Mesenteric artery response to head-up tilt-induced centralhypovolaemia and hypotension

Superior mesenteric artery (SMA) blood flow and impedance were evaluated byduplex ultrasound during head-up tilt (HUT)-induced central hypovolaemia and hypotension ineight healthy volunteers. HUT induced a reduction in cardiac stroke volume from88·8±6·3 to 64·7±6·3 ml(mean±SEM; P<0·01) and an increase in thoracic electricimpedance from 38·6±2·1 to 42·6±2·1Ω (P<0·01) reflecting a reduced central blood volume. Maintainedtilt provoked a 30% reduction in mean arterial pressure (from 87·1±3·3to 63·4±3·6 mmHg; P<0·01) and the appearanceof presyncopal symptoms. During both the normotensive and the hypotensive phase of HUT, theSMA diameter (5·7±0·03 mm) and blood flow (514±75 ml min^?1) did not change significantly, although the end-diastolic velocity increasedfrom 9·7±4·8 to 39·7±4·0 cm s^?1 (P<0·01). The increase in diastolic velocity, despite amaintained or reduced arterial pressure, supports a reduction in the SMA impedance as it wasreproduced during a meal test when a moderate reduction in mean arterial pressure (87±4to 80±4 mmHg; P=0·04) was accompanied by a ninefoldincrease in the end-diastolic velocity (P<0·01). The results indicate areduction in the mesenteric vascular impedance to the extent that superior mesenteric artery bloodflow is maintained during HUT-induced central hypovolaemia and hypotension.     

Change in pulse transit time and pre-ejection period during head-up tilt-induced progressive central hypovolaemia

Objective Traditional vital signs such as heart rate (HR) and blood pressure (BP) are often regarded as insensitive markers of mild to moderate blood loss. The present study investigated the feasibility of using pulse transit time (PTT) to track variations in pre-ejection period (PEP) during progressive central hypovolaemia induced by head-up tilt and evaluated the potential of PTT as an early non-invasive indicator of blood loss. Methods About 11 healthy subjects underwent graded head-up tilt from 0 to 80°. PTT and PEP were computed from the simultaneous measurement of electrocardiogram (ECG), finger photoplethysmographic pulse oximetry waveform (PPG-POW) and thoracic impedance plethysmogram (IPG). The response of PTT and PEP to tilt was compared with that of interbeat heart interval (RR) and BP. Least-squares linear regression analysis was carried out on an intra-subject basis between PTT and PEP and between various physiological variables and sine of the tilt angle (which is associated with the decrease in central blood volume) and the correlation coefficients (r) were computed. Results During graded tilt, PEP and PTT were strongly correlated in 10 out of 11 subjects (median r = 0.964) and had strong positive linear correlations with sine of the tilt angle (median r = 0.966 and 0.938 respectively). At a mild hypovolaemic state (20–30°), there was a significant increase in PTT and PEP compared with baseline (0°) but without a significant change in RR and BP. Gradient analysis showed that PTT was more responsive to central volume loss than RR during mild hypovolaemia (0–20°) but not moderate hypovolaemia (50–80°). Conclusion PTT may reflect variation in PEP and central blood volume, and is potentially useful for early detection of non-hypotensive progressive central hypovolaemia. Joint interpretation of PTT and RR trends or responses may help to characterize the extent of blood volume loss in critical care patients. Chan GSH, Middleton PM, Celler BG, Wang L, Lovell NH. Change in pulse transit time and pre-ejection period during head-up tilt-induced progressive central hypovolaemia.     

Blood volume distribution during head-up tilt induced central hypovolaemia in man

Summary. We evaluated regional electrical impedance (Z°) at 2.5 and 100 kHz to separate intra- and extracellular fluid changes and correlated Z° over the thorax (TI) to relative changes in the central blood volume (CBV) induced by head-up tilt. In nine experiments head-up tilt resulted in normotensive central hypovolaemia associated with a 3·7 & 0·4 Ohm (mean f SE) increase in TI_{100 kHz} after 60 min. In 24 experiments presyncopal symptoms were induced after 43±2 min, when TI_100kHz had increased 4·2 ± 0·2 Ohm. Head-up tilt instantly decreased the activity of technetium labelled erythrocytes (⁹⁹Tc^m) over the thorax by 24 ± 2%, and increased ⁹⁹Tc^m over the thigh by 68±10% (P< 0·01, n = 8) with no further changes during the sustained tilt. Haematocrite increased during head-up tilt from 43·1 ± 0·3 to 47·9 ± 0·6% (P<0·01, n= 8). Accordingly, the increase in TI (6·3 ± 0·6 vs. 4·5 0·4 Ohm, n= 6) and the decrease in Z° through one leg (7·2 ± 1·2 vs. 2·8 ± 0·5 Ohm, n= 6) at 2·5 kHz was more pronounced than at 100 kHz. Also the changes in TI were correlated to CBV as calculated from ⁹⁹T_c^m and haematocrite (r = 0.90, P < 0·01). The results suggest that: (1) Hypovolaemic shock is associated with a faster increase of TI than normotensive head-up tilt. (2) Head-up tilt is characterized by an initial decrease in CBV followed by a further decrease in plasma volume, which eventually leads to hypovolaemic shock. (3) Blood volume changes during head-up tilt are reflected in regional Z°.     

