Bursting pressures of CO2 laser-welded rabbit ileum

In this study, the short-term bond strength of laser-welded New Zealand white rabbit ileum was examined. Forty-eight longitudinally oriented 0.5-cm transmural, scalpel incisions were reanastomosed solely through the use of the CO2 continuous wave laser at low energy levels. Random power levels of 250, 500, 750, or 1,000 mW were delivered to weld sites by either continuous application for 30 seconds or a pulsating application (ie, 0.5 seconds on, 0.5 seconds off) for 60 seconds. This provided 53.6, 107.1, 160.7, and 214.3 J/cm2, respectively. With the aid of a plexiglass clamp and pressure monitored infusion system, each type of weld was tested six times to determine the intraluminal hydrostatic pressure required to burst the welded seam 1 minute after completing the weld. For the welds made with 107.1, 160.7, and 214.3 J/cm2 in both lasing modes, the mean bursting pressure was 40.7 mmHg (SD +/- 24.9) with no statistically significant difference in weld strengths at these energy densities. There was also no difference between continuous and pulsating delivery methods. However, the energy density of 53.6 J/cm2 in either method produced a mean bursting pressure significantly lower than those produced by the higher energy densities tested and below the estimated basal ileal intraluminal pressure of approximately 9 mmHg. Since 107.1 J/cm2 energy density caused the minimal gross tissue changes while producing an equally strong bond and since continuous is faster than pulsating, 500 mW of continuous delivery was considered the optimal setting for the CO2 laser welding of rabbit ileum.     

Vasovasostomy in the murine vas deferens: comparison of the Nd:YAG laser at 1.06 microns and 1.318 microns to the CO2 laser

A comparison is made of laser anastomoses of the murine vas deferens at different energies with the neodymium (Nd):YAG laser at 1.06 micron and 1.318 micron and with the CO2 laser. A total of 28 welds were performed with a free-hand technique employing a 600-micron silicon fiber with the Nd:YAG and a hand piece with a 500-micron spot size for the CO2. After 6 weeks, all animals were sacrificed and the vasa evaluated for patency. Fifteen out of 28 controls repaired with microsurgical techniques were found to be patent; 4/10 vasa were patent with use of the Nd:YAG at 1.318 micron at laser energies of 300 mW and 500 mW. At 1.06 micron, only 1/4 anastomoses was patent at a power setting of 1 W. None of the anastomoses performed with the CO2 laser was patent. Histologic study revealed intense fibrosis in all the lasered vasa, with sperm granuloma formation associated with most anastomoses. Although this is a preliminary study, it appears that the Nd:YAG laser at 1.318 micron and a power setting of 300-500 mW provides patency rates superior to the Nd:YAG at 1.06 micron and to the CO2 lasers and is equivalent to standard micro-surgical techniques in the murine vas deferens.     

Healing of unstented tubularized incised plate urethroplasty: an experimental study in a rabbit model

OBJECTIVE: To develop a rabbit model to study the temporal healing taking place after an unstented tubularized incised plate urethroplasty (TIPU). MATERIALS AND METHODS: The study comprised 13 New Zealand white rabbits (3-4 kg); the ventral wall of the penile urethra was excised to create a hypospadias-like defect. A vertical incision was made in the dorsal urethral plate and the incised urethra tubularized. Two animals were killed at 2 days and two at 5 days after surgery, and the remainder killed at 2, 6 and 12 weeks (three each). A retrograde urethrogram was taken at autopsy. Serial sections of the penis were stained with haematoxylin and eosin, and Masson trichrome for microscopy. RESULTS: There were no deaths related to the procedure and all animals voided spontaneously. Retrograde urethrograms showed no fistulae or stricture. Microscopic examination at 2 and 5 days showed partial coverage of the incision with regenerating urothelium. At 2 weeks there was full-thickness urothelium with a mild inflammatory reaction. At 6 and 12 weeks, remodelling of the peri-urethral connective tissue with minimal fibrosis completed the healing. CONCLUSION: The mechanism of healing of the incised urethral plate involves normal urothelial regeneration into the depth of the incised defect, which explains the gain in urethral diameter after TIPU. Urine flow, during normal voiding, might be responsible for keeping the incised plate open during urothelial regeneration. A urethral stent was not necessary for normal healing in this model.     

