cholecystectomy under different artificial ventilation modes].

A portable multigas monitoring system was used in 20 patients during labaroscopic cholecystectomy. The system was found to provide useful on-line information on ventilatory changes, which permitted the prevention of cardiopulmonary abnormalities during this type of surgery. Expiratory CO2 and CO2 production closely correlated with PaCO2.