Clinical Experience With a Novel Thermosensitive Temporary Coronary Artery Occluder (LeGoo)

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

A New Segmental Hepatectomy Approach Using Ultrasound-Guided Portal Branch Infusion of a Thermosensitive Gel in Pigs

BACKGROUND

The aim of this study was to evaluate the safety, feasibility, and efficacy of a new segmental hepatectomy (SH) approach using intraoperative ultrasound (IOUS) guided infusion of a reversible thermosensitive gel into the portal vein branch in pigs;

MATERIALS AND METHODS

Poloxamer 407 aqueous solution (20%, W/V) was mixed with indocyanine green (P407-ICG) in this study to make it green, and it remained liquid at room temperature and turned into a firm gel upon reaching body temperature. In experiment I, six pigs were used to detect the outcome of infusing the mixture into the biliary tract, liver parenchyma, and hepatic vein for a safety study. In experiment II, another 12 pigs were randomly segmented into two groups [SH group and partial hepatectomy (PH) group] to investigate the feasibility and efficacy of the new approach using IOUS-guided infusion of the mixture into the portal branch;

RESULTS

No thermosensitive gel-induced abnormal changes were observed in the safety study. In the SH group, IOUS-guided infusion of the P407-ICG solution was effective in occluding the portal blood temporarily and demarcating the target liver segment to achieve precise SH. The blood loss in the SH group was significantly less than that of the PH group;

CONCLUSIONS

SH assisted by IOUS-guided infusion of the reversible thermosensitive gel into the feeding portal vein branches is feasible, safe, simple, and effective.

Incidence and Predictors of New-Onset Silent Atrial Fibrillation after Coronary Artery Bypass Graft Surgery

AIMS

We investigated the incidence, risk factors, and prognostic impact of silent atrial fibrillation (AF) after coronary artery bypass graft (CABG) surgery.

METHODS

This observational study prospectively included 100 patients referred for CABG surgery. Holter ECG monitoring was used to record every arrhythmic event for 7 days. AF was defined as at least one episode >30 s. Episodes recorded on Holter ECG monitoring but not clinically identified were classified as silent AF.

RESULTS

Among 34 patients who developed new-onset AF, 13 had silent AF. Compared with patients with maintained sinus rhythm (SR), silent AF patients had a significantly higher logistic EuroSCORE (2.9 (1.5-5.2) versus 2.3 (1.4-3.7), p = 0.017) and were more likely to have previous sleep apnea (31% versus 8%, p = 0.016) and left atrial diameter >45 mm (36% versus 5%, p = 0.002). At one-year follow-up, 30% of silent AF patients had developed symptomatic AF versus 7% in the SR group (p = 0.03) and 11% in the clinical AF group (p = 0.21).

CONCLUSION

After CABG surgery, silent AF is common and may be associated with a higher incidence of recurrences at one-year follow-up than clinical AF. Improved screening for silent AF may help to reduce thromboembolic events in this high-risk population.

Low Circulating Levels of Growth Differentiation Factor-15 Before Coronary Artery Bypass Surgery May Predict Postoperative Atrial Fibrillation

OBJECTIVES

To assess the role of growth differentiation factor-15 (GDF-15) as a potential new predictor of postoperative atrial fibrillation (POAF) after off-pump (OFP) and on-pump (ONP) coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, single-center, observational study.

SETTING

University teaching hospital.

PARTICIPANTS

The first 50 patients planned for OFP surgery and the first 50 patients planned for ONP surgery among patients referred for CABG with the following exclusion criteria: age<18 or>80 years, previous atrial fibrillation/flutter, previous treatment with amiodarone, previous cardiac surgery, and emergency surgery.

INTERVENTIONS

Included patients were equipped with long-duration (7 days) Holter-ECG monitoring.

MEASUREMENTS AND MAIN RESULTS

POAF was defined as an AF episode lasting>30 seconds. All patients underwent preoperative echocardiography to assess left ventricular ejection fraction and left atrial diameter. GDF-15 levels were assessed after induction of anesthesia and 12 hours after arrival at the intensive care unit. Among the 100 patients, 34 (34%) developed POAF. In Cox multivariate regression analysis, the EuroSCORE, left atrial diameter>45 mm, and low GDF-15 levels at induction were associated independently with the onset of POAF. In contrast, preoperative NT-proBNP levels did not predict POAF. The use of ONP surgery was not associated with a higher incidence of POAF, even though baseline and follow-up characteristics in ONP and OFP patients were identical.

