Effect of Ilizarov tibial lengthening on limb blood flow

The experiment in 23 adult dogs was based on the study of volumetric blood flow velocity in the superficial femoral artery and femoral vein, pulse changes in blood filling of the m. gastrocnemius in the conditions of tibial lengthening to 17.5-23% from the initial length. Complex changes in the blood flow parameters were revealed after surgical intervention and within 7 distraction days. When the distraction ended, the volumetric blood flow velocity in the femoral artery was reduced by 19% and the blood flow out of the vessel was improved by 17%. When fixation was over, the volumetric blood flow velocity in the vessel increased by 37% and the improved outflow preserved. At each experimental stage, there was an increased volumetric blood flow velocity in the femoral vein as compared to its value in the control group, its correspondence to the superficial femoral artery as well as similar dynamics in blood flow changes in the femoral vessels and m. gastrocnemius. The findings show that the vascular system of bone regeneration provides accelerated arterial blood transportation into the venous system during organotypical bone area formation.     

Phrenic blood flow in cats with closed abdominal cavity]

By means of ultrasonic method, used in acute experiments on cats with closed abdominal cavity under nembutal narcosis, the authors studied the linear and volumetric blood flow velocity in left phrenic artery, the resistance of vascular bed of the phrenic artery, systemic blood pressure, respiration excursions during asphyxia, hypoxia, infusion of some biologically active substances. It was shown, that shortening of the diaphragm has definite influence on the blood flow and resistance of the vascular bed of the phrenic artery; the degree of the decrease of the blood flow in inspiration (on relation to the value of the blood flow in expiration, that passed as 100%) does not differ significantly in quiet and intensive respiration. Under the influences, the resistance of vascular bed of the phrenic artery decreases, the linear and volumetric blood flow increases, that indicates large reserve of the vascular bed of the phrenic artery for the increase of the blood flow.     

Diaphragmatic blood flow in hypoxia and hypercapnia]

By means of ultrasonic method, used in acute experiments on cats with closed abdominal cavity under nembutal narcosis, we studied the linear and volumetric blood flow velocity in the left phrenic artery, vascular resistance, systemic blood pressure, lung ventilation, arterial blood gases during different degrees of hypoxia and hypercapnia. It was shown that hypoxia and hypercapnia resulted in a decrease of the phrenic artery vascular resistance and an increase of the blood flow in the phrenic artery, not always proportional to hypoxia and hypercapnia degree. The correlation of an increase of the lung ventilation with an increase of the blood flow in the phrenic artery depends on the factor causing activation of the diaphragm performance. Some extreme conditions (prolonged asphyxia, blood loss, the exposure to 3% O2) lower phrenic vascular resistance, providing maximal blood supply of the diaphragm.     

Pulmonary circulation in experimental pneumonia

The ultrasonic technique was used in acute experiments on open-chest cats under controlled lung ventilation to test the blood flow in damaged and undamaged lung lobes in experimental pneumonia. It was shown that the absolute values of the linear and volumetric blood flow rate in the lower artery of the damaged lobe were similar to those in the analogous undamaged lobe. The blood flow in the damaged focus seems limited, while the blood volume passed through the vessels of the undamaged lobe is normal. This opinion is confirmed by high blood flow values in the artery supplying the damaged lobe with blood, when compared to the data on the absence of marked arterial hypoxaemia.     

Blood flow velocity--a constantly acting factor in dilatation of the large arteries

Acute experiments on cats have demonstrated the presence of renal artery sensitivity to the bloodstream velocity; the artery is enlarged with the blood flow increase and is narrowed with its decrease. The dilatation of the artery caused by the double increase of the blood flow (from 20 to 40 ml/min) is 23 +/- 8%. It has been established experimentally that carotid, femoral and renal arteries of cats respond to minor changes (of the order of 1 ml/min) in the volumetric velocity of the bloodstream by changing their diameters. Therefore, the arteries continuously follow the bloodstream velocity changes by changing their diameters. It may thus be concluded that the bloodstream itself is the artery dilatation factor.     

The role of the cardiac-pulmonary blood volume in the changes in left ventricle output during stimulation of the afferent fibers of somatic nerves

Stimulation of tibial nerve afferent fibers has revealed heterogeneous shifts of left ventricular output, as well as pulmonary artery and posterior vena cava blood flow in anesthetized cats. Uniform changes in left ventricular output and pulmonary artery blood flow were noted in the majority of cases, with venous return most often exceeding pulmonary artery blood flow. beta-adrenoreceptor blockade failed to influence changes in pulmonary artery blood flow. It is concluded that the increase in pulmonary artery blood flow depends on the rise in venous return, but not on neurogenic influence upon the right ventricle. The reduction in left ventricular output is the result of decreased right ventricular outflow due to its overload caused by pulmonary vasoconstriction.     

Circulation changes depending on manifestations in soft tissue tensioning in the leg lengthening process

Surgical intervention was found to intensify circulation in the limb and redistribute the blood flow. Leg lengthening led to arterial inflow limitation due to the magisterial artery strain. The changes were accompanied both by increase of functioning capillaries in number and increase of venous outflow dependence on blood inflow. The decreased after surgery oxygen tension in m. gastrocnemius did not change throughout distraction. The increase of functioning capillaries in number in resting contributed to maintenance of tissue oxygenation in the initial period of distraction, and in case of maximal tissue tensioning hydrostatic pressure increased in the capillaries due to arterial pressure rise. Restoration of the circulation parameters in the fixation period started with an increase of circulation volumetric rate in vessels with preservation of the rest mechanisms of the tissue oxygenation maintenance.     

Hemodynamic mechanisms of the pulmonary artery pressure and blood flow changes following vasoactive pressor drugs injection

The character and values of changes of the pulmonary and systemic hemodynamics following epinephrine, norepinephrine and angiotensin intravenous injection were studied in acute experiments on the anesthetized cats. After catecholamines injection pulmonary blood flow was always increased, meanwhile pulmonary artery pressure can be elevated (in the most observations) or decreased. In the cases of angiotensin administration the pulmonary blood flow could be augmented or decreased; pulmonary artery pressure had been increased or decreased independently from the character of changes of pulmonary flow. Thus, linear correlation between shifts of the pulmonary artery pressure and pulmonary blood flow had not been revealed. The changes of the pulmonary artery pressure were not correlated with the pulmonary vascular resistance ones; however they had strong relationship with the changes of the left atrial pressure. If the left atrial pressure was decreased the pulmonary artery pressure elevation was less, comparing with its values in experiments, where the left atrial pressure was increased; in the case of depressor shifts of pulmonary artery pressure, the left atrial pressure was also decreased. The character and values of the pulmonary blood flow changes were strongly correlated with the changes of the venous return; however they had no linear correlations with the right and left atrial pressures and pulmonary vascular resistance changes. Thus we concluded, that hemodynanics mechanisms of the pulmonary artery pressure and flow changes following vasoactive pressor drugs injection changes are different.     

Numerical Models of Auto-regulation and Blood Flow in the Cerebral Circulation

A two-dimensional time-dependent computational fluid dynamics model of the Circle of Willis has been developed. To simulate, not only the peripheral resistance of the cerebrovascular tree but also its auto-regulation function, a new "active" boundary condition has been defined and developed using control theory to provide a model of the feedback mechanism. The model was then used to simulate different common abnormalities of the Circle of Willis while a pressure drop, simulating a rapid compression of the right internal carotid artery, was imposed. Test results using a simple tube compared excellently with experiment. The total time-dependent flux for each efferent artery was tabulated and showed the important relationship between geometrical variations in the Circle of Willis and the auto-regulation of blood flow by vascular vaso-dilation and contraction. From this study, it was found that the worst case seemed to be that of a missing or dysfunctional right A1 segment of the anterior cerebral artery. The use of valid physiological models of the peripheral resistance allows for more realistic models of the blood flow in the Circle whilst allowing an easy extension to 3D patient specific simulations.     

Numerical simulations of the blood flow through vertebral arteries

Vertebral arteries are two arteries whose structure and location in human body result in development of special flow conditions. For some of the arteries, one can observe a significant difference between flow rates in the left and the right arteries during ultrasonography diagnosis. Usually the reason of such a difference was connected with pathology of the artery in which a smaller flow rate was detected. Simulations of the flow through the selected type of the vertebral artery geometry for twenty five cases of artery diameters have been carried out. The main aim of the presented experiment was to visualize the flow in the region of vertebral arteries junction in the origin of the basilar artery. It is extremely difficult to examine this part of human circulation system, thus numerical experiments may be helpful in understanding the phenomena occurring when two relatively large arteries join together to form one vessel. The obtained results have shown that an individual configuration and diameters of particular arteries can exert an influence on the flow in them and affect a significant difference between flow rates for vertebral arteries. It has been assumed in the investigations that modelled arteries were absolutely normal, without any pathology. In the numerical experiment, the non-Newtonian model of blood was employed.     

