Why Does Vascular Access Dysfunction Occur despite Brachial Artery Blood Flow Being Higher than Preset Blood Flow?

Background: In recent years, many reports have investigated the usefulness of brachial artery blood flow (BAF) measured by ultrasonography as an evaluation index for the vascular access (VA) stenosis of hemodialysis patients. However, the mechanism of VA dysfunction, despite BAF being higher than the preset blood flow, has not been clarified to date. Methods: The relationship between actual blood-removal flow and recirculation rate with decreasing VA flow was examined using a VA flow path model and pure water as a model fluid. The blood-flow rate was set at 180 mL/min, and the set VA flow rate was lowered stepwise from 350 to 50 mL/min. VA flow rate, blood-removal flow rate, and flow waveform measured between two needle-puncture sites were recorded, and then the actual blood-removal flow rate and recirculation rate were calculated. Results: Recirculation was observed at a VA flow rate < 300 mL/min. The recirculation was due to the VA flow rate, which was transiently reduced to the level below the blood-removal flow rate, resulting in backflow. In contrast, no decrease in the actual blood-removal flow rate was observed. Conclusion: It is suggested that the mechanism of the VA dysfunction, despite the BAF being higher than the preset blood-flow rate, was due to the diastolic BAF being lower than the blood-removal flow rate.

MRI evaluation of cerebral metabolic rate of oxygen (CMRO2) in obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) are at elevated risk of developing systemic vascular disease and cognitive dysfunction. Here, cerebral oxygen metabolism was assessed in patients with OSA by means of a magnetic resonance-based method involving simultaneous measurements of cerebral blood flow rate and venous oxygen saturation in the superior sagittal sinus for a period of 10 minutes at an effective temporal resolution of 1.3 seconds before, during, and after repeated 24-second breath-holds mimicking spontaneous apneas, yielding, along with pulse oximetry-derived arterial saturation, whole-brain CMRO2 via Fick’s Principle. Enrolled subjects were classified based on their apnea-hypopnea indices into OSA (N = 31) and non-sleep apnea reference subjects (NSA = 21), and further compared with young healthy subjects (YH, N = 10). OSA and NSA subjects were matched for age and body mass index. CMRO2 was lower in OSA than in the YH group during normal breathing (105.6 ± 14.1 versus 123.7 ± 22.8 μmol O2/min/100g, P = 0.01). Further, the fractional change in CMRO2 in response to a breath-hold challenge was larger in OSA than in the YH group (15.2 ± 9.2 versus 8.5 ± 3.4%, P = 0.04). However, there was no significant difference in CMRO2 between OSA and NSA subjects. The data suggest altered brain oxygen metabolism in OSA and possibly in NSA as well.

Hemodynamic Analysis of Pipeline Embolization Device Stent for Treatment of Giant Intracranial Aneurysm under Unsupervised Learning Algorithm

To treat large intracranial aneurysms, pipeline embolization device (PED) stent with unsupervised learning algorithms was utilized. Unsupervised learning model algorithm was used to screen aneurysm health big data, find aneurysm blood flow and PED stent positioning characteristic parameters, and guide PED stent treatment of intracranial aneurysms. The research objects were 100 patients with intracranial large aneurysm admitted to X Hospital of X Province from June 2020 to June 2021, who were enrolled into two groups. One group used the prototype transfer generative adversarial network (PTGAN) model to measure mean blood flow and mean vascular pressure and guide the placement of PED stents (PTGAN group). The other group did not use the model to place PED (control group). The PTGAN model can learn feature information from horizontal and vertical directions, with smooth edges and prominent features, which can effectively extract the main morphological and texture features of aneurysms. Compared with the convolutional neural network (CNN) model, the accuracy of the PTGAN model increased by 8.449% (87.452%–79.003%), and the precision increased by 8.347% (91.23%–82.883%). The recall rate increased by 7.011% (87.231%–80.22%), and the F1 score increased by 8.09% (89.73%–81.64%). After the adoption of the PTGAN model, the average blood flow inside the aneurysm body was 0.22 (m/s). After the adoption of the CNN model, the average blood flow inside the aneurysm body was 0.21 (m/s), and the difference was 0.01 (m/s), which was considerable ( p < 0.05 ). Through this research, it was found that the PTGAN model was better than the CNN model in terms of accuracy, precision, recall, and F1 score values. The PTGAN model was better than the CNN model in detecting the average blood flow rate and average blood pressure after treatment, and the blood flowed smoothly. Postoperative complications and postoperative relief were also better than those of the control group. In summary, based on the unsupervised learning algorithm, the PED stent had a good adoption effect in the treatment of intracranial aneurysms and was suitable for subsequent treatment.

