Nonabsorbable Polymer Research Articles

Techniques to Secure Renal Hilum in Laparoscopic Donor Nephrectomy

Laparoscopic donor nephrectomy is the standard of care in donor kidney procurement for renal transplantation. Use of nonabsorbing polymer locking clips for securing the renal artery in this procedure is widely practiced. The US FDA has given instructions contraindicating the use of Hem-o-lok clips in securing renal artery in donor nephrectomy. This article reviews the modalities for securing renal artery in laparoscopic nephrectomy published in the last decade.

Polypropylene‐containing synthetic mesh devices in soft tissue repair: A meta‐analysis

The acute and chronic host tissue response to synthetic and biologic mesh devices for abdominal hernia repair is thought to ultimately determine clinical outcomes such as adhesion formation, device shrinkage, cellular response, and neotissue formation. A meta-analysis of 38 publications was performed to assess these outcomes in six different treatment groups depending on mesh composition: polypropylene (PP), PP in combination with nonabsorbable polymers, PP in combination with absorbable polymers, non-PP polymers, non-PP in combination with absorbable polymers, and natural materials. Despite showing the least device shrinkage, meshes made entirely from PP generally showed the most adverse host tissue response. PP devices with an absorbable component elicited a more beneficial host response with respect to connective tissue adhesion and tissue inflammation than devices made from PP alone. These devices also provided a high level of mechanical stability resulting in a reduced level of adhesion formation and device shrinkage postapplication. However, the compositional heterogeneity within certain groups, that is, devices of non-PP polymers, non-PP in combination with absorbable polymers, and natural materials, did not allow for a more detailed evaluation or the identification of a single composition with superior host tissue response characteristics.

Open Versus Laparoscopic Donor Nephrectomy: Perioperative Parameters and Graft Functions

Objective With the developments in laparoscopic surgery, open donor nephrectomy has been widely replaced by laparoscopic donor nephrectomy. Presented herein is the comparison of laparoscopic live donor nephrectomy (LLDN) and open live donor nephrectomy (OLDN) results performed at our institute. Materials and Methods Patients who underwent OLDN between July 2006 and August 2008 or LLDN between August 2008 and July 2010 were included in this retrospective age- and gender-matched case-controlled study. OLDN was performed with a 45° semi-flank position using a self-retaining retractor. LLDN operations were performed used a 90° flank position by the transperitoneal route under 12–15 mm Hg carbon dioxide (CO 2) pressure. A Pfannenstiel incision was used in all LLDN for graft extraction. The renal artery and vein were controlled with Satinsky clamps in OLDN, whereas renal arteries were controlled with nonabsorbable polymer locking clips and renal veins with 2.5/45 mm EndoGIA vascular staplers in LLDN. Results Thirty patients underwent OLDN and 31 LLDN. The mean ages among the OLDN and LLDN patients were 44.9 ± 21.9 and 46.3 ± 18.4, respectively. There was no significant difference in mean age and gender distribution of patients between OLDN and LLDN groups by the design of the study. The OLDN group consisted of 4 (13%) right and 26 (87%) left nephrectomies; the LLDN group consisted of 3 (9%) right and 28 (91%) left nephrectomies. Mean operative time was 110 ± 18 and 101 ± 28 minutes for OLDN and LLDN, respectively ( P < .05; Mann-Whitney U test). Estimated blood loss was 35 ± 15 mL among the OLDN group and 15 ± 24 mL for the LLDN group. Mean hospitalization time in the OLDN and LLDN groups were 3.8 ± 0.5 and 2.6 ± 0.6 days, respectively. There were no conversions to open surgery in the LLDN group. Mean warm ischemia time in the OLDN and LLDN groups were 140 ± 58 seconds and 203 ± 21 seconds, respectively ( P < .05; Mann-Whitney U test). There was no difference in recipient serum creatinine levels at 1 week after surgery. Conclusion LLDN was superior to OLDN in terms of operative time, estimated blood loss, length of hospital stay, and postoperative pain. Longer warm ischemia time in the LLDN group did not translate into worse graft function in the recipients.

