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Biomedical subjects

D P Poppas

Publications and source records attributed to D P Poppas.

At least 19 recordsLinked to original sources
PubMed1998

Effects of endogenous absorption in human albumin solder for acute laser wound closure.

BACKGROUND AND OBJECTIVE: Human albumin is currently being used as a biological solder in laser tissue welding. Experiments were performed to characterize the effects of differing albumin concentrations on wound closure when a 1.32 microm Nd:YAG laser is used to repair skin incisions. MATERIALS AND METHODS: In vivo comparison of acute tensile strength was made in full thickness porcine skin wounds using different solder concentrations. Histology of the repairs was also completed to evaluate the thermal denaturation of the tissue and solder. Transmission measurements were completed for nondenatured and denatured albumin solders. Finally, the real time denaturation pattern of different solder concentrations during laser irradiation was investigated. RESULTS: A tissue solder consisting of 50% albumin provides the greatest tensile strength for acute in vivo skin closure. The transmission measurements verify that the primary absorber of 1.32-microm laser light was the solder solvent (water). A significant decrease in power transmission occurs when the 25% albumin solder was denatured. The real time denaturation profiles demonstrate that 1.32-microm laser light denatures 25% albumin solder from the outer surface, while in 50% albumin solder, denaturation occurs from within the solder bulk. Wound histology corroborates the pattern of denaturation seen in vitro. CONCLUSION: The combination of 1.32-microm laser light and 50% human albumin solder can be used to create a deep tissue weld resulting in higher acute repair tensile strength. This permits a deep to superficial closure of wounds, which may result in an optimal method of acute closure for full-thickness wounds.

Animals↗
PubMed1998

Solubility study of albumin solders for laser tissue-welding.

BACKGROUND/OBJECTIVE: Current albumin solders for tissue-welding are soluble in physiological fluids, prior to laser irradiation. These solders are therefore subjected to mechanical alterations, which can weaken the solder-tissue repair. In this study, an albumin solder (laser activated) was developed with low solubility and with the ability to retain (partially) its mechanical characteristics in saline solution. STUDY DESIGN/MATERIALS AND METHODS: Gauged protein samples of solder were immersed into 0.5 ml saline solution for fixed intervals of time. The solder samples contained four bovine serum albumin (BSA) concentrations: 56%, 66%, 70%, and 75% (by weight). A Bradford protein assay measured the BSA solubility of the solders. The 70% and 75% BSA solders were also used to weld in vitro Wistar rat intestine sections with a diode laser (lambda = 810 nm, power = 270 mW). RESULTS: The solubility of the 75% BSA solder was significantly decreased with respect to the other solders (Anova, P < 0.05). This solder also showed comparable weld strength (13 gm) to the 70% BSA solder. CONCLUSION: The 75% BSA solder strongly reduced the albumin solubility in saline solution, without affecting its tissue-welding properties.

Analysis of Variance↗
PubMed1998

Laser tissue welding.

Laser tissue welding is a technologic innovation that is beginning to move from the theoretical laboratory environment to the reality of clinical application. This article reviews the concepts, potential advantages, and techniques involved in laser tissue welding as they apply to urology.

Humans↗
PubMed1998

Laser tissue welding: a urological surgeon's perspective.

Laser tissue welding has proven its efficacy in the laboratory setting when compared with more traditional modalities of tissue reapproximation. In the clinical environment, several areas including urethral reconstructive surgery have shown great promise. Several technological advancements including solder development, chromophore enhancement and temperature control have improved upon the welding process and have added more precision and reproducibility to the technique. The current potential applications for laser welding in urology are numerous. On a molecular level, growth factor supplementation has certain potential in improving upon weld site healing and wound strength. Laparoscopic surgery with its need for less cumbersome modes of tissue closure is a field that will greatly benefit from the technology of laser tissue welding. Surgical specialties outside of urology are also participating in developing the field of laser welding. In particular, cardiothoracic surgery, otolaryngology, plastic surgery, neurosurgery among others, have utilized the concept of laser tissue welding. There are many ares that have potential use for laser welding that have yet to be explored. Further investigation will likely reveal more applications for this valuable technology.

