Jerry Vlasak

Initial human evaluation of argon laser—assisted vascular anastomoses

Forearm Brescia-Cimino arteriovenous fistulas were chosen for the initial clinical evaluation of argon laser-assisted anastomosis of human vessels. Ten patients with chronic renal failure had side-to-side radial artery/cephalic vein fistulas fused by laser. Incisions 1.2 to 1.5 cm in length were made in adjacent segments of artery and vein and were aligned for application of laser energy by four 6-0 polypropylene sutures. The sutures divided each fistula into four segments that were 5.0 to 6.5 mm long. Each segment was sealed satisfactorily in 75 to 100 seconds by use of 0.5 W, 1130 to 1520 joule/cm2 argon laser energy fluence. Seven (17.5%) of 40 bonds required an additional 7-0 biodegradable suture to close small gaps that did not fuse adequately. Serial prospective follow-up studies of the patients by physical examination and duplex scanning for periods of 12 to 20 months (15.4 +/- 2.8, n = 7) postoperatively have shown uniformly patent, compliant anastomoses with no evidence of hematomas, false aneurysms, or luminal narrowing. Histologic examination of two patent fistulas that were excised during revision procedures at 4 and 5 months postoperatively showed healing of the entire circumference of the anastomosis similar to that noted in extensive preclinical canine studies. We conclude from these preliminary results that argon laser vascular tissue fusion is possible in humans when reliable primary sealing of vascular anastomoses is achieved, and that healing occurs without aneurysmal dilatation during follow-up of up to 20 months.

Experimental and early clinical evaluation of vascular anastomoses with argon laser fusion and the use of absorbable guy sutures: A preliminary report

This study investigated the feasibility of forming vascular anastomoses by use of argon laser tissue fusion and absorbable, monofilament polydimethylsiloxane guy sutures. In initial animal studies femoral arteriovenous fistulas approximately 1.5 cm in length were created bilaterally in each of 10 dogs and were studied histologically at 2, 4, 8, 16, and 24 weeks (two animals in each interval). In each animal, one anastomosis (control) was formed with continuous 6-0 polypropylene suture, and the contralateral anastomosis (experimental) was performed with an argon laser (0.5 watt, 5 to 7 minutes exposure, energy fluence 1100 to 1500 joules/cm2 per 1 cm length) with stay sutures of 5-0 polydimethylsiloxane at 0.5 to 0.65 cm intervals. At removal, all anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 2 to 16 weeks demonstrated resorption of the biodegradable suture material by a local inflammatory reaction. By 24 weeks, laser-fused specimens had no evidence of suture material at the anastomotic line, and healing consisted of a bond between artery and vein wall tissues. Control suture specimens at the same intervals exhibited an organized fibrous tissue response to the suture. Clinical adaptability of this technology has subsequently been evaluated in five patients at 10 to 27 months (21.6 +/- 5.8) by physical examination and duplex scanning and demonstrate no evidence of abnormal healing. This study establishes the experimental and preliminary clinical feasibility of laser-fused anastomoses aligned by biodegradable guy sutures and supports further investigation and refinement of the technique.

Canine Peripheral Vascular Arteriosclerosis Following Myointimal Fragmentation and Atherogenic Diet

The development of arteriosclerotic peripheral vascular lesions following balloon catheter and mechanical fragmentation of the arterial myointima combined with an atherogenic diet was studied in a canine model. The ileofemoral arteries of five mongrel dogs (mean wt 22 +/- 2 kg) were selectively cannulated and subjected to balloon catheter and mechanical myointimal injury by repeated longitudinal and transverse shearing forces. Twenty grams of hydrogenated coconut oil and a 5.0% cholesterol diet were fed to the animals daily during the study period. Followup angiographic studies obtained at 4 weeks (n = 2), 10 weeks (n = 3), 16 weeks (n = 3), and 24 weeks (n = 2) demonstrated changes of progressive peripheral vascular occlusion. Concurrent duplex Doppler studies correlated well with the angiographic results. At 10 (n = 1), 18 (n = 2), and 24 (n = 2) weeks, the animals were sacrificed and the vessels were perfusion-fixed in situ with 2% glutaraldehyde or formaldehyde solutions and excised. Histological examination demonstrated extensive arteriosclerotic changes including (i) fragmentation and reduplication of the internal elastic membrane, (ii) myointimal hyperplasia with fibroblastic proliferation including the development of fibrous intimal plaques, and (iii) transmigration and proliferation of smooth muscle cells with scattered monohistiocytes. The specimens showed a range of stenotic changes from 25% to total occlusion of the vascular lumen. These preliminary data demonstrate the feasibility of providing intense arteriosclerotic myointimal histologic changes in the canine peripheral vasculature within a 24-week period. Further refinement of this methodology may provide a practical model for studies of localized peripheral vascular occlusive disease.

