Gaseous Emboli Research Articles

Validation of an algorithm that separates gaseous micro-embolic signals and artifacts during transcranial Doppler persistent foramen ovale examinations

ObjectivePersistent foramen ovale (PFO) is a risk factor for young stroke. Agitated saline serum is used to deliver small gaseous emboli to the brain in transcranial Doppler ultrasound (TCD) for the detection and grading of PFO. In this study we validated a PFO algorithm that can differentiate between gaseous emboli and artifacts. MethodsThe validation cohort comprised 18 patients with positive PFO examinations. The PFO algorithm uses a binary tree that separates high-intensity transients signals (HITs) into gaseous emboli or artifacts based on intensity, zero-crossing, and velocity parameters. ResultsThe cohort exhibited 385 macroscopic gaseous emboli meeting the >3 dB criterion. An additional 137 gaseous emboli were noticed below the 3-dB intensity cutoff value. The low-intensity gaseous emboli included both macroscopic and microscopic air bubbles observed in curtains. Nearly all emboli (98 %) above the 3-dB level showed overt frequency modulation. The overall accuracy of the PFO algorithm in discriminating macroscopic gaseous emboli and artifacts was 96.4 %, with a similar percentage of sensitivity and specificity (96.4 %). The inter-observer agreement of human experts was excellent (ic-CC 0.989 and 0.953). ConclusionsMacroscopic gaseous emboli and artifacts during PFO exams can be accurately discriminated by the PFO algorithm. The PFO algorithm cannot be used as a standalone system as microscopic air bubbles might escape proper identification. This knowledge will be important in the design of future PFO algorithms which should make it possible to classify the PFO grade without the interference of humans.

Diagnostic Accuracy of an Algorithm for Discriminating Presumed Solid and Gaseous Microembolic Signals During Transcranial Doppler Examinations.

The aim of the work described here was to assess the diagnostic accuracy of a new algorithm (SGA-a) for time-domain analysis of transcranial Doppler audio signals to discriminate presumed solid and gaseous microembolic signals and artifacts (SGAs). SGA-a was validated by human experts in an artifact cohort of 20 patients subjected to a 1-h transcranial Doppler exam before cardiac surgery (cohort 1). Emboli were validated in a cohort of 10 patients after aortic valve replacement in a 4-h monitoring period (cohort 2). The SGA misclassification rate was estimated by testing SGA-a on artifact-free test files of solid and gaseous emboli. In cohort 1 (n=24,429), artifacts were classified with an accuracy of 94.5%. In cohort 2 (n=12,328), the accuracy in discriminating solid/gaseous emboli from artifacts was 85.6%. The 95% limits of agreement for, respectively, the numbers of presumed solids and gaseous emboli, artifacts and microembolic signals of undetermined origin were [-10, 10], [-14, 7] and [-9, 16], and the intra-class correction coefficients were 0.99, 0.99 and 0.99, respectively. The rate of misclassification of solid test files was 2%, and the rate of misclassification of gaseous test files was 12%. SGA-a can detect presumed solid and gaseous microembolic signals and differentiate them from artifacts. SGA-a could be of value when both solid and gaseous emboli may jeopardize brain function such as seen during cardiac valve and/or aortic arch replacement procedures.

Haematic antegrade repriming to enhance recovery after cardiac surgery from the perfusionist side.

Background: New era of cardiac surgery aims to provide an enhanced postoperative recovery through the implementation of every step of the process. Thus, perfusion strategy should adopt evidence-based measures to reduce the impact of cardiopulmonary bypass (CPB). Hematic Antegrade Repriming (HAR) provides a standardized procedure combining several measures to reduce haemodilutional priming to 300mL. Once the safety of the procedure in terms of embolic release has been proven, the evaluation of its beneficial effects in terms of transfusion and ICU stay should be assessed to determine if could be considered for inclusion in Enhanced Recovery After Cardiac Surgery (ERACS) programs. Methods: Two retrospective and non-randomized cohorts of high-risk patients, with similar characteristics, were assessed with a propensity score matching model. The treatment group (HG) (n=225) received the HAR. A historical cohort, exposed to conventional priming with 1350mL of crystalloid confirmed the control group (CG) (n=210). Results: Exposure to any transfusion was lower in treated (66.75% vs. 6.88%, p<0.01). Prolonged mechanical ventilation (>10h) (26.51% vs. 12.62%; p<0.01) and extended ICU stay (>2d) (47.47% vs. 31.19%; p<0.01) were fewer for treated. HAR did not increase early morbidity and mortality. Related savings varied from 581 to 2741.94$/patient, depending on if direct or global expenses were considered. Discussion: By reducing the gaseous and crystalloid emboli during CPB initiation, HAR seems to have a beneficial impact on recovery and reduces the overall transfusion until discharge, leading to significant cost savings per process. Due to the preliminary and retrospective nature of the research and its limitations, our findings should be validated by future prospective and randomized studies.