The blood supply to the abdominal organs of the fetal guinea-pig

Guinea-pigs near term of pregnancy were anaesthetized with diazepam and sodium pentobarbitone. A fetus was exposed and the vitelline artery catheterized to measure blood pressure and heart rate or to render a reference sample of blood for the determination of organ blood flow by the microsphere technique. The radioactive microspheres were injected through a catheter in the right atrium. Mean arterial blood pressure was 4.0 kPa and heart rate was 261 beats min-1. The liver, spleen, pancreas and gut receive most of their blood supply from the same trunk as the vitelline artery. The sample from this vessel was also used to calculate blood flow to the adrenal glands, kidneys, urogenital tract, and placenta, assuming even mixing of microspheres and blood in the abdominal aorta. Umbilical blood flow, corrected to a fetal weight of 100 g, averaged 7.5 ml min-1. The adrenal glands, which are known to increase their cortisol secretion near term, had a very high rate of perfusion. If the microspheres were injected in the umbilical vein, almost all were trapped in the liver, confirming the absence of a ductus venosus in the guinea-pig fetus. Most of these microspheres were found in the quadrate lobe of the liver. Hepatic arterial blood flow was also unequally distributed, with more than two-thirds going to the right lobe of the liver. Although the distribution of portal venous blood flow is not known, it is evident that different areas of the liver are presented with blood of greatly varying oxygen saturation.     

孕妇UtA与胎儿UmA和MCA测量在胎儿宫内窘迫诊断中的价值

目的:探讨胎儿大脑中动脉(Middle cerebral artery,MCA)与脐动脉(umbilical artery,UmA)和孕妇子宫动脉(uterine artery,UtA)测量诊断胎儿宫内窘迫的临床价值。方法:将我院自2017年1月至2019年1月间收治的孕晚期发生胎儿宫内窘迫的孕妇80例作为研究组,选择同期入院各项指标正常的健康孕妇78例作为对照组,对比观察两组胎儿MCA与UmA和孕妇UtA预测胎儿窘迫的价值及胎儿MCA与UmA与新生儿Apgar评分的相关性。结果:研究组孕妇UtA血流参数脐血流搏动指数(pulsatility index,PI)、脐血流阻力指数(resistance index,RI)和收缩/舒张比(systole/diastole ratios,S/D)指标水平均明显高于对照组,研究组胎儿MCA血流参数PI、S/D均明显低于对照组,研究组患儿UmA的血流参数PI和S/D高于对照组(P<0.05),RI比较差异无统计学意义(P>0.05);研究组新生儿Apgar评分≤7分的比例为40.00%,明显高于对照组15.38%。研究组UmA-PI、UmA-RI和UmA-S/D随着Apgar评分的降低呈现升高的趋势,MCA-PI、MCA-S/D和MCA-S/D随着Apgar评分的降低呈现逐渐减低的趋势。UtA血流参数联合MCA血流参数诊断胎儿宫内窘迫的敏感度为97.50%,特异性为96.25%,均明显高于各项参数单独诊断在的敏感度和特异性(P<0.05)。结论:临床可利用孕晚期孕妇UtA、胎儿UmA和MCA的血流动力学参数改变来预测胎儿宫内窘迫发生的几率,根据胎儿UmA和MCA的血流指标随着Apgar评分的变化趋势,可指导临床早期干预,降低胎儿出生缺陷和死亡率,临床价值较高,可推广使用。     

Combined Hepatic Vein, Umbilicoportal Vein, and Superior Mesenteric Artery Catheterization in Portal Hypertension: Estimation of the Portal Fraction of Total Hepatic Blood Flow in Cirrhotic Patients

