New Generation Tissue Sealants and Hemostatic Agents: Innovative Urologic Applications

Abstract

Control of blood loss during urologic surgery is paramount to the success of patient recovery. Hemostatic agents and tissue sealants are used routinely to prevent excess blood loss and in reconstruction during surgical repair. Some of the available products include thrombin sealant, fibrin glue, bovine serum/albumin/glutaraldehyde, and gelatin matrix. Each of these agents differs in mechanism, cost, and application. Complications can include allergic reactions or thromboembolism and the risk of contracting bovine spongiform encephalitis or hepatitis. Many new hemostatic agents are being developed and approved. The benefits and risks of use of these agents versus conventional treatment need to be considered on a case-by-case basis by the surgeon.

Blood loss has always been a concern in surgery. Methods to control bleeding and repair wounds have existed for many years. Efforts have ranged from the use of raw meat by the Ancient Egyptians¹ to the use of dried plasma in World War I to achieve hemostasis.² More traditional techniques have included applying pressure, electrocautery, and suturing. Over the past 20 years, a number of hemostatic agents and tissue sealants have been developed and are currently used in various surgical disciplines. Hemostatic agents act to stop bleeding either mechanically or by augmenting the coagulation cascade, whereas tissue sealants are products that bind to and close defects in tissue. Herein, we provide an overview of the various types of tissue sealants and hemostatic agents. Their mechanisms of action, benefits, risks, and current urologic applications are described.

Overview of Coagulation Cascade

Hemostasis is blood clot formation at the site of vessel injury. It is a complex interaction between platelets, plasma proteins, and coagulation and fibrinolytic pathways. Platelets are activated at the site of injury and provide the initial hemostatic response. The clotting cascade involves the sequential activation of proenzymes in a stepwise response, which ultimately provides local generation of fibrin lattices that reinforce the platelet plug (Figure 1).

Figure 1.

Coagulation cascade. HMW, high molecular weight.

Fibrin Glue

Fibrin glue products were approved by the US Food and Drug Administration (FDA) in 1998 for reinforcement of colonic anastomoses, splenic trauma, and cardiothoracic surgery. These products provide topical hemostasis, have sealant properties, and promote tissue approximation. A precursor of this product class, thrombin powder, was first used on the battlefields of World War I.² It did not gain widespread acceptance due to high transmission rates of viral hepatitis. There has been increasing interest in this class of products since the 1970s. This is due to advancements in the ability to purify high concentrations of thrombin/fibrinogen as well as improved viral detection.

Mechanism

Fibrin glue mimics the final steps of the coagulation cascade. In the presence of thrombin, fibrinogen is converted to fibrin. Thrombin also activates factor XIII, which stabilizes the clot, by promoting polymerization (cross linking) of the fibrin chains to long fibrin strands. This process occurs in the presence of calcium ions. It proceeds independently from the remainder of the coagulation cascade, and provides some degree of hemostasis even with defects in other portions of this pathway.^3–5 There is subsequent proliferation of fibroblasts and formation of granulation tissue within hours of clot polymerization. Clot organization is complete 2 weeks after application. The fibrin clot caused by the sealant degrades physiologically. Fibrin sealant can be manufactured from pooled or single source donors. Currently, several products are available in the United States and abroad: Tisseel (Baxter HealthCare Corp., Irvine, CA), Hemaseel (Haemacure, Sarasota, FL), Beriplast P (Aventis Behring, Marburg, Germany), Bolheal (Fujisawa, Pharmaceuticals Osaka, Japan), and Quixil (Omrix, Brussels, Belgium). The composition of these products varies, but there are similarities: a 2-vial system containing fibrinogen, thrombin, factor XIII, and calcium (typically calcium chloride). Preparation takes approximately 15 minutes and once complete, the product is available for use for 4 hours. The fibrin glue is applied with a double-barrel syringe onto a dry tissue bed.

Fibrin sealants have been used in a variety of settings. Unfortunately, the evaluation of the efficacy of these compounds is hard to determine because they have been assessed only in animal models, case reports, and small series.

