Multiple Cannula Research Articles

Computational investigation of outflow graft variation impact on hemocompatibility profile in LVADs.

Hemocompatibility-related adverse events (HRAE) occur commonly in patients with left ventricular assist devices (LVADs) and add to morbidity and mortality. It is unclear whether the outflow graft orientation can impact flow conditions leading to HRAE. This study presents a simulation-based approach using exact patient anatomy from medical images to investigate the influence of outflow cannula orientation in modulating flow conditions leading to HRAEs. A 3D model of a proximal aorta and outflow graft was reconstructed from a computed tomography (CT) scan of an LVAD patient and virtually modified to model multiple cannula orientations (n = 10) by varying polar (cranio-caudal) (n = 5) and off-set (anterior-posterior) (n = 2) angles. Time-dependent computational flow simulations were then performed for each anatomical orientation. Qualitative and quantitative hemodynamics metrics of thrombogenicity including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell platelet activation potential (ECAP), particle residence time (PRT), and platelet activation potential (PLAP) were analyzed. Within the simulations performed, endothelial cell activation potential (ECAP) and particle residence time (PRT) were found to be lowest with a polar angle of 85°, regardless of offset angle. However, polar angles that produced parameters at levels least associated with thrombosis varied when the offset angle was changed from 0° to 12°. For offset angles of 0° and 12° respectively, flow shear was lowest at 65° and 75°, time averaged wall shear stress (TAWSS) was highest at 85° and 35°, and platelet activation potential (PLAP) was lowest at 65° and 45°. This study suggests that computational fluid dynamic modeling based on patient-specific anatomy can be a powerful analytical tool when identifying optimal positioning of an LVAD. Contrary to previous work, our findings suggest that there may be an "ideal" outflow cannula for each individual patient based on a CFD-based hemocompatibility profile.

Computational Investigation of Outflow Graft Variation Impact on Hemocompatibility Profile in LVADs

<h3>Purpose</h3> Hemocompatibility related adverse events (HRAE) such as pump thrombosis, stroke, and gastrointestinal (GI) bleeding occur commonly in patients with left ventricular assist devices (LVADs). It is unclear whether the outflow graft orientation can impact flow conditions leading to HRAE. This study, used a simulation-based approach to investigate the influence that the cannula orientation has in modulating flow conditions leading to HRAEs. <h3>Methods</h3> A 3D model of a proximal aorta and outflow graft was reconstructed from a computer tomography (CT) scan of an LVAD patient and virtually modified to account for multiple cannula orientations (n=10) by varying polar (n=5) and off-set (n=2) angles. Time-dependent computer flow simulations were then performed and flow metrics as time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell activation potential (ECAP), flow shear (S), particle residence time (PRT), and platelet activation potential (PLAP) estimated. <h3>Results</h3> Flow shear was highest and lowest at the proximal aorta closer to the anastomosis and aortic sinus, respectively, in all configurations. Among all angles, time and space-averaged flow shear values were lowest at polar angles of 65° and 75° for 0° and 12° off-set angles, respectively. Flow metrics associated to thrombosis such as low TAWSS and high PRT, OSI, and ECAP were high at the aorta proximal to the sinus. <h3>Conclusion</h3> Acuter polar angles are commonly associated to flow conditions leading to fewer HRAEs. Using a time-depend flow simulation, this study suggests that an "ideal acute" rather than an acuter polar angle might lead to such flow conditions.

A Novel Hybrid Single Ventricular Assist Device (SVAD) Strategy for a Neonate with Ventricular Septal Defect, Aortic Arch Hypoplasia, and Biventricular Dysfunction

