Feasibility and reliability of on-line automated microemboli detection after carotid endarterectomy. A transcranial Doppler study.

OBJECTIVES: recently, a new algorithm for transcranial Doppler (TCD) ultrasound detection of microembolic signals (MES) was developed. In the present study, we investigated its on-line performance in TCD monitoring after carotid endarterectomy (CEA) and assessed off-line its accuracy in detecting MES. MATERIALS AND METHODS: first, the feasibility of MES detection in TCD monitoring after CEA in a routine clinical setting was evaluated in 50 patients. Second, to test the reliability of the software a 2-h digital audio study tape was made and analysed by the algorithm and five human experts. The "gold standard" was defined as the agreement between human experts: a MES was considered to be present if at least three human observers agreed. RESULTS: TCD monitoring for emboli detection after CEA was well tolerated by the patients and could be performed reliably. In the study tape, the human gold standard detected 107 MES, with 93 MES having an intensity of > or =7 dB. The software detected 81 and 77 MES, respectively. Using the 7 dB intensity threshold, the software had no false positives and 16 false negatives. The kappa value between the human gold standard and the software was 0.91, the proportion of specific agreement was 0.83. CONCLUSIONS: the tested algorithm provides a reliable method for automated on-line microemboli detection after CEA. This makes monitoring of the effectiveness of antiplatelet agents in the prevention of stroke after CEA more practicable.     

Intraluminal ultrasound assessment of vascular stent deployment

This study assessed the utility of intraluminal ultrasound imaging during deployment of a self-expanding vascular stent and quantitated changes in arterial morphology produced by the stent. Cross-sectional images of arterial lumens (n=50) were obtained before stenting, in-vitro (n=35) from formalin-preserved human superficial femoral arteries and in-vivo (n=15) from canine iliac arteries containing laser-induced eccentric stenoses. Comparison of ultrasound-derived vessel dimensions (minimum and maximum diameter and cross-sectional area) with histological morphometric analysis of corresponding vessel sites showed good correlation by linear regression analysis (r=0.930–0.987, p=0.001–0.005). Following stent placement, 23 intraluminal ultrasound images were obtained from the stented vessel sites (in-vitro n=15, in-vivo n=8) and were compared to prestented cross-sectional areas. In the in-vitro vessels there was a small increase (p=0.023) in area, but there was no change in the in-vivo arteries (p=0.6). To assess the effect of stenting on luminal shape (ellipticity), minimum/ maximum diameter ratios were compared before and after stent deployment. There was an increase in this ratio in the in-vitro vessels (p=0.001) but no change in the in-vivo arteries (p=0.2). We conclude that intraluminal ultrasound produces clear and accurate images of the location, shape and degree of arterial pathology, ensuring good stent: vessel size matching and immediate quantitative assessment of the effects of arterial stent placement. Presented at the Ninth Annual Meeting of the Southern California Vascular Surgery Society, Newport Beach, California, September 22, 1990.     

微创治疗锁骨下动脉窃血综合征的探讨

目的:探讨经皮腔内血管成形术(PTA)及内支架置放术治疗锁骨下动脉窃血综合征(SSS)的疗效。方法:应用PTA及内支架置放术治疗锁骨下动脉狭窄所致SSS病人78例,其中单纯行PTA者22例,PTA加支架置放术56例。结果:78例病人全部获得成功。随访66例,随访时间1～71个月(平均27个月),随访率84.6%。随访病例经彩超及多普勒血流图检查,均未发生病变部位再狭窄,血流通畅良好,椎动脉均呈正常血流,放置支架无脱落及移位。结论:PTA及内支架置放术治疗锁骨下动脉起始段狭窄所引起的SSS是一种创伤小、疗效满意、安全可行的微创治疗方法,但操作应耐心、仔细和规范化。     

Stent-graft treatment of pseudoaneurysms and arteriovenous fistulae in the carotid artery

