Identification of microemboli during haemodialysis using Doppler ultrasound.

BACKGROUND: Doppler ultrasound methods were used during haemodialysis sessions for the detection of microemboli and determination of their origin. METHODS: A 2-MHz ultrasound probe (Multidop X(4) DWL((TM))) was used to assess the number of microembolic signals (MES) in the subclavian vein downstream from the arteriovenous fistula before the dialysis session and over two periods of 15 min at the beginning and end of haemodialysis sessions in 25 patients without previous cardiovascular disease. A similar probe was used during in vitro studies to detect MES at different sites in the dialysis machine (before and downstream from the blood pump, and before and downstream from the air trap). RESULTS: No MES were detected during in vivo studies before haemodialysis sessions. MES were registered in all patients (100%) at the beginning and end of the haemodialysis procedure at an average of 12.7+/-9 and 16. 7+/-11.5 signals/min respectively. The average intensity of MES was 19.2+/-5.0 dB and 19.4+/-3.9 dB respectively. No MES were detected on the arterial line during in vitro studies. In contrast, 19+/-6 MES/min were detected after the blood pump, 13+/-4.2 before the air trap, and 16.5+/-5.5 thereafter. CONCLUSIONS: In all patients, MES were recorded during haemodialysis sessions in the drainage vein from arteriovenous fistulae. The results of in vitro studies indicate that MES are formed by the blood pump of the haemodialysis machine. The intensity of the MES suggests that they correspond to synthetic particles or microbubbles, which are not detected by the air trap. The final destination of these microbubbles will be assessed in further studies.     

Detection of microemboli by transcranial Doppler ultrasonography in aneurysmal subarachnoid hemorrhage

OBJECTIVE: To determine the frequency and characteristics of microembolic signals (MES) in subarachnoid hemorrhage (SAH). METHODS: Twenty-three patients with aneurysmal SAH were monitored with transcranial Doppler ultrasonography for the presence of MES and vasospasm. Each middle cerebral artery was monitored for 30 minutes three times each week. Patients were excluded if they had traumatic SAH or cardiac or arterial sources of emboli. Monitoring was initiated 6.3 days (1-16 d) after SAH and lasted 6.6 days (1-13 d). Eleven individuals without SAH or other cerebrovascular diseases who were treated in the same unit served as control subjects. Each patient underwent monitoring of both middle cerebral arteries a mean of three times; therefore, 46 vessels were studied (a total of 138 observations). Control subjects underwent assessment of each middle cerebral artery once, for a total of 22 control vessels. RESULTS: MES were detected for 16 of 23 patients (70%) and 44 of 138 patient vessels (32%) monitored, compared with 2 of 11 control subjects (18%) and 2 of 22 control vessels (9%) (P < 0.05). MES were observed for 83% of patients with clinical vasospasm and 54% of those without clinical vasospasm. Ultrasonographic vasospasm was observed for 71 of 138 vessels monitored; MES were observed for 28% of vessels with vasospasm and 36% of those without vasospasm. Aneurysms proximal to the monitored artery were identified in 38 of 138 vessels, of which 34% exhibited MES, which is similar to the frequency for vessels without proximal aneurysms (31%). Coiled, clipped, and unsecured aneurysms exhibited similar frequencies of MES. CONCLUSION: MES were common in SAH, occurring in 70% of cases of SAH and one-third of all vessels monitored. Although MES were more frequent among patients with clinical vasospasm, this difference did not reach statistical significance. We were unable to demonstrate a relationship between ultrasonographic vasospasm and MES, and the presence of a proximal secured or unsecured aneurysm did not alter the chance of detection of MES. Further studies are required to determine the origin and clinical relevance of MES in SAH.     

Detection of microemboli in the subclavian vein of patients undergoing haemodialysis and haemodiafiltration using pulsed Doppler ultrasound.

