Howard Hufnagel

Arterial Reconstruction with Vascular Clips is Safe and Quicker Than Sutured Repair

BACKGROUND Non-penetrating, arcuate-legged vascular-closure staple clips made of titanium were initially developed for microvascular anastomoses with little experience of their use in larger vessels. The purpose of this study was to compare vascular-closure staple clips to sutured anastomoses in common iliac arteries in a porcine model. METHODS In an experimental study, transected iliac arteries on both sides of 11 pigs were randomly assigned to end-to-end anastomosis performed with vascular-closure staple clips or interrupted 6-0 polypropylene sutures. Angiographic, macroscopic and microscopic results were assessed after 2 months. RESULTS There was no significant difference in the patency rate, tensile strength of the anastomoses, vessel diameter at the repair site, intimal thickness or wall thickness of the arteries after either method of closure. The mean (s.d.) clamp time was 19.8 (6.1) minutes for clip repair, and 36.0 (6.9) seconds for suture repair (P < 0.001). The times required for the reconstruction of the anastomoses were 17.4 (6.1) and 35.5 (7.1) minutes, respectively (P < 0.001). CONCLUSIONS Arterial anastomoses performed with vascular-closure staple clips are faster than sutured anastomoses, and result in comparable wound healing when assessed for patency, tensile strength, degree of narrowing and intimal reaction.

Arterial and venous repair with vascular clips: comparison with suture closure.

PURPOSE Nonpenetrating, arcuate-legged titanium vascular closure staple (VCS) clips were initially developed for microvascular anastomoses with little experience of their use in larger vessels. The purpose of this study was to compare the VCS clips with standard suture closure of arteriotomies and venotomies in common iliac vessels of pigs. METHODS In nine pigs, longitudinal 1 cm iliac arterial and venous incisions were repaired with VCS clips on one side and continuous 6-0 polypropylene suture on the other, and the macroscopic and microscopic results were assessed after 3 months. RESULTS The time required for vessel repair was significantly shorter with clips than with sutures both in arteries (51 +/- 9 vs 414 +/- 36 seconds) and in veins (100 +/- 32 vs 439 +/- 45 seconds). There was no significant difference in the inner diameter, intimal thickness, or intima-to-media height ratios of the arteries or veins after either method of closure. CONCLUSIONS Repair of 1 cm incisions in small-diameter arteries and veins with VCS clips results in wound healing as good as that achieved with standard suture closure, when assessed for patency, leakage, degree of narrowing, and intimal reaction. The time required for clip closure is considerably shorter than for suture closure.

A quick and simple method to close vascular, biliary, and urinary tract incisions using the new Vascular Closure Staples

Traditional suture reconstruction of tubular organs creates a perforating needle injury, leaves suture material on the endothelial or mucosal surfaces, and is cumbersome when done endoscopically. One alternative method of reconstruction of tubular organs could use the new non-penetrating clip to create an everted closure. In five pigs, a longitudinal incision of the infrarenal aorta, inferior vena cava, left ureter, gallbladder, and the common bile duct (in two) was closed with Vascular Closure Staples (VCS-clips). Four weeks after surgery, all ten blood vessels remained patent with no thrombosis. There was a well-healed wound with continuous intimal layer. The ureteral, gallbladder, and common bile duct wounds healed without leakage or obstruction in all animals. There was complete mucosal bridging of the wound, although in some specimens one or two clips were exposed to the lumen. The VCS-clips are easily and quickly applied and are safe insofar as can be determined by short-term follow-up.

Early resuscitation with low-volume polyDCLHb is effective in the treatment of shock induced by penetrating vascular injury

OBJECTIVE To study the efficacy of an oxygen-carrying solution in early resuscitation of hemorrhagic shock induced by penetrating vascular injury. DESIGN Experimental study with anesthetized rats. MATERIALS AND METHODS Severe hemorrhagic shock was induced by a 25-gauge needle puncture to the infrarenal aorta. Forty animals were resuscitated 10 minutes after injury with either lactated Ringers solution (LR; 60 mL/kg), 7.5% hypertonic saline (HTS; 5 mL/kg), or modified diaspirin cross-linked hemoglobin (PolyDCLHb; 5 or 20 mL/kg) or were not resuscitated (NR) and followed for 6 hours. RESULTS Total blood loss was similar in all treatment groups. Mean arterial pressure was restored to baseline values, base deficit was corrected to base excess, and venous oxygen saturation improved with PolyDCLHb and more slowly with LR but persisted below baseline values with HTS and NR. The 6-hour mortality rates were zero of eight (low-dose PolyDCLHb), three of eight (high-dose PolyDCLHb), two of eight (LR), six of eight (HTS), and six of eight (NR). CONCLUSION Early resuscitation with low-volume hemoglobin is effective in restoring tissue perfusion and improving survival in uncontrolled hemorrhagic shock.

Expression of genes for platelet-derived growth factor in adult human venous endothelium: a possible non-platelet-dependent cause of intimal hyperplasia in vein grafts and perianastomotic areas of vascular prostheses