Micropatterning: Ultrafast Large‐Area Micropattern Generation in Nonabsorbing Polymer Thin Films by Pulsed Laser Diffraction (Small 6/2011)

AbstractAn ultrafast, parallel, and beyond‐the‐master micropatterning technique for ultrathin (30−400 nm) nonabsorbing polymer films by diffraction of laser light through a 2D periodic aperture is reported. The redistribution of laser energy absorbed by the substrate causes self‐organization of polymer thin films in the form of wrinklelike surface relief structures caused by localized melting and freezing of the thin film. Unlike conventional laser ablation and laser writing processes, low laser fluence is employed to only passively swell the polymer as a pre‐ablative process without loss of material, and without absorption/reaction with incident radiation. Self‐organization in the thin polymer film, aided by the diffraction pattern, produces microstructures made up of thin raised lines. These regular microstructures have far more complex morphologies than the mask geometry and very narrow line widths that can be an order of magnitude smaller than the openings in the mask. The microstructure morphology is easily modulated by changing the film thickness, aperture size, and geometry, and by changing the diffraction pattern.

Ultrafast Large‐Area Micropattern Generation in Nonabsorbing Polymer Thin Films by Pulsed Laser Diffraction

An ultrafast, parallel, and beyond-the-master micropatterning technique for ultrathin (30-400 nm) nonabsorbing polymer films by diffraction of laser light through a 2D periodic aperture is reported. The redistribution of laser energy absorbed by the substrate causes self-organization of polymer thin films in the form of wrinklelike surface relief structures caused by localized melting and freezing of the thin film. Unlike conventional laser ablation and laser writing processes, low laser fluence is employed to only passively swell the polymer as a pre-ablative process without loss of material, and without absorption/reaction with incident radiation. Self-organization in the thin polymer film, aided by the diffraction pattern, produces microstructures made up of thin raised lines. These regular microstructures have far more complex morphologies than the mask geometry and very narrow line widths that can be an order of magnitude smaller than the openings in the mask. The microstructure morphology is easily modulated by changing the film thickness, aperture size, and geometry, and by changing the diffraction pattern.

Technical Modifications in Laparoscopic Appendectomy

The technique of laparoscopic appendectomy has been modified several times in the past 20 years. In this report, we have described our modifications regarding the position of ports placement and closure of the base of appendix. Three surgeons successfully performed laparoscopic appendectomy in 108 cases with these modifications during the 3-year period. The first 10 mm port is placed in the periumbilical region. The second 10 mm and third 5 mm ports are inserted in the left and right side of abdomen below the pubic hairline respectively. Then the telescope is transferred from the periumbilical to the left suprapubic port. This mode of access leads to optimal ergonomics and cosmesis. For securing the base of appendix, only one Hem-o-lok clip (nonabsorbable polymer clip) is applied on each side. The use of Hem-o-lok clip is simple, safe and decreases the time and cost of laparoscopic appendectomy.

Comparison of Renal Artery Occlusion Techniques in Hand-Assisted Laparoscopic Living Donor Nephrectomy

This study assessed differences in outcomes between left renal artery clipping and stapling techniques in hand-assisted laparoscopic living donor nephrectomy (HALDN). From 2003 to 2007, 55 HALDN procedures were performed by one laparoscopy-trained urologist. During the first 30 months, 27 consecutive HALDN patients underwent renal artery occlusion with two nonabsorbable polymer locking clips (group 1). The subsequent 18 months saw 28 consecutive HALDN patients receive three-row vascular stapling to occlude the renal artery (group 2). The preoperative patient factors were age, sex, body mass index, serum creatinine (Cr), and presence of supernumerary left renal artery. Intraoperative factors included estimated blood loss (EBL), operative time (OT), and warm ischemia time (WIT). Postoperative data were 24-hour Cr and hemoglobin concentration, transfusion requirement, hospitalization time, and complications. Data are presented as mean +/- standard deviation and analyzed using parametric tests (alpha = 0.05). No significant difference was found between groups with respect to preoperative factors, OT, and EBL; however, WIT was shorter in group 2 (3.6 +/- 0.2 vs 2.6 +/- 0.3, P = 0.048). Within-group comparisons revealed longer WIT for patients with supernumerary renal artery compared with those with a single artery (group 1, P = 0.044; group 2, P = 0.042). Moreover, no major between-group variations were seen in postoperative donor outcomes. Left renal artery ligation during HALDN using a three-row vascular stapler is safe and yields donor outcomes comparable to dual polymer clips. In addition, left renal artery stapling may decrease WIT compared with dual clipping.

