Andrew G. Harrell

Prospective histologic evaluation of intra-abdominal prosthetics four months after implantation in a rabbit model

BackgroundPlacement of an intraperitoneal prosthetic is required for laparoscopic ventral hernia repair. The biocompatibility of these prosthetics determines the host’s inflammatory response, scar plate formation, tissue ingrowth, and subsequent mesh performance, including prosthetic compliance and prevention of hernia recurrence. We evaluated the host response to intraperitoneal placement of several prosthetics currently used in clinical practice.MethodsA 4-cm × 4-cm piece of mesh was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included expanded polytetrafluoroethylene (ePTFE) (DualMesh®), ePTFE and polypropylene (Composix®, heavyweight polypropylene), polypropylene and oxidized regenerated cellulose (Proceed®, midweight polypropylene), and polypropylene (Marlex®, heavyweight polypropylene). At four months, standard hematoxylin and eosin and Milligan’s trichrome stains of the mesh-tissue interaction were analyzed by three observers blinded to the mesh types. Each specimen was evaluated for scar plate formation, inflammatory response, and tissue ingrowth. Each of these three categories was graded on a standard scale of 1–4 (1 = normal tissue and 4 = severe inflammatory response). The scores were analyzed using Wilcoxon rank sum test with p < 0.05 as significant.ResultsTen samples of each mesh type were evaluated. There was no difference in tissue incorporation between the groups. The mean scar plate formation was greater in the heavyweight polypropylene meshes than for DualMesh (p = 0.04). With Proceed, the reduction in scar plate formation compared with that for Composix and Marlex approached statistical significance (p = 0.07). The mean number of inflammatory cells was greater around the ePTFE when compared with the midweight polypropylene (p = 0.02) but equal to the other meshes.ConclusionsThe four prosthetic materials evaluated in this study demonstrate comparable host biocompatibility as evidenced by the tissue ingrowth. Scar plate formation around DualMesh was significantly less than that around Composix and Marlex. Interestingly, more inflammatory cells were noted surrounding the DualMesh which was equal to that of the heavyweight meshes. Proceed, a midweight polypropylene mesh, has the potential for improved patient tolerance compared to heavyweight polypropylene meshes based on its favorable histologic findings.

Evaluation of the Efficacy of the Electrosurgical Bipolar Vessel Sealer (LigaSure) Devices in Sealing Lymphatic Vessels

Various sources of ultrasonic and thermal energy have been developed to facilitate blood vessel ligation. However, their efficacy in sealing lymphatics has not been clearly established to date. We hypothesized that the electrosurgical bipolar vessel sealer (EBVS) produces reliable and durable sealing of large lymphatic vessels in a porcine model. Thoracic ducts from 4 adult pigs were explanted and sealed at multiple levels by using 3 different EBVS devices: LigaSure Atlas, XTD, and V. Fifteen seals (5 per group) were analyzed for sealing time and visual quality. Seal burst strength was measured by using a graduated pressure saline injection system. Twelve intact seals also underwent a histologic analysis. The mean overall burst strength of the seals was 271 78 mm Hg (127 to 360 mm Hg). The burst pressures in the 3 groups were not statistically different. The overall mean time to achieve a seal was 5.1 2.2 seconds (3 to 10 seconds). Seals were achieved significantly faster in the V group (4.1 0.6 seconds) compared with the Atlas (6.3 2.3 seconds) and XTD (6.4 2.6 seconds) groups. Qualitative seal assessment revealed minimal sticking and charring, a favorable degree of seal tissue clarity, and desiccation in the 3 groups. Histologic analysis demonstrated a fusion of lymphovascular channels with a complete obliteration of the lumens. We demonstrated that the use of EBVS results in a fast and effective sealing of large porcine lymphatic vessels. The seals created by all 3 devices burst at markedly supraphysiologic intraluminal pressures. Ongoing randomized human trials may prove the clinical benefits of the routine use of EBVS devices for various tissue dissections.