Tissue Fusion With Argon, CO2 And Nd:YAG Lasers; Thermal And Histological Comparison

Two mechanisms of laser tissue fusion, thermal and photochemical, are currently being proposed in several types of tissue. In this study we examined the thermal and histologic components of laser fusion in blood vessels and bowel. CO2 and Argon lasers were used to fuse 1 cm canine arteriotomies and 1 cm rabbit enterotomies. Thermal images were concurrently recorded with an AGA Thermovision camera and computer analyzed. Tissue samples from each weld were subsequently prepared for histologic examination.

Laser Vascular Welding: A Comparison Of Thermal Properties Of Argon And CO 2 Energy

The thermal properties and maximum temperatures attained during CO2 (n=20) and Argon (n=20) laser welded repair of arteries were compared in a canine model. An AGA 782 digital thermographic system with spatial and thermal resolution of +0.2mm and +0.2°C was used to continually record and analyze the measurements. Longitudinal incisions of 1 cm length were made in each vessel with a 6-0 prolene stay suture at each apex and the midpoint, forming two 5mm segments. A Sharplan CO2 laser was used at an energy fluence of 1500 J/cm2, 150mw power, spot size of .00049 cm2 and exposure of 5 seconds to induce fusion of each 0.5 cm of vessel wall. Argon fusion was accomplished with the HGM Argon laser using a 300 micron diameter fiber held 1 cm from the surface of the vessel, energy fluence of 570 J/cm2, 500mw power, spot size of 0.066cm2 and total exposure of 75 seconds per 0.5cm length. Continuous irrigation of room temperature saline at 1 drop/second (approx. 3m1/min) was used during argon welding. With CO2 laser welding temperature increased quickly to its maximum (MAX=84.0, MEAN=60.7+ 9.8°C) which was maintained as the laser energy moved slowly (0.1cm/sec) along the vessel edges. In contrast the argon laser welding temperatures rose to a maximum (MAX=48.8, MEAN=45.1+2.7°C) and returned to a baseline temperature with each drop of saline. The thermal difference with these two laser wavelengths may bring about different welding mechanisms and provide an explanation for the increased incidence of thrombus aneurysm formation that has been reported in CO2 laser fusion.

Enterotomy Fusion with Laser Energy: Preliminary Results in Rabbit Ileum

The utility of enterotomy closure with the argon and CO2 lasers was examined in New Zealand white rabbit ileum. Thermal properties of 10 argon (0.5 W power for 30 s, energy fluence 230 J/cm2) and 10 CO2 (1.0 W power for 30 s, energy fluence 2700 J/cm2) laser-fused enterotomies were determined during acute fusion experiments using an AGA 782 digital thermographic camera. Healing of the fusions created by the two lasers was subsequently assessed in an additional group of 28 rabbits by comparing three 1.0-cm longitudinal ileal enterotomies, with each rabbit having both types of laser-welded closures and a sutured control. Thermal measurements made from the 10 closures with each laser revealed that the CO2 fusions generated significantly higher temperatures (max. 198 degrees C, mean 106 +/- 37 degrees C, n = 100) than argon (max. 85.2 degrees C, mean 60.5 + 8.1 degrees C, n = 100) p less than 0.001. In the healing studies, four rabbits died from weld failures (one argon and one CO2 disruption, two rabbits with both welds disrupted). Two additional rabbits died at 1 day and one at 10 days for undetermined reasons. The remainder of the animals were sacrificed at 1 (n = 11), 2 (n = 2) and 4 (n = 9) weeks postoperatively. Sutured closures exhibited more granulation tissue and adhesions surrounding the wounds than did welded closures and seven microabscesses were noted adjacent to sutured repairs. One of the CO2 repairs had an abscess at 4 weeks and none of the argon laser fusions had evidence of disruption or abscess.(ABSTRACT TRUNCATED AT 250 WORDS)