Research Spotlight

McLaughlin, C. M., M. Bennett, N. Channabasappa, J. Journeycake and H. G. Piper (2018). “Anticoagulation results in increased line salvage for children with intestinal failure and central venous thrombosis.” J Pediatr Surg. Feb 7. [Epub ahead of print].

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PURPOSE: The purpose of this study was to investigate whether anticoagulation (AC) results in thrombus resolution and increased line longevity in children with intestinal failure (IF) and catheter-associated central venous thrombosis (CVT). METHODS: A retrospective, single institution review was performed of children with IF who were dependent on parenteral nutrition with known CVT between 2006 and 2017. Frequency of catheter-related complications including infection, occlusion, and breakage were compared 18months prior to and after starting AC. Thrombus resolution during anticoagulation was also determined. Data were analyzed using Poisson regression. p-Values <0.05 were considered significant. RESULTS: Eighteen children had >/=1 CVT, with the subclavian vein most commonly thrombosed (44%). All children were treated with low molecular weight heparin, and 6 patients (33%) had clot resolution on re-imaging while receiving AC. Bloodstream infections decreased from 7.9 to 4.4 per 1000 catheter days during AC (p=0.01), and the number of infections requiring catheter replacement decreased from 3.0 to 1.0 per 1000 catheter days (p=0.01). There were no significant differences in line occlusions or breakages. CONCLUSION: Anticoagulation for children with intestinal failure and central venous thrombosis may prevent thrombus propagation, and decrease blood stream infections and line replacements. Further research is needed to determine optimal dosing and duration of therapy. LEVEL OF EVIDENCE: III; Retrospective Comparative Study.

Lima, B., O. Dur, J. Chuang, T. Chamogeorgakis, D. J. Farrar, K. S. Sundareswaran, J. Felius, S. M. Joseph, S. A. Hall and G. V. Gonzalez-Stawinski (2018). “Novel Cardiac Coordinate Modeling System for Three-Dimensional Quantification of Inflow Cannula Malposition of HeartMate II LVADs.” Asaio j 64(2): 154-158.E

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Optimal function of left ventricular assist devices (LVADs) depends on proper alignment of the inflow cannula (IC). Quantitative guidelines for IC angulation are lacking because of variation in cardiac geometry and difficulty in analyzing three-dimensional (3D) cannula orientation relative to the left ventricle (LV). Based on contrast-enhanced computed tomography images from five normal and five clinically malpositioned IC cases in patients with HeartMate II LVADs, we developed a method for 3D quantification of IC malpositioning. Using Mimics image software (Materialise, Leuven, Belgium), the native heart, major arteries, and LVAD were segmented to create patient-specific 3D models, allowing LV cavity volume and long-axis length to be measured directly. The deviation of the IC was quantified in a cylindrical coordinate system at the IC insertion point relative to the mitral valve and septum, and IC occlusion was assessed by the distance between cannula inlet and the proximal endocardium. Compared with normal cases, patients with malpositioned pumps had shorter LV length (p = 0.03) and reduced pump pocket depth (p = 0.009). Malpositioned pumps may experience greater obstruction by the nearby myocardium. This quantitative 3D modeling tool may help identify different modes of pump malalignment and migration and may facilitate preoperative planning and minimally invasive approaches via virtual LVAD implantation.

Lee, L., J. Kelly, G. J. Nassif, D. Keller, T. C. Debeche-Adams, P. A. Mancuso, J. R. Monson, M. R. Albert and S. B. Atallah (2018). “Establishing the learning curve of transanal minimally invasive surgery for local excision of rectal neoplasms.” Surg Endosc 32(3): 1368-1376.

