Use of pocket-sized ultrasound device in vascular surgery. / Bruk av ultralydapparat i lommeformat ved karkirurgi.

BACKGROUND: Ultrasound is widely used in vascular surgery. Pocket-sized ultrasound devices have limited functionality compared to conventional ultrasound scanners, but are cheaper and highly portable. The aim of this study was to investigate whether vascular surgeons could benefit from using a pocket ultrasound device in everyday clinical practice. MATERIAL AND METHOD: Pocket-sized ultrasound devices were made available in the Department of Vascular Surgery at St. Olavs Hospital, Trondheim University Hospital, for a 10-month period. Eleven doctors participated and were free to choose between a conventional ultrasound scanner and a pocket ultrasound device. After each use of a pocket ultrasound device, participants completed a form describing the indication for use, whether the clinical question was answered, the image quality experienced and the need for supplementary diagnostic imaging. At the end of the study period, each user completed a questionnaire. RESULTS: Pocket ultrasound devices were mainly used preoperatively. The clinical question was answered in 51 (85 %) of 60 registered examinations with a pocket ultrasound device. Image quality was subjectively rated as good in 32 (53 %) examinations, moderate in 21 (35 %) and poor in 7 (12 %), with the clinical question answered in 94 %, 90 % and 29 % of cases, respectively. Doctors with less than five years of experience with ultrasound chose pocket ultrasound more frequently than more experienced users. INTERPRETATION: For the examinations selected, the images supplied by the pocket ultrasound device were generally of sufficient quality and often answered the clinical question. Pocket ultrasound devices can be a useful supplementary tool in vascular surgery, especially for venous examinations.

Bronchial microdialysis monitoring of inflammatory response in open abdominal aortic aneurysm repair; an observational study.

Aortic surgery results in ischemia-reperfusion injury that induces an inflammatory response and frequent complications. The magnitude of the inflammatory response in blood and bronchi may be associated with the risk of immediate complications. The purpose of the study was to evaluate bronchial microdialysis as a continuous monitoring of cytokines in bronchial epithelial lining fluid (ELF) and to determine whether bronchial ELF cytokine levels reflect the ischemia-reperfusion injury and risk for complications during open abdominal aortic aneurysm (AAA) repair. We measured cytokines in venous blood using microdialysis and in serum for comparison. Sixteen patients scheduled for elective open AAA repair were included in a prospective observational study. Microdialysis catheters were introduced into a bronchi and a cubital vein. Eighteen cytokines were measured using a Bio-Plex Magnetic Human Cytokine Panel. Samples were collected before and during cross-clamping of the aorta as well as from 0 to 60 min and from 60 to 120 min of reperfusion. The ELF levels of several cytokines changed significantly during reperfusion. In particular, IL-6 increased more than 10-fold and IL-13 more than 5-fold during ischemia and reperfusion. Also, the venous levels of several inflammatory and anti-inflammatory cytokines increased and exhibited their highest concentration during reperfusion. Both bronchial and venous cytokine levels correlated with duration of the procedure, intensive care days, and preoperative kidney disease. Three patients suffered organ failure as a direct consequence of the procedure, and in these patients the bronchial ELF concentrations of 17 of 18 cytokines differed significantly from patients without such complications. Bronchial microdialysis is suited for continuous monitoring of inflammation during open AAA repair. The bronchial ELF cytokine levels may be useful in predicting immediate complications such as organ failure in patients undergoing vascular surgery.

Preoperative White Blood Cell Count in Patients with Abdominal Aortic Aneurysms and Its Relation to Survival following Surgery.