Forecasting↗
PubMed1998

Intravesical bacille Calmette-Guérin induces the antiangiogenic chemokine interferon-inducible protein 10.

OBJECTIVES: Intravesical bacille Calmette-Guérin (BCG) induces a variety of cytokines into the urine of patients with superficial transitional cell carcinoma (TCC) of the bladder. Recent data have shown that some cytokines have antiangiogenic activity. We sought to determine whether the potently antiangiogenic chemokine interferon-inducible protein 10 (IP-10) and its inducing antiangiogenic cytokines, interferon-gamma (IFN-gamma) and interleukin-12 (IL-12), are increased during intravesical BCG immunotherapy of bladder TCC. METHODS: Voided urine samples were collected sequentially from 8 patients before and after each weekly intravesical BCG treatment and from 4 patients receiving maintenance BCG treatments. The urinary output of IP-10, IFN-gamma, and IL-12 over 12 post-treatment hours was assessed by enzyme-linked immunosorbent assay. In vitro BCG and cytokine stimulations of human TCC and primary endothelial cell lines were also performed, and their supernatants were studied for IP-10. RESULTS: In all cases after intravesical BCG, patient urine was found to contain significant elevations of IP-10. Urinary IFN-gamma and IL-12 levels also increased in similar patterns after intravesical BCG. The peak weekly cytokine response per patient usually occurred between the fourth and sixth treatment for IFN-gamma and IP-10, but was less predictable for IL-12. Human TCC and endothelial cell lines were able to secrete IP-10 in response to BCG or interferon stimulation in vitro. CONCLUSIONS: Our small series demonstrates that IP-10 and its inducing cytokines are elevated in response to intravesical BCG. These data suggest that, in addition to a cellular immune response, BCG may induce a cytokine-mediated antiangiogenic environment that aids in inhibiting future tumor growth and progression.

Administration, Intravesical↗
PubMed1998

Flexible transinguinal laparoscopy to assess the contralateral ring in pediatric inguinal hernias.

The incidence of contralateral patent processus vaginalis (CPPV) is >50% in infants with clinical unilateral inguinal hernia (CUIH) and decreases only slowly with advancing age. Laparoscopy through the hernia sac (transinguinal laparoscopy) to detect suspected CPPV is a safe and efficient way to minimize routine contralateral inguinal exploration, but can be technically difficult. We used flexible urologic instruments and/or angled cystoscopic lenses to make transinguinal laparoscopy easier. Over a 3-year period, 37 patients (34 boys and 3 girls) ranging in age from 4 months to 12 years (mean age 59 months) with CUIH underwent ipsilateral groin exploration and diagnostic transinguinal laparoscopy. Laparoscopy was performed with flexible 17F cystoscopes (26 cases), flexible 9F ureteroscopes (2 cases), and rigid 70 degrees cystoscope lenses (9 cases). We detected eight CPPV (22%) in our series of 20 right and 17 left inguinal hernias, in a mean transinguinal laparoscopy time of 4.5 minutes. At 26-month mean follow-up, no patient whose contralateral inguinal ring was deemed closed had developed a hernia. Flexible fiberoptic urologic scopes and/or angled cystoscope lenses make transinguinal laparoscopy easy and efficacious in the pediatric population. Our series represents the longest longitudinal study of transinguinal laparoscopy for the diagnosis of CPPV.

Child↗
PubMed1997

Laparoscopic surgery in children with ventriculoperitoneal shunts: effect of pneumoperitoneum on intracranial pressure--preliminary experience.