CO2 and argon laser vascular welding: acute histologic and thermodynamic comparison

CO2 and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO2 and argon laser welding of 1-cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of +/-0.2 mm and +/-0.2 degree C, respectively, were analyzed. A HGM argon laser using a 300-microns optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO2 welds were performed with a Sharplan CO2 laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon-n = 20; power = 500 mW; energy fluence = 1,400 J/cm2; Tmax = 48.8 degrees C; T mean +/- S.D. = 45.1 +/- 2.7 degrees C; CO2-n = 20; power = 150 mW; energy fluence = 3,000 J/cm2; Tmax 84.0 degrees C; T mean +/- S.D. = 60.7 +/- 9.8 degrees C. There was a significant difference (P less than .05) in thermal measurements between successful CO2 and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO2 laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

CO2 laser annular thermokeratoplasty: a preliminary study.

Since most techniques of refractive surgery currently in use or being developed have the potential for significant side effects, there is a need for investigating alternative procedures. We herein report on the use of a pulsed CO2 laser beam delivered through a pair of complementary axicons to produce a ring of stromal collagen contraction resulting in the flattening of the corneal apex of cadaver eyes. Irradiances of 29 W/cm2 and 23 W/cm2 were used for rings of 5.5 mm and 7.0 mm, respectively. The creation of a ring of 7.0 mm in diameter did not affect the corneal curvature significantly but when the diameter was reduced to 5.5 mm, substantial flattening proportional to the dose of radiation took place. In our system, it was possible to achieve up to 11.3 diopters of mean keratometry flattening (90 joules, 5.5 mm of diameter). In addition, a 1 mm posterior displacement of the corneal dome without histological evidence of closure of the iridocorneal angle was observed. Annular thermokeratoplasty (ATK) may minimize side effects encountered with other refractive procedures since it does not require ablation, incisions, or interaction with the central optical zone.     

Primary closure of choledochotomy using CO2 laser: Comparison with suture closure

This study was designed to compare laser welding to suture closure of the common bile duct (CBD). A 12 mm linear choledochotomy was closed in 12 mongrel dogs using tissue welding lowenergy CO₂ laser. Tissue welding was accomplished at 5.0 w/cm² for 120 sec. Twelve similar mongrel dogs (control) were treated with CBD closure using 5/0 Vicryl (polyglactin 910, Ethicon, Inc., Somerville, NJ) interrupted simple stitches. All animals were sacrificed at six weeks. Gross and histologic evaluation of the choledochotomy site were performed. There were no statistical differences in parameters of comparison in the two groups. These parameters were pre- and post-treatment measurements of liver function tests, stenosis, and dehiscence. However, it must be noted that there was a 33% (4/12) incidence of dehiscence and death in the CO₂ laser welded choledochorrhaphy. This result, although not statistically significant, is clinically significant. We conclude that the tensile strength of CO₂ laser welded CBDs must be optimized and that these results are preliminary and still unreliable to recommend for clinical adaptability. © 1993 Wiley-Liss, Inc.     

Long-term angiogenic activity of free grafts and pedicle flap in a rabbit urethroplasty model

Purpose

We studied the late angiogenic activity of free grafts and a pedicle flap in a rabbit urethroplasty model to determine whether angiogenic activity plays a role in late outcomes of urethral reconstruction in rabbits.

Methods

Twenty-eight rabbits were randomly divided into five groups according to the method used to bridge a urethral defect as an onlay patch: Control, simple closure of urethral defect (Group O₁); free penile skin graft (FPSG, Group A₁); buccal mucosal graft (BuMG, Group B₁); bladder mucosal graft (BlMG, Group C₁); and pedicle penile skin flap (PPSF, Group D₁). Angiogenic activity of the patch on postoperative day 84 was assessed by immunohistochemistry.