BACKGROUND: The aim of the present study was to explore whether preoperative white blood cell (WBC) count may predict 30-day mortality and long-term survival following surgery for abdominal aortic aneurysm (AAA). Secondarily, we wanted to assess the potential sex differences in WBC in these patients. METHODS: The study was carried out as a retrospective cohort study. Patients undergoing surgery for intact and ruptured AAA (rAAA) at our institution consecutively in the time period 1994-2007 were included. Patients were either treated with open aneurysm repair or with endovascular aneurysm repair. Data were collected from the patients' medical records, including laboratory reports for WBC count prior to surgery. Mortality and long-term survival were extracted from The Patient Administrative System. RESULTS: A total of 988 patients were included, 712 (72%) patients were treated for intact AAA and 276 (28%) underwent surgery for rAAA. Patients with WBC ≥11 ×109/L had a 8.7-fold higher risk of 30-day mortality undergoing surgery for intact AAA compared to patients with WBC <11 ×109/L (95% confidence interval [CI]: 3.2-23.3, P < 0.001). Patients with a high WBC tended to have inferior long-term survival. However, when excluding 30-day mortality, no statistically significant difference was found (hazard ratio, 1.4; 95% CI: 0.9-2.0, P = 0.121). No association between WBC count and 30-day mortality or long-term survival was observed among patients treated for rAAA. We could not identify any sex differences in WBC, neither in intact AAA nor in rAAA. We were not able identify any association between WBC and specific causes of death. CONCLUSIONS: This study suggests that patients with WBC count ≥11 ×109/L prior to surgery for intact AAA have a higher 30-day mortality compared to patients with WBC <11 ×109/L. We could not identify any substantial difference in long-term survival when excluding 30-day mortality. We did not observe any association between preoperative WBC count and case fatality or long-term survival in patients undergoing surgery for rAAA. No sex differences in WBC were found.

Registration of Real-Time 3-D Ultrasound to Tomographic Images of the Abdominal Aorta.

The purpose of this study was to develop an image-based method for registration of real-time 3-D ultrasound to computed tomography (CT) of the abdominal aorta, targeting future use in ultrasound-guided endovascular intervention. We proposed a method in which a surface model of the aortic wall was segmented from CT, and the approximate initial location of this model relative to the ultrasound volume was manually indicated. The model was iteratively transformed to automatically optimize correspondence to the ultrasound data. Feasibility was studied using data from a silicon phantom and in vivo data from a volunteer with previously acquired CT. Through visual evaluation, the ultrasound and CT data were seen to correspond well after registration. Both aortic lumen and branching arteries were well aligned. The processing was done offline, and the registration took approximately 0.2 s per ultrasound volume. The results encourage further patient studies to investigate accuracy, robustness and clinical value of the approach.

Bedside dressing changes for open abdomen in the intensive care unit is safe and time and staff efficient.

BACKGROUND: Patients with an open abdomen (OA) treated with temporary abdominal closure (TAC) need multiple surgical procedures throughout the hospital stay with repeated changes of the vacuum-assisted closure device (VAC changes). The aim of this study was to examine if using the intensive care unit (ICU) for dressing changes in OA patients was safe regarding bloodstream infections (BSI) and survival. Secondary aims were to evaluate saved time, personnel, and costs. METHODS: All patients treated with OA in the ICU from October 2006 to June 2014 were included. Data were retrospectively obtained from registered procedure codes, clinical and administrative patients' records and the OR, ICU, anesthesia and microbiology databases. Outcomes were 30-, 60- and 90-day survival, BSI, time used and saved personnel costs. RESULTS: A total of 113 patients underwent 960 surgical procedures including 443 VAC changes as a single procedure, of which 165 (37 %) were performed in the ICU. Nine patients died before the first scheduled dressing change and six patients were closed at the first scheduled surgery after established OA, leaving 98 patients for further analysis. The mean duration for the surgical team performing a VAC change in the ICU was 63.4 (60.4-66.4) minutes and in the OR 98.2 (94.6-101.8) minutes (p < 0.001). The mean duration for the anesthesia team in the OR was 115.5 minutes, while this team was not used in the ICU. Personnel costs were reduced by €682 per procedure when using the ICU. Forty-two patients had all the VAC changes done in the OR (VAC-OR), 22 in the ICU (VAC-ICU) and 34 in both OR and ICU (VAC-OR/ICU). BSI was diagnosed in eight (19 %) of the VAC-OR patients, seven (32 %) of the VAC-ICU and eight (24 %) of the VAC-OR/ICU (p = 0.509). Thirty-five patients (83 %) survived 30 days in the VAC-OR group, 17 in the VAC-ICU group (77 %) and 28 (82 %) in the VAC-OR/ICU group (p = 0.844). CONCLUSIONS: VAC change for OA in the ICU saved time for the OR team and the anesthesia team compared to using the OR, and it reduced personnel costs. Importantly, the use of ICU for OA dressing change seemed to be as safe as using the OR.