CONCLUSIONS

In patients with no history of AF, a low plasma level of GDF-15 before CABG surgery was a strong independent predictor of POAF. Moreover, preoperative plasma GDF-15 levels added an incremental predictive value to classic risk factors of POAF.

Achieving hemostasis in dermatology-Part II: Topical hemostatic agents

Bleeding is a common occurrence during any dermatologic surgery that disrupts blood vessels. The complications of excess bleeding can include delayed wound healing, hematoma formation, infection, dehiscence, and necrosis. In part one of this review, we discussed the pre-operative, intra-operative, and post-operative management of patients undergoing dermatologic surgery. In Part two, we discuss traditional and new topical hemostatic agents used to achieve hemostasis in dermatological procedures and surgery. We will evaluate the caustic and non-caustic hemostatic agents as well as hemostatic dressings. The mechanisms of action, side effect profile, and advantages and disadvantages of the topical hemostatic agents are provided. Sources for this article were found searching the English literature in PubMed for the time period 1940 to March 2012. A thorough bibliography search was also performed and key references examined.

LeGoo polymer injection into hydatid cyst would eliminate intraoperative spillage of scolices

BACKGROUND

Hydatid disease is caused by the tapeworm Echinococcus granulosus or Echinococcus multilocularis or Echinococcus Vogeli. It is the most severe helminthic zoonosis, with a major medical, social, and economic burden in endemic areas such as the Mediterranean region, South America, Australia, Turkey, New Zealand, Alaska, Canada, and the Middle East. The cornerstone in the management of hydatid cysts is surgery, and its recurrence is due mainly to the spillage of hydatid scolices rich fluid into the surrounding tissues.

AIM

In this study, we test a polymer benefit in intraoperative scolices spillage prevention, this polymer is called LeGoo.

METHODS

The LeGoo polymer was used here in vivo animal's hydatid cysts and in vitro hydatid cysts excised from human beings.

RESULT

Microscopic examination of the aspirated fluid from human being and sheep hydatid cysts before LeGoo injection showed numerous alive scolices. All sheep lung hydatid cysts with LeGoo injection transformed into a solid gelatinous mass, microscopic examination of the content swabs showed no scolices. LeGoo polymer injection into human hydatid cysts in vitro changed them into a solid gelatinous mass that can be mobilized easily with negative swabs for scolices.

Effects of temporary vascular occluder poloxamer 407 gel on the endothelium

Background

Coronary occlusion techniques during OPCAB may lead to an endothelial damage to the target vessel. The adverse effects of these techniques are well-known, and researches have been trying to find out new materials to occlude the coronary artery without an endothelial damage. In the present study, we investigate to the endothelial damage in the rat aorta which is occluded by Poloxamer 407 gel.

Methods

Forty-five rats were randomized in three groups: (1) segment of the aorta was occluded with Poloxamer 407 gel in P 407 group; (2) segment of the aorta was occluded with microvascular clamp in MV clamp group; and (3) no onclusion was available in the Control group. The rats were sacrificed of observation, and a 15mm segment of the aorta was obtained as a specimen. Integrity of the endothelial lining was observed with a scanning electron microscopy.

Results

Scanning electron microscopy revealed a statistically significant difference among the 3 groups (p<0,001) using the SPSS 13.0 test. No difference was found between the Control group and the P 407 group (p=0,059). The differences between MV clamp–Control group (p<0,001) and MV clamp–P 407 group were statistically significant (p<0,002).

Conclusions

We suggest that Poloxamer 407 gel occlusion may be a safer and more effective method compared to the microvascular clamp occlusion.

Investigations of a thermosensitive gel to temporarily occlude crural arteries in femoro-distal bypass surgery

OBJECTIVES

Long occlusions in calcified crural arteries are a major cause of endovascular technical failure in patients with critical limb ischaemia. Therefore, distal bypasses are mainly performed in patients with heavily calcified arteries and with consequently delicate clamping. A new reverse thermosensitive polymer (RTP) is an alternative option to occlude target vessels. The aim of the study is to report our technical experience with RTP and to assess its safety and efficiency to temporarily occlude small calcified arteries during anastomosis time.