The purpose of this study was to assess the safety and efficacy of stent-graft placement in the management of arteriovenous fistulae (AVF) and pseudoaneurysms (PAs) involving the carotid artery (CA). Twenty-two patients (16 men, 6 women) with a CA AVF (n = 5) or PA (n = 17) owing to a gunshot or stab wound, carotid endarterectomy, blunt trauma, a tumor, spontaneous dissection, or a central venous catheter were treated with percutaneous placement of stent grafts. The patients presented with tumor, bruit, headache, mouth and tracheostomy bleeding, transitory hemiparesis, seizure, or stroke. Diagnoses were made by using computed tomographic angiography (CTA) and digital subtraction angiography. Fourteen lesions were in the common CA; eight were in the internal CA. Homemade devices and stent grafts from a variety of manufacturers were employed. Follow-up evaluations included clinical, CTA, and Doppler ultrasound assessments. All patients had resolution of the PA or AVF. In one patient with a large petrous PA, acute occlusion of the CA developed after placement of three balloon-expandable stent grafts, but there were no neurologic complications because the circle of Willis was functional. During follow-up ranging from 2 months to 13 years, asymptomatic 90% stenosis owing to stent compression was observed on Doppler ultrasound and angiographic examinations in a patient with an autologous vein-covered stent graft in the internal CA. Three other patients died of causes unrelated to stent-graft placement. In all other patients, the stent graft remained patent. Our results indicate that stent grafting is an acceptable alternative to surgery in the treatment of AVF and PAs in the CA.     

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.     

Prevalence of micro-emboli in symptomatic high grade carotid artery disease: a transcranial Doppler study.

BACKGROUND AND PURPOSE: Echolucent carotid plaques, as well as downstream micro-embolisation, may be associated with an increased risk of stroke. However, the relationship between carotid plaque ultrasound characteristics and micro-embolic signals (MES) detected in the middle cerebral artery (MCA) is still controversial. The purpose of this study was to investigate the prevalence of MES in patients with symptomatic high-grade internal carotid artery (ICA) stenosis and to identify predisposing factors, such as plaque echogenicity and intra stenotic blood flow velocity pattern. METHODS: 197 patients (mean age 69.5+/-8.6, 161 males) with confirmed symptomatic high-grade ICA stenosis and anti-platelet treatment underwent bilateral MES monitoring for 30 minutes within the anterior circulation, using Power M-mode transcranial Doppler techniques (TCD). Carotid artery plaques were characterized by Gray-Weale scaling. RESULTS: In 32.0% of the patients, we detected MES by TCD within the MCA on the symptomatic side, but the same finding was made in only 4.5% on the corresponding asymptomatic site (p<0.0001). The presence or absence of MES was associated with neither ultrasonic plaque characteristics nor the intrastenotic blood flow velocities at peak systole and end diastole. The median time since the last ischemic event symptoms was shorter in the patient group with MES [+] than in MES [-] (p=0.013). CONCLUSIONS: Despite optimum standard anti-platelet therapy, cerebral micro-embolisation occurs in 30% of patients with symptomatic carotid artery disease, which might therefore be a possible risk factor for recurrent neurological symptoms. However, the presence of MES is independent of intrastenotic blood flow disturbances and grey scale ultrasound plaque characteristics. The presence of MES as an indicator of unstable plaque and thereby a possible risk factor for stroke should be evaluated prospectively using various algorithms for plaque classifications.     

腹腔动脉和肠系膜上动脉狭窄的介入治疗

目的评价介入技术治疗腹腔动脉（CA）和肠系膜上动脉（SMA）狭窄的安全性和临床疗效。方法对8例CA／SMA局限性狭窄患者进行了经皮穿刺经腔球囊血管成型术（PTA）和支架置入术,单纯CA狭窄2例、单纯SMA狭窄4例、CA和SMA均有狭窄2例。4例患者有典型进餐后腹痛,5例有上腹部血管杂音,8例于发病后均有不同程度的体重下降（平均8kg）。7例患者病因为动脉硬化,1例为膈肌中脚压迫综合征（MALS）所致。结果PTA和支架置人均成功,其中治疗CA狭窄3例、SMA狭窄5例,7例用1个支架,1例用2个支架。治疗结束时复查造影显示置人支架的血管血流通畅,管径接近正常。术后于穿刺侧腹股沟区出现小血肿2例,无须外科处理、自行吸收。术后腹痛完全消失5例、有所减轻2例、无改善1例;术后3个月时,体重恢复至发病前水平者6例。8例患者随访6-72个月（平均42个月,中位值28个月）,复查Doppler超声波无明确再狭窄证据。5例无症状、1例仍然有间歇性腹痛,2例分别于术后14个月、24个月死于其他原因。结论PTA和支架置入术是治疗CA、SMA局限性狭窄的安全有效方法,尤适宜于存在外科治疗高风险的患者。     

Incidence and clinical significance of distal embolization during percutaneous interventions involving the superficial femoral artery