Investigations of spectral resolution and angle dependency in a 2-D tracking Doppler method.

An important source of error in velocity measurements from conventional pulsed wave (PW) Doppler is the angle used for velocity calibration. Because there are great uncertainties and interobserver variability in the methods used for Doppler angle correction in the clinic today, it is desirable to develop new and more robust methods. In this work, we have investigated how a previously presented method, 2-D tracking Doppler, depends on the tracking angle. A signal model was further developed to include tracking along any angle, providing velocity spectra which showed good agreement with both experimental data and simulations. The full-width at half-maximum (FWHM) bandwidth and the peak value of predicted power spectra were calculated for varying tracking angles. It was shown that the spectra have lowest bandwidth and maximum power when the tracking angle is equal to the beam-to-flow angle. This may facilitate new techniques for velocity calibration, e.g., by manually adjusting the tracking angle, while observing the effect on the spectral display. An in vitro study was performed in which the Doppler angles were predicted by the minimum FWHM and the maximum power of the 2-D tracking Doppler spectra for 3 different flow angles. The estimated Doppler angles had an overall error of 0.24° ± 0.75° when using the minimum FWHM. With an in vivo example, it was demonstrated that the 2-D tracking Doppler method is suited for measurements in a patient with carotid stenosis.

Combined vector velocity and spectral Doppler imaging for improved imaging of complex blood flow in the carotid arteries.

Color flow imaging and pulsed wave (PW) Doppler are important diagnostic tools in the examination of patients with carotid artery disease. However, measurement of the true peak systolic velocity is dependent on sample volume placement and the operator's ability to provide an educated guess of the flow direction. Using plane wave transmissions and a duplex imaging scheme, we present an all-in-one modality that provides both vector velocity and spectral Doppler imaging from one acquisition, in addition to separate B-mode images of sufficient quality. The vector Doppler information was used to provide automatically calibrated (angle-corrected) PW Doppler spectra at every image point. It was demonstrated that the combined information can be used to generate spatial maps of the peak systolic velocity, highlighting regions of high velocity and the extent of the stenotic region, which could be used to automate work flow as well as improve the accuracy of measurement of true peak systolic velocity. The modality was tested in a small group (N = 12) of patients with carotid artery disease. PW Doppler, vector velocity and B-mode images could successfully be obtained from a single recording for all patients with a body mass index ranging from 21 to 31 and a carotid depth ranging from 16 to 28 mm.

Simultaneous quantification of flow and tissue velocities based on multi-angle plane wave imaging.

A quantitative angle-independent 2-D modality for flow and tissue imaging based on multi-angle plane wave acquisition was evaluated. Simulations of realistic flow in a carotid artery bifurcation were used to assess the accuracy of the vector Doppler (VD) technique. Reduction in root mean square deviation from 27 cm/s to 6 cm/s and 7 cm/s to 2 cm/s was found for the lateral (vx) and axial (vz) velocity components, respectively, when the ensemble size was increased from 8 to 50. Simulations of a Couette flow phantom (vmax = 2.7 cm/s) gave promising results for imaging of slowly moving tissue, with root mean square deviation of 4.4 mm/s and 1.6 mm/s for the x- and z-components, respectively. A packet acquisition scheme providing both B-mode and vector Doppler RF data was implemented on a research scanner, and beamforming and further post-processing was done offline. In vivo results of healthy volunteers were in accordance with simulations and gave promising results for flow and tissue vector velocity imaging. The technique was also tested in patients with carotid artery disease. Using the high ensemble vector Doppler technique, blood flow through stenoses and secondary flow patterns were better visualized than in ordinary color Doppler. Additionally, the full velocity spectrum could be obtained retrospectively for arbitrary points in the image.