Risks

Bovine thrombin can cause an IgE-mediated allergic reaction. Antibodies formed against bovine factor V or thrombin can cross react with human factor V, causing significant hemorrhage. 3 Thromboembolic events can result if the sealant is introduced into large blood vessels. Bovine products have the theoretic risk of transmission of bovine spongiform encephalitis.⁴ The risk of transmitting hepatitis A, B, and C as well as HIV (type 1 or 2) exists. Methods for reducing the viral loads include vapor heating, filtration, pH modulation, and solvent detergent exposure, resulting in viral clearance greater than 10.6 log₁₀.⁶

Urologic Applications

Urinary Fistulas and Surgical Complications

Papadopoulos and colleagues⁷ created a vesicovaginal fistula model in rabbits. Ten animals underwent repair with a conventional suture technique with a recurrence rate of 33%; a second group underwent suture repair augmented with fibrin glue (n = 10) with no recurrences. Schneider and associates⁸ reported endoscopic treatment of vesicovaginal fistulas in 6 patients with a success rate of 66%, compared with an 88% success rate in 6 patients who underwent conventional open surgical repair. Morita and Tokue⁹ reported a “composite” approach for vesicovaginal fistula in which bovine collagen is initially injected to facilitate the retention of fibrin glue. Evans and colleagues¹⁰ reported their experience using fibrin sealants to treat 7 iatrogenic urinary tract injuries during gynecological and general surgical procedures, 7 complex urinary fistulas, and 5 urological surgical complications. Successful resolution of injuries/fistulas was obtained after a single application of sealant in 18 patients (94.7%). Although the aforementioned results are encouraging, there is limited experience with this approach; thus, patients should be carefully selected and duly informed that this is not standard therapy.

Renal Sparing Surgery

Some of the challenges facing urologists during a partial nephrectomy include control of bleeding and repair of the collecting system. Several groups have demonstrated the usefulness of fibrin glue during partial nephrectomy, where fibrin glue is applied to the cut surface of the kidney.^11,12 Delayed hemorrhage was not reported, suggesting that fibrin sealant is effective for renal hemostasis. Pruthi and colleagues¹³ performed 15 consecutive hand-assisted laparoscopic partial nephrectomies using argon beam coagulation and fibrin glue, and reported no acute or delayed bleeding, and no urinary leak in 2 cases where the collecting system was entered. Kouba and colleagues¹⁴ investigated the intrinsic strength of the fibrin sealant bond when applied to the parenchyma and urinary collecting system in a porcine partial nephrectomy model. Two groups underwent repair with fibrin glue only; half had an in vivo sealant hardening time of 10 minutes and half had a time of 60 minutes, whereas the controls were treated with monopolar electrocautery alone. The strength of the vascular and pelvicaliceal repair was evaluated by infusing saline into the renal artery or retrograde infusion of the collecting system. Fibrin sealant was successful at supraphysiologic levels with a mean renal vascular and pelvicaliceal burst pressure of 378 and 166 mm Hg, respectively, as compared with 250 and 87 mm Hg in the control subjects.

Ureteral Reconstruction

Laparoscopic pyeloplasty and ureteroureterostomy can be technically challenging and time consuming. To assess the feasibility of an alternative technique, Eden and associates¹⁵ performed fibrin sealant laparoscopic pyeloplasty in 9 patients. Two stay sutures were placed to approximate the urothelium and the anastomoses were then completed with fibrin glue. The average operating room time was 180 minutes, there were no postoperative urine leaks, and all ureters were unobstructed at 1 to 2 years of follow-up. The use of fibrin glue for ureteral surgery has been assessed in a number of animal models. Barrieras and colleagues¹⁶ performed pyeloplasty in a porcine model using standard technique or a suture-assisted fibrin glue anastomosis. Immediate anastomotic leak point pressure was significantly lower in the fibrin group (3.5 ± 1.5 mm Hg) versus the control (17.3 ± 5.4 mm Hg; P = .038). Of the animals in the fibrin glue group (n = 9), 6 developed urinomas, whereas the remaining 3 had unobstructed pressure flow studies. These results suggest that this technique had limited efficacy in this model. In contrast, Wolf and colleagues¹⁷ demonstrated that fibrin glue produces good radiographic findings and flow characteristics, when fibrin glue was used to close ureterostomies in swine. Anidjar and colleagues¹⁸ performed laparoscopic ureteroureterostomy in swine using fibrin glue without stay sutures. The operative time was 15 minutes per anastomosis. Immediate fluoroscopy demonstrated patency in all 10 anastomoses; however, there was leakage in 2. The latter 2 animals died postoperatively, and necropsy demonstrated anastomotic disruption and large urinomas in both. The aforementioned findings suggest that fibrin glue may prove to be a useful adjunct for ureteral anastomosis. However, it does not appear that it will become a useful primary method for ureteral approximation.