Flow Manipulation and the Association with Myocardial Systolic Function During Extracorporeal Life Support

Background:Peripheral veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is used to support circulatory failure refractory to conventional therapy. However, data on the heart-ECMO interaction at different levels of ECMO blood flow during the immediate period after ECMO initiation are sparse. We evaluated the effects of varying ECMO blood flow rate on left ventricular systolic function.Methods:Adult patients who were supported by peripheral V-A ECMO in a tertiary referral center were recruited. Serial hemodynamic and cardiac performance parameters were measured by transthoracic echocardiogram within the first 48 hours after implementation of V-A ECMO. Measurements at 100%, 120%, and 50% of target blood flow (TBF) were compared.Results:A total of 45 patients were included, 32 (71.1%) were male, and the median age was 57 (50-64) years. The main indications for V-A ECMO were myocardial infarction 25 (55.6%) and myocarditis 6 (13.3%). With a decrease in extracorporeal blood flow from 100% to 50% of TBF, mean arterial pressure dropped from 75±18 to 67±20 mmHg (p<0.001), but stroke volume increased from 15 (8-25) to 21 (13-34) mL (p<0.001), and cardiac index increased from 0.8 (0.5-1.3) to 1.2 (0.7-1.7) L/min/m2 (p<0.001). All indices of left ventricular contractility improved at 50% compared with 100% TBF: the global longitudinal strain improved from -2.8 (-5.4-0) to -4.7 (-8.2- -1.1)% (p<0.001); left ventricular ejection fraction increased from 16.8 (10.0-28.5) to 28.2 (18.0-35.5)% (p<0.001); and left ventricular outflow tract velocity time integral increased from 4.7 (2.7-7.8) to 7.7 (3.9-11.3) cm (p<0.001). The addition of echocardiographic parameters improved the discrimination of the SAVE score in predicting hospital mortality (AUROC 0.71 vs 0.58).Conclusions:In the initial period of V-A ECMO support, left ventricular systolic function quantified bedside echocardiography was inversely related to ECMO blood flow rate. The heart-ECMO interaction should be considered when determining goals of ECMO flow after initiation.

IMPROVING THE EFFECTIVENESS OF CONSERVATIVE TREATMENT OF ERECTILE DYSFUNCTION IN PATIENTS WITH PEYRONIE'S DISEASE USING THE "BTL 6000" SHOCK WAVE THERAPY APPARATUS AND THE "TIVORTIN" DRUG

Исследовалось эффективность комплексной терапии эректильной дисфункции у пациентов с болезнью Пейрони, с применением препарата "Тивортин", который является субстратом для NO-синтазы - фермента, который катализирует синтез оксида азота в эндотелиоцитах, тем самым вызывая стабилизацию скорости кровотока в артериях полового члена, а также способствует восстановлению морфологической структуры, измененной белочной оболочки; и аппарата ударно-волновой терапий "БТЛ 6000", предназначенный для дезинтеграции бляшек в стадии кальцификации, которая купирует болевые ощущения в 91% случаев и уменьшает деформацию полового члена в 31% случаев, путем ударно-волновой терапии, и улучшения микроциркуляции в кавернозных телах полового члена, тем самым повышает эффективность лечения эректильной дисфункции у больных с болезнью Пейрони. The effectiveness of complex therapy of erectile dysfunction in patients with Peyronie's disease was studied with the use of the drug "Tivortin", which is a substrate for NO-synthase, an enzyme that catalyzes the synthesis of nitric oxide in endotheliocytes, thereby causing stabilization of the blood flow rate in the arteries of the penis, and also contributes to the restoration of the morphological structure, the altered protein envelope; and the shock wave therapy apparatus "BTL 6000", designed for the disintegration of plaques in the calcification stage, which relieves pain in 91% of cases and reduces the deformation of the penis in 31% of cases, by shock wave therapy, and improves microcirculation in the cavernous bodies of the penis, thereby increasing the effectiveness of treatment of erectile dysfunction in patients with Peyronie's disease.