BACKGROUND: The pathophysiology leading to pulmonary side effects during haemodialysis and haemodiafiltration is not yet fully understood. Chronic microembolization, which can be demonstrated by pulsed Doppler ultrasound, may be one cause. METHODS: The study cohort consisted of 24 long-term dialysis patients undergoing haemodialysis (n=21) and online-haemodiafiltration (n=3), respectively. The subclavian vein downstream to the venous access was investigated during different phases of the procedure using a 2-MHz pulsed ultrasound device. RESULTS: In all periods investigated (connection, dialysis, disconnection), numerous microembolic signals (MES) were found in the subclavian vein. The numbers of MES detected during haemodiafiltration (314-709 MES per 10 min) were higher than during haemodialysis (0-81 MES per 10 min). CONCLUSIONS: The composition (gaseous or solid) and origin (pump, tubing system or shunt) of the microemboli detected remains unclear. Chronic microembolization may be one cause of pulmonary complications of haemodialysis and haemodiafiltration. The detection method described in this article will help us to better understand this process and to determine what role microemboli might play in pulmonary and central nervous system disorders. It may also help to optimize the devices and techniques used.     

彩色多普勒超声诊断周围型肝内胆管细胞癌的价值

目的 探讨彩色多普勒超声对周围型肝内胆管细胞癌的诊断价值.方法 回顾性分析95例经病理证实的周围型肝内胆管细胞癌,总结其彩色多普勒超声特征.结果 总共102个病灶,大小范围为20 mm×20 mm～130 mm×100 mm.灰阶图像上大部分病灶表现为回声不均匀(75个,73.5％)、边界模糊(70个,68.6％)、分叶状(55个,53.9％).彩色多普勒超声示大部分病灶能检测到血流(75个,73.5％),以簇状、短线状及彩点状血流为主,其中大部分血流的阻力指数大于0.6(65个,86.7％).102个病灶中,见条索样高回声的有37个(36.3％),后方回声出现轻度衰减的有29个(28.4％),出现“脐凹”现象的有22个(21.6％).超声诊断的符合率为84.2％(80/95).结论 周围型肝内胆管细胞癌的彩色多普勒超声表现具有一定的特征,充分认识其声像图特征可提高超声诊断的准确率.     

Detection of venous emboli using Doppler ultrasound.

OBJECTIVES: To detect emboli in the venous system using a Doppler ultrasound device with embolism detecting software. METHODS: Pulmonary embolism (PE) was induced by injecting thrombus through the iliac vein of castrated swine under general anaesthesia. Data recorded from the Doppler system were analysed for high intensity transient signals (HITS) using receiver operating characteristic curves. Four different thrombi (5 or 10mm long and 3 or 5mm in diameter) were then injected to assess the quantitative analysis. RESULTS: Thrombus could be detected in the venous system by the Doppler ultrasound device with an embolism detecting function. Appropriate confidence level was 60%. If thrombus were assumed to travel at the maximum flow rate (30 cm/s) in the inferior vena cava, the estimated embolism size was 10.4 S.D. 2.8mm for 3mm and 10.8 S.D. 4.9 mm for 5mm, both of which were close to 10mm. CONCLUSION: Thrombi could be detected as high intensity transient signals in the venous system. The appropriate confidence level was 60%. The size of emboli can be estimated if they are more than 3mm in diameter when the venous flow rate is 30 cm/s or less. Our results suggest that it may be possible to detect emboli in the subclavian vein, axillary vein or inferior vena cava in clinical cases.     