METHODS

Between July 2010 and December 2011, we used RTP to occlude crural arteries in 20 consecutive patients with 20 venous distal bypasses. We recorded several operative parameters, such as volume of injected RTP, duration of occlusion and anastomotic time. Quality of occlusion was subjectively evaluated. Routine on-table angiography was performed to search for plug emboli. Primary patency, limb salvage and survival rates were reported at 6 months.

RESULTS

In all patients, crural artery occlusion was achieved with the RTP without the use of an adjunct occlusion device. Mean volume of RTP used was 0.3 ml proximally and 0.25 ml distally. Mean duration of occlusion was 14.4 ± 4.5 min, while completion of the distal anastomosis lasted 13.4 ± 4.3 min. Quality of occlusion was judged as excellent in eight cases and good in 12 cases. Residual plugs were observed in two patients and removed with an embolectomy catheter, before we amended the technique for dissolution of RTP. At 6 months, primary patency rate was 75% but limb salvage rate was 87.5%. The 30-day mortality rate was 10%.

CONCLUSIONS

This study shows that RTP is safe when properly dissolved and effective to occlude small calcified arteries for completion of distal anastomosis.

Temporary targeted renal blood flow interruption using a reverse thermosensitive polymer to facilitate bloodless partial nephrectomy: a swine survival study

What's known on the subject? and What does the study add? Lumagel™ is a reverse thermosensitive polymer (RTP) that has previously been described in the literature as providing temporary vascular occlusion to allow for bloodless partial nephrectomy (PN) while maintaining blood flow to the untargeted portion of the kidney. At body temperature, Lumagel™ has the consistency of a viscous gel but upon cooling rapidly converts to a liquid state and does not reconstitute thereafter. This property has allowed for it to be used in situations requiring temporary vascular occlusion. Previous experience with similar RTPs in coronary arteries proved successful, with no detectable adverse events. We have previously described our technique for temporary vascular occlusion of the main renal artery, as well as segmental and sub-segmental renal branches, to allow for bloodless PN in either an open or minimally invasive approach. These experiments were performed in the acute setting. This study is a two-armed survival trial to assess whether this RTP is as safe as hilar clamping for bloodless PN. Surviving animals showed normal growth after using the RTP, absence of toxicity, no organ dysfunction, and no pathological changes attributable to the RTP. We conclude that Lumagel™ is as safe as conventional PN with hilar clamping, while adding the advantage of uninterrupted perfusion during renal resection.

OBJECTIVE

To examine whether randomly selected regions of the kidney could undergo temporary flow interruption with a reverse thermosensitive polymer (RTP), Lumagel™ (Pluromed, Inc., Woburn, MA, USA), followed by partial nephrectomy (PN), without adding risks beyond those encountered in the same procedure with the use of hilar clamping.

MATERIALS AND METHODS

A two-armed (RTP vs hilar clamp), 6-week swine survival study was performed. Four swine underwent PN using hilar clamps, while six underwent PN with flow interruption using the RTP. The RTP, administered angiographically, was used for intraluminal occlusion of segmental or subsegmental arteries and was compared with main renal artery clamping with hilar clamps. The resection site was randomized for each swine. Laboratory studies were performed preoperatively, and at weeks 1, 3 and 6. Before killing the swine, repeat angiography was performed with emphasis on the site of previous flow interruption. Gross and microscopic examination of kidney, liver, lung, heart, skeletal muscle was later performed, and the vessel that had supported the previous plug was examined.

RESULTS

All animals survived. No abnormal chemistry or haematology results were encountered over the 6 weeks. There were no surgical complications in either group. Using angiography we found 100% patency of vessels that had been occluded with the polymer 6 weeks previously for PN. The only gross or microscopic abnormalities were related to the renal resection and scar formation, and were similar in the two groups.

CONCLUSION

Targeted flow interruption with the RTP added no additional risk to PN while allowing bloodless resection and uninterrupted flow to untargeted renal tissue.