Laparoscopic expertise increases hospital volume of adrenal surgery.

The laparoscopic approach is preferred for most adrenal tumors but technical challenges limit its use. We evaluated the effects of the availability of laparoscopic expertise on the volume of the adrenal surgery at a tertiary care hospital. Patients undergoing adrenalectomy 5 years before and 5 years after an advanced laparoscopic program was established were retrospectively reviewed. The average annual volume increased from 2 cases during the first period to 15 cases during the 5 years (1999-2003) after laparoscopic expertise became available. The average distance of travel to the hospital was significantly greater for the latter patients and significantly more patients were referred from outside of a 30-mile radius. Although the average statewide annual number of adrenalectomies has not significantly changed, the proportion of adrenalectomies performed at our institution rose. Offering a laparoscopic approach has altered physicians’ referral patterns and has significantly increased the volume of adrenal surgery at the institution.

Thrombosis in the portal venous system after elective laporoscopic splenectomy

It was with great interest that we read the article by Pietrabissa et al. [2] on portal system thrombosis after laparoscopic splenectomy. This work, once again, described venous thrombosis as a potentially catastrophic postoperative event. We agree that vigilance, thorough investigation, and aggressive management are of paramount importance in symptomatic patients. However, we question several of their assertions. First, the influence of thrombocytosis on portal system thrombosis is not well established and was not referenced in the paper. Although it may be logical to assume that higher platelet counts would predispose a patient to hypercoagulability and thrombotic sequelae [4], this effect was not demonstrated in this report and lacks support in general. In fact, it appears that none of the patients in this series who developed a thrombosis had platelet counts >1 million. In addition, the postoperative platelet counts were not statistically different in their patients with and without portal system thrombosis. Overall, the study did not demonstrate a relationship between severe thrombocytosis and postoperative thrombosis. The authors also suggested that plasma exchange therapy is appropriate for patients with postoperative platelet counts >1 million. This assertion is not supported by evidence in their report or elsewhere in the medical literature; moreover, it is debatable whether prophylactic aspirin or other anti-platelet therapy for patients with thrombocytosis is effective or warranted [1, 4]. They recommend frequent platelet surveillance, yet they reported checking a platelet count themselves only on the 3 postoperative day. Based on the evidence provided, the need for plasma exchange, anti-platelet therapy, or frequent platelet count assessment for patients undergoing splenectomy has not been proven. The prospective nature of the study enabled the authors to establish a 22% rate of postoperative portal system thrombosis. However, the natural history of asymptomatic splenic and/or portal vein thrombosis after laparoscopic splenectomy is not known [3]. Their recommendation that an immediate anticoagulation protocol be initiated for all patients with a thrombus in any branch of the portal system appears to be rational and may be even appropriate, but it is not truly supported. Given the long history of splenectomy, both open and laparoscopic, and combining this long history with the reported 22% incidence of portal system thrombosis, why are we not seeing significant numbers of patients who present with major morbidity or die from intestinal infarction or portal hypertension? Considering as well that systemic anticoagulation therapy in the early postoperative period can carry significant morbidity (two patients in their series required reoperation for bleeding), the overall risk/benefit ratio of anticoagulating asymptomatic patients with thrombosis of the splenic vein or branches of the portal system remains unknown. Finally, the authors call for an aggressive outpatient screening program to detect silent thrombotic events in all laparoscopic splenectomy patients is not based on evidence and is premature. Only when the link between asymptomatic thrombosis of the splenic vein or portal system branches and clinical complications is established will prophylactic imaging become routine. Although we congratulate the authors on their contribution to the literature on this topic, we believe that the suggested role of plasma exchange in thrombocytosis, as well as radiographic screening and anticoagulation therapy for asymptomatic patients after laparoscopic splenectomy, is not evidence-based to date and that the resolution of these issues needs further investigation.