Angiography of collateral cerebral circulation

Zusammenfassung Während die klinischen Symptome, der Verlauf und die pathologischanatomischen Untersuchungen bei Gefäßverschlüssen uns die Lokalisation des Prozesses ermöglichen, gibt uns die cerebrale Angiographie die Möglichkeit, die Vaskularisationsverhältnisse, insbesondere die Bildung des Kollateralkreislaufes in vivo zu studieren.Die angiographischen Untersuchungen bestätigen die Befunde der Anatomen, daß die Hirnarterien nicht Endarterien sind, sondern mehrere Vaskularisationsringe aufweisen, die wieder miteinander an verschiedenen Stellen kommunizieren.Jede der 4 großen Hirnarterien ist imstande, falls keine angeborenen Anomalien vorliegen, die anderen über die zahlreich vorhandenen Kollateralen zu kompensieren.Die zuerst vonCooper (1831) vorgenommene Ligatur der 4 Hirnarterien bei Hunden und die vielen späteren Versuche bestätigen die Kollaterale-Bildung über die Haut-, Muskel- und Spinalarterien, welche bei in phylogenetisch höheren Stufen stehenden Menschen nicht in gleichem Maße vorhanden ist. Seit der ersten Ligatur beim Menschen der A. carotis (Warner-Ellis, 1775) und der A. vertebralis (Maissonneuve-Favrod, 1852), wurde das Fehlen, Aplasie und Ligatur einer oder 2 der Hirnarterien ohne Folgeerscheinungen durch die Anatomen, Kliniker und Röntgenologen in zahlreichen Fällen publiziert.Die Bildung des kollateralen Kreislaufes ist nicht allein von hydro- bzw. hämodynamischen Gesetzen abhängig, sondern von weiteren verschiedenen anderen Faktoren, welche ausführlich anhand des eigenen Materials und desjenigen der einschlägigen Literatur besprochen wurde.In der vorliegenden Arbeit werden die Kollateralen innerhalb der intracraniellen Vaskularisationsringe untereinander und derjenigen des extracraniellen Vaskularisationsringes anhand eigener Angiogramme und derjenigen der Literatur besprochen. Die Bedeutung der Kollateralen über die Äste der A. carotis externa zur A. ophthalmica und A. vertebralis wird besonders hervorgehoben.Unter Berücksichtigung dieser Tatsachen werden schließlich die gegenwärtig möglichen chirurgischen und medikamentös-therapeutischen Wege in einer Richtlinie zusammengefaßt.

---

Resumen Mientras que los signos clínicos, la evolución y el examen anatomopatológico nos permiten el diagnóstico de localización de una oclusión vascular, la angiografia cerebral nos da la possibilidad de estudiar la vascularización residual y la colateral in vivo.Los examenes angiográficos confirman los estudios anatómicos, demostrando que las arterias cerebrales no son terminales, sino que por la presencia de varios anillos de vascularización intercomunican a diverses nivelés.Cada una de las 4 grandes arterias cerebrales puede compensar a las restantes a través de las multiples colaterales existentes, siempre que no exista una anomalia congenita.La ligadura de las 4 arterias cerebrales porCooper (1831) y multiples experimentos posteriores confirman la formación de colaterales a través del tejido muscular, piel y arterias espinales, que no existe en tal extension en el hombre, mas avanzado en la escala filogenética. Desde que se ligaran por primera vez la arteria carótida en el hombre (Werner-Ellis, 1775) y la arteria vertebral (Maissonneuve-Favrod, 1852) se han sucedido muchos casos publicados donde la falta, ligadura o aplasia de una o dos arterias ha sido tolerada sin trastornos.El desarrollo de la circulación colateral no depende unicamente de factores hidro- o hemodinámicos, sino de una serie de otras causas, que han sido tratadas exhaustivamente en base a nuestro material y las publicaciones.En el presente trabajo son comentadas las colaterales del anillo de vascularización intracranial y extracranial en base a angiogramas proprios y de la literatura correspondiente.La importancia de la circulación colateral a través de la arteria oftálmica y la arteria vertebral ha merecido special consideración.Respetando estos hechos se resumen las posibilidades medicamentosas y quirúrgicas actuates.