Do Multilayer Crystals Nucleate in Suspensions of Colloidal Rods?

We study the isotropic-to-crystal transformation in a mixture of colloidal hard rods and nonabsorbing polymer using computer simulations. We determine the height of the nucleation barrier and find that the critical cluster consists of a single crystalline layer growing laterally for all polymer fugacities considered. At lower supersaturation, the free energy of a single hexagonally packed layer increases monotonically with size, while the nucleation barrier of a second crystalline layer is extremely high. Hence, the nucleation of multilayer crystals is never observed. Multilayer crystals form only in the spinodal decomposition regime, either where, in an intermediate stage, single crystalline membranes coalesce into multilayer clusters or where, at higher polymer fugacity, smaller clusters of rods stack on top of each other to form long filaments. Eventually, these transient structures evolve into a thermodynamically stable bulk crystal phase.

Multidetector computed tomographic characteristics of nonabsorbable polymer versus titanium ligature clips in a vascular model

Multidetector cardiac computed tomography is commonly performed to evaluate coronary bypass grafts, but titanium clips result in significant image artifact. Multidetector cardiac computed tomographic characteristics of newly developed nonabsorbable polymer clips are unknown. This study was undertaken to compare the image characteristics of polymer clips and titanium clips applied to a vascular model. A vascular model was created with two porcine internal thoracic arteries. Branches were ligated with 5 titanium clips on one vessel and 6 polymer clips on the other. Vessels were imaged under pressure with normal saline solution in a 16-detector computed tomographic scanner. Image intensity was quantified in absolute Hounsfield units for clips and adjacent lumen and then normalized to the average lumen intensity. No difference in absolute intensity was found between polymer clips and adjacent lumen (polymer clip 1021.2 +/- 19.0 absolute Hounsfield units, adjacent lumen 1001.7 +/- 15.7 absolute Hounsfield units, P = .095). A statistically significant difference was noted between titanium clips and adjacent lumen (titanium clips 3408.8 +/- 177.3 absolute Hounsfield units, adjacent lumen 1072.7 +/- 52.1 absolute Hounsfield units, P < .0001). A statistically significant difference was also noted between titanium and polymer clips (P < .0001). The use of polymer clips in coronary bypass grafts should result in significantly improved multidetector cardiac computed tomographic image quality.

Single Access Site Laparoscopic Radical Nephrectomy: Initial Clinical Experience

We present the initial clinical experience with single access site (SAS) laparoscopic radical nephrectomy. An 86-year-old woman presented with an 8-cm central-enhancing right renal lesion. The patient elected to undergo a laparoscopic radical nephrectomy. A 7-cm paramedian incision was made just lateral to the left rectus muscle and cranial to the umbilicus. A GelPort was inserted into the incision. Three trocars (12 mm, 10 mm, and 5 mm) were placed through the access port, and only standard laparoscopic instruments were used. The kidney was mobilized in the standard fashion. Controlling the renal artery with nonabsorbable polymer clips and the renal vein with a stapling device, the specimen was manipulated into a laparoscopic retrieval bag and removed intact. Hemostasis was confirmed, the GelPort was removed, and the 7-cm incision was closed. The procedure was completed in 96 minutes without complications. Blood loss was estimated to be 10 mL. Postoperatively, the patient was treated with intermittent intravenous and oral analgesics. She was discharged on postoperative day 2 and tolerated a regular diet. This represents the initial report of an SAS laparoscopic radical nephrectomy, with intact specimen extraction. Using standard laparoscopic instrumentation, the procedure was performed safely and effectively, with minimal blood loss, and short hospitalization. Additional evaluation and development of this type of approach and instrumentation may allow for further expansion of SAS laparoscopic surgery in the future.