Improving Trendelenburg position effectiveness by varying cardiopulmonary bypass flow.

Trendelenburg position (TP) is used to transport gaseous emboli away from the cerebral region during cardiac surgery. However, TP effectiveness has not been fully considered when combined with varying the cardiopulmonary bypass (CPB) flow. This study simulated the supine and TP at different pump flows and assessed the trapped emboli and embolic load entering the aortic arch branch arteries (AABA). A computational fluid dynamics (CFD) approach used a centrally cannulated adult patient-specific aorta model replicating a CPB circuit. Air emboli of 0.1mm, 0.5mm, and 1.0mm (n = 700 each) were injected into the aorta placed in the supine position (0°) and the TP (-20°) at 2L/min and 5L/min. The number of emboli entering the AABA were compared. An aortic phantom flow experiment was performed to validate air bubble behaviour. TP at 5L/min had the lowest 0.1mm mean (±SD) embolic load compared to the supine 2L/min (55.3 ± 30.8 vs 64.3 ± 35.4). For both the supine and TP, the lower flow of 2L/min had the highest number of simulated trapped emboli in higher elevated regions than at 5L/min (541 ± 185 and 548 ± 191 vs 520 ± 159 and 512 ± 174), respectively. The flow experiment demonstrated that 2L/min promoted bubble coalescence and high amounts of trapped emboli and 5L/min transported air emboli away from the AABA. TP effectiveness was improved by using CPB flow to manage air emboli. These results provide insights for predicting emboli behaviour and improving emboli de-airing procedures.

A prospective observational study of emboli exposure in open versus closed chamber cardiac surgery.

Exposure to cerebral emboli is ubiquitous and may be harmful in cardiac surgery utilizing cardiopulmonary bypass. This was a prospective observational study aiming to compare emboli exposure in closed-chamber with open-chamber cardiac surgery, distinguish particulate from gaseous emboli and examine cerebral laterality in distribution. Forty patients underwent either closed-chamber procedures (n = 20) or open-chamber procedures (n = 20). Emboli (gaseous and solid) were detected using transcranial Doppler in both middle cerebral arteries in two monitoring phases: 1, initiation of bypass to the removal of the aortic cross-clamp; and 2, removal of aortic cross-clamp to 20 minutes after venous decannulation. Total (median (interquartile range)) emboli counts (both phases) were 898 (499-1366) and 2617 (1007-5847) in closed-chamber and open-chamber surgeries, respectively. The vast majority were gaseous; median 794 (closed-chamber surgery) and 2240 (open-chamber surgery). When normalized for duration, there was no difference between emboli exposures in closed-chamber and open-chamber surgery in phase 1: 6.8 (3.6-15.2) versus 6.4 (2.0-18.1) emboli per minute, respectively. In phase 2, closed-chamber surgery cases were exposed to markedly fewer emboli than open-chamber surgery cases: 9.6 (5.1-14.9) versus 43.3 (19.7-60.3) emboli per minute, respectively. More emboli (total) passed into the right cerebral circulation: 985 (397-2422) right versus 376 (198-769) left. Patients undergoing open-chamber surgery are exposed to considerably higher numbers of cerebral arterial emboli after removal of the aortic cross-clamp than those undergoing closed-chamber surgery, and more emboli enter the right middle cerebral artery than the left. These results may help inform the evaluation of the pathophysiological impact of emboli exposure.

Cerebral Emboli Monitoring Using Transcranial Doppler Ultrasonography in Adults and Children: A Review of the Current Technology and Clinical Applications in the Perioperative and Intensive Care Setting.

Transcranial Doppler (TCD) ultrasonography is the only noninvasive bedside technology for the detection and monitoring of cerebral embolism. TCD may identify patients at risk of acute and chronic neurologic injury from gaseous or solid emboli. Importantly, a window of opportunity for intervention-to eliminate the source of the emboli and thereby prevent subsequent development of a clinical or subclinical stroke-may be identified using TCD. In this review, we discuss the application of TCD sonography in the perioperative and intensive care setting in adults and children known to be at increased risk of cerebral embolism. The major challenge for evaluation of emboli, especially in children, is the need to establish the ground truth and define true emboli identified by TCD. This requires the development and validation of a predictive TCD emboli monitoring technique so that appropriately designed clinical studies intended to identify specific modifiable factors and develop potential strategies to reduce pathologic cerebral embolic burden can be performed.

Micro-embolic risks during radiofrequency and cryoballoon-ablation of atrial fibrillation -analysis from real-time carotid artery doppler monitoring-

Abstract Background Catheter ablation of atrial fibrillation (AF) is associated with risks of silent cerebral events. However, the timing of intraprocedural micro-embolic events or differences between open-irrigated radiofrequency (RF) and cryoballoon (Cryo) ablation are unclear. Newly developed real-time carotid artery Doppler is a simple non-invasive method to detect micro-embolic signals (MESs) during ablation. Objective We investigated the timing of detecting MESs during RF and Cryo ablation of AF. Methods During the first pulmonary vein isolation (PVI) session of AF, MESs were monitored by real-time carotid artery Doppler monitoring throughout the procedure. The MES counts were collected and evaluated separately during the different steps of the procedure (Figure). Results Thirty-three AF patients (RF/Cryo: 22/11 cases, 9 females, 69.5±11.6 y.o) were included. PVI was successfully accomplished in all patients with no major complications. The MES count was significantly greater in the RF group than Cryo group (table). In both groups, left atrial (LA) access (interatrial puncture) and sheaths insertion to the LA generated a significant number of MESs (RF: 1690 of 9116 MESs [18.5% of the total MESs], Cryo: 793 of 2285 MESs [34.7%]). In the RF group, MESs were observed incessantly during PVI (Figure). The LA dwell time was significantly longer in the RF group than Cryo group (table). In the RF group, the MES count was significantly greater in the longer LA dwell time group (LA dwell time &amp;gt;130min) than the shorter group (464.2±179.7 vs 302.6±138.2: P=0.049). During the cryo-applications in the Cryo group, the MESs were greatest during the first cryoballoon application (625 of 2285 MESs [27.4%]). Conclusions There were more MESs during RF ablation than cryoablation. MESs were recorded during a variety of steps throughout the procedure. In the RF group, most of MESs were recorded incessantly during radiofrequency ablation and greater number of MESs were recorded in patients with longer LA dwell time. In the Cryo group, most of MESs occurred during phases with a high probability of gaseous emboli. Funding Acknowledgement Type of funding source: None

In vivo analysis of the origin and characteristics of gaseous microemboli during catheter-mediated irreversible electroporation.

Aims Irreversible electroporation (IRE) ablation is a non-thermal ablation method based on the application of direct current between a multi-electrode catheter and skin electrode. The delivery of current through blood leads to electrolysis. Some studies suggest that gaseous (micro)emboli might be associated with myocardial damage and/or (a)symptomatic cerebral ischaemic events. The aim of this study was to compare the amount of gas generated during IRE ablation and during radiofrequency (RF) ablation.Methods and resultsIn six 60–75 kg pigs, an extracorporeal femoral shunt was outfitted with a bubble-counter to detect the size and total volume of gas bubbles. Anodal and cathodal 200 J IRE applications were delivered in the left atrium (LA) using a 14-electrode circular catheter. The 30 and 60 s 40 W RF point-by-point ablations were performed. Using transoesophageal echocardiography (TOE), gas formation was visualized. Average gas volumes were 0.6 ± 0.6 and 56.9 ± 19.1 μL (P < 0.01) for each anodal and cathodal IRE application, respectively. Also, qualitative TOE imaging showed significantly less LA bubble contrast with anodal than with cathodal applications. Radiofrequency ablations produced 1.7 ± 2.9 and 6.7 ± 7.4 μL of gas, for 30 and 60 s ablation time, respectively.Conclusion Anodal IRE applications result in significantly less gas formation than both cathodal IRE applications and RF applications. This finding is supported by TOE observations.

Assessing the Efficacy of Commercially Available Filters in Removing Air Micro-Emboli in Intravenous Infusion Systems.

The presence of gaseous air emboli in the vasculature has the potential to cause significant morbidity and mortality. Once viewed as a rare complication of high-risk surgeries, air embolism is now also being associated with even minor and routine procedures such as peripheral venous catheterization. With increasing recognition, various preventive measures have emerged, the most important of which is the use of air-eliminating filters. However, studies on these devices are currently lacking. Therefore, in this present study, we aimed to evaluate the effectiveness of two commercially available filters in removing air within intravenous (IV) lines. An IV infusion system was created, designed to resemble standard conditions used in real clinical practice. Testing was completed using a .9% NaCl solution at room temperature with a flow rate set at 75 mL/h and involving three different filter orientations. The test bed was configured to inject air every 2 minutes with volumes ranging between 5 and 600 μL. The two filter models tested were GVS .2-μM and Braun SUPOR membrane air-eliminating filters. Data was collected at pre-filter and post-filter sites. The Braun SUPOR membrane filter (B Braun, Bethlehem, PA) reduced air micro-emboli by 100.0% (p < .0001) both by volume and count compared with -.6 ± 3.5% by volume and -.8 ± 1.5% by count for the control. The reduction seen with the GVS .2-μM filter was 99.8 ± .2% (p < .0001) by volume and 86.2 ± 21.1% (p < .0001) by count compared with the control. There was no statistically significant difference in the removal efficacy between the two filter models. As the use of air-eliminating filters becomes a common standard of care, establishing the validity of the commercially available filter models is important to minimize the risk of vascular air embolism.

Assessing the Efficacy of Commercially Available Filters in Removing Air Micro-Emboli in Intravenous Infusion Systems

The presence of gaseous air emboli in the vasculature has the potential to cause significant morbidity and mortality. Once viewed as a rare complication of high-risk surgeries, air embolism is now also being associated with even minor and routine procedures such as peripheral venous catheterization. With increasing recognition, various preventive measures have emerged, the most important of which is the use of air-eliminating filters. However, studies on these devices are currently lacking. Therefore, in this present study, we aimed to evaluate the effectiveness of two commercially available filters in removing air within intravenous (IV) lines. An IV infusion system was created, designed to resemble standard conditions used in real clinical practice. Testing was completed using a .9% NaCl solution at room temperature with a flow rate set at 75 mL/h and involving three different filter orientations. The test bed was configured to inject air every 2 minutes with volumes ranging between 5 and 600 μL. The two filter models tested were GVS .2-μM and Braun SUPOR membrane air-eliminating filters. Data was collected at pre-filter and post-filter sites. The Braun SUPOR membrane filter (B Braun, Bethlehem, PA) reduced air micro-emboli by 100.0% (p&lt; .0001) both by volume and count compared with −.6 ± 3.5% by volume and −.8 ± 1.5% by count for the control. The reduction seen with the GVS .2-μM filter was 99.8 ± .2% (p&lt; .0001) by volume and 86.2 ± 21.1% (p&lt; .0001) by count compared with the control. There was no statistically significant difference in the removal efficacy between the two filter models. As the use of air-eliminating filters becomes a common standard of care, establishing the validity of the commercially available filter models is important to minimize the risk of vascular air embolism.

Aortic cannula orientation and flow impacts embolic trajectories: computational cardiopulmonary bypass.