Neointimal fibromuscular hyperplasia (NFH) in vein grafts and perianastomotic zones of vascular prostheses has been attributed to the effects of platelet-derived growth factor (PDGF) released by platelets interacting with bypass conduits. But inhibition of platelet aggregation often fails to prevent NFH, and recurrent growth of intact, platelet-free endothelium over perianastomotic areas where NFH occurs is inconsistent with the concept of sustained PDGF release from platelets causing NFH progression at late times after surgical procedures. Cultured bovine aortic endothelial cells (ECs) and human umbilical vein ECs have been shown to release a PDGF-like molecule. We report that confluent cultured fourth passage adult human saphenous vein ECs (AHSVECs) grown in the presence of heparin (100 micrograms/ml) and retina-derived growth factor (RDGF) studied by Northern blotting transcribed a messenger ribonucleic acid (mRNA) of 3.9 kb, strongly hybridizing to PDGF B chain probes, and two species of 2.0 and 2.6 kb hybridizing to PDGF A chain probes. Withdrawal of RDGF and heparin from these cultures for 48 hours before mRNA extraction amplified the scanning densitometric mRNA signal per cell by 8.0 +/- 7.6 fold (mean +/- SD) (N = 4 cultures) for B chain mRNA and 5.2 +/- 3.6 fold (N = 3 cultures) for A chain mRNA. In addition, AHSVEC cultures released a PDGF-like substance, because 50% vol/vol AHSVEC-conditioned serum-free medium increased tritiated thymidine uptake elevenfold in PDGF receptor-bearing 3T3 cells whereas an excess (50 micrograms/ml) of nonspecific goat anti-human-PDGF antibody significantly reduced this increase by a mean of 30% to 7.0 +/- 3.4 fold (N = 6 trials, p less than 0.001). Flow cytometry determined AHSVEC cultures to be proliferating with a mean of 6.2% +/- 1.9% (N = 3 culture lines) of ECs in S phase even at confluence when deprived of EC mitogens for 48 hours. Adult human ECs, which proliferate on bypass conduits and host vessels after perioperative injury, may play a role in causing NFH by stimulating proliferation of adjacent smooth muscle cells. Prevention of NFH may require not only antiplatelet agents but also ways to prevent EC release of smooth muscle cell mitogens in response to perioperative EC injury.

Ureteral Repair with Titanium Staples: Comparison with Suture Closure

OBJECTIVES Vascular closure staple (VCS) clips made of titanium were initially developed for microvascular anastomoses with little knowledge of their effectiveness in larger tubular tissue structures. This study compares VCS clips and sutures in the closure of longitudinal ureterotomy incisions. METHODS In 9 pigs, 1-cm-long anterior, longitudinal ureterotomy incisions were randomly assigned to closure with either 4-0 interrupted polyglactin sutures or VCS clips. RESULTS Clip closure was significantly faster (74+/-28 versus 534+/-182 seconds). All 18 ureters were patent and without signs of leakage, calculus formation, or stenoses after 3 months. Clip closure resulted in slightly but not statistically significantly less narrowing of the duct lumen, but there was no difference in wall thickness at the repair site. At histologic examination, all 18 incisions healed without signs of acute inflammation or marked fibrosis. CONCLUSIONS Ureterotomy closure with VCS clips results in wound healing that is as effective as suture closure, with a comparable degree of narrowing. The time required for clip closure is only about 1/7 that required for suture closure.

Platelet survival and serotonin content after placement of arterial prostheses in dogs: Effects of neointimal coverage and high- and low-dose aspirin

Because prosthetic neointima produces much less prostacyclin (PGI2) than arterial intima and may be more susceptible to cyclooxygenase inhibition, aspirin treatment might enhance surface thrombogenesis. To test this hypothesis, aortic prostheses were placed in eight dogs and measurements of platelet survival and platelet serotonin (5HT) were made under conditions of no treatment and treatment with low-dose (2mg/kg) and high-dose (30 mg/kg) aspirin. These doses equally suppressed platelet function. Measurements were performed preoperatively, 6 to 8 weeks postoperatively (when little neointima was present), and 28 to 32 weeks postoperatively (neointima fully developed). Platelet survival and 5HT levels were markedly reduced 6 to 8 weeks postoperatively and returned to normal at 28 to 32 weeks after implantation. At all times, low-dose aspirin improved platelet survival and this effect was most apparent 6 to 8 weeks postoperatively. Treatment with either aspirin dose decreased platelet 5HT levels at the 28 to 32 week postoperative period but not at other times. At recovery of prostheses, 90% of the luminal surface was covered with endothelialized neointima. Neointimal production of PGI2 was one half to one third that of aortic production. Despite this, low- and high-dose aspirin equally suppressed PGI2 production from both neointima and aorta. Furthermore, aspirin did not increase labeled platelet uptake on neointima. We conclude that (1) aspirin treatment does not render prosthetic neointima thrombogenic and (2) aspirin alters platelet survival and 5HT levels by mechanisms other than inhibition of platelet and neointima cyclooxygenase.

Platelet serotonin changes in dogs with prosthetic aortic grafts

Abstract The purpose of this study was to elucidate the mechanisms underlying the striking reduction in platelet serotonin found after placement of prosthetic aortic grafts in dogs. Changes in platelet serotonin paralleled changes in platelet survival time. Both were reduced after graft placement, remained depressed for up to a year, and then returned to normal. In vivo release of serotonin was assessed by labeling autologous platelets with 51 Cr (a nonreleasable, cytoplasmic label) and 14 C-serotonin (a releasable, storage granule label). In dogs with grafts, 14 C-serotonin persisted in the circulation beyond the life span of 51 Cr-labeled platelets. The ratio of platelet 14 C/ 51 Cr activity over 5 days following infusion of double-labeled platelets markedly increased. These data indicated in vivo release and reutilization of labeled serotonin. In vitro platelet uptake of 14 C-serotonin was assessed in separate experiments and was found to be depressed following graft placement. We conclude that the reduction in platelet serotonin stems from platelet interaction with aortic prostheses. Platelets adhere to the prosthetic surface, release serotonin, and recirculate. Reutilization of released serotonin occurs but may be limited by depressed platelet uptake. The net effect is a reduction in platelet serotonin. These findings support our view that platelet interaction with prosthetic surfaces is, in large measure, a reversible phenomenon, with platelets reentering the circulation in an altered state.