OBJECTIVE: Distal embolization of plaque or thrombus may cause organ ischemia following percutaneous peripheral interventions. The purpose of this study was to evaluate the incidence and clinical significance of particulate embolization during percutaneous superficial femoral artery (SFA) intervention by monitoring with continuous Doppler ultrasound. The rate and timing of embolization at various phases of intervention such as guidewire crossing, balloon angioplasty, stent deployment, and directional atherectomy were analyzed and compared. METHODS: Sixty patients underwent SFA intervention. Of these 60 patients, 10 patients underwent percutaneous transluminal angioplasty (PTA) alone, 40 patients underwent PTA with stenting, and 10 patients underwent plaque excision with the SilverHawk atherectomy device (8) or Spectranetics excimer laser (2) with or without additional PTA or stent placement. A 4-MHz Doppler probe was used for continuous monitoring in the ipsilateral popliteal artery. Distal embolization was registered as embolic signals (ES). ES were quantitatively assessed during critical portions of the procedure including guidewire crossing, balloon angioplasty, stent deployment and/or atherectomy. ES during different phases of intervention were compared using analysis of variance (ANOVA). RESULTS: ES was noted in every patient during wire crossing, angioplasty, stent deployment and atherectomy. The average number of ES noted during guidewire crossing was 8, PTA was 12, stent deployment was 28, SiverHawk atherectomy was 49, and Spectranetics excimer laser was 51. The frequency of ES was statistically higher during stent deployment vs wire crossing or balloon angioplasty but equivalent to that generated by plaque excision. ES was observed more frequent during balloon angioplasty than during wire crossing. In one patient who was treated with the excimer laser, a single runoff vessel was occluded with embolic debris but patency was restored angiographically after thrombolysis. The patient went on to require below knee amputation. During follow-up, all patients with claudication reported improved symptoms and those with ulcers or gangrene demonstrated healing. The average increase in ankle-brachial index following intervention was 0.31. CONCLUSION: While ES were recorded at each step of SFA intervention, the frequency was greatest during stent deployment. Despite the frequency of these events, only one patient developed angiographically and clinically significant embolization. Thus, our findings do not support the routine use of protection devices during percutaneous SFA intervention.     

Color Doppler ultrasonography percutaneous transluminal angioplasty of vascular access grafts

Percutaneous transluminal angioplasty (PTA) is a possible treatment for stenosis. This study aimed to verify the impact of a vascular access (VA) surveillance protocol, based on the detection of functional changes and their correction by a new PTA method for VA performed under color Doppler ultrasonography (CDU) guidance. We divided the patients into two groups: group A, before May 1999 (retrospective study) without the surveillance protocol, and group B, from 1 May 1999 to January 2001 (prospective study) with the surveillance protocol. Access blood flow (Qa) was assessed every 4 weeks by ultrasound velocity dilution. In cases of a reduction of >or=35% from the baseline value, VA was examined using CDU: if a stenosis >50% was detected, angioplasty was performed. In cases of Qa reduction <35% we continued monitoring. By Coxs multivariate analyses, only the use of PTA with or without stenting reduced the relative risk of thrombosis by 64% during the follow-up (p=0.017 confidence intervals 88%-15%) in group B patients. Secondary patency was 80% for VA in which we performed PTA with or without stenting at 18 months, and 58% at 18 months in which we did not perform PTA. Our data show how PTA under CDU is useful to maintain and to improve graft patency. This PTA under CDU guidance allows patients to avoid surgical intervention, hospitalization, and adverse reactions to contrast media and exposure to ionizing radiation, with reduced cost and with better graft survival.     

The Usefulness of Transcutaneous Oximetry in Assessing the Success of Percutaneous Transluminal Angioplasty

OBJECTIVE: to identify whether monitoring transcutaneous oxygen pressure (TcpO(2)) can provide an objective method of assessing the results of PTA. MATERIALS AND METHODS: fifty-seven patients (39 Fontaine stage II, <18 stage III or IV) had ABI, TcpO(2) at rest (stages III and IV) or during exercise (stage II) and total work capacity of the leg (stage II) measured before, 24-48 h, 2 and 6 weeks after PTA. RESULTS: a significant increase of ABI in both groups of patients was detected immediately after successful PTA. TcpO(2) measured on the foot at rest increased in stages III and IV patients immediately after PTA (from 14 (IQR)18 to 25 (IQR)32 mmHg,p <0.05) and again after 6 weeks in comparison to follow up two (from 25 (IQR)32 to 35 (IQR)21 mmHg,p <0.05). In patients in stage II TcpO(2) decreased in a typical fashion during exercise. Total oxygen drop was most evident before treatment (352 (IQR)458 smmHg) and decreased significantly immediately after PTA (148 (IQR)175 smmHg, p<0.001). CONCLUSIONS: TcpO(2) measurement is an useful method for investigating the success of PTA. While the macrocirculation improves immediately after successful recanalisation, complete normalisation of the microcirculation may take some weeks, especially stages III and IV disease.     