---

Résumé L'angiographie cérébrale est susceptible de contribuer à l'étude de la circulation collatérale en cas d'un processus vasculaire obstructive. Les données angiographiques confirment les constatations anatomiques que les artères cérébrales ne sont pas des artères terminales.Les artères cérébrales forment des cercles vasculaires. Chacune des 4 grandes artères cérébrales peut compenser les autres — sauf les cas d'une anomalie innée.Cooper (1831) a été le premier de ligaturer les 4 artères cérébrales primitives sur le chien. Ces recherches et beaucoup d'autres prouvent l'action des branches anastomotiques des artères de la peau, des muscles et des artères spinales qui cependant ne sont pas présentes en même qualité chez l'homme. Depuis la première ligature de l'artère carotide chez l'homme (Warner-Ellis, 1775) et de l'artère vertébrale (Maissonneuve-Favrod, 1852) l'aplasie, l'atrésie et la ligature d'une ou de deux artères cérébrales sans déficit clinique a été publiée dans plusieurs travaux anatomiques, cliniques et radiologiques.Les auteurs discutent les facteurs haemo-dynamiques, vasculaires et d'autres méchanismes qui sont à base de la formation des cercles vasculaires collatéraux et intra- et extracrâniens à l'aide d'images angiographiques personnels et de la littérature. On souligne l'importance des branches anastomotiques entre la carotide externe et l'art. ophtalmique. — La conclusion est l'indication pour le traitement chirurgicale et médicale.

---

Riassunto Mentre la sintomatologia e l'evoluzione clinica e l'esame anatomopatologico ci permettono di precisare la sede di occlusione vascolare, l'angiografia cerebrale ci offre la possibilità di studiare sul vivo la vascolarizzazione e in particolare la formazione del circolo collaterale.Le ricerche angiografiche confermano i reperti degli anatomici secondo cui le arterie cerebrali non sono delle arterie terminali ma presentano parecchi anelli di vascolarizzazione che comunicano di nuovo in varie località.Ognuna delle 4 grandi arterie cerebrali può, dato che non esistano anomalie congenite, compensare le altre attraverso le numerose collaterali.Le legature delle 4 arterie cerebrali praticata per la prima volta sul cane daCooper (1831) ed i numerosi sperimenti eseguiti più tardi confermano la formazione del circolo collaterale attraverso le arterie cutanee, muscolari e spinali il quale non si verifica in tale misura nell'uomo. Dacchè fu praticata per la prima volta nell'uomo la legatura della carotide (Warner-Ellis, 1775) risp. della vertebrale (Maissonneuve-Favrod, 1852), numerosi casi di agensia, aplasia e legatura di 1 o 2 arterie cerebrali senza sequele cliniche sono stati riportati da anatomici, clinici e radiologi.La formazione del circolo collaterale non dipende dalle sole leggi emorisp. idrodinamiche ma da vari fattori ulteriori. Questi vengono discussi in base al materiale proprio ed alla letteratura.Vengono trattate in base alle angiografie proprie ed a quelle della letteratura le collaterali tra gli anelli di vascolarizzazione endocranici entro loro corne pure tra questi e l'anello di vascolarizzazione estracranico.Si mette in rilievo il significato del circolo collaterale attraverso i rami della carotide esterna verso le arterie oftalmica e vertebrale.Per rispetto ai fatti sudetti le possibilità attuali di terapia chimrgica e medicamentosa vengono riassunte nel senso direttivo.

     

Pulse oximetry compared with Doppler ultrasound for assessment of collateral blood flow to the hand

Ischaemic injury to the hand after arterial cannulation is a rare but well documented complication and routine testing of the adequacy of collateral circulation is widely advocated. The widespread availability of the pulse oximeter in the operating theatre. its applicability in circumstances where the patient is unable to cooperate, and its dependence on pulsatile blood flow suggest that this device could potentially be usefully applied to the assessment of collateral blood flow. The reliability of the pulse oximeter to detect the presence or absence of collateral circulation was prospectively compared to Doppler ultrasound in 109 hands from 64 adult patients. Nine hands demonstrated inadequate ulnar collateral flow, one hand demonstrated inadequate radial collateral flow and a persistent median artery was found in one hand. In all patients the results of pulse oximeter testing (probe placed on the thumb correlated precisely with the results obtained with the Doppler device (probe located over the lateral aspect of the superficial palmar arch). These results demonstrate pulse oximetry to be a reliable method of assessing collateral blood flow to the hand before arterial cannulation.     

