Search PubMed⌕ Search

Biomedical subjects

D P Poppas

Publications and source records attributed to D P Poppas.

At least 19 recordsLinked to original sources
PubMed1996

Temperature-controlled laser photocoagulation of soft tissue: in vivo evaluation using a tissue welding model.

BACKGROUND AND OBJECTIVES: Laser surgical procedures involving photocoagulation of soft tissue have relied on subjective visual endpoints. The thermal damage to the denatured tissue in these procedures is highly dependent on the tissue temperatures achieved during laser irradiation. Therefore, a system capable of real time temperature monitoring and closed loop feedback was used to provide temperature controlled photocoagulation (TCPC). STUDY DESIGN/MATERIALS AND METHODS: The TCPC system consisted of a 1.32 microns Nd:YAG laser, an infrared thermometer, and a microprocessor for data acquisition and feedback control. A porcine skin model was used. Tissue welds were completed to evaluate the photocoagulation effects at different predetermined temperatures. A quantitative measurement of tissue photocoagulation was obtained by tensile strength measurements of the laser repairs. Histology of the irradiated tissue was used to determine the extent of thermal injury associated with different photocoagulation temperatures. RESULTS: The TCPC system was capable of maintaining a relatively constant temperatures (+/- 4 degrees C) during laser irradiation. The tensile strengths of acute repairs increased with temperature over the range studied (65-95 degrees C). Tensile measurements made after several days of healing showed that higher temperature (95 degrees C) welds had lower strengths than repairs completed at lower (65 degrees C or 75 degrees C) temperatures and were significantly lower at 3 days. Acute histology showed that the amount thermal damage was strongly dependent on the tissue temperature and increased both in tissue depth and lateral to the repair with temperature. The histologic results suggest that the increase in the acute repair tensile strength as the weld temperature increased was due to an increase in the depth of tissue photocoagulation. The increase in the lateral tissue injury measured histologically for higher temperature welds likely resulted in the decreased chronic tensile strengths, as a healing response to excessive thermal damage. CONCLUSION: Tissue temperatures can be controlled during laser photocoagulation of skin. The degree of acute and chronic tissue damage is highly dependent on the temperature during welding. By controlling the tissue temperature during laser procedures, the surgical outcome can be more reliably predicted and reproduced, as compared to the conventional open loop methods. In addition, the use of a TCPC system should significantly reduce the learning curve for photothermal surgical procedures.

Animals↗
PubMed1996

Human albumin solders for clinical application during laser tissue welding.

BACKGROUND AND OBJECTIVE: Fifty percent human albumin solder significantly improves weld strength when compared to lower concentrations [Wright et al., ASLMS meeting, April, 1995]. We developed a method for preparing 50% human albumin that may be considered compatible for clinical applications. STUDY DESIGN/MATERIALS AND METHODS: Fifty percent human albumin solder was prepared from 25% commercially available human albumin using a lyophilization technique. Assessment of sterility, viscosity, pH, and peak absorption wavelength were performed. RESULTS: This report describes the methodology used to prepare a 50% human albumin solder that is compatible with clinical use. Maintenance of the structural integrity of the albumin was confirmed by polyacrylamide gel electrophoresis. CONCLUSION: This solder preparation can be used alone or with the addition of exogenous chromophores. The final product is sterile, incorporates viral free protocols, maintains high viscosity, and can be applied easily during open or laparoscopic procedures.

Absorption↗
PubMed1996

Human albumin solder supplemented with TGF-beta 1 accelerates healing following laser welded wound closure.