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.     

锁骨下动脉闭塞的血管腔内治疗

目的：探讨经皮血管内成形术(PTA)和血管内支架置放术治疗锁骨下动脉起始段闭塞的疗效。方法：应用经皮血管内成形术(PTA)和血管内支架安置术治疗5例锁骨下动脉起始段闭塞的病人。结果：5例手术均获成功。术后患肢动脉搏动恢复正常，多普勒测压双上肢血压压差由术前平均54mmHg降至术后9．6mmHg．术后随访1～3月；彩超提示支架无脱落及移位，病变部位血流通畅，椎动脉恢复为正常人颅血流。结论：PTA和血管内支架安置术是治疗锁骨下动脉起始段闭塞的一种微创、安全可行和疗效满意的方法。     

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.     

Percutaneous transluminal angioplasty and stent placement for recurrent carotid artery stenosis

OBJECT: Treatment consisting of percutaneous transluminal angioplasty (PTA) and stent placement has recently been proposed as an alternative to surgical reexploration in patients with recurrent carotid artery stenosis following endarterectomy. The authors retrospectively reviewed their experience after performing 25 procedures in 21 patients to assess the safety and efficacy of PTA with or without stent placement for carotid artery restenosis. METHODS: The mean interval between endarterectomy and the endovascular procedures was 57 months (range 8-220 months). Seven arteries in five patients were treated by PTA alone (including bilateral procedures in one patient and repeated angioplasty in the same vessel in another). Early suboptimum results and recurrent stenosis in some of these initial cases prompted the authors to combine PTA with stent placement in the treatment of 18 arteries over the past 3 years. No major periprocedural deficits (neurological or cardiac complications) or death occurred. There was one periprocedural transient neurological event, and in one patient a pseudoaneurysm of the femoral artery (at the access site) required surgical repair. In the 16 patients who each underwent at least 6 months of follow-up review, no neurological events ipsilateral to the treated artery had occurred after a mean follow-up period of 27 months (range 6-57 months). Three of five patients who underwent PTA alone developed significant (>50%) asymptomatic restenoses that required repeated angioplasty in one and PTA with stent placement in two patients. Significant restenosis (55%) was observed in only one of the vessels treated by combined angioplasty and stent placement. CONCLUSIONS: Endovascular PTA and stenting of recurrent carotid artery stenosis is both technically feasible and safe and has a satisfactory midterm patency. This procedure can be considered a viable alternative to surgical reexploration in patients with recurrent carotid artery stenosis.     

Coronary artery bypass grafting on the beating heart evaluated with integrated backscatter

BACKGROUND: In beating heart coronary artery bypass grafting (CABG) the effect of ischemic insult during coronary occlusion could not be evaluated immediately. Using transesophageal echocardiography, myocardial performance can be evaluated with analysis of integrated backscatter. METHODS: In 15 beating heart CABGs, cyclic variation (CV) of integrated backscatter of the anterior wall before, during, and after the left internal thoracic artery to left anterior descending (LAD) branch anastomosis was measured with transesophageal echocardiography. The patients were divided into two groups according to collateral vessels status (good collateral group n = 6, poor collateral group n = 9). RESULTS: In all patients, CV increased significantly after revascularization (8.56+/-2.50 to 11.47+/-3.32 dB, p < 0.0001). During LAD occlusion, significant decrease in CV was found in patients who had poor collateral arteries. At 15 minutes of LAD occlusion, CV decreased from the preocclusion value of 7.51+/-2.21 to 3.23+/-4.03 dB (p < 0.01). CONCLUSIONS: Measurement of CV can detect the ischemic insult during coronary occlusion and the effect of revascularization in beating heart CABG.     

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.     

