Pressure Drops in a Distensible Model of End-to-side Anastomosis in Systemic-to-pulmonary Shunts

The modified Blalock-Taussig shunt is a surgical procedure used as a palliation to treat complex congenital heart defects. It consists of an interposing prosthetic tube between the innominate/subclavian artery and the right pulmonary artery. Previous experience indicates that the pressure drop across the shunt is affected by the pulmonary pressure at the distal anastomosis combined with the distensibility of the anastomosis. In this study, a computational fluid-structure interaction approach is presented to investigate the haemodynamic behaviour. Steady-state fluid dynamics and structural analyses were carried out using commercial codes based on the finite element method (FIDAP and ABAQUS) coupled by means of a purposely-developed procedure to transfer boundary conditions. Both prosthetic tube and artery walls were characterised by non-linear material properties. Three different pulmonary pressures (2, 5 and 15 mmHg) and two volume flow rates (0.4 and 0.8 l/min) were investigated. Results indicate that the effects of distensibility at the distal anastomosis on the shunt pressure drop are relevant only when the distal anastomosis on the shunt pressure drop are relevant only when the distal anastomosis is not fully distended, which occurs when the pulmonary pressure is lower than 5 mmHg.     

不同麻醉方式对子宫切除患者血液动力学的影响*

目的:探索全麻复合硬膜外麻醉和全身麻醉用于子宫切除术对血液动力学的影响。方法:36例行子宫切除术患者,随机分成全麻组(A组,18例)和硬膜外+全麻组(B组,18例),采用Swan-Ganz导管技术,监测手术时血液动力学变化。结果:A组HR、MAP、CVP、SVR及CI均明显增加,SV无明显变化;B组除CVP明显上升外,其余各指标均无明显变化。结论:全麻复合硬膜外麻醉下施行子宫切除术,能减轻术中应激反应,稳定血液动力学。     

Numerical simulation of haemodynamics of the descending aorta in the non-diabetic and diabetic rabbits

Diabetes mellitus (DM) is a predisposing risk factor leading to macrovascular diseases. Changes in haemodynamics of the diabetic aortas remain largely unclear and relevant computational analyses are lacking in the literature. Ten adult rabbits (1.6–2.2 kg) were collected and the type I diabetic rabbit model was induced by injection of alloxan. A total of five control and five diabetic rabbit aortas were considered for subsequent numerical simulation. The CT scanning was performed to reconstruct three-dimensional model of the individual rabbit descending aorta. The flow velocity waveforms were measured by ultrasound machine and were set to be the inlet boundary conditions. The reconstructed aortas were then imported into ANSYS to perform mesh generation and computational analysis. Results showed that the distributions of haemodynamic indicators time-averaged wall shear stress (TAWSS), oscillating shear index (OSI) and transverse wall shear stress (transWSS) in the non-diabetic rabbit aortas were similar to those in the diabetic rabbit aortas. However, the mean values of TAWSS and transWSS in the non-diabetic rabbit aortas were significantly higher than those values in the diabetic rabbit aortas (TAWSS: p = 0.04; transWSS: p = 0.02). The back of right renal artery tended to have high OSI in both the non-diabetic and the diabetic rabbit aortas. Notably, the regions with high OSI tended to have intense disturbed flow and low TAWSS in the most diabetic rabbit aortas. The results suggest that diabetes leads to changes in haemodynamic parameters in the rabbit aortas. In particular, the lower TAWSS and the higher OSI within the diabetic aortas may further contribute to aortic wall remodeling.     