Temporary vascular occlusion by rapid reverse phase polymer: a preliminary in vitro study of retrograde injection

During vascular surgical operations, there is a need for a simpler and more reliable method of temporary arterial occlusion than those currently employed, especially of heavily calcified arteries. A thermosensitive polymer, LeGoo (LG) (Pluromed, Woburn, MA), has been used successfully for temporary vascular occlusion. It has hitherto been injected by a cannula that has been introduced into the artery to be occluded, here henceforth called the “cannulation method.” Injection into arterial ostia without cannulation, using an injection device that arrests blood flow during the injection, here henceforth called “a retrograde method” may enable temporary hemostasis when ostial stenoses render it impossible to inject LG using the cannulation method. The objective of the present study was to study the feasibility of a retrograde method and to compare it with the cannulation method in an in vitro model, incorporating a narrow orifice to simulate ostial stenosis, using tap water at 37°C instead of blood. The retrograde method of LG injection, using a modified paediatric Foley catheter, turned out to be feasible to produce a durable LG plug more reliably, at higher water pressure and with less deep LG injection than with the cannulation method.

Feasibility of bloodless liver resection using Lumagel, a reverse thermoplastic polymer, to produce temporary, targeted hepatic blood flow interruption

BACKGROUND

  Lumagel, a reverse thermosensitive polymer (RTP), provides targeted flow interruption to the kidney by reversibly plugging segmental branches of the renal artery, allowing blood-free partial nephrectomy. Extending this technology to the liver requires the development of techniques for temporary occlusion of the hepatic artery and selected portal vein branches.

METHODS

  A three-phased, 15 swine study was performed to determine feasibility, techniques and survival implications of using Lumagel for occlusion of inflow vessels to targeted portions of the liver. Lumagel was delivered using angiographic techniques to sites determined by pre-operative 3-D vascular reconstructions of arterial and venous branches. During resection, the targeted liver mass was resected without vascular clamping. Three survival swine were sacrificed at 3 weeks; the remainder at 6 weeks for pathological studies.

RESULTS

  Six animals (100%) survived, with normal growth, blood tests and no adverse events. Three left lateral lobe resections encountered no bleeding during resection; one right median resection bled; two control animals bled significantly. Pre-terminal angiography and autopsy showed no local pathology and no remote organ damage.

CONCLUSIONS

  Targeted flow interruption to the left lateral lobe of the swine liver is feasible and allows resection without bleeding, toxicity or pathological sequelae. Targeting the remaining liver will require more elaborate plug deposition owing to the extensive collateral venous network.

Targeted endovascular temporary vessel occlusion with a reverse thermosensitive polymer for near-bloodless partial nephrectomy: comparison to standard surgical clamping techniques

PURPOSE

To determine whether reversible blood flow interruption to a randomly chosen target region of the kidney may be achieved with the injection of a reverse thermoplastic polymer through an angiographic catheter, thereby facilitating partial nephrectomy without compromising blood flow to the remaining kidney or adding risks beyond those encountered by the use of hilar clamping.

METHODS

Fifteen pigs underwent partial nephrectomy after blood flow interruption by vascular cross-clamping or injection of polymer (Lumagel™) into a segmental artery. Five animals were euthanized after surgery (three open and two laparoscopic resection, cross-clamping n = 2), and 10 (open resection, cross-clamping n = 4) were euthanized after 6 weeks' survival. Blood specimens were obtained periodically, and angiogram and necropsy were performed at 6 weeks.

RESULTS

Selective renal ischemia was achieved in all cases. Surgical resection time averaged 9 and 24.5 min in the open and laparoscopic groups, respectively. Estimated blood loss was negligible with the exception of one case where an accessory renal artery was originally overlooked. Reversal of the polymer to a liquid state was consistent angiographically and visually in all cases. Time to complete flow return averaged 7.4 and 2 min for polymer and clamping, respectively. Angiography at 6 weeks revealed no evidence of vascular injury. Laboratory data and necropsies revealed no differences between animals undergoing vascular clamping or polymer injection.

CONCLUSION

Lumagel was as effective as vascular clamping in producing a near bloodless operative field for partial nephrectomy while maintaining flow to the uninvolved portion of the affected kidney.