Use of Nonabsorbable Polymer Ligaclip in Hand-Assisted Laparoscopic Nephrectomy for Living Donor

Background Laparoscopic living donor nephrectomy for kidney transplantation is a technique that began in South America only recently. This procedure offers several advantages compared with open nephrectomy due to the minor pain, better cosmetic results, and shorter length of hospital stay. Herein we have described our experience with the use of nonabsorbable polymer ligaclip (NPL) to control the renal artery, vein, and ureter in hand-assisted laparoscopic donor nephrectomy (HALN). Methods We performed a review of 85 HALNs for renal transplantation at our institution between January 2004 and August 2007. We evaluated the preoperative characteristics of the donor, surgical parameters, and complications. Results Fifty six percent of donors were men. Mean donor age was 34.4 years (range = 18 to 60). Left-sided nephrectomy was performed in 85%. Mean surgical time was 132 minute (range = 90 to 240) and among the last 35 nephrectomies, 120 minute (range = 90 to 180). Mean warm ischemia time was 240 seconds (range = 120 to 420). Conversion rate was 1.1%. Mortality was one case (1.1%) secondary to an episode of massive pulmonary thromboembolism. Mean length of hospital stay was 2.5 days (range 2 to 5) and mean blood loss, 125 mL. No complication related to the NPL was observed. Conclusions Laparoscopy living donor nephrectomy was a safe procedure for kidney transplantation. The training and experience of the surgeon was reflected in shorter times of surgery. The NPL was safe and cost-effective, not increasing morbidity of the procedure.

The Use of Polymer Clips in Transperitoneal Laparoscopic Nephropexy

Here we report a patient with symptomatic mobile kidney (nephroptosis) who was treated successfully with transperitoneal laparoscopic nephropexy with the use of nonabsorbable polymer clips. In this procedure, clips were used on Gerota's fascia to fix the kidney to the transversus abdominis fascia and the triangular ligament. This method is easier and requires less time than previously reported techniques.

Late-Appearing Abscesses after Injections of Nonabsorbable Hydrogel Polymer for HIV-Associated Facial Lipoatrophy

A 46-year-old HIV-positive male with a history offacial lipoatrophy presented with 3 days of acuteswelling, redness, and tenderness of the left cheek.He had received a series of facial Bio-Alcamid in-jections 3 years prior at a Tijuana, Mexico, clinicknown to specialize in Bio-Alcamid injections fortreatment of HIV facial lipoatrophy. The patientreported no problems with the implant until he un-derwent a dental procedure where the dentist sus-pected that the Bio-Alcamid implant may have beenpunctured with a needle used to deliver intraoralanesthesia. Within 24 hours after the dental proce-dure, he developed acute tenderness and swelling ofthe left cheek at which point 875mg of amoxicillinclavulanate three times daily was initiated. He wasreferred to our clinic (D.H.J.) 3 days later when theapparent abscess failed to respond to antibiotictherapy.Physical exam revealed a healthy male in no acutedistress. There was an 8.5 7-cm tender, fluctuantabscess on the left cheek. The HIVinfection was wellcontrolled on antiretroviral therapy, with a recentCD4 count of 500 and a viral load of 20,000. Anincision and drainage procedure was performed witha No. 11 blade stab incision under 1% lidocainewith epinephrine. Copious amounts of thick, puru-lent, yellow contents were drained. Routine cultureof the drained material was negative, while ananaerobic culture grew 21Propionibacteriumacnes (note that the patient was taking amoxicillinclavulanate at the time of the incision and drainageprocedure). Routine histology of the drained

Early and Late Complications after a Nonabsorbable Hydrogel Polymer Injection: A Series of 14 Patients and Novel Management

GOLDAN, OREN MD; GEORGIOU, IOANNIS MD; GRABOV-NARDINI, GIL MD; REGEV, ELI MD; TESSONE, ARIEL MD; LIRAN, ALON MD; HAIK, JOSEF MD; MENDES, DAVID MD; ORENSTEIN, ARIE MD; WINKLER, EYAL MD* Author Information

Late-Appearing Abscesses after Injections of Nonabsorbable Hydrogel Polymer for HIV-Associated Facial Lipoatrophy