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INTRODUCTION: Transanal minimally invasive surgery (TAMIS) is an endoscopic operating platform for local excision of rectal neoplasms. However, it may be technically demanding, and its learning curve has yet to be adequately defined. The objective of this study was to determine the number of TAMIS procedures for the local excision of rectal neoplasm required to reach proficiency. METHODS AND PROCEDURES: All TAMIS cases performed from 07/2009 to 12/2016 at a single high-volume tertiary care institution for local excision of benign and malignant rectal neoplasia were identified from a prospective database. A cumulative summation (CUSUM) analysis was performed to determine the number of cases required to reach proficiency. The main proficiency outcome was rate of margin positivity (R1 resection). The acceptable and unacceptable R1 rates were defined as the R1 rate of transanal endoscopic microsurgery (TEM-10%) and traditional transanal excision (TAE-26%), which was obtained from previously published meta-analyses. Comparisons of patient, tumor, and operative characteristics before and after TAMIS proficiency were performed. RESULTS: A total of 254 TAMIS procedures were included in this study. The overall R1 resection rate was 7%. The indication for TAMIS was malignancy in 57%. CUSUM analysis reported that TAMIS reached an acceptable R1 rate between 14 and 24 cases. Moving average plots also showed that the mean operative times stabilized by proficiency gain. The mean lesion size was larger after proficiency gain (3.0 cm (SD 1.5) vs. 2.3 cm (SD 1.3), p = 0.008). All other patient, tumor, and operative characteristics were similar before and after proficiency gain. CONCLUSIONS: TAMIS for local excision of rectal neoplasms is a complex procedure that requires a minimum of 14-24 cases to reach an acceptable R1 resection rate and lower operative duration.

Kraeutler, M. J., K. V. Patel, A. Hosseini, G. Li, T. J. Gill and J. T. Bravman (2018). “Variability in the Clock Face View Description of Femoral Tunnel Placement in ACL Reconstruction Using MRI-Based Bony Models.” J Knee Surg. Feb 8. [Epub ahead of print].

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Though controversial, the “clock face view” of the intercondylar notch remains a way some surgeons communicate regarding placement of the femoral tunnel in anterior cruciate ligament reconstruction. The purpose of this study was to quantify the differences in angle measurement between several previous descriptions of the clock face view by using a new reference standard. Three-Tesla magnetic resonance imaging (MRI) was used to scan 10 human knees to create three-dimensional MRI-based bony models which were used for measurements. A standardized clock face view was developed with the knee flexed to 90 degrees using the junction of the cartilage and cortex of the medial and lateral surfaces of medial and lateral femoral condyles as the 3 o’clock and 9 o’clock, respectively, with the 12 o’clock established as the midpoint of the roof of the intercondylar notch. With the knee viewed at 90 degrees of flexion, an “idealized” femoral tunnel position was plotted on the medial wall of the lateral femoral condyle at 30 degrees (corresponding to the 10 o’clock or 2 o’clock position). The clock faces as described by Edwards et al, Heming et al, and Mochizuki et al were each then overlaid on this same model and the difference in measurement calculated. The average angles measured when the previously described clock faces were projected onto the idealized clock face view comparing a mark made at 30 degrees were 47.7 degrees , 7.2 degrees , and 49.8 degrees for the methods described by Edwards et al, Heming et al, and Mochizuki et al, respectively (all p < 0.001). Significant variation exists between angle measurements in simulated femoral tunnel placement based on the varying descriptions of the intercondylar clock face.

Kim, P. T. W. and G. B. Klintmalm (2018). “Reply to Gastaca on portal vein flows and outcomes after liver transplantation.” Liver Transpl. Feb 16. [Epub ahead of print].

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We appreciate the comments provided by Gastaca et al. on our previously published study on the impact of portal flows after portal vein thrombendvenectomy in liver transplantation, and we share their enthusiasm for the study of portal flows in liver transplantation. The authors’ comments were based on their interesting study that documented a correlation between portal vein flows and outcomes after liver transplantation. In their study, contrary to what the authors had conveyed in their comments, low portal flow of less than 1000 mL/minute was in fact associated with a higher rate of primary nonfunction, and there was a trend toward lower graft survival rates in the lower portal flow group, which did not reach statistical significance due to the small sample size. The emphasis on the rate of early graft dysfunction as the main variable of the study may be unfounded because this is not a common variable that is studied. We do agree with the authors that the portal flow may be dependent on the donor and recipient factors such as degree of portal hypertension, the size of the recipient, and the size of the graft. Therefore, we do need to be cognizant of these factors when making intraoperative decisions regarding portal flow. The authors suggest that portal flow of <80 mL/minute/100 g graft weight is an important value that is associated with a significantly higher risk of developing early graft dysfunction. This is an interesting value, but it may correlate with 1000 mL/minute after all when the fact that an average weight of a deceased donor liver of over 1000 g is taken into account. It would be helpful for the authors to provide the details of the graft weight, actual portal vein flows, and whether any biases may have been introduced for this analysis, which was based on 148 patients only. We agree that more studies are needed to further characterize the impact of different demographic variables on portal vein flows and that the strategies to provide liver allographs with adequate flow are of paramount importance for graft survival. (Full text of this letter to the editor; no abstract available.)