Interrelation of cognitive functions and neural networks with blood flow velocity through the internal jugular vein in patients with chronic cerebral ischemia

Understanding age-related and functional changes in cerebral venous circulation is critical for the development of new preventive, diagnostic and therapeutic approaches to maintaining brain health in the elderly. Chronic cerebral ischemia is one of the widespread socially significant vascular diseases caused by a decrease in the level of blood circulation. To assess the role of venous outflow through the internal jugular veins in cognitive decline and neural networks in patients with chronic cerebral ischemia, 30 men and 40 women (average age 66.5 years), cognitive functions and organization of neural networks were studied at high and low levels of cerebral venous blood flow through the internal jugular veins. To assess the venous outflow, the systolic blood flow rate was measured by the internal jugular veins. A higher rate of venous outflow through internal jugular veins is associated with a more successful performance of the Luria test for verbal memory. A higher or lower blood flow rate affects the formation of neural networks of the brain. At a higher blood flow rate, the predominant areas of the resting neural networks (the passive mode network of the brain and the salient network) are localized in the frontal regions, at a low blood flow rate, the predominant neural network (frontal-parietal) is located in the left hemisphere. The state of faster and slower venous outflow forms neural networks using different neural formations that affect verbal memory. Reorganization of neural networks in this case, apparently, is the central mechanism responsible for cognitive decline in chronic cerebral ischemia (2 figs, 1 table, bibliography: 10 refs)

Comparison between different methods of calculating Kt/V as the marker of adequacy of dialysis

Objectives: To compare different methods of calculating adequacy of hemodialysis in terms of Kt/V. Methods: This was an observational, quantitative study undertaken after the approval of Internal Review Board at the Hemodialysis Unit of Nephrology department, Mayo Hospital, Lahore from 1st December 2018 to 30th June 2019. Sixty hemodynamically stable patients of end stage renal disease undergoing hemodialysis for more than three months with age 18 to 70 years were included in the study by convenience non probability sampling. Critically ill patients with multiple co-morbidities like sepsis (i.e. total leukocyte count >11000 or <4000 x 109/L), ischemic heart disease, pace- makers, malignancies, cirrhosis etc were excluded. Patients who were not adherent to dialysis prescription or hemodynamically unstable were also excluded. One way ANOVA and Pearson’s correlation were used to find correlation between three methods of measuring Kt/V. Results: Mean ultrafiltration was 2.1+ 0.76 liter/session. Pre dialysis weight was 64.7 +14.7 kgs, mean post dialysis weight was 62.5 + 14.7 kgs. For every patient blood flow rate was 300 ml/m and dialysis flow rate was 500 ml/min. The mean values of Kt/V measured by Daugirdas formula was 1.35 ± 0.33, mean online clearance monitoring (OCM) value was 1.17 ± 0.29 and by normogram was 1.36 ± 0.33. There was positive significant correlation between values of Daugirdas formula, Normogram and online clearance monitoring (OCM) i.e. r = 0.897 (p-value < 0.001) measured by Pearson’s correlation and one way-ANOVA. Conclusion: Online clearance monitoring can be used for measuring adequacy of hemodialysis, but OCM slightly underestimates Kt/V as compared to Daugirdas formula and Normogram. doi: https://doi.org/10.12669/pjms.38.1.4281 How to cite this:Fazl-e-Mateen, Ahmad S, Elahi I, Anees M. Comparison between different methods of calculating Kt/V as the marker of adequacy of dialysis. Pak J Med Sci. 2022;38(1):167-171. doi: https://doi.org/10.12669/pjms.38.1.4281 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The role of venous pressure variability during hemodialysis in the prediction of impending arteriovenous graft occlusion

Background: Elevated venous pressure during hemodialysis (VPHD) is associated with arteriovenous graft (AVG) stenosis. This study investigated the role of VPHD variations in the prediction of impending AVG occlusion. Methods: Data were retrieved from 118 operations to treat AVG occlusion (occlusion group) and 149 operations to treat significant AVG stenosis (stenosis group). In addition to analyzing the VPHD values for the three hemodialysis (HD) sessions prior to the intervention, VPHD values were normalized to mean blood pressure (MBP), blood flow rate (BFR), BFR × MBP, and BFR2 × MBP to yield ratios for analysis. The coefficient of variation (CV) was used to measure relative variations. Results: The within-group comparisons for both groups revealed no significant differences in the VPHD mean and CV values among the three HD sessions prior to intervention. However, the CVs for VPHD/MBP, VPHD/(BFR × MBP), and VPHD/(BFR2 × MBP) exhibited significant elevation in the occlusion group during the last HD session prior to intervention compared with both the penultimate and antepenultimate within-group HD data ( p < 0.05). In the receiver operating characteristic curve analysis, the CV for VPHD/(BFR2 × MBP) was the only parameter able to discriminate between the last and the penultimate HD outcomes ( p < 0.001). According to a multivariate analysis, after controlling for covariates, CV for VPHD/(BFR2 × MBP) >8.76% was associated with a higher risk of AVG thrombosis (odds ratio: 3.17, p < 0.001). Conclusions: Increasing the variation in VPHD/(BFR2 × MBP) may increase the probability of AVG occlusion.