Emboli events are associated with the aortic cannula insertion and final position in the ascending aorta. However, the impact of subtle changes in aortic cannula movement and flow influencing embolic transport throughout the aortic arch is not well understood. The present study evaluated the aortic cannula's outflow and orientation effect on emboli entering the aortic branch arteries. A simplified aortic computational model was anteriorly cannulated in the distal ascending aorta with a 21-French straight aortic cannula, and two orientations were analysed by injecting gaseous and solid emboli at pump flows 2, 3 and 5 L/minute. The first aortic cannula orientation (forward flow cannula) was directed towards the lesser curvature. The second aortic cannula orientation (rear flow cannula) was tilted slightly backwards by 15°, providing flow in the retrograde direction. Forward flow cannula produced a primary arch flow, whereas rear flow cannula produced a secondary arch flow resulting in four times longer emboli arch resident times than forward flow cannula. The rear flow cannula had the highest percentage of gaseous emboli entering the brachiocephalic artery of 8%, 12% and 36% (at 2, 3 and 5 L/minute, respectively). Rear flow cannula provided a positive aortic branch arterial flow at all pump flows, whereas at forward flow cannula, the brachiocephalic artery experienced retrograde flows of -1.0% (3 L/minute) and -4.0% (5 L/minute), with the left common carotid -0.23% (5 L/minute). No significant number of solid emboli entered the aortic branch arteries. This numerical study illustrated distinct trajectory behaviours between gaseous and solid emboli where slight changes in aortic cannula orientation influenced idealised emboli direction with higher pump flows magnifying the effects.

Can venous cannula design influence venous return and negative pressure with a minimally invasive extracorporeal circulation?

Recent advances to make cardiopulmonary bypass more physiological include the use of kinetic-assisted venous drainage but without a venous reservoir. Despite manipulation of intravascular volume and patient positioning, arterial flow is frequently reduced. Negative venous line pressures can be generated, which may elicit gaseous microemboli. We investigated the influence of venous cannula design on venous return and negative venous line pressures. In a single-centre, single-surgeon, prospective, randomized, double-blind trial, 48 patients undergoing isolated coronary artery, aortic valve or combined coronary artery and aortic valve surgery, with a minimally invasive circuit, were randomized to a conventional two-stage (2S) or three-stage venous cannula (3S), or to a three-stage venous cannula with additional 'fenestrated' ridges (F3S). Blood flow, venous line pressures and gaseous microemboli number and size were measured. The pump flow achieved was the same between groups, but in each case fell below the target range of 2.2-2.4 L min-1 m-2. The three-stage cannula recorded significantly lower negative pressure than the other cannulae. The total count and volume of gaseous emboli detected with the F3S cannulae was very high in some cases, with wide heterogeneity. The low negative pressures recorded with three-stage cannula, despite having a larger drainage orifice area, suggest that negative pressure may be more influenced by lumen diameter and vena cava collapse rather than drainage hole size. The additional fenestrations resulted in flow characteristics and negative pressures similar to the larger two-stage cannula but are associated with generation of gaseous microemboli.

PC058. A Novel Aortic Arch Flow Model to Test the Efficacy of Cerebral Embolic Protection Devices Using Transcranial Doppler