BACKGROUND AND OBJECTIVE: We examined the possibility that human albumin solder can be used as a vehicle for site specific delivery of growth factors for the purpose of accelerating tissue repair following laser welded wound closure. Certain human recombinant growth factors have been shown to accelerate wound healing in model systems. Pilot in vitro studies have established that several growth factors, including TGF-beta 1, maintain bioactivity following exposure to temperatures achieved during laser tissue welding. Using a temperature controlled laser delivery system (TCL) to precisely maintain welding temperatures, it is now possible to avoid thermal denaturation of exogenous bioactive molecules such as growth factors. STUDY DESIGN/MATERIALS AND METHODS: HB-EGF, bFGF, and TGF-beta 1 were tested in vitro for maintenance of bioactivity after exposure to 80 degrees C. In vivo experiments using porcine skin determined the efficacy of solders augmented with growth factors. Incisions were repaired using human albumin alone or supplemented with HB-EGF (2 micrograms), bFGF (10 micrograms), or TGF-beta 1 (1 microgram). Wounds were excised at 3, 5, and 7 days post-operatively. Tensile strength, total collagen content, and histology were performed. RESULTS: At 3 days, tensile strength (TS) of TGF-beta 1 wounds were 36% (P < 0.05) and 20% (n.s.) stronger than laser alone and suture closures, respectively. By 5 days the TS of the TGF-beta 1 group increased by 50% (P < 0.05) and 59% (P < 0.02) over laser alone and suture groups, respectively. At 7 days the TGF-beta 1 group was 50% (P < 0.05) and 79% (P < 0.01) stronger than laser solder alone or suture, respectively. The HB-EGF and bFGF groups were equivalent to the laser solder group at all time points. Total collagen TGF-beta 1 Accelerates Healing Following Laser Welding content at 7 days increased in the TGF-beta 1 group by 7% (n.s.) over the suture group and 21% (P < 0.05) in the laser group. CONCLUSION: Human albumin solder supplemented with TGF-beta 1 increases the early post-operative strength of laser welded wounds. This novel application of laser tissue soldering augmented with a growth factor has the potential to bring about immediate fluid tight seals while providing site specific delivery of biological modifiers. This may lead to an overall improvement in post-operative convalescence, wound infections, and hospital costs.

Albumins↗
PubMed1996

Laparoscopic orchiopexy: clinical experience and description of technique.

PURPOSE: We reviewed the experience, early followup and technique of laparoscopic treatment of the nonpalpable undescended testis at our institution. MATERIALS AND METHODS: Charts of patients who underwent laparoscopic treatment of an intra-abdominal testis from September 1992 to October 1994 were reviewed. RESULTS: A total of 13 laparoscopic orchiopexies was performed on 11 children with nonpalpable undescended testes. In 10 cases sufficient length was gained on the spermatic vessels using laparoscopic dissection to perform tension-free orchiopexy without the need for division of the spermatic vessels. CONCLUSIONS: When localization of an intra-abdominal testis is confirmed, orchiopexy can be performed safely with minimal morbidity using a laparoscopic approach. Length of hospital stay and postoperative morbidity may be improved in comparison to traditional techniques.

Child↗
PubMed1996

Laparoscopic laser assisted auto-augmentation of the pediatric neurogenic bladder: early experience with urodynamic followup.

PURPOSE: We report our initial experience with laparoscopic laser assisted bladder auto-augmentation for treatment of the symptomatic pediatric neurogenic bladder. MATERIALS AND METHODS: Laparoscopic auto-augmentation of the bladder was performed in 2 children with myelodysplasia and high pressure neurogenic bladders unresponsive to medical management. Detrusorotomy was done using the KTP-532 laser. Laser energy was directed to the tissue to evaluate long-term effects of the procedure. RESULTS: Laparoscopic bladder auto-augmentation can be performed easily and with less morbidity compared to open auto-augmentation. Although results at 6 weeks showed improvement, enterocystoplasty was ultimately performed in both cases due to symptomatic recurrence of incontinence associated with increasing peak detrusor pressure and decreasing compliance. CONCLUSIONS: While this technique has the potential to offer minimally invasive correction in patients with low capacity, high pressure bladders, further modifications will be required to achieve long-term success.

Child↗
PubMed1995

Laser tissue welding in genitourinary reconstructive surgery: assessment of optimal suture materials.