Sonographic diagnosis of inferior mesenteric artery aneurysm and marginal artery of Drummond

We report the case of a patient in whom sonographic examination revealed an aneurysm of the inferior mesenteric artery with severe proximal stenosis and poststenotic dilatation--the enlargement of the proximal portion of the artery of Drummond. This collateral pathway should be kept in mind when studying bowel ischemia, especially when stenosis is present or when there is occlusion of the superior mesenteric artery.     

糖尿病视网膜血管病变彩色多普勒超声检测与血浆同型半胱氨酸的关系探讨

目的观察糖尿病视网膜病变时,彩色多普勒超声检测眼动脉(OA),视网膜中央动脉(CRA)和睫状后动脉(PCA)等血流参数,探讨同型半胱氨酸(Hcy)血症与视网膜病变之间的关系。方法同步检测30例正常人,55例糖尿病视网膜病及45例无视网膜病变者的OA、CRA和PCA的彩色多普勒超声以及血浆Hcy水平。结果视网膜病变组中CRA的收缩期峰值流速PVS、舒张期末流速(EDV)、阻力指数(RI)以及PCA中的EDV和RI与正常对照组相比,有明显差异;视网膜病变组中的血糖、Hcy明显升高。结论彩色多普勒超声检查对评估视网膜病变时CRA和PCA的血流动力学变化是一种有效的方法,高Hcy和视网膜病变的发生密切相关,是一种高危因素。     

In vivo validation of image-directed Doppler measurement of superior mesenteric artery blood flow.

Image-directed Doppler measurement of superior mesenteric artery blood flow in volunteers was validated in two artificial models with either a venous or an arterial flow profile. In the "venous" model, the Doppler device overestimated the real flow velocity by 86 +/- 7%, and in the "arterial" model by 24 +/- 9%. The areas under the time-frequency curves (AUCs) from the arterial model were measured by planimetry. A correction factor of 1.47 between flow velocities calculated after planimetry and real flow was established. Correction for this factor resulted in a flow velocity of 19.5 +/- 4.7 cm/s and a blood flow rate of 377 +/- 166 ml/min in the volunteers.     

结肠肿瘤及炎症患者肠系膜下动脉血流变化及其意义

目的观察结肠肿瘤及炎症患者肠系膜下动脉（IMA）血流动力学参数的变化。方法应用彩色多普勒超声分别测定23例结肠、直肠肿瘤患者,27例活动期溃疡性结肠炎（UC）患者和32例正常人的IMA血流动力学参数。结果结肠、直肠肿瘤患者IMA血流动力学参数与正常人比较存在显著差异（P〈0．05）,结肠肿瘤及炎症患者血流指标存在相似变化,其IMA的内径、血流速度和血流量高于正常人,而搏动指数显著降低,阻力指数变化不显著。结论结肠肿瘤及炎症患者IMA血流动力学参数较正常人显著变化,可作为了解直肠存在某种疾病的征象。     

正常人颈总动脉、肱动脉、胫后动脉牛顿射血力分析

目的 运用多普勒超声技术检测正常人颈总动脉、肱动脉、胫后动脉的牛顿射血力,探讨正常人体多处外周动脉牛顿射血力变化的意义.方法 纳入30例正常人,将多普勒超声探头分别置于受试者左侧颈总动脉起始段、左侧肱动脉、左侧胫后动脉,测量以上动脉的血管内径、血流加速度及加速期流速积分,根据牛顿第二定律F=ma计算出牛顿射血力.结果 30例正常人左侧颈总动脉的血管内径为(0.59±0.05)cm,血管截面积为(0.28±0.05)cm2,血流加速度为(1 681.53±1 590.88)cm/s2,加速期流速积分为(4.31±1.01)cm,牛顿射血力为(1 941.73±958.68)dynes.左侧肱动脉的血管内径为(0.32±0.04)cm,血管截面积为(0.08±0.02)cm2,血流加速度为(1018.40±287.28)cm/s2,加速期流速积分为(3.21±1.17)cm,牛顿射血力为(319.57±228.93)dynes.左侧胫后动脉的血管内径为(0.21±0.03)mm,血管截面积为(0.03±0.01)cm2,血流加速度为(658.13±173.94)cm/s2,加速期流速积分为(2.28±1.15)cm,牛顿射血力为(68.11±69.34)dynes.结论 通过检测人体多处外周动脉牛顿射血力可以分析从心脏到外周血管轴向力的分布,分析人体动脉长度、血管内径、血管弹性变化及动能势能转换对牛顿射血力传导的影响,为该参数的临床应用提供科学依据.     