Detection of distal emboli in patients with peripheral arterial stenosis before and after iliac angioplasty: A prospective study

Purpose: Embolism is believed to be the major cause of end-organ damage after angioplasty and endoluminal procedures. Recently, Doppler ultrasound scanning has been used to detect asymptomatic cerebral emboli. We determined whether asymptomatic embolic signals (ES) could be detected distal to a significant iliac artery stenosis of >60% both before and soon after iliac percutaneous transluminal angioplasty (PTA). Methods: A 2-MHz Doppler scan probe was used to monitor for ES in the common femoral artery before and after 10 successful iliac artery PTAs and at various standardized times in the following 24 hours. The same protocol was used to study 10 patients in the control group after renal PTA. In addition, a single recording was performed in a second nonoperative control group of 10 patients who had no evidence of peripheral vascular disease. The Doppler scan signals were recorded on tape for a later blinded analysis. Results: In the 24 hours before iliac PTA, asymptomatic ES were detected in four of 10 patients during a 1-hour recording but in no controls (P = .025). After iliac PTA, ES were detected at 30 minutes in nine of 10 iliac subjects but in only one of 10 renal subjects (P = .0003) and at 2 hours in eight of 10 iliac subjects but in only one of 10 renal subjects (P = .001). The occurrence of ES became less frequent, and ES were present at a lower frequency in eight of 10 iliac PTA subjects at 4 hours and in five of 10 at 24 hours but in no renal PTA subjects at these time points. Conclusions: ES can be detected in the common femoral artery with Doppler ultrasound scanning in patients with iliac artery stenosis both before and soon after iliac PTA despite preangioplasty aspirin and intra-angioplasty heparin therapies. The occurrences of ES were particularly frequent in the 2 hours after PTA. This technique can be used further to study factors that control plaque stability and to evaluate the effect of therapeutic interventions. (J Vasc Surg 1999;29:345-51.)     

Efficacy and risk profile of self-expandable stents in the management of pediatric esophageal pathology

PurposeThe purpose of this study was to evaluate the efficacy and risk profile of esophageal stents in the management of complicated pediatric esophageal disease.MethodsAn IRB-approved, single-center, retrospective review was performed on all pediatric patients (n = 13) who underwent esophageal stent placement (2005–2017). Demographic, perioperative, and outcome data were analyzed (p < 0.05).ResultsForty-one stents were placed due to recalcitrant strictures (n = 36), perforations (n = 2), and/or fistulae (n = 3). Median age at initial stent placement was 23.8 months (range, 50 days to 16 years), and median stent duration was 36 days (range, 3–335). The recurrence rate for strictures after initial stent removal was 100%. Four (31%) children subsequently underwent definitive operative repair. There were 5 deaths, including 2 related to stent placement. Seventy-one percent of stents were associated with an adverse event, most commonly intraluminal migration (56%). Younger children experienced an increased risk for airway compression and retching (p = 0.010).ConclusionThese data suggest that stents are associated with high complication rates and are not effective as definitive therapy for recalcitrant strictures in children. Although there may be a temporizing role for stents in selected patients, further refinements in stent technologies are needed to help manage this difficult patient population.Level of evidenceLevel IV     

Cerebral ischemia during carotid clamping: diagnosis and prevention

A serious complication in carotid endarterectomy (CEA) is the occurrence or aggravation of neurological deficits caused by insufficient collateral cerebral blood flow during cross-clamping. At the moment, patients with failure of collateral circulation at this point cannot be identified preoperatively. Thus, intraoperative monitoring and methods to prevent clamping-related cerebral ischemia are required. To put this strategy into clinical practice there are several methods of monitoring cerebral function (e.g. surgery performed in awake patients, electroencephalography, somatosensory evoked potentials), changes of hemodynamic (e.g. carotid stump pressure, transcranial Doppler ultrasonography) or metabolic parameters (e.g. jugular bulb oximetry or transcranial oximetry). One technique that meets nearly all requirements of an ideal monitoring under general anesthesia is the use of somatosensory evoked potentials (SEPs). Registration of SEPs is simple to perform and indicates with a high sensitivity and specificity critical cerebral hypoperfusion during cross-clamping. Thus, SEPs monitoring indicates the necessity of shunt placement. As a result, the use of an indwelling shunt as the most effective method to prevent clamping ischemia can be limited to selected cases, avoiding the risks of shunting in patients with sufficient collateral flow. In addition, correct shunt function is immediately indicated by recovering potentials. Whether a combination of SEPs with transcranial Doppler measurements will be successful to provide additional information about cerebral embolisation should be determined.