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Adaptation, Psychological↗
Biomedical subjects
L S Bass
Publications and source records attributed to L S Bass.
In vivo comparison of THC:YAG laser welding to sutured closure of biliary tissue.
Percutaneous endoscopic approaches to cholelithiasis are an alternative to extracorporeal shockwave lithotripsy which offer advantages of fewer restrictions on stone size and type as well as avoidance of fragmented stone passage complications. Endoscopic techniques would be facilitated by methods of welding gallbladder tissues. The technical constraints imposed by the endoscopic approach favor nonsuture methods of fusing gallbladder tissues. To evaluate a laser method for fusing biliary tissue, we have compared the healing response of laser-welded versus polyglycolic acid suture-closed incisions in canine gallbladder tissue in vivo. The laser used was a thulium-holmium-chromium:YAG laser producing 200-microsecond, 300-millijoule pulses at 2.15 microns. Serial sacrifice of dogs that underwent laser or suture closure of incisions made in the fundus of the gallbladder revealed that all repairs healed without evidence of leakage or infection. Laser-welded cholecystotomy sites had complete fibrous healing of the wound by two weeks postoperatively and reepithelialization by three weeks after operation. Suture-closed wounds were still without complete epithelization four weeks after the procedure. Laser welding may be a useful technique in endoscopic biliary surgery.
Animals↗
Reinforcement of colonic anastomoses with a laser and dye-enhanced fibrinogen.
The incidence of anastomotic leakage in colonic surgery is approximately 10%. We evaluated a technique of laser-fibrinogen reinforcement to strengthen experimental colonic anastomoses. The technique consisted of the topical application of indocyanine green dye-enhanced fibrinogen to the serosal surface of two-layer inverting anastomoses, followed by exposure with an 808-nm diode laser. In the 28 rabbits used for this study, mean bursting pressure at time 0 was 108 +/- 13 mm Hg in the group receiving anastomoses with sutures alone and 173 +/- 20 mm Hg in the group for which the sutured anastomosis was reinforced with laser-fibrinogen. The difference in bursting pressures between the two groups was statistically significant at time 0. However, at 1, 3, 5, and 7 days, the anastomosis became stronger in both groups and the difference in strength was reduced; the sutured group had more exceptionally weak (less than 110 mm Hg) bonds than the group treated by laser. Thus, laser-fibrinogen reinforcement significantly enhances the early strength of sutured colonic anastomoses. This technique may reduce the incidence of leakage during the first postoperative week and the associated complications in a clinical setting.
Anastomosis, Surgical↗
Strength of laser vascular fusion: preliminary observations on the role of thrombus.
We hypothesized that autologous clot deposited on the luminal surface of laser vascular welds immediately after creation would produce higher time zero bursting pressures that could be achieved in welds perfused with saline alone. To test this hypothesis, we compared bursting pressures of welds created in isolated rabbit aortic segments 1) with saline perfusion only, 2) with blood perfusion, and 3) with blood perfusion followed by infusion of urokinase. Tissue welds with saline perfusion had a mean bursting pressure of 159 +/- 45 mm Hg; tissue welds following blood perfusion had a mean pressure of 262 +/- 29 mm Hg; tissue welds with blood perfusion followed by urokinase infusion had a mean bursting pressure of 187 +/- 35 mm Hg. The saline and urokinase groups were not significantly different. However, the blood-perfused group was significantly higher than both the saline group and the urokinase group. Thus, the addition of urokinase eliminates the beneficial effects noted after blood reperfusion. These observations suggest that the enhancement of weld strength following exposure to blood is due predominantly to the adherence of fibrin-platelet aggregates at the site of the weld.
Anastomosis, Surgical↗
Anastomosis of biliary tissue with high-frequency electrical diathermy.
Laser tissue fusion results from the conversion of light to thermal energy, creating tissue heating and protein denaturation. Accurately controlled tissue heating from smaller, less expensive, non-laser sources should be able to duplicate the fusion or welding of tissues, which has been demonstrated with a variety of lasers. We examined the capability of high-frequency electrical diathermy to create effective tissue fusion with limited collateral thermal damage. Using an electrical diathermy device with up to 14 W output power at 13.56 MHz, the cystic ducts of freshly harvested canine gallbladders were fused shut. Immediately after closure of the cystic ducts, bursting pressure was determined. Welding time was approximately 60 s. Mean bursting strengths immediately after closure were 207 mm Hg (+/- 94.3) in air (n = 10) and 202 mm Hg (+/- 44.7) under water immersion (n = 9). Histologic sectioning revealed a full-thickness denaturation of collagen fibers with fusion. Our preliminary investigations suggest that high-frequency electrical diathermy may provide practical advantages for fusion of biliary tissues when compared with conventional suture closure and laser fusion.