Renal artery stenosis on duplex ultrasound due to inferior vena cava filter leg impingement

We present a case study of renal artery duplex findings for new onset of hypertension in a young woman with a history of inferior vena cava filter placed a year prior and failed percutaneous retrieval. Duplex ultrasound showed significantly elevated velocities in the mid-right renal artery, consistent with renal artery stenosis. Computed tomography angiography images suggested that a leg from the inferior vena cava filter was impinging on her right renal artery, with perforation through the vena cava possibly into the wall of her duodenum. Open surgical intervention was required to disentangle the filter legs from the wall of the duodenum and relieve impingement on the right renal artery with thrombolysis of clot found within the right renal artery.     

Color Doppler sonographic diagnosis of dissecting aneurysm of the superior mesenteric artery

We report a case of dissecting aneurysm of the superior mesenteric artery (SMA) diagnosed on gray-scale and color Doppler sonography and confirmed on angiography. Spontaneous dissection of the SMA is rare, and there are few reported cases of the color Doppler sonographic findings. Gray-scale sonography revealed an aneurysmal dilatation of the SMA 3-4 cm from the SMA's origin, with an echogenic linear membrane (an intimal flap) within the aneurysm. Color Doppler sonography showed color flow within the aneurysm and showed that the intimal flap separated the aneurysm into 2 lumina. Spectral analysis revealed anterograde flow in the anterior (ie, true) lumen and retrograde flow in the posterior (ie, false) lumen.     

彩色多普勒超声评价足月窒息儿进餐前后肠系膜上动脉血流动力学改变及其与喂养耐受性的关系

目的探讨足月窒息儿餐前、餐后肠系膜上动脉血流动力学变化规律及其与喂养耐受性的关系。方法采用彩色多普勒超声检测40例足月窒息儿第1次喂养及足量喂养(150ml·kg-1·d-1)餐前、餐后肠系膜上动脉血流动力学变化,并记录有无发生喂养不耐受及达足量喂养的天数。结果根据临床表现及实验室检测本组喂养耐受组22例,不耐受组18例。第1次喂养后与不耐受组比,耐受组餐前、餐后肠系膜上动脉血流动力学参数值配对比较差异均有统计学意义(P<0.05);足量喂养时,不耐受组餐前、餐后肠系膜上动脉RI和PI配对比较差异无统计学意义(P>0.05),而耐受组PI值配对比较差异有统计学意义(P<0.05);耐受组第1次喂养餐前、餐后肠系膜上动脉血流动力学参数变化与达足量喂养天数无相关关系。结论喂养可使肠系膜上动脉血流动力学发生变化;可通过检测足月窒息儿第1次喂养和达足量喂养时餐前、餐后肠系膜上动脉血流动力学改变来评估喂养风险,从而及时调整喂养方案。     

Ultrasonic doppler spectral broadening in the diagnosis of internal carotid artery stenosis

In a clinical study, 78 carotid bifurcations were examined by pulsed Doppler ultrasonography and X-ray arteriography. Maximum Doppler frequencies 3 kHz diagnosed stenoses of 25% diameter reduction with a sensitivity of 73% and specificity of 79%. A quantitative analysis of the degree of spectral broadening was obtained from the ratio of the maximum to mean frequency at peak systole and improved the sensitivity and specificity to 90% and 98% respectively. All vessels > 40% stenosis were correctly classified as stenosed and all > 20% stenosis were classified as normal.     

代谢综合征患者颈动脉与肠系膜上动脉病变的相关性研究

目的 探讨代谢综合征（MS）患者颈动脉与肠系膜上动脉（SMA）病变的相关性研究.方法 应用彩色多普勒超声对72例MS患者（MS组）及70例健康体检者（对照组）同时作颈动脉和SMA检查,检测两支动脉血管壁病变及颈总动脉内-中膜厚度（IMT）、收缩期峰值速度（PSV）、舒张末期速度（EDV）、搏动指数（PI）、阻力指数（RI）,以研究两支动脉血管病变的相关性.结果 72例MS患者中,48例存在颈动脉病变,39例存在SMA病变,38例同时伴有两处病变,颈动脉病变与SMA病变存在79.2%重合现象.MS组颈总动脉和SMA的PI、RI均较对照组减慢（P〈0.05）,MS组颈动脉PSV、ESV均较对照组减低,SMA的PSV、ESV则均较对照组加快（P〈0.05）,且两支血管间各参数指标存在显著相关性（r=0.804）.结论 MS患者易发生头颈部动脉病变,同样也可以引起腹腔主要供血动脉如SMA发生相应病变,而且两支动脉血管病变之间存在显著相关性.     