JONES, DEREK H. MD*; CARRUTHERS, ALASTAIR MD†; FITZGERALD, REBECCA MD‡; SARANTOPOULOS, G. PETER MD§; BINDER, SCOTT MD§ Author Information

A Tertiary Amino-Containing Polymethacrylate Polymer Protects Mucus-Covered Intestinal Epithelial Monolayers Against Pathogenic Challenge

We examined the cytoprotective influences of the mucoadhesive polymer, poly(DMAEMA), on human mucus-producing intestinal epithelial monolayers against two bacterial exotoxins and S. typhimurium. Direct anti-bacterial effects were also assessed against S. typhimurium. In the presence and absence of mucus, untreated or poly(DMAEMA)-exposed monolayers were challenged with S. typhimurium or supernatants containing either cholera (CTx) or C. difficile toxins. Assays included LDH, cytokine secretion, cyclic AMP (cAMP) and microscopy to visualise bacterial adherence by monolayers. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of poly(DMAEMA) against S. typhimurium were established, along with a time-kill study. CTx and C. difficile toxin induced LDH release from E12 monolayers. CTx also elevated intracellular epithelial cAMP, while S. typhimurium induced basolateral IL-8 secretion. Pre-treatment of E12 monolayers with poly(DMAEMA) reduced these effects, but only in the presence of mucus. The polymer co-localised with S. typhimurium in mucus and reduced bacteria-epithelia association. Poly(DMAEMA) was directly bactericidal against S. typhimurium at 1 mg/ml within 30 min. Poly(DMAEMA) may have potential as a non-absorbed polymer therapeutic against infection. These effects were mediated by a combination of physical interaction with mucus and by direct bacterial killing.

Mechanisms of Hemostatic Failure During Laparoscopic Nephrectomy: Review of Food and Drug Administration Database

To compare the complications with endovascular stapling devices, nonlocking titanium clips, and nonabsorbable polymer ligating (Hem-o-lok) clips during laparoscopic nephrectomy. The Food and Drug Administration Manufacturer and User Facility Device Experience Database was retrospectively reviewed for reports dated from January 1992 to March 2006 using the key words "nephrectomy" and "kidney." All episodes of pure and hand-assisted laparoscopic nephrectomy were evaluated. Of 2172 total nephrectomy or kidney-related reports, 352 reported failure using laparoscopic hemostatic devices to secure the renal vasculature, and 223 complications (63%) resulted during the use of endovascular stapling devices, 111 (33%) from nonlocking titanium clips and 18 (5%) from locking clips. The leading causes of failure reported in stapling devices were staple line malformation (47%) and locking up (29%). In titanium clips, jamming/feeding difficulties (27%) and trouble closing or "scissoring" clips (26%) were the most common. In locking clips, dislodgement (44%) was most frequently reported. Three, one, and three deaths were reported after the use of the stapling device, titanium clip, and locking clip device, respectively. All three methods used to secure the renal hilum in laparoscopic nephrectomy can result in malfunction. Because the overall denominator of use is not known, it would be inappropriate to conclude that one device is safer than another. When they occurred, these device malfunctions were potentially serious. Knowledge of the possible mechanisms of failure seen with each device could allow surgeons to anticipate potential complications and, therefore, perform laparoscopic surgery more safely.

Hem-o-Lok Clips to Control Both the Artery and the Vein during Laparoscopic Nephrectomy: Personal Experience and Review of the Literature

Control and division of the renal vessels is a critical step in laparoscopic nephrectomy. Although the linear cutting stapler is easy to use, a 1.7% malfunction rate has been reported, and the consequences of this failure can be serious, including often-emergency conversion to an open procedure and even death. We reviewed the purely laparoscopic nephrectomies performed in our center, in which both the renal artery and the vein were secured using only nonabsorbable polymer ligating (NPL) clips. Our purpose was to evaluate the reliability, safety, and cost-effectiveness of this surgical approach. We retrospectively reviewed our 31 laparoscopic nephrectomies performed from November 2002 to November 2005. In all the procedures, both the renal artery and the renal vein were secured using only NPL clips. For each patient, the operative time, estimated blood loss, early and late complications, and length of hospital stay were analyzed. Further, we performed a MEDLINE search for laparoscopic nephrectomies in which both the renal artery and the vein were secured using only Hem-o-lok clips. No renal vessel injuries, cases of clip dislodgement or slippage, or bleeding were recorded. Worthy of note, we achieved a meaningful reduction in the cost per procedure. To the best of our knowledge, renal-pedicle control exclusively with Hem-o-lok clips during purely laparoscopic nephrectomy has not been yet published. Any device or technique for vascular control is prone to malfunction in either open or laparoscopic surgery. The described approach is safe, reliable, rapid, and inexpensive.