Infertility

Vasovasotomy and vasoepididymostomy. A major advantage of a fibrin-assisted technique is time and simplicity. Several authors^19,20 have demonstrated in animal models that fibrin glue-assisted vasovasotomy has comparable anatomic success. Vankemmel and colleagues¹⁹ compared conventional 1-layer closure versus 3 transmural sutures followed by fibrin sealant in rats. Patency rates were 85% for the former and 92% for the latter, with a significantly shorter operative time with the use of fibrin glue. Wagenknecht²¹ reported results using this technique in humans.

Shekarriz and colleagues²² used fibrin glue for a modified invagination technique of vasoepididymostomy in a rat model and reported comparable patency rates in a standard end-to-side approach. Further investigation of these techniques is required to establish their clinical utility.

Pediatrics

Reconstruction. Fibrin sealant has been used to augment hypospadias repairs. Kinahan and Johnson²³ reported using Tisseel, a fibrin glue preparation, to augment hypospadias repairs in children. When this adjunct was used, the fistula rate was lower, 9% (n = 78) versus 28% (n = 97). Hafez and colleagues²⁴ reported an experimental model in rabbits using fibrin glue to patch a 15 × 15 mm defect created in the ventral tunica albuginea. The repair was evaluated at 2, 6, and 12 weeks. There were no hematomas, no evidence of corporal narrowing, and no venous leakage on cavernosography. Histopathologic evaluation demonstrated a fibrin sealant layer with angiogenesis and cellular infiltrate at 2 weeks, and regeneration of normal tunica albuginea without scarring at 6 and 12 weeks. These findings suggest that this might prove to be useful in the treatment of select patients with congenital or acquired chordee.

Circumcision. Patients with hemophilia or other bleeding diatheses are at increased risk of hemorrhage when undergoing circumcision. Augmenting hemostasis could diminish postoperative bleeding and reduce the amount of factor replacement required; thus limiting costs as well.^25–27 Avanoglu and colleagues²⁵ demonstrated a significant decrease in the cost of circumcision when using fibrin glue as an adjunct.

Miscellaneous

Radical retropubic prostatectomy. Diner and colleagues²⁸ examined fibrin sealants’ role in radical retropubic prostatectomy. One group underwent standard radical retropubic prostatectomy and fibrin sealant was applied to the completed anastomosis in the other. Drain output was significantly less in the latter cohort. However, the studies were not undertaken to determine if the drainage fluid contained urine. Therefore, the “true anastomotic sealant effect” could not be assessed.

Gelatin Matrix/Thrombin Sealants

FloSeal® Matrix Hemostatic Agent (FloSeal) (Baxter HealthCare, Deerfield, IL) is composed of thrombin and a proprietary gelatin matrix that is manufactured by extracting collagen from bovine corneal tissue. The collagen then undergoes gelatinization and cross linking/stabilization with glutaraldehyde. This compound is then ground to 500- to 600-µm particles.²⁹ The thrombin component, Thrombin-JMI® (King Pharmaceuticals, Inc., Bristol, TN), is of bovine origin and is supplied as a sterile freeze-dried powder that is reconstituted in 0.9% sodium chloride and mixed with the gelatin matrix in the operating room just before use. The preparatory time is approximately 1 minute and, once complete, the mixture is usable for 2 hours.

Mechanism

Both components work independently and synergistically to promote clot formation at the bleeding site. The granular nature of the compound conforms to the wound’s shape. The granules swell 10% to 20%, causing tamponade in the wound bed on contact with blood or other fluid. This reduces bleeding and provides a matrix on which a clot can form. The thrombin activates platelets; factors V, VII, and XII; and promotes the conversion of fibrinogen to fibrin. Fibrin traps the granular matrix, which promotes stability of this complex. Absorption of the gelatin complex typically occurs 6 to 8 weeks after application. The unique property of this product is the requirement for the presence of blood at its application site for activation.

The FDA approval of FloSeal was based on results in which this agent was used in cardiothoracic, vascular, and general surgery in a multi-centered setting.³⁰ The use of this product for urologic surgery has been mainly in trauma and partial nephrectomy where it has been assessed in animal models and clinical case series.

Risks

Treatment risks of this agent include developing bovine spongiform encephalitis,⁴ thromboembolic events if injected directly into medium to large blood vessels, immunologically induced coagulopathy, and IgE-mediated anaphylaxis.¹ There is also a theoretical risk of this substance serving as a nidus for infection, although this has not been reported.