Renal artery stenosis secondary to neurofibromatosis in children: Detection by Doppler ultrasound

Renal artery stenosis was diagnosed in two adolescents with neurofibromatosis using Doppler ultrasound. The diagnosis was confirmed by angiography. The renal vascular lesion in neurofibromatosis usually affects the proximal segment of the artery, which is the part most optimally visualized by ultrasound. We suggest that Doppler ultrasound of the renal arteries may be a useful technique in the investigation of hypertensive children with neurofibromatosis.     

Detection thresholds of nonocclusive intestinal hypoperfusion by Doppler ultrasound, photoplethysmography, and fluorescein

Because clinical assessment of bowel viability is unreliable, other methods of determining intestinal perfusion have been recommended. Since none of these quantifies intestinal blood flow, we measured flow at the detection thresholds of Doppler ultrasound, photoplethysmography, and intravenously administered fluorescein, perfused the intestines at these threshold levels, and assessed histologic evidence of ischemic damage. The intestines of five anesthetized dogs were perfused for 4 hours via an in-line pulsatile extra-corporeal circuit assembled between the iliac and superior mesenteric arteries at either relatively physiologic (approximately 20 ml/min/kg body weight) levels or reduced levels representing the flow detection thresholds of Doppler ultrasound or photoplethysmographic probes (approximately 4 ml/min/kg). Intravenously administered fluorescein was detected at even lower perfusion levels (approximately 2.1 ml/min/kg). Clear-cut ischemic changes were documented histologically in all subjects perfused at Doppler/PPG flow detection thresholds but in none of those perfused at normal levels. We conclude that threshold blood flow detection by any one of these methods, especially fluorescein, occurs at levels inadequate to guarantee tissue viability.     

Therapeutic angiogenesis in peripheral arterial disease: can biotechnology produce an effective collateral circulation?

The physiological processes of angiogenesis, vasculogenesis and arteriogenesis contribute to the growth of collateral vessels in response to obstructive arterial disease causing lower limb or myocardial ischaemia, but in clinical practice the endogenous angiogenic response is often suboptimal or impaired, e.g. by factors such as ageing, diabetes or drug therapies. Therapeutic angiogenesis is an application of biotechnology to stimulate new vessel formation via local administration of pro-angiogenic growth factors in the form of recombinant protein or gene therapy, or by implantation of endothelial progenitor cells that will synthesize multiple angiogenic cytokines. Numerous experimental and clinical studies have sought to establish 'proof of concept' for therapeutic angiogenesis in PAD and myocardial ischaemia using different treatment modalities, but the results have been inconsistent. This review summarises the mechanisms of angiogenesis and the results of recent trials evaluating the efficacy and safety of different gene therapy, recombinant protein and cellular-based treatment approaches to enhance collateral vessel formation.     

Characteristics of peripheral microembolization during iliac stenting: Doppler ultrasound monitoring.

OBJECTIVE: To evaluate the characteristics of distal microembolic signals (MES) during iliac stenting using Doppler ultrasound monitoring. DESIGN: Prospective clinical study. METHODS: A 2-MHz probe was used to monitor continuously at the ipsilateral tibioperoneal trunks during technically and hemodynamically successful iliac stenting in 10 patients without infrainguinal occlusive lesion. MESs at guide-wire, balloon, or stent crossing (phase 1), predilatation (phase 2), stent deployment (phase 3), postdilatation (phase 4), and contrast medium or heparinized saline injection (at injection) were analyzed. Differentiation of gaseous emboli from particulate emboli was achieved by calculation of the sample volume length. RESULTS: No distal embolic complications were observed. Five hundred and forty-one MESs were detected. The MES incidence and intensity in phase 3 were significantly higher than those in phase 1, phase 2, and phase 4 (p<0.05). The MES intensity at injection was significantly higher than that in each of four phases (p<0.0001). CONCLUSIONS: Both the MES incidence and intensity were highest at stent deployment. Further study is required of microembolism during endovascular procedures in the lower extremities.     

Doppler ultrasound monitoring for detection of microembolic signals in peripheral arteries.