Anastomosis, Surgical↗
Canine colonic anastomoses reinforced with dye-enhanced fibrinogen and a diode laser.
Leakage from colonic anastomoses is a common cause of morbidity in patients recovering from bowel surgery. We evaluated a technique of laser-fibrinogen reinforcement to strengthen colonic anastomoses in a canine model. After creation of eight single-layer interrupted suture anastomoses in six dogs, indocyanine green-dye-enhanced fibrinogen was topically applied to the serosal surface and exposed to 808 nm diode laser energy. Immediately following colonic anastomosis, the mean leakage pressure was 137 +/- 22 mm Hg in the group (n = 8) using sutures alone and 326 +/- 67 mm Hg (P less than 0.001) in the group (n = 8) after the sutured anastomosis was reinforced with lasered-fibrinogen. On histological examination, no evidence of thermal injury to the tissue edges was noted and a layer of fibrinogen bridged the anastomotic gap. Laser dye-enhanced fibrinogen reinforcement significantly enhances the strength of sutured colonic anastomoses without causing appreciable thermal injury to the host tissues.
Anastomosis, Surgical↗
Tissue soldering by use of indocyanine green dye-enhanced fibrinogen with the near infrared diode laser.
Anastomoses welded by laser have been strengthened by applying a solder of fibrinogen combined with a laser energy absorbing dye (indocyanine green, maximum absorbance 805 nm) to the anastomotic site before continuous-wave diode laser exposure (808 +/- 1 nm, 4.8 W/cm2). Immediately after creation, the bursting pressures of welds created without fibrinogen (262 +/- 29 mm Hg, n = 11) were significantly less than repairs with fibrinogen (330 +/- 75 mm Hg, n = 11) (p less than 0.05). When repairs performed with fibrinogen were exposed to urokinase (25,000 IU) the bursting pressures were not significantly different from baseline (290 +/- 74 mm Hg, n = 5). Aortotomies closed by suture did not burst but leaked at pressures significantly below those of vessels closed by laser (165 +/- 9 mm Hg, n = 11) (p less than 0.01). Twenty-two repairs soldered with fibrinogen were incorporated into survival studies in rabbits and examined from 1 to 90 days after operation. No anastomotic ruptures, thromboses, or aneurysms were identified. Soldered sites rapidly regenerated a new intimal surface and healed by myofibroblast proliferation. No significant foreign body response was identified; the fibrinogen was resorbed. Laser soldering with exogenous fibrinogen is feasible without topical administration of additional clotting agents, significantly improves the bursting strength of primary laser welded anastomoses, and appears to result from urokinase-resistant fibrinogen cross-linking.
Anastomosis, Surgical↗
Welding of gallbladder tissue with a pulsed 2.15 microns thulium-holmium-chromium:YAG laser.
Percutaneous endoscopic approaches to cholelithiasis would be facilitated by methods for welding gallbladder tissues. We evaluated the bursting pressure and histologic appearance of canine gallbladder tissue welded with a thulium-holmium-chromium:YAG (THC:YAG) laser producing a 2.15 microns pulsed output. The tissue absorption characteristics at this wavelength as well as the pulsed nature of the output permit tissue welding with limited collateral thermal damage. The THC:YAG is compatible with a flexible fiberoptic delivery system. Bursting strengths of the welded junctions averaged 42 mm Hg, which is above physiologically encountered pressures. Histologic sections of the bonded tissues revealed tissue fusion and limited thermal injury to the surrounding tissue. We feel that THC:YAG laser welding may be a useful technique in the clinical development of percutaneous endoscopic biliary surgery.
Animals↗
In vitro comparison of thulium-holmium-chromium: YAG and argon ion lasers for welding of biliary tissue.
Laser welding offers several potential advantages over suture closure, including improved healing, lack of a nidus for stone formation, and greater speed and ease. We examined in vitro gallbladder cystic duct welds created by two different systems, the thulmium-holmium-chromium (THC):YAG (2,150 nm) and argon ion (488-514 nm) lasers, in an effort to define suitable parameters for tissue fusion. Mean bursting pressures for argon welds were 95 mm Hg at 1.5 W CW and 26 mm Hg at 1.5 W, 50 msec chopped delivery. For the THC:YAG laser, the mean bursting pressure for welds created with 300 mJ pulses was 45 mm Hg. Full-thickness tissue fusion and limited collateral thermal damage were observed histologically for both the CW argon and pulsed THC:YAG welds. Examination of the suggested mechanisms of tissue fusion for these photothermal lasers suggests that increased duration of tissue heating at the appropriate temperature results in more extensive collagen crosslinking and a stronger weld.