Urologic Applications

Nephron Sparing Surgery

FloSeal has been used to facilitate open and laparoscopic partial nephrectomy. Gill and colleagues³¹ reported on using FloSeal as an adjunct for laparoscopic partial nephrectomy. One cohort underwent conventional suture renorrhaphy, whereas FloSeal was applied to the resection bed before suturing in the other cohort. The amount of blood loss, duration of warm renal ischemia, and length of hospitalization were comparable between groups. However, the use of FloSeal resulted in significantly fewer major complications. Richter and colleagues³² performed partial nephrectomy with use of FloSeal in 25 consecutive patients with exophytic renal masses. Fifteen patients underwent open surgery; 10 patients underwent laparoscopic surgery. There were no hemorrhagic complications in either group.

Trauma

FloSeal may also facilitate renorrhaphy for trauma. Hick and colleagues³³ assessed this in a porcine model of a grade 4 renal injury. One group (I) underwent repair with temporary occlusion of the renal artery and placement of gelatin foam in the defect followed by bolster suturing. FloSeal was applied to the exposed renal surface after renal artery occlusion in another group (II), and this was also done but without vascular control in another group (III). Mean operative blood loss in treatment groups II and III (81 ± 50 mL and 99 ± 94 mL, respectively) was substantially less than that in the control group (I) (192 ± 140 mL, P = .036). Renal artery control did not have a significant impact on total blood loss but it did result in quicker times to achieve satisfactory hemostasis. Postoperative imaging studies demonstrated that urinary extravasation was less common in the FloSeal groups, suggesting that this agent may help seal the renal collecting system in traumatized kidneys.

Percutaneous Nephrolithotomy

Tubeless percutaneous nephrolithotomy has been performed in carefully selected patients at several centers. Lee and colleagues³⁴ described a small series (n = 7) in which the nephrostomy tract was occluded retrogradely with a balloon catheter and FloSeal was introduced to seal the tract. All patients in this small series had stable postoperative hemoglobin levels and no evidence of renal or perirenal bleeding as assessed with CT scans done on postoperative day 1. We question the utility of this practice because it increases the cost of percutaneous nephrolithotomy, and there is the theoretical risk of this substance migrating into the collecting system where it could cause obstruction or serve as a nidus for stone formation. Uribe and colleagues³⁵ assessed the risks for the latter occurrences in an in vitro model where various hemostatic agents were placed in human urine. They found that FloSeal remained as a fine particle suspension (500–600 µm) when in contact with urine. Fibrin glue formed a solid clot that was maintained through 72 hours, and at 5 days this clot became a cohesive mucoid gel. Polyethylene glycol forms a solid clot maintained through 5 days. The same group performed a study in which percutaneous access was obtained in swine, and Tisseel, FloSeal, CoSeal™ (Cohesion Technologies, Palo Alto, CA), or BioGlue® (Cryolife, Inc., Kennesaw, GA) was injected into the access tract and collecting system. Fifty percent of these renal units were demonstrated to be obstructed at both 1 and 5 days after injection. This study illustrates the potential for morbidity with this approach and if it is considered, a retrograde occlusion balloon catheter should be used to prevent migration of these agents into the collecting system.

Cyanoacrylate

Cyanoacrylate, better known as “superglue,” was first used as a tissue sealant in the 1940s; however, its use was limited due to the intense local inflammation it generated. Synthetic cyanoacrylate (2-octyl cyanoacrylate), Dermabond® (Ethicon, Inc., Somerville, NJ), was approved by the FDA in 1998 for skin closure. Several studies^36,37 have since demonstrated that n-butyl-2-cyanoacrylate and Dermabond have low toxicity and produce limited local inflammation. Grummet and colleagues³⁸ studied 2-octyl cyanoacrylate and concluded it is not suitable as the sole method for the vesicourethral anastomoses during radical retropubic prostatectomy. Seifman and associates³⁶ reported that 2-octyl cyanoacrylate was suitable for closure of a large cystotomy in a rabbit model while producing an inflammatory response similar to that in conventional suture closure. Bardari and colleagues³⁹ reported use of n-butyl-2-cyanoacrylate to treat 7 patients with a variety of urinary fistulas not responding to catheter drainage or stenting. Patients underwent endoscopic filling of a fistula with sealant. When the fistula involved the bladder, the urethral catheter was removed 48 to 96 hours after treatment. This resulted in eradication of the fistula in 5 of 7 patients (71%) at a median follow-up of 24 months. Further experience is needed with this approach to confirm its efficacy.