强迫跑步等复合因素对Wistar大鼠左心室血流动力学的影响

目的　检测控食、强迫跑步及大剂量心得安等复合因素对Wistar大鼠左心室血流动力学的影响。方法　实验组实验全过程采用控食及强迫跑步的方法造模 ,第 17天起每日灌服心得安溶液 ,连续 4d。第 2 1天测定血流动力学。然后将余下的大鼠再平均分为药物反证组和鉴别反证组。药物反证组灌服补心气口服液 ,连续 12d。鉴别反证组灌服滋心阴口服液 ,连续 12d ,最后测定血流动力学。结果　实验组最大心室内压、平均 +dp dtmax、平均Vpm等指标均小于正常组 ,且差异有显著性。最小心室内压、平均 dp dtmax等指标均大于正常组 ,差异亦有显著性。结论　控食、强迫跑步及大剂量心得安等复合因素可抑制Wistar大鼠的心功能     

Target renal damage: the microvascular associations of increased aortic stiffness in patients with COPD

Background

Although renal impairment has been described in COPD, there is opportunity to evaluate further to determine nature and consider optimal management. Increased aortic stiffness, as seen in COPD, leads to reduced buffering of pulsatile flow. We hypothesised that urinary albumin creatinine ratio (UACR) would reflect glomerular damage related to aortic stiffness.

Methods

Patients with COPD and controls underwent spirometry, blood pressure, arterial stiffness - aortic pulse wave velocity (PWV) and provided a spot urine sample for UACR, with other renal biomarkers measured.

Results

The UACR was increased in patients (n = 52): 0.80 mg/mmol compared to controls (n = 34): 0.46 mg/mmol, p < 0.05. Aortic PWV was related to log₁₀ UACR in all subjects (r = 0.426, p < 0.001) and COPD patients alone. Aortic PWV was a significant variable for UACR with oxygen saturations, after accounting for potential confounders. Eight subjects (7 patients) reached a defined clinical microalbuminuria threshold, with aortic PWV greater in these patients compared to those patients without, although albuminuria is a continuum. Proximal tubular damage biomarkers, unlike the glomerular marker, were not different between patients and controls.

Conclusions

There is glomerular damage in patients with COPD evidenced by increased UACR, related to increased aortic stiffness. Besides the macrovascular prognostic implications of increased aortic stiffness, the microvascular state in COPD management should be considered.     

帕瑞昔布钠超前镇痛对妇科腹腔镜手术全凭静脉麻醉效果的影响

目的:评价帕瑞昔布钠超前镇痛对妇科腹腔镜手术异丙酚-芬太尼静脉麻醉效果的影响。方法:选择在我院行妇科腹腔镜手术的患者60例,ASA分级为Ⅰ级或Ⅱ级,年龄分布在21-53岁,体重为41-72 kg。将所有患者随机分为帕瑞昔布钠组(P组)和生理盐水组(NS组),每组各30例。在麻醉诱导前15 min,对P组患者采取静脉注射帕瑞昔布钠40 mg,NS组患者则采取静脉注射等容积的生理盐水。两组麻醉诱导方法相同,术中以脑电双频指数(bispectral index,BIS)为麻醉深度指标,根据BIS值调节异丙酚血浆靶浓度以维持麻醉。记录拔管期间患者的心率(HR),平均动脉压(MAP)变化情况,苏醒时间,拔管时间,苏醒期不良反应及拔管后5 min疼痛VRS评分。结果:①两组患者血流动力学平稳,P组在T3至T6各时点的MAP和T3至T5各时点的HR均明显低于NS组,差异有统计学意义(P0.05);②两组苏醒时间和拔管时间无明显差别(P0.05);P组苏醒期躁动发生率为10%,明显低于NS组的26.7%,差异有统计学意义(P0.05);③P组拔管后5 min疼痛VRS评分为2.0,明显低于NS组的3.6,差异有统计学意义(P0.05)。结论:帕瑞昔布钠超前镇痛能减轻异丙酚-芬太尼静脉麻醉下妇科腹腔镜手术过程中血流动力学波动,减少苏醒期躁动的发生和疼痛VRS评分。     