OBJECTIVES: Laser tissue welding in genitourinary reconstructive surgery has been shown in animal models to decrease operative time, improve healing, and decrease postoperative fistula formation when compared with conventional suture controls. Although the absence of suture material is the ultimate goal, this has not been shown to be practical with current technology for larger repairs. Therefore, suture-assisted laser tissue welding will likely be performed. This study sought to determine the optimal suture to be used during laser welding. METHODS: The integrity of various organic and synthetic sutures exposed to laser irradiation were analyzed. Sutures studied included gut, clear Vicryl, clear polydioxanone suture (PDS), and violet PDS. Sutures were irradiated with a potassium titanyl phosphate (KTP)-532 laser or an 808-nm diode laser with and without the addition of a light-absorbing chromophore (fluorescein or indocyanine green, respectively). A remote temperature-sensing device obtained real-time surface temperatures during lasing. The average temperature, time, and total energy at break point were recorded. RESULTS: Overall, gut suture achieved significantly higher temperatures and withstood higher average energy delivery at break point with both the KTP-532 and the 808-nm diode lasers compared with all other groups (P < 0.05). Both chromophore-treated groups had higher average temperatures at break point combined with lower average energy. The break-point temperature for all groups other than gut occurred at 91 degrees C or less. The optimal temperature range for tissue welding appears to be between 60 degrees and 80 degrees C. CONCLUSIONS: Gut suture offers the greatest margin of error for KTP and 808-nm diode laser welding with or without the use of a chromophore.

Evaluation Studies as Topic↗
PubMed1995

Urologic causes of gynecomastia: approach to diagnosis and management.

A 27-year-old man presented with bilateral painful breast enlargement and recent onset right testicular swelling. After appropriate evaluation, a radical orchiectomy was performed, and a Leydig cell tumor was found. The various urologic etiologies for gynecomastia are presented, as are the potential interventions. A rational approach to the patient with new onset breast swelling is presented.

Adrenal Gland Neoplasms↗
PubMed1995

Use of a catheter limiter during intermittent catheterization.

We report on the use of a new device, the catheter limiter, to facilitate clean intermittent catheterization. The device limits the length of catheter entering the urethra. This provides a means to reduce the risk of mechanical injury and perforation, minimizes incomplete emptying, and improves safety and patient acceptance of intermittent catheterization.

Equipment Design↗
PubMed1995

Laparoscopic laser-assisted bladder autoaugmentation.

OBJECTIVES: The purpose of this study is to examine the feasibility of performing a laparoscopic bladder autoaugmentation and to assess the urodynamic characteristics of an autoaugmented bladder. METHODS: Laparoscopic bladder autoaugmentation was performed in 9 female canines (20 to 30 kg). Following laparoscopic access to the peritoneal cavity, a midline bladder seromyotomy was performed using the potassium titanyl phosphate 532 nm laser. This produced a large bladder diverticulum. Changes in bladder volume and compliance were quantified over a 3-month period of follow-up. RESULTS: Urodynamic evaluation demonstrated an increase in bladder capacity 6 weeks postoperatively in 8 of 9 dogs, with an average volume increase of 45%. Bladder compliance improved in 7 of 9 dogs with an average increase in compliance of 67%. Three months postoperatively, bladder capacity remained increased in 5 of 9 dogs, with an average increase in volume of only 5.3%. An improvement in compliance was sustained in 5 of 9 animals with an average increase of 13.9%. Laparoscopic exploration revealed grossly normal bladders with adhesions of omentum to the seromyotomy site in all canines and the anterior abdominal wall in 2 of 9 canines. Histologically, the seromyotomy site was devoid of muscle with an intact urothelium and a proliferation of loose connective tissue. CONCLUSIONS: The technique of laparoscopic bladder autoaugmentation can be performed easily in the canine model. Although results at 6 weeks show significant improvement, the longer term, 3-month results were not statistically significant. This technique has the potential to offer a minimally invasive correction for patients with low-capacity, high-pressure bladders that have failed pharmacologic treatment.