OBJECTIVE: to use Doppler ultrasound to detect peripheral microemboluation. METHODS: standard Transcranial Doppler equipment was used to peripheral detect peripheral embolic high intensity transient signals (HITSs) in a pig model following injection of microparticles and atheroma, and in 23 patients who underwent open repair of an abdominal aortic aneurysm (AAA), six patients with blue toe syndrome and 10 age matched healthy subjects. RESULTS: the pig study showed increasing signal intensity with particle size. Particles of 100 (n=24), 200 (n=17), and 400 microm (n=31) elicited 14, 25, 33 dB signals, respectively (p<0.05). During AAA surgery, the intensity (median) of HITSs before clamping (n=226) and after declamping (n=1216) were 14, and 20dB, respectively (p<0.001). Quite a few HITSs were detected after surgery. In patients with blue toe syndrome, a total of 63 HITSs could be detected, and the frequency of HITSs (median: 5.72/30min) was significantly higher than that in patients with AAA before surgery (0.065/30min) (p<0.001).CONCLUSIONS: Doppler ultrasound technique may be a clinically useful test to guide the treatment of patients at risk of distal atheroembolic events.     

The significance of microemboli detection by means of transcranial Doppler ultrasonography monitoring in carotid endarterectomy

Purpose: Carotid endarterectomy (CEA) performed with continuous transcranial Doppler monitoring provides a unique opportunity to determine the number of cerebral microemboli and to relate their occurrence to the surgical technique. The purpose of this study was to assess in CEA the impact of cerebral microembolism on clinical outcome and brain architecture. We also evaluated the influence of the audible transcranial Doppler signal on the surgeon and his or her technique.Methods: In a prospective series of 301 patients, CEA was monitored with electroencephalography and transcranial Doppler ultrasonography of the ipsilateral middle cerebral artery. Preoperative and intraoperative risk factors were entered in a logistic regression analysis program to assess their correlation with cerebral outcome. To evaluate the impact of cerebral microembolism on brain architecture, we compared preoperative and postoperative computed tomography scans or magnetic resonance images of the brain in two subgroups of 58 and 40 patients, respectively.Results: Seven (2.3%) patients had intraoperative transient ischemic symptoms, three (1%) had intraoperative strokes, 1 (0.3%) had transient ischemic symptoms after operation, and 10 (3.3%) had postoperative strokes. Four (1.3%) patients died. Microemboli (>10) noticed during dissection were related to both intraoperative (p < 0.002) and postoperative (p < 0.02) cerebral complications. Microemboli that occurred during shunting were also related to intraoperative complications (p < 0.007). Microembolism never resulted in new morphologic changes on postoperative computed tomography scans. On the contrary, the phenomenon of more than 10 microemboli during dissection was significantly (p < 0.005) related to new hyperintense lesions on postoperative T2-weighted magnetic resonance images.Conclusions: During CEA the presence of microembolism (>10 microemboli) during dissection shows a statistically significant relationship with perioperative cerebral complications and with new ischemic lesions on magnetic resonance images of the brain. Moreover, microembolism during shunting is also related to intraoperative complications. Surgeons can be guided by the audio Doppler and emboli signals by changing their technique. This change may result in a decrease of microembolism and consequently in a decline of the intraoperative stroke rate. (J VASC SURG 1995;21:963-9.)     

Evaluation of ischemic intestine by Doppler ultrasound

Intraoperative Doppler ultrasound examination of ischemic intestine was used to determine viability and to establish margins of resection, even when the findings differed from the surgeon's clinical appraisal. Ten of 25 segments in 23 patients were clinically judged nonviable, but because arterial flow within the segments was detected by Doppler ultrasound, none was resected. The subsequent benign clinical courses of the patients demonstrated the viability of the segments. Two segments were judged clinically viable, but because Doppler signals were absent, both were resected. Histologic examination demonstrated severe ischemic changes in both segments. Nine segments were judged both by clinical criteria and by Doppler ultrasound examination to be nonviable, and all nine were resected. Histologic examination confirmed ischemia or infarction in all.Doppler ultrasound was a more reliable intraoperative predictor of viability of ischemic intestine than clinical assessment alone, and its use averted postoperative complications and unnecessary second-look procedures.