Hemodynamic data were obtained in 13 cirrhotic patients with severe portal hypertension, undergoing combined hepatic vein, umbilicoportal vein, and superior mesenteric artery catheterization. The relative clearance of indocyanine green, the portohepatic gradient (difference between the free portal venous pressure and the free hepatic venous pressure), and the estimated hepatic blood flow were measured. The portal fraction (PF) of total hepatic blood flow was calculated in all patients using indicator dilution curves obtained from the portal bifurcation, a right hepatic vein, and when possible a left hepatic vein (six cases) after injection of ⁵¹Cr-labeled red blood cells (⁵¹Cr RBC) into the superior mesenteric artery. Flows were overestimated because of loss of indicator through spontaneous portosystemic shunts; however, the ratio between hepatic and portal indicator dilution curves can be used to calculate the portal fraction of total hepatic blood flow since no extrahepatic shunts existed after the bifurcation of the portal vein (as shown on portography). In 10 patients, 15 series of curves were calculable and the PF varied between 30.1 and 100% (mean ± SE: 71.1 ± 6.2%). In the three other patients, only delayed activity from recirculation was detected from portal and hepatic vein samples and PF was 0%; in these three cases, portography and arteriography revealed spontaneous portacaval shunting with reverse and/or stagnant circulation in the portal vein. In the 13 patients, no correlation existed between PF and the relative clearance of indocyanine green or the portohepatic gradient, parameters generally used as indices of severity in cirrhosis. In 10 patients, no correlation was found between PF and the estimated hepatic blood flow.     

On the detection of messages carried in arterial pulse waves

The hypothesis is made that a disturbance in blood flow at one place can be detected in the arterial pulse waves at a distant site. This hypothesis was motivated by the traditional Chinese medicine which uses arterial pulse waves as a principal means of diagnosis. We formulated a test by asking whether a disturbance to the blood flow in a leg can be detected by changes in the pulse waves in the radial arteries. In particular, we ask whether the radial artery can differentiate a disturbance in the right leg from that in the left leg. We put force transducers on the radial arteries, depressed them by a specific amount, and recorded the force waves in response to a 2-min occlusion of the blood flow in the right or left tibial artery. The results show that the radial artery force waves do change in response to the flow disturbance. For a given individual, the force varies with the location of the force transducer on the radial artery, the specific amount of initial depression, and the right or left leg occlusion. Generally, an occlusion in the right leg reduces the force level in both radial arteries, the more so in the right radial artery than in the left. Although the discrimination is not very strong, the phenomenon is novel, and warrants further investigation.     

Pressure in the pulmonary artery and transbronchial electroplethysmography in rats

A complex technique for pulmonary circulation study involving catheterization of pulmonary artery and transbronchial electroplethysmography has been tested in rats. The technique permits pulmonary artery pressure measurement and registration of electrical resistance in the lung lobe of closed-chest animals with the subsequent estimation of blood flow, blood volume and air content in the lungs expressed in adequate units per unit of organ volume. The experimental data characterizing standard values of the above parameters in rats are presented.     

Outcomes of Middle Cardiac Vein Arterialization via Internal Mammary/Thoracic Artery Anastomosis

Objective

Cardiac vein arterialization is seldom applied for treating right coronary artery disease. This study aimed to improve outcomes of cardiac vein arterialization in a porcine model using intramammary artery anastomosis.

Methods

A chronic, stenotic coronary artery model was established in 12 of 14 Chinese experimental miniature pigs of either sex, which were randomly divided into equal control (n = 6) and experimental (n = 6) groups. In experimental animals, blood flow was reconstructed in the right coronary artery using intramammary artery. Arterialization involved dissection of right internal mammary artery from bifurcation to apex of thorax followed by end-to-side anastomosis of internal mammary artery and middle cardiac vein plus posterior descending branch of right coronary artery. Intraoperative heart rate was maintained at 110 beats/min. Graft flow assessment and echocardiography were performed when blood pressure and heart rate normalized.

Results

The experimental group had significantly higher mean endocardial and epicardial blood flow postoperatively than control group (mean endocardial blood flow: 0.37 vs. 0.14 ml/(g*min), p<0.001; mean epicardial blood flow: 0.29 vs. 0.22, p = 0.014). Transmural blood flow was also higher in experimental group than in control group (0.33 vs. 0.19, p<0.001); ejection fraction increased from 0.46% at baseline to 0.51% (p = 0.0038) at 6 hours postoperatively, and mean blood flow of internal mammary artery was 44.50, perfusion index 0.73 at postoperative 6 months, 43.33 and 0.80 at 3 months.

Conclusion

Successful cardiac vein arterialization via intramammary artery in a porcine model suggests that this may be a viable method for reconstructing blood flow in chronic, severe coronary artery disease.     