Clinically apparent stroke occurs in up to 6% of patients undergoing thoracic endovascular aortic repair and up to 4% of patients undergoing carotid artery stenting. However, clinically silent cerebral infarction is seen on postoperative diffusion-weighted magnetic resonance imaging in >60% of patients undergoing thoracic endovascular aortic repair and leads to an increased risk of future stroke and dementia. Embolic protection devices are associated with lower stroke rates and smaller volume of ischemic lesions on diffusion-weighted magnetic resonance imaging. We created a novel aortic arch flow model and tested the efficacy of the FilterWire EZ (Boston Scientific, Marlborough, Mass) using transcranial Doppler ultrasound. By employing a three-dimensional printed aortic arch, we created a closed-circuit flow model that can simulate continuous and pulsatile blood flow (Fig, A-C). Dissolved cornstarch particles simulate circulating red and white blood cells, which typically range in size from 6 to 15 μm, to provide a background signal for detection of solid and gaseous emboli on transcranial Doppler ultrasound (Fig, D and E). A 38-μm filter placed in series ensures that injected microparticles do not recirculate and the circuit is deaired. We then prepared and deployed a FilterWire EZ, a uniform 110-μm pore filter commonly used during carotid artery stenting, according to the instructions for use. Embozene Microspheres (Boston Scientific) of known sizes were diluted in saline to 1 mL of particles per 10 mL of solution. High-intensity transient signals (HITS) were recorded during filter deployment, injection of 1 mL of solution, and filter retrieval. This process was repeated for Embozene particles of 75-, 100-, 250-, and 400-μm diameters. Each continuous 1-second shower of emboli was counted as 15 HITS. Despite preparation of the FilterWire EZ according to instructions for use, there were on average 41 ± 7 (range, 31-49) HITS during filter deployment and 7 ± 7 (range, 1-17) HITS during filter retrieval. Average number of HITS during injection was 87 ± 130 (range, 4-315), and more HITS were seen distal to the filter on injection of microparticles that were smaller than the 110-μm pore size (142 ± 150 vs 5 ± 1; P = .31). Mean velocity (cm/s) of the fluid decreased by 18% ± 2% after filter deployment and 50% ± 34% during injection of microparticles and returned to baseline after filter retrieval. We created and validated a novel aortic arch flow model. HITS were seen during all stages of the procedure using the FilterWire EZ. This model can be used to test the efficacy of all available embolic protection devices and methods of deairing stent grafts.

Flow Awareness as a New Safety Device for Cardiopulmonary Bypass

Safety devices such as bubble detectors and level detectors have been in use for more than 40 years and initially reduced the risks associated with gaseous emboli during cardiopulmonary bypass; however, the risks have not been eliminated. This research explored a new safety device designed to further reduce these risks: Flow Awareness Technology. This device visually alerts the perfusionist when the ratio of venous return does not equal the amount of arterial flow. To determine the efficacy of this device, 33 participants with no perfusion background were randomly assigned to Group A (flow awareness only), Group B (level detector only), or Group C (control). These participants were instructed to turn off the arterial pump when they noticed that the fluid in the venous reservoir had begun to drop or if their assigned safety device was triggered. The venous line was fully occluded at times unknown to the participants. These times coincided with before, during, or after times that the participants were expected to paper-chart known values. Each participant’s amount of fluid lost (in milliliters) from the reservoir and reaction time (in seconds) to shut off the arterial roller pump were measured. Group A lost an average of 80.8 mL, Group B lost an average of 173.6 mL, and Group C lost an average of 140.3 mL. Average measured time for each group is as follows: Group A took 2.16 seconds, Group B took 4.31 seconds, and Group C took 4.09 seconds to shut off the arterial pump. Statistics support the hypothesis that Flow Awareness Technology significantly reduces the reaction time to an adverse event such as a sudden occlusion of the venous line, thus reducing the amount of fluid lost during such an event.

The Clinical Implication of Transcranial Doppler Detection of Microembolic Signals in Patients with Heartmate II.

We aimed to elucidate the clinical relevance of transcranial Doppler (TCD) in the detection of microembolic signals in patients with Heartmate II (HM-II). Twenty patients with HM-II underwent TCD examinations, and microembolic signals were rarely detected in stable patients. However, they were detected in patients with hemolysis and/or thromboembolic events. Further, TCD examination under oxygen inhalation revealed that, both, solid emboli and gaseous emboli exist in patients with HM-II.

Patterns of solid particle embolization during transcatheter aortic valve implantation and correlation with aortic valve calcification.

To evaluate solid embolization during transcatheter aortic valve implantation (TAVI) and correlate this with aortic valve calcification. There is a known stroke risk with TAVI, thought partly to be due to dislodgement of native aortic valve particles during implantation. However, to date there is little evidence that aortic valve calcification actually impacts embolic risk. Transcranial Doppler (TCD) was performed on consecutive suitable patients undergoing TAVI, using hardware and software enabling differentiation between solid and gaseous emboli. Data was analyzed by time points during the TAVI procedure. These results were correlated with aortic valve calcification. TCD was successfully performed on 63 patients. The median number of solid emboli was 76.0. The most common time point for solid embolization was during valve positioning. Forty-five of these patients had an appropriate CT scan which could be analyzed for an Agatston calcium score. The mean scores in the aortic valve and aortic root were 3382.4 and 754.9. There were significant correlations between the total number of solid emboli and valve calcium score (P = 0.033) and solid emboli during valve positioning and valve calcium score (P = 0.035). There was no relationship between gaseous emboli and valve calcium score. TAVI is associated with significant solid particle embolization, with the most common time point being during valve positioning. Solid embolization correlates with aortic valve calcium score, suggesting that valve calcification is a factor in embolic risk. This should be taken into consideration along with other clinical factors when assessing embolic risk.