Sorghum Bran in the Diet Dose Dependently Increased the Excretion of Catechins and Microbial-Derived Phenolic Acids in Female Rats

Sorghum bran is concentrated with procyanidins (predominately polymers), which may be beneficial for health in humans; however, the bioavailability of procyanidins is not well-understood. Female Sprague-Dawley rats were fed an AIN93G diet containing 0, 5, 10, 20, or 40% Hi-tannin sorghum bran (n = 5-7 for each group) for 50 days. Sorghum bran contained 23.3 mg/g of procyanidins. The urinary excretions of catechin, epicatechin, methylated catechins, and phenolic acids were analyzed using liquid chromatography-tandem mass spectrometry. Sorghum bran dose dependently increased the urinary excretion of catechin (0-2.2 nmol/day) and 3'-O-methylcatechin (0-9.5 nmol/day). Their serum concentrations also increased with dose (range of 0-14 nM for 3'-O-methylcatechin). Among the 14 phenolic acids analyzed, 3,4-dihydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, and 4-hydroxyphenylacetic acid dominated in the serum (1.8-8 micromol/L). In the urine, 3-methoxy-4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and 3-hydroxyphenylpropionic acid dominated and their excretion increased significantly with the level of sorghum bran in the diet. The summed phenolic acid excretion was 0.8 micromol/day in the control group and increased to 23 micromol/day for 40% sorghum bran group. The hippuric acid excretion ranged from 2.2 to 16.2 micromol/day and peaked in the 10% sorghum bran group. On the basis of chromic oxide, a nonabsorbable marker, total procyanidins and polymers disappeared progressively, and significant degradation occurred in the cecum and colon. Catechins and procyanidins in sorghum were bioavailable; however, bacteria-derived phenolic acids were the predominant metabolites of procyanidins. Procyanidins degraded in the gastrointestinal tract. Depolymerization was not observed.

Reported Failures of the Polymer Self-Locking (Hem-O-Lok) Clip: Review of Data from the Food and Drug Administration

New technology has played an important role in the proliferation of laparoscopy within urology. A central issue remains meticulous hemostasis, particularly for larger vessels (e.g., renal artery and vein). This paper presents available information regarding failure of the widely utilized nonabsorbable polymer Hem-o-lok clip (Weck Closure Systems, Research Triangle Park, NC), introduced in 1999. The Food and Drug Administration Center for Devices and Radiological Health maintains a compendium of reports of adverse events involving medical devices (MAUDE). We performed multiple searches of MAUDE using a variety of key words, including Weck, Hem-o-lok, laparoscopy, nephrectomy, and clip. Within the MAUDE database, we identified 27 reports of problems with the Hem-o-lok clip until July 6, 2005. Of these events, only 1 (4%) involved application during open surgery, with the remainder occurring during laparoscopy. Minimal morbidity resulted from applicator difficulty during laparoscopic cholecystectomy (N = 7; 26%), with one case of open conversion. Forty-eight percent (N = 13) of the failures occurred during urologic laparoscopy; of these, bleeding was the primary problem in 77%. Delayed exploration, immediate open conversion, and death resulted in 38% (N = 5), 8% (N = 1), and 15% (N = 2), respectively. No clear etiology for the events could be found, although in all situations, multiple clips had been applied with apparent initial vessel control intraoperatively. Reported difficulty with the Hem-o-lok clip occurs primarily during laparoscopic surgery. Cases of failure after laparoscopic nephrectomy require urgent exploration, although it is unclear whether device or user error is the underlying cause. Regardless, care must be taken in securing the renal vessels, surgeons must be educated regarding proper use and techniques, and consideration should be given to using transfixing techniques.