OBJECTIVES: We monitored changes in intracranial pressure (ICP) in 2 children with myelodysplasia undergoing laparoscopic bladder autoaugmentation. Both children had ventriculoperitoneal shunts (VPS) secondary to Arnold-Chiari malformations (type II). METHODS: ICP was monitored through a 23-gauge needle placed into the shunt reservoir and connected to a pressure transducer and drainage system. Intraoperative mean arterial pressure, end-tidal CO2 (ETCO2), ICP, abdominal pressure, and cerebral perfusion pressures were all monitored. RESULTS: Both children demonstrated rapid onset and sustained increases in ICP of greater than 12 mm Hg above baseline to a maximum pressure of 25 mm Hg. The average cerebrospinal fluid removed from each patient was 30 cc, thereby lowering ICP with no adverse neurologic sequela. The pCO2 remained constant throughout the procedures, as measured by ETCO2. CONCLUSIONS: We believe that intracranial hypertension (IH) results from a "Valsalva-like" phenomenon, which causes cerebral vascular engorgement. In addition, the pneumoperitoneum may increase the resistance to outflow through the distal peritoneal catheter, causing a partial or complete shunt obstruction. Untreated IH may result in adverse neurologic sequelae from brain herniation in these children with hindbrain anomalies and potentially altered brain compliance. We believe it is prudent to perform intraoperative ICP monitoring in this subgroup of patients undergoing laparoscopic surgery and that IH should be treated by ventricular drainage.

Child↗
PubMed1997

Comparison of fibrin glue, laser weld, and mechanical suturing device for the laparoscopic closure of ureterotomy in a porcine model.

PURPOSE: We evaluated fibrin glue, laser welding, and a mechanical suturing device (Endo-Stitch) as alternatives to standard laparoscopic suturing with a free needle. METHODS: In 14 pigs, 22 linear proximal ureterotomies were closed laparoscopically with one of 4 different methods: fibrin glue, laser welding, Endo-Stitch suture placement (4-0 polyglactin), and free-needle suture placement (4-0 polyglactin). The ureterotomy was left open in 6 ureters. Acute leakage was tested by instillation of methylene blue. After 12 weeks, the ureters were assessed with radiography, ex-vivo pressure-flow studies, bursting pressures, and histology. RESULTS: All alternative closure techniques were more rapid than free-needle suturing, and less frequently allowed acute leakage. Closure with fibrin glue yielded significantly higher flow rates than control, whereas the other closure techniques yielded flow rates similar to that of unclosed ureters. All alternative closure methods demonstrated histological evidence of healing that were superior to free-needle suturing. In multifactorial analysis, leakage at the ureterotomy site was the factor most significantly associated with subsequent poor ex-vivo flow characteristics. CONCLUSIONS: All of the alternative laparoscopic ureteral closure methods compared favorably with standard free-needle suturing. Fibrin glue produced better radiographic findings, flow characteristics, and histology, suggesting that it currently has the most promise as an alternative or adjunct to laparoscopic suturing. Development of alternative laparoscopic techniques is ongoing, however, and thus the current state-of-the-art techniques used in this study may well be supplanted by other technologies in the future.

Animals↗
PubMed1997

Effect of laser wavelength and protein solder concentration on acute tissue repair using laser welding: initial results in a canine ureter model.

Successful tissue approximation can be performed using low power laser energy combined with human albumin solder. In vitro studies were undertaken to investigate the acute repair strengths achieved using different laser wavelengths. Furthermore, we evaluated the change in repair strength with that resulted from changes in protein solder concentration. Intraluminal bursting pressure following ureterotomy repair was measured for the following laser wavelengths: 532, 808, 1,320, 2,100, and 10,600 nm. The tissue absorption characteristics of the 808-nm diode and the KTP-532-nm lasers required the addition of the exogenous chromophores indocyanine green and fluorescein, respectively. A 40% human albumin solder was incorporated in the repair of a 1.0-cm longitudinal defect in the canine ureter. Following determination of an optimal welding wavelength, human albumin solder of varying concentrations (25%, 38%, 45%, and 50%) were prepared and tested. The 1,320-nm YAG laser achieved the highest acute bursting pressure and was the most effective in this model. Of the concentrations of albumin tested, 50% human albumin yielded the greatest bursting pressures. We conclude that of the laser wavelengths evaluated, the 1,320-nm YAG achieves the strongest tissue weld in the acute ex vivo dog ureter model. In addition, when this laser system is used, the acute strength of a photothermal weld appears to be directly proportional to the concentration of human albumin solder in the range of 25 to 50%.

Albumins↗
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↗