The HYSTER study: the effect of intracervically administered terlipressin versus placebo on the number of gaseous emboli and fluid intravasation during hysteroscopic surgery: study protocol for a randomized controlled clinical trial

BackgroundTranscervical resection of myoma or endometrium is a safe, hysteroscopic, minimally invasive procedure. However, intravasation of distension fluid is a common phenomenon during these procedures. In a previous study we observed venous gas emboli in almost every patient. The severity of hysteroscopic-derived embolization has been shown to be correlated to the amount of intravasation. In addition, paradoxical gas embolism, which is potentially dangerous, was observed in several patients.Studies have shown a reduction of intravasation by using intracervically administered vasopressin during hysteroscopy. We think that its analog, terlipressin, should have the same effect. In our previous research we observed more gaseous emboli as intravasation increased. Whether or not the insertion of intracervically administered terlipressin leads to a lower incidence and severity of gas embolism is unknown. We hypothesize that intracervically administered terlipressin leads to a reduction of intravasation with a lower incidence and severity of gas embolism. Terlipressin may be of benefit during hysteroscopic surgery.Methods/designForty-eight patients (ASA 1 or 2) scheduled for transcervical resection of large, types 1–2 myoma or extensive endometrium resection will be included. In a double-blind fashion patients will be randomized 1:1 according to surgical treatment using either intracervically administered terlipressin or placebo. Transesophageal echocardiography will be used to observe and record embolic events. A pre- and post-procedure venous blood sample will be taken to calculate intravasation based on hemodilution. Our primary endpoint will be how terlipressin influences the severity of embolic events. Secondary endpoints include the effect of terlipressin on the amount of intravasation and on hemodynamic parameters.DiscussionIf terlipressin does indeed reduce the number of gaseous emboli and intravasation occurring during hysteroscopic surgery, it would be a simple method to minimize potential adverse events. It also allows for prolonged operating time before the threshold of intravasation is reached, thereby reducing the need for a second operation.Trial registrationNederlands Trial Register (Dutch Trial Register), ID: NTR5577. Registered retrospectively on 18 December 2015.

Thromboembolic Risks of the Procedural Process in Second-Generation Cryoballoon Ablation Procedures: Analysis From Real-Time Transcranial Doppler Monitoring.

Atrial fibrillation ablation is associated with substantial risks of silent cerebral events (SCEs) or silent cerebral lesions. We investigated which procedural processes during cryoballoon procedures carried a risk. Forty paroxysmal atrial fibrillation patients underwent pulmonary vein isolation using second-generation cryoballoons with single 28-mm balloon 3-minute freeze techniques. Microembolic signals (MESs) were monitored by transcranial Doppler throughout all procedures. Brain magnetic resonance imaging was obtained pre- and post-procedure in 34 patients (85.0%). Of 158 pulmonary veins, 152 (96.2%) were isolated using cryoablation, and 6 required touch-up radiofrequency ablation. A mean of 5.0±1.2 cryoballoon applications was applied, and the left atrial dwell time was 76.7±22.4 minutes. The total MES counts/procedures were 522 (426-626). Left atrial access and Flexcath sheath insertion generated 25 (11-44) and 34 (24-53) MESs. Using radiofrequency ablation for transseptal access increased the MES count during transseptal punctures. During cryoapplications, MES counts were greatest during first applications (117 [81-157]), especially after balloon stretch/deflations (43 [21-81]). Pre- and post-pulmonary vein potential mapping with Lasso catheters generated 57 (21-88) and 61 (36-88) MESs. Reinsertion of once withdrawn cryoballoons and subsequent applications produced 205 (156-310) MESs. Touch-up ablation generated 32 (19-62) MESs, whereas electric cardioversion generated no MESs. SCEs and silent cerebral lesions were detected in 11 (32.3%) and 4 (11.7%) patients, respectively. The patients with SCEs were older than those without; however, there were no significant factors associated with SCEs. A significant number of MESs and SCE/silent cerebral lesion occurrences were observed during second-generation cryoballoon ablation procedures. MESs were recorded during a variety of steps throughout the procedure; however, the majority occurred during phases with a high probability of gaseous emboli.