Bovine Serum/Albumin/Glutaraldehyde

BioGlue (Cryolife, Inc.) is a proprietary compound approved in 2000 by the FDA as an adjunct to standard methods of hemostasis in adults undergoing vascular surgery.

Mechanism

BioGlue is a 2-component system consisting of purified bovine serum albumin and glutaraldehyde. Glutaraldehyde bridges the amine groups from the bovine serum albumin to extracellular matrix proteins of the target tissue forming a covalent bond between the tissue and adhesive. Hewitt and colleagues⁴⁰ used BioGlue during vascular anastomoses in an animal model, and, at 3 months, found minimal to no absorption of this adhesive and lack of an inflammatory response.

Application

The 2 component systems are mixed in a predefined ratio at the time of application. It works optimally when applied to a dry target field, with complete polymerization occurring in approximately 3 minutes.

Applications

Rotker and colleagues⁴¹ performed vascular anastomoses in an animal model where BioGlue was the only method of approximation. Four months after the procedure, all anastomoses were patent, intact, and without aneurysm or hematoma. The characteristics of this compound could lead it to be an excellent agent to provide sealant and hemostatic aid in tissues other than arteries. There is an issue of possible tissue-related toxicity. As previously described, Hewitt and associates⁴⁰ observed no fibrotic, granulomatous, or giant cell reaction. However, some researchers have reported otherwise.^42,43 Furst and Banerjee⁴² allowed BioGlue to polymerize and then overlaid saline, and the resultant supernatant contained 100 to 200 mg/mL of glutaraldehyde. This was then applied to the liver, aorta, and lung of rabbits. This tissue was evaluated 2 and 7 days later. The lung and hepatic tissue were found to have severe inflammation, edema, and toxic necrosis, whereas aortic inflammation was less intense.

BioGlue has demonstrated efficacy in cardiac and peripheral vascular surgery.^44,45 Long-term studies are needed to better define its inflammatory profile. Its role in urology has not been assessed but it may prove to be useful to help control bleeding in procedures where intense inflammation already exists and the major blood vessels need to be exposed and skeletonized, such as post-chemotherapy retroperitoneal lymphadenectomy.

Polyethylene Glycol Hydrogels

CoSeal (Cohesion Technologies, Inc.) and AdvaSeal-S (Genzyme Corp., Cambridge, MA) are polyethylene glycol (PEG)-based substances that polymerize at the site of application. They were approved by the FDA in 2000 for use as pulmonary sealants. Both are applied after being reconstituted in a syringe. They are degraded approximately 30 days after application. Ramakumar and colleagues⁴⁶ demonstrated that PEG hydrogels are polymerized on the resection bed in a porcine laparoscopic partial nephrectomy model and provide an adherent bond that is hemostatic at physiologic renal perfusion pressures. Furthermore, Park and colleagues⁴⁷ noted no detectable humoral- or cell-mediated immune responses at 2 weeks after application.

Conclusion

There are a number of tissue sealants and hemostatic agents available to facilitate urologic surgery. The efficacy of some applications has been established, but others are awaiting further evaluation and confirmation. When one of these adjuncts is used, the surgeon must be sure that this approach will provide equal or better results than results with standard methods. They should also consider the cost, pitfalls, and potential complications associated with these agents when choosing to use 1 or more of them. We think that this is an exciting and innovative area and anticipate that further product development and refinement is on the horizon.

Main Points.

• Hemostatic agents and tissue sealants are used in a number of surgical disciplines. Hemostatic agents stop bleeding either mechanically or by augmenting the coagulation cascade, whereas tissue sealants are products that bind to and close defects in tissue.

• Fibrin glue products provide topical hemostasis, have sealant properties, and promote tissue approximation; however, they require further study in humans.

• The granular nature of the thrombin and gelatin matrix compound allows conformation to the wound’s shape—the granules swell 10% to 20%, causing tamponade in the wound bed on contact with blood or other fluid.

• More experience is required with cyanoacrylate to assess its efficacy in clinical use.

• BioGlue (bovine serum albumin and glutaraldehyde) works best in a dry-field application.

• Polyethylene glycol hydrogels cause minimal inflammation and allergic reactions with superior hemostasis.

• Surgeons must consider cost, application, side effects, and efficacy when choosing a hemostatic agent or tissue sealant for use in certain surgical procedures.