Three-dimensional electromagnetic navigation vs. fluoroscopy for endovascular aneurysm repair: a prospective feasibility study in patients.

PURPOSE: To evaluate the in vivo feasibility of a 3-dimensional (3D) electromagnetic (EM) navigation system with electromagnetically-tracked catheters in endovascular aneurysm repair (EVAR). METHODS: The pilot study included 17 patients undergoing EVAR with a bifurcated stent-graft. Ten patients were assigned to the control group, in which a standard EVAR procedure was used. The remaining 7 patients (intervention group) underwent an EVAR procedure during which a cone-beam computed tomography image was acquired after implantation of the main stent-graft. The 3D image was presented on the navigation screen. From the contralateral side, the tip of an electromagnetically-tracked catheter was visualized in the 3D image and positioned in front of the contralateral cuff in the main stent-graft. A guidewire was inserted through the catheter and blindly placed into the stent-graft. The placement of the guidewire was verified by fluoroscopy before the catheter was pushed over the guidewire. If the guidewire was incorrectly placed outside the stent-graft, the procedure was repeated. Successful placement of the guidewire had to be achieved within a 15-minute time limit. RESULTS: Within 15 minutes, the guidewire was placed correctly inside the stent-graft in 6 of 7 patients in the intervention group and in 8 of 10 patients in the control group. In the intervention group, fewer attempts were needed to insert the guidewire correctly. CONCLUSION: A 3D EM navigation system, used in conjunction with fluoroscopy and angiography, has the potential to provide more spatial information and reduce the use of radiation and contrast during endovascular interventions. This pilot study showed that 3D EM navigation is feasible in patients undergoing EVAR. However, a larger study must be performed to determine if 3D EM navigation is better than the existing practice for these patients.

[Carotid stenosis--assessment and treatment]. / Carotisstenose--utredning og behandling.

BACKGROUND: About 12,000 people suffer an ischemic stroke in Norway every year; 20 % of them may be caused by emboli from precerebral arteries. We discuss the epidemiology of carotid artery stenoses and assessment upon suspicion, and provide an overview of medical treatment and indications for surgery. MATERIAL AND METHODS: The article is based on literature identified through non-systematic searches in PubMed, core medical journals and textbooks and the authors' experience from a vascular surgical department and stroke unit. RESULTS: Stroke symptoms or recurrent transient ischemic attacks (TIAs) should lead to direct admission to hospital, while patients with single TIAs should be assessed as out-patients in a hospital within a few days. Risk-factors should be investigated, and the carotid arteries should be examined with duplex ultrasound upon suspicion of stenosis. There is only a weak correlation between a neck bruit and an ipsilateral carotid artery stenosis, but a connection can usually be clarified by use of duplex ultrasound. All patients with a carotid artery stenosis should have medical treatment to prevent complications of atherosclerotic disease; i.e. antithrombotic, and for the majority cholesterol-lowering treatment and possibly antihypertensive medication. Patients with a symptomatic carotid artery stenosis of more than 50 % diameter reduction should be considered for surgical treatment within 14 days. Surgery for asymptomatic carotid artery stenoses seems to have a marginal effect. INTERPRETATION: Patients with stroke-like symptoms should be examined by a doctor as soon as possible. Quick diagnosis and treatment of patients with cerebrovascular events is demanding for the logistics of our hospitals.

Reduced strain in abdominal aortic aneurysms after endovascular repair.

PURPOSE: To compare in vivo strain in abdominal aortic aneurysms before and after endovascular aneurysm repair (EVAR), thereby obtaining a quantitative measure of changes in mechanical burden on the aneurysm wall. METHOD: Transabdominal ultrasound was acquired from 10 patients (9 men; median age 76 years, range 61-83) 1 day before and 2 days after elective EVAR. Strain was estimated as the relative cyclic elongation and contraction of the wall tissue in a number of connected segments along the aneurysm circumference. For each time instance of the cardiac cycle, the maximum and the average strain values along the circumference were recorded. The temporal maximums of these parameters (defined as the maximum strain and the peak average strain, respectively) were compared before and after EVAR. RESULTS: Both maximum strain and peak average strain were reduced following EVAR by 41% (range 35%-63%) and 68% (range 41%-93%), respectively. Despite the reduction, cyclic strain was still evident after the stent-graft was placed, even when no evidence of endoleak was found. Further, the strain values were inhomogeneous along the circumference, both before and after treatment. In 2 cases, endoleak was proven by routine computed tomography; the relative reduction in maximum strain was slightly less in these cases (35% and 38%) compared to those without endoleak (45%, range 38%-63%). No difference was found in reduction of peak average strain. CONCLUSION: Strain is significantly reduced after EVAR, but there may still be a certain level of strain after the treatment. The strain values are inhomogeneous along the circumference both before and after treatment. These results encourage further investigation to evaluate the potential for using circumferential strain as an additional indicator of outcome after endovascular repair.