Animals↗
Dye-enhanced laser tissue welding.
For vascular anastomosis, use of topical photosensitizing dye enhances selective delivery of laser energy to target tissue, thus reducing the amount of collateral thermal injury and threshold power required for welding. For fluorescein isothiocyanate (FITC)--stained rabbit aorta in vitro, the threshold for tissue blanching was 15 seconds of 100 mW exposure of cw argon ion laser compared with 15 seconds at 300 mW for unstained tissue. The threshold power density needed for argon laser welding of abdominal aortotomies in rabbits in vivo was 3.8 W/cm2 with FITC and 7.6 W/cm2 without the dye. However, bursting pressures for the two groups (164 mm Hg with FITC, 147 mm Hg without FITC) were not significantly different. Histology revealed decreased collateral thermal damage in FITC-enhanced welds. Use of photosensitizing dyes for tissue welding is feasible and may allow arterial welding with lower power laser systems and cause less thermal trauma by lowering threshold power levels.
Animals↗
Sutureless microvascular anastomosis using the THC:YAG laser: a preliminary report.
Laser anastomosis of the rat carotid artery was performed using a new mid-infrared laser, the pulsed thulium-holmium-chromium: YAG (THC:YAG) laser (2.15 microns). Solid silicone stents made stay sutures unnecessary for coaptation of vessel edges during laser bonding. Grossly, the laser anastomoses displayed minimal thermal distortion of the vessel contour and no tissue carbonization. Of the 30 anastomoses performed, 27 were patent and 3 had separation of the weld shortly after the approximator clamp was released. Mean anastomotic time was 4 min 48 sec. Mean bursting pressure for the 9 vessels tested was 400 mm Hg. Thrombosis did not occur at any time during our examination of these anastomoses. Fusion of collagen fibers in the media was confirmed histologically. Unlike the CO2 laser, the THC:YAG is transmissible through flexible silica fibers, which greatly facilitates delivery of the laser in a microsurgical operative field. The THC:YAG provides shallower absorption depth than Nd:YAG and argon lasers but somewhat deeper tissue penetration than CO2. For microvessels, this intermediate absorption results in full-thickness fusion of the media, with minimal thermal damage to vascular tissue adjacent to the anastomosis.
Anastomosis, Surgical↗
The Sdx antigen and antibody: biochemical studies on the inhibitory property of human urine.
Anti-Sdx is an IgM complement-binding autoantibody that defines a red cell antigen which is independent of I, i, Sp1 (Pr) and Gd. Hemagglutination by the antibody is unusually sensitive to variation in pH, salt, or other charged molecular species. The antibody is inhibited by urine from Sd(a+) persons, but inhibition is a nonspecific effect caused by charged molecules. No specific Sdx substance could be demonstrated, and Sdx antigen does not appear to be directly associated with the Sid blood group. In view of these findings we propose that this antibody should be renamed anti-Rx.
Animals↗
Absolute stereochemistry and dopaminergic activity of enantiomers of 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine.
Resolution of the unique dopamine receptor agonist 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine (1) was achieved by a stereospecific multistep conversion of the readily separated enantiomers of its O,O,N-trimethylated precursor 2. The absolute stereochemistry of the antipodes of 2-MeI was determined by single-crystal X-ray diffractometric analysis, thus permitting assignment of the configuration of stereospecifically related 1, as well as that of the synthetic intermediates. High-performance liquid chromatography of diastereoisomeric derivatives was utilized to determine the enantiomeric excess of the R (greater than 97%) and S (greater than 89%) isomers of 1. Examination of the isomers in several in vitro and in vivo tests for both central and peripheral dopaminergic activity revealed that activity resided almost exclusively in the R isomer. The results suggest that the properly oriented 1-phenyl substituent of 1 is important for dopamine-like activity; it may contribute to receptor binding by interaction with a chirally defined accessory site. Configurational and conformational requirements for receptor binding of 1 are considered in relationship to previously described dopaminergic agents. These studies, in accord with previous suggestions, indicate that (R)-1 interacts with dopamine receptors in a conformation in which the catecholic hydroxyls and basic nitrogen are at least nearly maximally separated.
2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