An automated microemboli detection and classification system using backscatter RF signals and differential evolution.

Embolic phenomena, whether air or particulate emboli, can induce immediate damages like heart attack or ischemic stroke. Embolus composition (gaseous or particulate matter) is vital in predicting clinically significant complications. Embolus detection using Doppler methods have shown their limits to differentiate solid and gaseous embolus. Radio-frequency (RF) ultrasound signals backscattered by the emboli contain additional information on the embolus in comparison to the traditionally used Doppler signals. Gaseous bubbles show a nonlinear behavior under specific conditions of the ultrasound excitation wave, this nonlinear behavior is exploited to differentiate solid from gaseous microemboli. In order to verify the usefulness of RF ultrasound signal processing in the detection and classification of microemboli, an in vitro set-up is developed. Sonovue micro bubbles are exploited to mimic the acoustic behavior of gaseous emboli. They are injected at two different concentrations (0.025 and 0.05µl/ml) in a nonrecirculating flow phantom containing a tube of 0.8mm in diameter. The tissue mimicking material surrounding the tube is chosen to imitate the acoustic behavior of solid emboli. Both gaseous and solid emboli are imaged using an Anthares ultrasound scanner with a probe emitting at a transmit frequency of 1.82MHz and at two mechanical indices (MI) 0.2 and 0.6. We propose in this experimental study to exploit discrete wavelet transform and a dimensionality reduction algorithm based on differential evolution technique in the analysis and the characterization of the backscattered RF ultrasound signals from the emboli. Several features are evaluated from the detail coefficients. It should be noted that the features used in this study are the same used in the paper by Aydin et al. These all features are used as inputs to the classification models without using feature selection method. Then we perform feature selection using differential evolution algorithm with support vector machines classifier. The experimental results show clearly that our proposed method achieves better average classification rates compared to the results obtained in a previous study using also the same backscatter RF signals.

Hemodynamic Instability Following Airway Spray Cryotherapy.

Spray cryotherapy (SCT) of airway lesions is used to effectively palliate respiratory symptoms related to airway obstruction, but significant intraoperative hemodynamic complications have been noted. We reviewed the experience at a single institution using SCT for the treatment of obstructive airway tumors. A retrospective review of a single institution experience with intraoperative and postoperative hemodynamic complications associated with SCT was performed. Descriptive statistics were performed. Between June 2009 and April 2010, 34 treatment sessions were performed on 28 patients. Median age was 60 years (range, 15-88 years). Tumor characteristics were as follows: 13 primary lung cancers (43%), 11 pulmonary metastases (50%), 1 direct extension of an esophageal cancer (3%), and 2 benign pulmonary lesions (7%). Twenty-one tumors (75%) were distal to the carina; 14 (50%) were >95% occlusive. Median procedure length was 78 minutes (range, 15-176 minutes). Eleven sessions (31%) led to severe hypotension and/or bradycardia, with 2 patients requiring cardiopulmonary resuscitation. One patient died intraoperatively after cardiac arrest; a second patient was stable intraoperatively but died within 24 hours of SCT. Four patients required reintubation and short-term mechanical ventilation. Unpredictable life-threatening hemodynamic instability can follow endobronchial SCT. We propose that the most likely cause is pulmonary venous gaseous emboli entering the right heart, the coronary arteries, and the systemic circulation. Although SCT may offer advantages over airway laser therapy (such as no risk of fire and rapid hemostasis), further study is needed to delineate the relative likelihood of therapeutic benefit versus catastrophic complications.