[Surgical treatment of carotid stenosis in Norway]. / Kirurgisk behandling ved carotisstenose i Norge.

BACKGROUND: Our purpose was to explore indications, preoperative investigation and operative technique for carotid endarterectomy in Norway. MATERIAL AND METHODS: A questionnaire was sent to 22 departments performing vascular surgery. Questions included an evaluation of the volume of carotid surgery, indications, preoperative examination, surgical technique and postoperative follow up. We requested the number of carotid endarterectomies performed in 2002, and whether the hospital also performed endovascular treatment for carotid artery stenosis. RESULTS: Carotid endarterectomy was performed in 19 hospitals, with an average of 16 operations per department. Among the surgeons, 18 stated that the number of carotid endarterectomies in Norway was too low. Endovascular treatment was performed in three hospitals. There was agreement on the indications for carotid endarterectomy for symptomatic stenosis, while the practice for asymptomatic stenosis varied widely. Patients who had undergone a minor stroke, were offered surgery after more than 4 weeks in 10 cases. In 11 departments a neurologist always examined the patient preoperatively. Duplex ultrasound examination of the carotid arteries was usually done by a neurologist; only 6 departments did preoperative conventional angiography in all cases. More than half of the surgeons always used a shunt during the operation, while only a few used intraoperative monitoring. Nine out of 20 surgeons closed the arteriotomy with a patch. INTERPRETATION: Consensus regarding the indications for carotid endarterectomy should be sought and more patients probably be offered surgery soon after the occurrence of symptoms.

Parameters describing motion in carotid artery plaques from ultrasound examination: A reproducibility study.

We have previously developed a method for quantifying motion in carotid artery plaques from sequences of ultrasound (US) radiofrequency images. Here, we examine the intraoperator reproducibility of the results. Five independent recordings were made on each of six symptomatic and six asymptomatic patients, and processed off-line into 29 motion parameters, representing motion amplitude, stretch/compression and shear motion. For the statistical analysis, we used a linear mixed model and investigated the parameters for contributions from individual patients, contributions from recordings on each patient and contributions from heart cycles within each recording. The model was valid for seven parameters calculated over the entire heart cycle (four calculated over the systole only), which all showed good reproducibility (intraclass coefficient for variance over all patients rho(alpha) >/= 0.4). Averaging three recordings of two heart cycles each gives acceptable accuracy (normalised variance of patient means lambda < 0.3). This acquisition scheme is reasonable in a clinical situation.

A new method for analysis of motion of carotid plaques from RF ultrasound images.

Motion of carotid artery plaques during the cardiac cycle may contribute to plaque disruption and embolism. We have developed a computerized method that objectively analyzes such motion from a sequence of ultrasound (US) radiofrequency (RF) images. A displacement vector map is obtained by 2-D correlation of local areas in consecutive images. From this map, motion dynamics can be quantified and presented as function of time, spatial (image) coordinates or as single numbers. Correct functionality has been verified on laboratory data. Applied to patient data, the method gives temporal results that correlate well with ECG data and the calculated peak systolic velocities of typically 10 mm/s agree well with values reported in the literature. The spatial analysis demonstrates that different plaque regions may exhibit different motion patterns that may cause internal stress, leading to fissures and plaque disruption. Thus, the motion analysis method may provide new and important information about the plaque characteristics and the prospective risk of cerebrovascular events.