title: Local hemostasis during laparoscopic partial nephrectomy using biodegradable hydrogels: initial porcine results.
abstract: OBJECTIVE
  Despite the advance of laparoscopic partial nephrectomy, significant technical limitations remain with regard to control of bleeding and closure of the collecting system. An attractive approach on the horizon for local hemostatic and wound control is the use of local tissue sealants. To date, sealants remain largely derived from natural biologic products and are difficult to apply laparoscopically with precise local control. In this study, we examined the novel strategy of forming occlusive tissue-adherent hydrogels utilizing a synthetic biodegradable polyethylene glycol-lactide copolymer (PEG-lactide) as an in situ occlusive barrier for hemostasis and wound control. Specifically, the objects of this study were to determine if PEG-lactide hydrogels could be formed intraperitoneally on renal tissue, to test the adhesiveness of the hydrogels to injured renal parenchyma, and to evaluate the ability of adherent hydrogel barriers to limit renal parenchymal bleeding and collecting system leakage following renal pole amputation or wedge excision.
  
  
  METHODS
  Five kidneys from three female pigs were used in a nonsurvival study. A standardized model for laparoscopic partial nephrectomy was created by performing wedge excision or polar amputation under vascular control using a laparoscopic Satinsky clamp. Bleeding briskness following injury was assessed utilizing a scoring system and free blood quantitated comparing a conventional "clamp and wait" strategy with an adherent hydrogel strategy. For the hydrogel group, PEG-lactide hydrogel primer and macromer were applied through laparoscopic ports. The hydrogel was polymerized using a xenon light source, and the pedicle clamp was released to observe for bleeding. A subsequent opposite polar injury was created to confirm renal perfusion and the sites were compared. The kidneys were removed, and the adhesion of the hydrogel to the renal parenchyma was examined.
  
  
  RESULTS
  The PEG-lactide macromer was effectively applied to five kidneys following partial nephrectomy. In all cases, successful intraperitoneal in situ polymerization was achieved, with resultant hydrogel formation. Polymeric hydrogel adhesion to the cut renal parenchyma was assessed semiquantitatively following vigorous cyclic washing. In all cases, polymer gels remained adherent without any evidence of peeling, delamination, or separation from the underlying tissue surface. In the control group, the mean bleeding score was 2.63 +/- 0.48 v 0.00 +/- 0.00 in the gel-treated group (P < 0.001). Blood loss in the control group was 56 +/- 5 ml v 0.00 +/- 0.00 in the gel-treated group (P < 0.001). In an ex vivo retrograde ureteral perfusion, no leakage was observed at pressure as high as 100 mm Hg.
  
  
  CONCLUSIONS
  In this feasibility study, a biodegradable PEG-lactide polymer system photopolymerized rapidly in situ on exposed renal parenchymal surfaces, forming adherent hydrogel barriers. When applied during vascular clamping, an adequate physical bond and patch-like cap was created to prevent bleeding at physiologic renal perfusion pressures. Use of locally applied occlusive hydrogels holds promise for hemostasis and local wound control during laparoscopic urologic procedures.
authors.affiliation: James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, 4940 Eastern Avenue, Baltimore, MD 21224, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Ramakumar
authors.forename: William W
authors.initials: WW
authors.lastname: Roberts
authors.forename: Oscar E
authors.initials: OE
authors.lastname: Fugita
authors.forename: Peter
authors.initials: P
authors.lastname: Colegrove
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Nicol
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Jarrett
authors.forename: Louis R
authors.initials: LR
authors.lastname: Kavoussi
authors.forename: Marvin J
authors.initials: MJ
authors.lastname: Slepian
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials / Q000627:therapeutic use; D001673:Biodegradation, Environmental; D016063:Blood Loss, Surgical / Q000517:prevention & control; D005240:Feasibility Studies; D005260:Female; D006488:Hemostasis, Surgical / Q000379:methods*; D006489:Hemostatic Techniques; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000627:therapeutic use*; D010535:Laparoscopy; D023421:Models, Animal; D009392:Nephrectomy / Q000379:methods*; D011092:Polyethylene Glycols / Q000627:therapeutic use*; D013552:Swine
chemical_list: D001672:Biocompatible Materials; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols