Yoon Sang Chung

Synthesis of ZnO Nanoparticles Embedded in a Polymeric Matrix; Effect of Curing Temperature

We studied ZnO nanoparticle formation in a polyimide (PI) film. Polyamic acid (PAA) was spin-coated onto Zn thin films and PAA/metal films were cured at various temperatures. Transmission electron microscopy was used to characterize oxide nanoparticles in the polyimide film. Nanosize ZnO particles were formed in the polyimide film regardless of the curing temperature. The size and the density of ZnO particles depended on the curing temperature. Th

Is Stopping Heparin Safe in Patients on Extracorporeal Membrane Oxygenation Treatment

Anticoagulation treatment during extracorporeal membrane oxygenation (ECMO) treatment is unavoidable. However, discontinuation of heparin infusion is necessary when challenges associated with the use of heparin, such as bleeding and thrombocytopenia, are encountered. The medical records of 94 adult (age ≥ 18 years) patients treated with ECMO from January 2011 to March 2015, at Chung-Ang University Hospital, Seoul, Korea, were reviewed. Among the 94 patients, 55 patients underwent ECMO treatment for three or more days. In 52.7% of these patients (n = 29, group A), heparin was stopped for three or more days because of thrombocytopenic events (< 50,000 cells/mm3), higher than target range (> 230 seconds) activated clotting time (ACT), bleeding complications, or the need for other surgical procedures. In 43.6% of patients (n = 24, group B), heparin was continuously infused during the entire ECMO process. The mean length of ECMO support after the initiation of heparin discontinuation in patients in group A was 10.2 ± 14.7 days. There were no intracardiac, intravascular, or intracircuit thrombotic complications in group A. There was no difference in the ECMO weaning success rate between the two groups (41.4% in group A vs. 54.2% in group B, p = 0.353). Heparin discontinuation can be considered in a select group of patients with coagulation abnormalities or bleeding.

Mechanical thrombectomy in cardiac myxoma stroke: a case report and review of the literature

Cardiac myxoma is the most common primary tumor of the heart. It is a rare cause of acute ischemic stroke and commonly not detected until after the stroke. There is no current guideline for the treatment of cardiac myxoma stroke and only a few cases of mechanical thrombectomy have been reported. We present a case of cardiac myxoma stroke in a 4-year-old boy treated with a stent-retrieval device and review the literature describing the safety and efficacy of mechanical thrombectomy in cardiac myxoma stroke. We also describe imaging features of the myxoma clot on susceptibility weighted images.

Comparison of Metal-Oxide Nanoparticle Formation in the Cu and Sn Thin Films by the Reaction with Polyimide

We developed a simple method of producing metal oxide nanoparticles by reacting a polyamic acid (PAA) with Cu or Sn metal films. Respective particle size, distribution, and morphology were characterized by transmission electron microscopy (TEM). The morphology of metal oxides dispersed in the polyimide is different in Cu and Sn metal films. The Cu2O particles were formed by the dissolution reaction between the polyamic acid and the Cu films. During curing, PAA dehydrates and converts to polyimide, accompanied by precipitation of Cu2O particles. The synthesized Cu2O particles were randomly dispersed within the polyimide. And their particle size was relatively uniform, having a narrow distribution. Mostly nanosize Cu2O particles were formed in the specimen made from 10 nm thick Cu film and the mixture of nanosize particles and Cu layers were observed in the 30 nm thick Cu film. On the other hands, the Sn film undergoes surface reaction with the polyamic acid. Therefore, the synthesized SnO2 particles existed only at the surface of the substrate. SnO2 particle size distribution was not uniform in the polyimide. Although particles were not distributed uniformly in the polyimide, they were confined in a monolayer. The different particle distributions were attributed to the reactivity difference of PAA with Cu and Sn films.

Effect of Temperature-Sensitive Poloxamer Solution/Gel Material on Pericardial Adhesion Prevention: Supine Rabbit Model Study Mimicking Cardiac Surgery

Objective We investigated the mobility of a temperature-sensitive poloxamer/Alginate/CaCl2 mixture (PACM) in relation to gravity and cardiac motion and the efficacy of PACM on the prevention of pericardial adhesion in a supine rabbit model. Methods A total of 50 rabbits were randomly divided into two groups according to materials applied after epicardial abrasion: PACM and dye mixture (group PD; n = 25) and saline as the control group (group CO; n = 25). In group PD, rabbits were maintained in a supine position with appropriate sedation, and location of mixture of PACM and dye was assessed by CT scan at the immediate postoperative period and 12 hours after surgery. The grade of adhesions was evaluated macroscopically and microscopically two weeks after surgery. Results In group PD, enhancement was localized in the anterior pericardial space, where PACM and dye mixture was applied, on immediate post-surgical CT scans. However, the volume of the enhancement was significantly decreased at the anterior pericardial space 12 hours later (P < .001). Two weeks after surgery, group PD had significantly lower macroscopic adhesion score (P = .002) and fibrosis score (P = .018) than did group CO. Inflammation score and expression of anti-macrophage antibody in group PD were lower than those in group CO, although the differences were not significant. Conclusions In a supine rabbit model study, the anti-adhesion effect was maintained at the area of PACM application, although PACM shifted with gravity and heart motion. For more potent pericardial adhesion prevention, further research and development on the maintenance of anti-adhesion material position are required.