Results

The angiogenic activity in Groups O₁, A₁, B₁, C₁, and D₁ was 23.33 ± 4.92 (means ± SD), 42.89 ± 6.52, 55.78 ± 3.46, 53.61 ± 6.17, and 24.11 ± 9.07 vessels per optical field, respectively. There were statistically significant differences (p < .001) between Group O₁ and A₁ B₁, C₁, Group A₁ and B₁, C₁, D₁, Groups B₁ and D₁ and Groups C₁ and D₁, but not between Groups O₁ and D₁ (p = 1.000) and Groups B₁ and C₁ (p = .872). The long-term angiogenic activity of all the groups was significantly lower (p < .001) than in the corresponding early groups.

Conclusions

Although the angiogenic activity of all the groups decreased in the late assessment, the buccal mucosal graft continued to exhibit elevated angiogenesis above bladder or skin (free or pedicle) graft. Therefore, buccal mucosal patch graft might be preferable because of its easier harvesting.     

Ab-interno neodymium:YAG versus erbium:YAG laser sclerostomies in a rabbit model.

This study was undertaken to determine whether thermally-induced tissue necrosis was a factor in ab-interno contact-laser sclerostomy failure. A rabbit model was used to compare the continuous-wave Neodymium (Nd):YAG with the pulsed Erbium (Er):YAG laser with respect to such failure. Laser energy was focused into a fused-silica fiber optic (400 microns) for the Nd:YAG laser (12 W; 3 to 5 seconds), and into a single-crystal, uncladded sapphire fiber optic (250 microns) for the Er:YAG laser (7 to 8 mJ; 250 microseconds; 6 to 8 pulses). The Nd:YAG and Er:YAG lasers required from 21 to 35 J and from 42 to 64 mJ, respectively, to create the sclerostomies. Filtering blebs and intraocular pressure reduction lasted longer (log-rank test; P less than .03) and surgical complications were fewer in the Er:YAG group than in the Nd:YAG group. By creating sclerostomies with minimal thermal damage, the Er:YAG laser may offer significant clinical advantages over lasers producing larger thermal effects.     

The addition of O2 to the CO2 does not prevent the systemic effects of the CO2 pneumoperitoneum in a rabbit model

CO2 pneumoperitoneum used in endoscopic surgery induces systemic effects by CO2 absorption. It was claimed that a reduction in CO2 pneumoperitoneum-induced metabolic hypoxemia was achieved by the addition of small amounts of O2 to the CO2 in a rabbit ventilated model. We reevaluated the effects of the addition of O2 to the CO2 pneumoperitoneum upon CO2 absorption in a rabbit model. The effects of a pneumoperitoneum using 100% CO2, 90% CO2 + 10% O2, 95% CO2 + 5% O2, or 100% O2 on arterial blood gases, acid base and O2 homeostasis were evaluated in nonintubated rabbits. A pneumoperitoneum pressure of 10 cm H2O (approximately 7.35 mm Hg) was used. CO2 pneumoperitoneum of 120 minutes affected blood gases and acid base homeostasis. Whereas partial pressure of CO2 and HCO3 increased (P < 0.001) during pneumoperitoneum, pH and partial pressure of O2 decreased (P < 0.001). Similar results were obtained in O2-CO2 pneumoperitoneum (P > 0.05). CO2 pneumoperitoneum profoundly affected blood gases and acid base homeostasis, resulting in metabolic hypoxemia. The addition of O2 to the CO2 did not prevent the systemic effects of CO2 pneumoperitoneum in nonintubated animals.     

CO2 laser in septic surgery.

Authors have performed 29 septic operations by a TLS61 60 W CO2 laser apparatus. In accordance with international experience, favorable results have been obtained in laser surgery of vascularized, hemophilic and bacterium penetrated alterations and infected wounds.     

The evaluation of rhytidectomy flap healing after CO2 laser resurfacing in a pig model.