Temporary targeted hemostasis to facilitate bloodless partial nephrectomy

OBJECTIVE

To extend previous robotic-assisted techniques developed in the swine model to studies of laparoscopic and open partial nephrectomy conducted in pigs and calves, designed to encompass vessel diameters similar to those encountered in humans. Lumagel (Pluromed, Woburn, MA), a nontoxic polymer, can be administered intra-arterially under fluoroscopic guidance to obtain a bloodless operative field during partial nephrectomy while maintaining normal circulation to uninvolved renal tissue.

METHODS

A total of 10 animals (7 pigs and 3 calves) underwent flow interruption to the kidney, 2 with cross-clamping of the main renal artery, the remaining with Lumagel. Other than the first pig and calf, all the animals then underwent partial nephrectomy.

RESULTS

Using Lumagel, targeted blood flow interruption was achieved and circulation to the uninvolved renal tissue was maintained. Hemostasis lasted for ≥30 minutes. The surgical resection time averaged 11 minutes (range 10-13) and 23.3 minutes (range 9-40) in the open and laparoscopic groups, respectively. The estimated blood loss was negligible, with the exception of 2 cases, 1 in which an error in angiographic assessment led to an unoccluded vessel near the resection site and a second case in which a guidewire was inadvertently passed through a vessel. The interval to complete flow return, as determined by direct visualization of the kidney and its corresponding angiogram, averaged 7 and 2.5 minutes for Lumagel and arterial clamping, respectively.

CONCLUSION

Lumagel provides reliable and reproducible intraluminal blood flow interruption and flow restoration in both main and segmental renal arteries. By providing blood-free resection, the techniques described could facilitate partial nephrectomy without global renal ischemia.

Clampless anastomosis with an intraluminal thermosensitive gel: first application in reconstructive microsurgery and literature review

Microvascular clamps of various designs provide a bloodless field for a safe anastomosis but can cause intimal lesions, occupy space in confined sites and have a risk of backwalling due to vessel flattening. They are often insufficient in their haemostatic effect in plaque-filled atherosclerotic vessels. A new, CE-certified thermosensitive gel (LeGoo™) clinically proven in cardiovascular surgery allows a clampless microanastomosis technique. We operated on a series of five consecutive patients aged 24-71 years with six flaps for lower-extremity reconstruction using a clampless anastomosis technique with LeGoo™. We transplanted one fabricated chimaeric fibula plus gracilis, three gracilis muscle and one anterolateral thigh (ALT) flap. Pre- and postoperative protocols were similar to a 'standard' procedure with micro-clamps. All flaps survived completely except for a small area on fibula skin island, which was unrelated to gel use. The gel-assisted technique has a quick learning curve, according to this case series. The veins should be sutured first to prevent stasis in the flap. The gel provides circular stenting and gentle distension of the vessels for a safe and blood-free anastomotic site. It is completely dissolved after completion of the anastomosis with cold saline irrigation. Repolymerisation in the periphery will not occur, making it safe for microvascular flap surgery. From the experiences from this series and other specialities, the use of the thermosensitive gel LeGoo™ permits a safe clampless microanastomosis technique minimising mechanical vessel manipulation and compression. This makes it an attractive alternative to micro-clamps, especially for atherosclerotic arteries and confined anastomosis sites.

The Use of Reverse Thermosensitive Polymer (LeGoo) for Temporary Vessel Occlusion in Clampless Peripheral Vascular Surgery

Introduction: There is a need to develop methods of vascular hemostasis, which limit vessel trauma. LeGoo is a reverse thermosensitive polymer (poloxamer) which is a viscous liquid at room temperature, becoming a firm plug at body temperature. We aimed to describe early single center experience in clampless peripheral vascular surgery. Methods: Single surgeon experience using LeGoo during peripheral vascular surgery between February and October 2010 was analyzed. Results: LeGoo was used in 13 anastomoses in 11 patients. A satisfactory bloodless field without the use of conventional occlusion devices was achieved in 92% of anastomoses. At a median of 36 weeks follow-up, total conduit patency was 91%. Conclusions: In this small series, LeGoo was seen to be safe and effective in the provision of a clamp-free bloodless field in the context of peripheral vascular surgery. Prospective comparative study is necessary to determine performance against conventional vascular clamps.