超声多普勒功率及其在检测颅内血流分布上的应用

本文结合背向散射超声多普勒信号模型对超声多普勒功率的概念及其特性进行了阐述，并提出了一种用超声多普勒功率来检测颅内血管血流分布的方法。实验结果证明，该方法能在噪声背景下灵敏准确地反应沿声束指向一维空间各个位置是否存在血流以及血流强度的大小。这一方法已被用于经颅多普勒（ＴＣＤ）脑血流分析仪中，解决了现有经颅多普勒检查时只能凭经验盲目搜寻颅内血管的问题，并提供了颅内血管分布的相对位置信息以帮助临床医生更方便准确地判定所检测的是哪一根血管。     

彩色多普勒超声对糖尿病患者视网膜中央动脉和睫状动脉血流动力学的研究

目的:研究糖尿病患者视网膜中央动脉(CRA)、睫状动脉(PCA)的血流变化规律以及视网膜中央动脉血流参数与糖化血红蛋白(GHb)间的相关性。材料与方法:彩色多普勒超声检测67例(67只右眼)糖尿病患者和40例正常对照者的CRA、PCA的收缩期血流峰值速度(PSV)、舒张末期血流速度(EDV)、阻力指数(RI),同时检测患者GHb水平,分析CRA血流参数与GHb的关系。结果:糖尿病各组随病情的加重,CRA、PCA的血流速度呈逐渐减低趋势,RI呈增高趋势;且在无视网膜病变时就存在眼血流动力学的异常,CRA改变明显于PCA;GHb与CRA血流速度呈负相关,与RI呈正相关。结论:在无视网膜病变时,糖尿病患者不仅视网膜而且脉络膜都表现出血流动力学的异常,GHb水平与CRA血流参数有密切的相关性。     

肠系膜上动脉彩色多普勒超声检查方法学研究

目的 建立肠系膜上动脉(SMA)彩色多普勒超声检查方法.方法 选择来我院体检的正常人40名,男女各20名.所有受试者首先对其SMA进行常规彩色多普勒超声检查,然后口服自制混合型小肠声学造影剂后,再次对其SMA进行彩色多普勒超声检查,观察其SMA主干及各级分支的彩色血流图像,测量SMA主干内径、收缩期峰值流速(PS)、阻力指数(RI)和搏动指数(PI).结果 所有受试者行常规彩色多普勒超声检查SMA中上段均可显示,其中9名可显示SMA主干全段,但其分支均未显示.口服自制混合型小肠声学造影剂后,所有受试者行彩色多普勒超声检查均能全面获得SMA主干及各级分支的彩色血流图像,显示率达100%.彩色多普勒显示SMA主干走行较直,至末端呈蝎尾状,各分支走行各异,大部分呈树枝状走行,少数分支可见迂曲回旋,SMA血管网的血流相互交织,呈网络状或菊花状,SMA分支支动脉进入肠壁间呈环状血流.男性正常人SMA主干内径为(0.692±0.059)cm,女性为(0.704±0.094)cm,两者之间的差异无统计学意义(t=-0.437,P＞0.05);男性正常人SMA主干PS为(1.089±0.328)m/s,RI 为(0.835±0.045),PI为(2.495±0.436),与女性的(1.078±0.273)m/s、(0.860±0.421)、(2.889±0.702)比较差异无统计学意义(t=0.323、-0.621、-1.079,P均＞0.05);男性正常人SMA一级分支PS为(0.520±0.226)m/s,RI为(0.772±0.066)、PI为(1.956±0.506),与女性的(0.645±0.156)m/s、(0.833±0.070)、(2.847±0.909)比较差异无统计学意义(t=-2.742、-1.698、-5.217,P均＞0.05);男性正常人SMA二级分支PS为(0.344±0.143)m/s,RI为(0.661±0.045),PI为(1.306±0.268),与女性的(0.392±0.134)m/s、(0.781±0.072)、(2.185±0.754)比较差异无统计学意义(t=-0.981、-2.571、-6.127,P均＞0.05);男性正常人肠壁间动脉PS为(0.196±0.061)m/s,RI为(0.619±0.080),PI为(1.101±0.315),与女性的(0.224±0.100)m/s、(0.716±0.072)、(1.617±0.453)比较差异无统计学意义(t=-1.018、-0.877、-1.399,P均＞0.05).结论 口服自制混合型小肠声学造影剂可对SMA主干及各级分支进行全面的彩色多普勒超声检查.