Application of Lidocaine Jelly on Chest Tubes to Reduce Pain Caused by Drainage Catheter after Coronary Artery Bypass Surgery

The objective of this study was to assess the effect of lidocaine jelly application to chest tubes on the intensity and duration of overall pain, chest tube site pain and the required analgesics for postoperative pain relief in coronary artery bypass graft (CABG) patients. For patients in group L, we applied sterile 2% lidocaine jelly on the chest tubes just before insertion, and for patients in group C, we applied normal saline. Overall visual analogue scale (VAS), maximal pain area with their VAS were documented postoperatively, and the frequency that button of patient-controlled analgesia was pressed (FPB) and total fentanyl consumption were assessed. The number of patients who complained that tube site was the most painful site was significantly higher in group C than in group L (85% vs. 30% at extubation, P<0.001). The overall VAS score was significantly higher in group C than in group L (39.14±12.49 vs. 27.74±13.76 at extubation, P=0.006). After all of the tubes were removed, the VAS score decreased more in group C (5.74±4.77, P<0.001) than in group L (3.05±2.48, P<0.001). FPB and total fentanyl consumption were significantly higher in group C than in group L (73.00, 59.00-78.00 vs. 34.00, 31.00-39.25, P<0.001; 2,214.65±37.01 vs. 1,720.19±361.63, P<0.001, respectively). Lidocaine jelly application is a very simple way to reduce postoperative pain by reducing chest tube site pain after CABG. (Clinical Trials Registry No. ACTRN 12611001215910)

Intermetallic growth between Sn-Ag-(Cu) solder and Ni

The intermetallic formation between Sn-Ag-(Cu) solders and metal pads was characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffractometry (XRD). The intermetallic phase formed in the interface between Sn-Ag-Cu and Au/Ni/Cu pad in a tape BGA package is likely to be a ternary compound of Cu-Ni-Sn from EDS analysis. Cu was also segregated in the solder/Ni interface. XRD analysis confirmed that /spl eta/-Cu/sub 6/Sn/sub 5/ type intermetallic phase formed in the interface between Cu containing solders and Ni substrates and Ni/sub 3/Sn/sub 4/ intermetallic formed in the Sn-Ag solder/Ni interface. The Cu atoms in the solder seem to diffuse in the solder/Ni interface and to form /spl eta/-Cu/sub 6/Sn/sub 5/ type intermetallic in the Sn-Ag-Cu specimens. The increase in the Cu concentration of the solder increased the intermetallic thickness after reflow.

Neonatal Patent Ductus Arteriosus Ligation Operations Performed by Adult Cardiac Surgeons

Background Patent ductus arteriosus (PDA) ligation is usually performed by congenital cardiac surgeons. However, due to the uneven distribution of congenital cardiac surgeons in South Korea, many institutions depend solely on adult cardiac surgeons for congenital cardiac diseases. We report the outcomes of PDA ligations performed by adult cardiac surgeons at our institution. Methods The electronic medical records of 852 neonates at Chung-Ang University Hospital, Seoul, South Korea from November 2010 to May 2014 were reviewed to identify patients with PDA. Results Of the 111 neonates with a diagnosis of PDA, 26 (23%) underwent PDA ligation. PDAs were ligated within 28 days of birth (mean, 14.5±7.8 days), and the mean gestational age of these patients was 30.3±4.6 weeks (range, 26 to 40 weeks) with a mean birth weight of 1,292.5±703.5 g (range, 480 to 3,020 g). No residual shunts through the PDA were found on postoperative echocardiography. There was 1 case of 30-day mortality (3.8%) due to pneumonia, and 6 cases of in-hospital mortality (23.1%) after 30 days, which is comparable to results from other centers with congenital cardiac surgery programs. Conclusion Although our outcomes may not be generalizable to all hospital settings without a congenital cardiac surgery program, in select centers, PDA ligations can be performed safely by adult cardiac surgeons if no congenital cardiac surgery program is available.

An abnormal chord inserting to a subaortic membrane in hypertrophic cardiomyopathy: rare anatomical combination

Figure 1: A rod-like shadow (circle) in the left ventricular outflow tract of a 45-year-old female hypertrophic cardiomyopathy patient on echocardiogram (A) and cardiac magnetic resonance imaging (B). Mildly thickened subaortic membrane (C, Video 1). A thickened chorda, originating from the abnormal head of the anterolateral papillary muscle inserting to the subaortic membrane (D, Video 1). Specimens (E).