Abdominal Muscles↗
PubMed1994

Development and initial application of a real time thermal control system for laser tissue welding.

The ability to sense and control continuously surface temperatures of a tissue being exposed to laser radiation could standardize parameters and eliminate subjective interpretation of results during laser tissue repair. We describe the development and testing of a control system that enables the operator to maintain relatively specific tissue temperatures for the purpose of laser welding. After initial development, the infrared thermal control system combined with an argon laser was used to repair urethral defects in 45 adult male rats. Repairs were completed using various predetermined temperatures of 50, 60, 70, 80 or 90C. The integrity of each weld was quantitatively determined by measuring intraluminal bursting pressure immediately after repair. In all temperature groups bursting pressures were in excess of 85 mm. Hg. Those performed at 80C produced the strongest weld (analysis of variance p = 0.0001). However, welding temperatures above 70C sacrificed the integrity of the underlying urothelium producing obvious damage when viewed microscopically. We were able to demonstrate that temperature is an objective parameter of tissue welding that can be continuously assessed and controlled during the laser repair of tissue defects to produce effective, predictable welds.

Animals↗
PubMed1994

An unusual cause of duodenal obstruction: ureteropelvic junction obstruction and the renoalimentary relationship.

Ureteropelvic junction obstruction may present with a variety of urologic and gastrointestinal complaints. The constellation of symptoms is most often attributed to shared visceral pathways. In cases of giant hydronephrosis, mechanical obstruction of the gastric outlet or duodenal sweep may play an additional role in presentation. We present an unusual case of duodenal obstruction caused by ureteropelvic junction stenosis. The anatomic and autonomic renoalimentary relationships are reviewed.

Adult↗
PubMed1994

Cryptorchidism.

Explore the source record for details and available documents.

Adult↗
PubMed1993

Preparation of human albumin solder for laser tissue welding.

Previous studies have demonstrated that the addition of a protein solder to augment the laser tissue weld significantly improves postoperative results. Herein we describe a method for the preparation of human albumin for use as a laser tissue solder. We also review the brief history of laser tissue solders and discuss recent advances using this technology.

Animals↗
PubMed1993

CO2 laser welding versus conventional microsuture repair in patch-graft urethroplasty.

This study evaluates the repair of urethral tissue using microsurgery and a combination of laser welding techniques. Using the rat as a model, a patch-graft urethroplasty was performed with either conventional microsuture repair, laser-assisted microsuture repair, or laser-assisted microsuture with protein solder. Repairs were assessed at various time periods (days 0, 1, 7, and 21). Analysis of success rate, bursting strength, histology, and operative time were completed. The laser with protein solder had the highest success rate at each time period and demonstrated advanced healing with the least amount of inflammation. Operative time was decreased by 30 percent using the laser. In conclusion, the laser solder repair was significantly better than either laser alone or conventional microsutures.

Animals↗
PubMed1993

Patch graft urethroplasty using dye enhanced laser tissue welding with a human protein solder: a preclinical canine model.

We investigated the use of the KTP-532 laser to perform a patch graft urethroplasty in 24 adult male dogs using the inner preputial skin as the donor site. In group 1 (12 dogs) repairs were completed with conventional microsuturing techniques, while in group 2 (12 dogs) they were completed using the KTP-532 laser. In the laser welding group the addition of a protein solder (40% human albumin) doped with fluorescein was used. Assessment parameters included a preoperative and postoperative retrograde urethrogram, measurement of intraluminal bursting pressure in the first 6 animals in each group, operative time and histology. Operative time was 42% faster and acute intraluminal bursting pressures were significantly higher in the laser-solder group. No fistulas occurred in the laser-solder group compared to a 50% fistula rate in the suture group. Significant radiographic abnormalities were seen in the urethras of the suture repair group.

Albumins↗