Introduction Neonates requiring biventricular VAD (BiVAD) support remain a high-risk population. Common challenges include limited space for multiple cannulae, poor wound healing, and difficulties establishing adequate VAD fill and ejection. Given these concerns, we present a unique case using a hybrid procedure and SVAD implant in a neonate with two-ventricle(2V) circulation. Case Report Female term neonate (birth weight 3.2 kg; BSA 0.2 kg/m2) born with a moderate-sized ventricular septal defect (VSD), aortic arch hypoplasia, and severe biventricular dysfunction due to a MHY7 mutation. In light of her weight, likely need for biventricular support given her underlying cardiomyopathy and need for extensive arch repair, we elected to proceed with a hybrid SVAD support strategy. We hypothesized that this approach would decrease the duration of bypass and minimize the number of cannula over the traditional approach of VSD and arch repair with BiVAD support. We also hoped this strategy would provide improved LV decompression, thus improving pulmonary mechanics and nutritional support. On day 6 of life, she underwent atrial septectomy, bilateral PA band placement, and implant of a 10 ml Berlin EXCOR using a 6 mm EXCOR cannula in the right atrium and a 5 mm EXCOR cannula in the main pulmonary artery. A PDA stent was placed using a perventricular approach. She progressed well post-operatively with discontinuation of inotropic support on post-operative day (POD) 3 and extubation on POD 4. VAD fill and ejection have been appropriate. The clinical course is noteworthy for diaphragm paralysis requiring plication and ongoing BiPAP support. Additionally, she developed NEC on POD 23 and has only tolerated ∼30% of her nutritional needs enterally. To date, she has remained on VAD support > 100 days while awaiting transplant. Summary We present a unique case of a neonate with 2V congenital heart disease who has been supported with a hybrid SVAD strategy using a Berlin EXCOR. While this approach has been advantageous in avoidance of VSD and arch repair and requiring fewer cannulae, it also has had challenges; namely, the need for ongoing respiratory and feeding support. We speculate that this may reflect the challenges of optimal PA band placement as well as difficulties providing balanced systemic and pulmonary flow on SVAD support.

A procedure for dual simple t-cannulation in the small intestine of pigs using a single right flank laparotomy

Singular cannulation in the small intestine of pigs is a common methodology for studying nutrient digestibility, delivering compounds into the gastrointestinal tract, or repeated tissue and digesta sampling. In that respect, it is an important tool for nutritionists and researchers. However, there is a dearth of detailed methodologies describing multiple intestinal cannulations using modern techniques. The objective of this experiment was to develop a single right flank laparotomy technique that allowed for imsertion of multiple cannulas in the small intestine, with minimal variation, and allowed for externalisation of both cannulas on the same lateral side as the laparotomy. Thirty gilts (L337 × Camborough) with an initial body weight of 30.2±0.78 kg underwent the procedure. Each gilt was equipped with a simple t-cannula in the terminal ileum, approximately 10 cm cranial to the ileocecal valve, and a second t-cannula in the jejunum 240 cm distal from where the duodenum is visually posterior to the transverse colon. The procedure used hallmarks of commonly implemented terminal ileal cannulation techniques, but modified the laparotomy location and cannula externalisation sites and used a novel approach for determining the more proximal cannula location to mitigate the need of a second laparotomy. Gilts were allowed to recover for a minimum of 7 d and were used for an average of 67 days in subsequent experimental trials. Cannula longevity was from 30 to 73 kg of body weight. Pigs were necropsied for surgical site gross examination and small intestine measurements at the end of the experiment. The jejunal cannula had a mean placement of 298.90±9.96 cm distal to the pyloric sphincter with a coefficient of variation of 3.33%. Hence, this procedure provided a single laparotomy technique for obtaining digesta from multiple locations of the small intestine, with minimal variation in proximal cannula placement.

Internal comparison between deuterium oxide (D2O) and L-[ring-13C6] phenylalanine for acute measurement of muscle protein synthesis in humans.

Stable isotope tracer methodologies are becoming increasingly widespread in metabolic research; yet a number of factors restrict their implementation, such as, i.v infusions, multiple cannulae, tissue samples, and significant cost. We recently validated the sensitivity of the orally administered stable isotope tracer deuterium oxide (D2O) for quantifying day-to-day changes in muscle protein synthesis (MPS). This method is less invasive, restrictive, and more cost-effective than traditional amino acid (AA) tracer techniques. In the present study, we hypothesized the sensitivity of our analytical techniques (GC-Pyrolysis-IRMS) would permit D2O-derived measurements of MPS over much shorter periods (i.e., hours) usually only possible using AA-tracer techniques. We recruited nine males (24 ± 3 year, BMI: 25 ± 3 kg·m−²) into an internally controlled comparison of D2O versus 13C AA-tracers. The day before the acute study subjects consumed 400 mL D2O, and on the study day, received a primed (0.3 mg·kg−1) continuous (0.6 mg·kg·h−1) i.v infusion of L-[ring-13C6]-phenylalanine to quantify MPS under both: (1) basal [postabsorptive] and; (2) stimulated [postprandial] that is, consumption of 20 g EAA, conditions. Measures of MPS yielded indistinguishable technique differences with respect to EAA, 13C: 0.065 ± 0.004 to 0.089 ± 0.006%·h−1 (P < 0.05) and D2O: 0.050 ± 0.007 to 0.088 ± 0.008%·h−1 (P < 0.05) with qualitatively similar increases. Our findings reveal that acute measurement of MPS, usually only possible using AA-tracers, are feasible over shorter periods with orally administered D2O when used in tandem with GC-Pyrolysis-IRMS. We conclude that this D2O approach provides a less invasive, cost-effective, and flexible means by which to quantify MPS acutely over several hours.