Numerical models of auto-regulation and blood flow in the cerebral circulation

A two-dimensional time-dependent computational fluid dynamics model of the Circle of Willis has been developed. To simulate, not only the peripheral resistance of the cerebrovascular tree but also its auto-regulation function, a new "active" boundary condition has been defined and developed using control theory to provide a model of the feedback mechanism. The model was then used to simulate different common abnormalities of the Circle of Willis while a pressure drop, simulating a rapid compression of the right internal carotid artery, was imposed. Test results using a simple tube compared excellently with experiment. The total time-dependent flux for each efferent artery was tabulated and showed the important relationship between geometrical variations in the Circle of Willis and the auto-regulation of blood flow by vascular vaso-dilation and contraction. From this study, it was found that the worst case seemed to be that of a missing or dysfunctional right A1 segment of the anterior cerebral artery. The use of valid physiological models of the peripheral resistance allows for more realistic models of the blood flow in the Circle whilst allowing an easy extension to 3D patient specific simulations.     

Pulmonary circulation in experimental toxic edema of the lungs

By means of ultrasonic method used in acute experiments on cats with open chest under artificial lung ventilation the authors studied the blood flow in low-lobar pulmonary artery and the vein, the blood pressure in pulmonary artery as well as the balance between output of right and left ventricles in experimental pulmonary edemas caused by intravenous infusion of mixture fatty acids. It was shown, that acute injury of lungs vessels produces redistribution of blood flow to the lesser circulation, increases the pressure in pulmonary artery. The pattern of pulsating blood flow in lobar artery and vein changes. The authors assume that in situation, when lung vessels permeability is already deranged redistribution of the blood to the lesser circulation aggravates the degree of edema.     

缺血性眩晕大鼠模型的建立

目的建立缺血性眩晕大鼠模型,为研究相关治疗药物奠定基础。方法采用手术结扎右侧颈总动脉（common carotid artery,CCA）和右侧锁骨下动脉（subclavian artery,SCA）致大鼠右侧半脑不完全脑缺血建立缺血性眩晕大鼠模型。记录逃避电刺激所需的时间（潜伏期）作为衡量眩晕严重程度的指标,测量造模前后右侧前庭神经核组织血流量,计算血流量变化率,评价脑供血状况。结果 1.与假手术组相比,模型组大鼠潜伏期明显延长（P〈0.01）,造模成功;与模型组比较,盐酸地芬尼多和天保宁能够明显缩短大鼠潜伏期（分别缩短61.9%、52.0%,P〈0.01）。2.结扎右侧CCA及SCA后,与对照组相比,模型组大鼠前庭神经核组织血流量明显减少（P〈0.01）,造模成功;与模型组相比,天保宁能明显增加结扎动脉后组织血流量,在结扎后5、10、15、20、25、30 min血流量分别增加92.8%、83.8%、77.3%、77.9%、65.7%、55.8%（P〈0.01）。结论该模型持久稳定,动物脑部缺血明显,并且能够很好地反映动物眩晕时间及眩晕程度,可有效应用于抗缺血性眩晕药物的实验研究。     

Mechanisms of oxygen demand/supply balance in the right ventricle

Few studies have investigated factors responsible for the O2 demand/supply balance in the right ventricle. Resting right coronary blood flow is lower than left coronary blood flow, which is consistent with the lesser work of the right ventricle. Because right and left coronary artery perfusion pressures are identical, right coronary conductance is less than left coronary conductance, but the signal relating this conductance to the lower right ventricular O2 demand has not been defined. At rest, the left ventricle extracts approximately 75% of the O2 delivered by coronary blood flow, whereas right ventricular O2 extraction is only ~50%. As a result, resting right coronary venous PO2 is approximately 30 mm Hg, whereas left coronary venous PO2 is approximately 20 mm Hg. Right coronary conductance does not sufficiently restrict flow to force the right ventricle to extract the same percentage of O2 as the left ventricle. Endogenous nitric oxide impacts the right ventricular O2 demand/supply balance by increasing the right coronary blood flow at rest and during acute pulmonary hypertension, systemic hypoxia, norepinephrine infusion, and coronary hypoperfusion. The substantial right ventricular O2 extraction reserve is used preferentially during exercise-induced increases in right ventricular myocardial O2 consumption. An augmented, sympathetic-mediated vasoconstrictor tone blunts metabolically mediated dilator mechanisms during exercise and forces the right ventricle to mobilize its O2 extraction reserve, but this tone does not limit resting right coronary flow. During exercise, right coronary vasodilation does not occur until right coronary venous PO2 decreases to approximately 20 mm Hg. The mechanism responsible for right coronary vasodilation at low PO2 has not been delineated. In the poorly autoregulating right coronary circulation, reduced coronary pressure unloads the coronary hydraulic skeleton and reduces right ventricular systolic stiffness. Thus, normal right ventricular external work and O2 demand/supply balance can be maintained during moderate coronary hypoperfusion.