OBJECTIVE: This study was conducted to determine when it becomes safe to perform laser resurfacing after rhytidectomy flap elevation. STUDY DESIGN: Eighty-four sites on 12 domestic Yorkshire pigs were selected; 4 x 10-cm skin flaps were elevated in 72 of the 84 sites and shortened 10%. The 12 remaining sites (controls) were treated with laser resurfacing alone. Laser resurfacing was also performed at days 0, 7, 14, 21, and 28 after closing the skin flaps. The healing time for the laser-resurfaced sites without flap elevation were compared to that of the skin flaps treated with the laser at days 0, 7, 14, 21, and 28. Twelve "skin flap" controls were elevated, shortened 10%, and closed without laser treatment. Resurfacing was performed using 2 passes with the Sharplan Silk Touch CO(2) laser. RESULTS: The average healing time for the skin flaps treated with the laser at day 0 was 23.9 days. All of these flaps showed skin slough with delayed healing followed by scar formation. The areas treated with the laser alone (controls), and the subsequent skin flaps treated with the laser postoperatively at days 7, 14, 21, and 28 days completely re-epithelialized in an average of 7.8, 8.1, 7.3, 7.4, and 7.3 days, respectively. There were no statistically significant differences in healing time between the controls and flaps treated with the laser on or after 7 days (P > 0.05). However, there were statistically significant differences in healing time between the laser-treated skin flaps at day 0 and the controls, between the laser-treated flaps on day 0 and day 7, and between the laser-treated flaps on day 0 and day 14 (P < 0.001). Because there was little difference in healing time after 14 days, only the healing times for laser-treated skin flaps up to 14 days were compared using paired t tests. CONCLUSIONS: From our observations using a pig model, we conclude that skin flaps may be safely laser resurfaced about 1 week postoperatively. On the other hand, simultaneous flap elevation and laser resurfacing results in delayed healing with subsequent scar formation.     

Development of a carbon dioxide laser cystoscope

CO₂ laser lesions were created at varying power densities on the exteriorized canine bladders. A 50-watt carbon dioxide continuous laser coupled to a Zeiss surgical microscope was used. A schematic power curve was developed indexing depth of bladder penetration by the laser against laser energy output. Once the optimal power settings for the carbon dioxide laser were established, vertical heat transmission, hemostasis, and healing were studied. A prototype carbon dioxide laser cystoscope was then constructed that allowed endoscopic delivery of the CO₂ laser beam into the intact canine bladder. The beam was focussed by a germanium lens and directed out the end of the endoscope, using a movable mirror. Eight dogs were then endoscopically studied in vivo.     

Toward a common therapeutic framework in castration-resistant prostate cancer: A model for urologic oncology and medical oncology interaction

BackgroundThe rapid evolution of palliative therapeutic choices in the last few years for patients with advanced castration-resistant prostate cancer (CRPC) has resulted in a dilemma currently troubling a few other epithelial malignancies: which systemic agent to choose and at what time? In addition, which specialty specifically directs the delivery of such care—Urology or Medical Oncology—has not been clearly established.ApproachRecognizing the lack of consensus, we propose a framework for Urology and Medical Oncology interactions that is founded on models that have succeeded in the past.ConclusionThis approach aims to focus the care on the patient with CRPC rather than on his physicians and promises to improve patient outcomes in this disease state.     

Experimental CO2 laser myringotomy.

OBJECTIVE: The purpose of this study was to compare closure rates of CO2 laser myringotomies with those produced conventionally with a knife. STUDY DESIGN AND SETTING: We investigated closure rates in 3 experimental groups of chinchillas: (1) semicircular myringotomy in both ears either produced with a knife or CO2 laser; (2) CO2 laser myringotomy, round in one ear and kidney shaped in the other; (3) CO2 laser myringotomy, incisional in one ear and kidney shaped in the other. RESULTS: Patency of knife myringotomies was shorter (P < 0.01) than of similar laser myringotomies, means 10.0 and 21.8 days, respectively. The patency of kidney-shaped laser myringotomies was longer (P < 0.05) than of round ones. Incisional laser myringotomies remained open longer (P < 0.01) than round ones. CONCLUSION: Use of CO2 laser as well as certain geometries delay the closure of myringotomies. By allowing perforations of different shapes and sizes, CO2 laser myringotomy may become an alternative in the treatment of otitis media.