Local chemotherapy in the rat brainstem with multiple catheters: a feasibility study

Technical aspects of local chemotherapy in inoperable brainstem gliomas by convection-enhanced delivery (CED) are still under experimental considerations. In this study, we characterize the feasibility of multiple cannula placements in the rat brainstem. In 38 male Fisher rats, up to three guided screws were positioned in burr holes paramedian at 2.5 mm anterior and posterior to as well as at the lambdoid suture. Using Alzettrade mark pumps (1 microl/h flow rate over 7 days) either vehicle (5% dextrose) or 0.1 mg carboplatin was delivered via one, two, or three cannulas, respectively. During cannula insertion, electrocardiogram and respiratory rate was monitored. All rats were subsequently evaluated neurologically for 8 days. For drug distribution in coronal sections, the brain tissue concentration of platinum was measured. HE staining was used to evaluate the local site of drug delivery. Heart and respiratory rate remained within normal range during surgical procedure. Neurological scoring showed only mild neurological impairment in the groups receiving two or three cannulas, which resolved after vehicle delivery. However, after carboplatin delivery, this deficit remained unchanged. Drug distribution was more homogeneous in the three cannula group. Histological slices visualized edematous changes at the sight of cannula placement. The unilateral application of up to three cannulas in the brainstem of rats for local drug delivery studies is feasible. The remaining neurological deficit in carboplatin-treated animals underlines the need of low toxicity drugs for CED in the brainstem.

Overlapping Ablation Using a Coaxial Radiofrequency Electrode and Multiple Cannulae System: Experimental Study in ex-Vivo Bovine Liver

ObjectiveTo assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver.Materials and MethodsFor ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction.ResultsAt gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity.ConclusionUsing a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

Deep hypothermic circulatory arrest: Current status and indications

A number of groups have directed clinical and laboratory research efforts to define and delineate the limits of hypothermic circulatory arrest. The deleterious effects of cardiopulmonary bypass in small children are reviewed to place into historical perspective the impetus behind the development of hypothermic circulatory arrest. Among the advantages of deep hypothermic circulatory arrest are decreased exposure to cardiopulmonary bypass with its sequelae, improved operative field exposure, avoidance of multiple cannulas, and reduced postoperative edema. Because of concern regarding the effectiveness of the neurologic protection afforded by deep hypothermic circulatory arrest, a body of literature has developed that includes both clinical (eg, the Boston Circulatory Arrest Study) and laboratory investigations of the influence of pH strategy, hematocrit level, oxygen strategy, intermittent reperfusion, and their interaction on outcome measures. Concomitantly, changes in both cardiopulmonary bypass and circulatory arrest techniques have led surgeons to reconsider the indications for deep hypothermic circulatory arrest use in children. In the future it will be important to focus an equal degree of attention to refine methods of continuous cardiopulmonary bypass including innovative methods that allow avoidance of circulatory arrest. No clear guidelines are presently available for the congenital surgeon regarding how low flow can be reduced, at what temperature repair should be undertaken, and what duration of low flow can be used for particular circumstances of pH, hematocrit, and collateral return. Until this information is collected, the comprehensive information regarding circulatory arrest that has already been gathered allows this technique to be used more safely than innovative but unproven methods of continuous cardiopulmonary bypass. Copyright © 2002 by W.B. Saunders Company

A convenient and inexpensive method for chronically implanting multiple intracranial cannulae

A simple and inexpensive method is described for the chronic implantation of multiple cannulae in small animals. This method employs a simple die cast from dental acrylic cement which is then repeatedly used to retain the cannulae during implantation. No special workshop tools are required and assembly is rapid.