Image segmentation methods for intracranial aneurysm haemodynamic research

Patient-specific haemodynamic technology is being increasingly utilised in clinical applications. Under normal circumstances, computational haemodynamic simulation is performed using geometric results obtained via medical image segmentation. However, even when employed upon the same set of medical imaging data, both the geometry and volume of intracranial aneurysm models are highly dependent upon varying insufficiently validated vascular segmentation methods. In this study, we compared three segmentation methods to segment the geometry of the aneurysm. These include: the Region Growing Threshold (RGT), Chan-Vese model (CV) and Threshold-Based Level Set (TLS). The results obtained were evaluated via measurement of arterial volume differences (VD), local geometric shapes, and haemodynamic simulation results. In total, 45 patient-specific aneurysm cases with three different anatomy locations were assessed in this study. From this, we discovered that the average VD of all three segmentation methods lay in the vicinity of 9.3% (SD=±4.6%). The computational haemodynamic simulation was performed via the use of the vessel geometries. Analyses produced an average of 23.2% (SD=±8.7%) difference in energy loss (EL) between the varying segmentation methods, with the difference in Wall Shear Stress (WSS) averaging 24.0% (SD=±8.5%) and 126.4% (SD=±124.4%) for the highest and lowest volumes of WSS respectively. The results of the lowest WSS, was seen to be significantly dependent upon the geometry of the aneurysm surface. It is therefore essential, in order to confirm the quality of segmentation processes in the application of patient-specific analyses of cerebrovascular haemodynamics – to validate these individual segmentation methods.     

Cardiovascular responses to an orthostatic challenge and electrical-stimulation-induced leg muscle contractions in individuals with paraplegia

The purpose of this study was to investigate the cardiovascular and haemodynamic responses that occur during moderate orthostatic challenge in people with paraplegia, and the effect of electrical stimulation (ES)-induced leg muscle contractions on their responses to orthostatic challenge. Eight males with complete spinal lesions between the 5th and 12th thoracic vertebrae (PARA) and eight able-bodied individuals (AB) volunteered for this study. Changes in heart rate (fc), stroke volume (SV), cardiac output (Qc), mean arterial pressure (MAP), total peripheral resistance (TPR), limb volumes and indices of neural modulation of fc, [parasympathetic (PNS) and sympathetic (SNS) nervous system indicators] were assessed during: (1) supine rest (REST), (2) REST with lower-body negative pressure at -30 torr (LBNP -30, where 1 torr = 133.32 N/m2), and (3) for PARA only, LBNP -30 with ES-induced leg muscle contractions (LBNP + ES). LBNP -30 elicited a decrease in SV (by 23% and 22%), Qc (by 15% and 18%) and the PNS indicator, but an increase in fc (by 10% and 9%), TPR (by 23% and 17%) and calf volume (by 1.51% and 4.04%) in both PARA and AB subjects, respectively. The SNS indicator was increased in the AB group only. Compared to LBNP -30, LBNP + ES increased SV (by 20%) and Qc (by 16%), and decreased TPR (by 12%) in the PARA group. MAP was unchanged from REST during all trials, for both groups. The orthostatic challenge induced by LBNP -30 elicited similar cardiovascular adaptations in PARA and AB subjects. ES-induced muscle contractions during LBNP -30 augmented the cardiovascular responses exhibited by the PARA group, probably via reactivation of the skeletal muscle pump and improved venous return.     

超声心动图对缺血性二尖瓣反流血流动力学的研究

目的:应用超声心动图研究缺血性二尖瓣反流(IMR)所致左室、二尖瓣环动力学变化。方法:超声心动图检测86例缺血性二尖瓣反流患者(前壁心肌梗死49例,下壁心肌梗死37例)和30例正常人的心脏,测量左室参数及二尖瓣环形态参数。结果:IMR组左室EDV、ESV增加,LVEF减低,但与对照组无显著差异;二尖瓣环面积及位移与对照组有显著差异;不同部位心肌梗死均发生明显左室重构;下壁梗死组PPM-AMP明显延长。结论:超声心动图作为心肌梗死患者的常规检查,可以针对不同患者进行不同的参数检查,这也为临床医生选择个性化治疗方案和疗效评价提供了依据。