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Biomedical subjects

J Denstedt

Publications and source records attributed to J Denstedt.

13 recordsLinked to original sources
PubMed2001

Oral fluoroquinolone therapy results in drug adsorption on ureteral stents and prevention of biofilm formation.

The oral administration of ciprofloxacin (250mg bid) and ofloxacin (300mg bid) in 40 patients with ureteral stents, led to drug levels on all the device surfaces that were higher than the minimum inhibitory concentration (MIC) of Escherichia coli (0.004--0.015 mg/l), the most common uropathogen. The drug levels in the film were higher than the MIC of other common pathogens, namely Pseudomonas aeruginosa (0.25--1.0 mg/l), Enterococcus faecalis (0.25--2.0 mg/l) and Staphylococcus aureus (0.12--0.5 mg/l) in a few cases (six, three and 14 cases out of 40, respectively). For both antibiotics, the concentrations were greater than the MIC of many uropathogens on the film surrounding the devices (0.89 vs 0.31 mg/l respectively, P=0.05), and on the devices themselves (0.22 vs. 0.12 mg/l, P=0.207). Adsorption of the antibiotics was higher to the film than to the stent (P<0.0001). Ciprofloxacin concentration on the film surrounding the stents was significantly higher than that of ofloxacin (P=0.05), while there was no statistical concentration difference between the two antibiotics adsorbed onto the actual devices (P=0.207). No bacteria were found in patients' urine and no biofilms were detected. This is the first report of an oral antibiotic being adsorbed onto medical devices. It potentially provides a new approach of preventing infection, and avoids the need to pre-coat devices with agents whose use will be restricted once bacteria develop resistance to them. If biomaterial properties can be enhanced to increase further the adsorptive concentration of drug, the risk of infections and recalcitrant biofilm formation could be significantly reduced in a highly susceptible patient population.

Administration, Oral↗
PubMed2001

Imaging and the Internet.

Internet-based imaging is changing the way urology services are delivered by allowing rapid communication between remote locations. This review focuses on Internet-based imaging modalities, the hardware needed to transmit and view these images, and current applications. With the continuing expansion of Internet-based resources, all physicians must become accustomed to integrating the Internet and Internet-based imaging into their practices.

Diagnostic Techniques, Urological↗
PubMed2001

Randomized trial of 10 mL and 20 mL of 2% intraurethral lidocaine gel and placebo in men undergoing flexible cystoscopy.

PURPOSE: To determine if 20 mL of 2% intraurethral lidocaine gel is superior to 10 mL of 2% lidocaine or sterile lubricant for flexible cystoscopy in men. PATIENTS AND METHODS: A randomized, double-blind, placebo-controlled trial was conducted. Sixty men scheduled to undergo diagnostic flexible cystoscopy were randomized to receive either 20 mL of placebo gel (Group I), 10 mL, of 2% lidocaine gel (Group II) or 20 mL of 2% lidocaine gel (Group III). A penile clamp was applied for 15 minutes to ensure consistent indwelling time in all patients. Patients recorded their pain on a 10-cm non-graphical visual analog scale prior to cystoscopy as a baseline, during the procedure, and immediately after the procedure. Patients also recorded their pain and willingness to have the same anesthetic on a 4-point descriptive scale. Heart rate and mean arterial blood pressure (MAP) were recorded at specific intervals throughout the procedure, and increases in mean arterial pressure were considered objective evidence of patient pain. RESULTS: Pain perception was not statistically different in the groups (Group I 4.65, Group II 3.93, Group III 3.57; P = 0.406). Pain assessment and willingness to have the same anesthetic also did not differ statistically among the groups. Similarly, differences in the increases in MAP were not statistically significant between groups. CONCLUSION: Instillation of 20 mL or 10 mL of 2% lidocaine gel has no advantage over plain lubricant in providing anesthesia for flexible cystoscopy in men.

Adult↗
PubMed2000

Intended and stray radiofrequency electrical currents during resectoscopic surgery.

STUDY OBJECTIVE: To test the hypothesis that electrical burns of the genital tract and urethral strictures after hysteroscopic endometrial ablation and transurethral prostatectomy, respectively, are related to capacitive coupling and/or stray currents induced by intact and defective electrodes and/or resectoscopes. DESIGN: Basic in vitro measurements. SETTING: Laboratory. MATERIALS: Porcine muscle and liver, resectoscope, electrosurgical unit (ESU), and ESU analyzer. INTERVENTION: We measured electrical coagulation and cutting currents of rollerball and loop electrodes and the external sheath of the resectoscope from 80 to 200 W through a resistance load of 200 and 250 ohms, using intact electrodes and conditions simulating potential insulation defects along the shaft of the electrodes. MEASUREMENTS AND MAIN RESULTS: Approximately 20% to 25% of current was induced by capacitive coupling to the resectoscope sheath. Touching porcine muscle or liver with small areas of the sheath while the generator was activated resulted in superficial tissue burn. Surrounding large segments of the sheath with tissue did not result in visible burns, indicating that under normal conditions the sheath acts as a dispersive electrode. Defective insulation of distal segments of the electrodes resulted in 100% transfer of current to the sheath and caused extensive electrical burns of tissue in contact with the sheath. CONCLUSIONS: Capacitive coupled currents induced by intact resectoscopes and electrodes may cause thermal injury to surrounding tissue during prolonged resectoscopic surgery. Stray currents from defective insulation of the electrodes result in direct coupling of current to the telescope and sheath and cause extensive burns of surrounding tissues in contact with the sheath.

Animals↗
PubMed2000

Flexible ureteroscopy and lithotripsy with the Holmium: YAG laser.

Extracorporeal shock wave lithotripsy (ESWL), Dornier Medical Systems, remains the main form of therapy for most urinary stones. The minimally invasive nature of ESWL makes it an attractive form of therapy to both patients and physicians. Many patients however may be most effectively managed by an endoscopic procedure either percutaneously or by transurethral ureteroscopy. Recent years have seen considerable advancement in endoscope technology such that flexible, actively deflectable ureteroscopes of 7.5 F or smaller in diameter have become available for performing upper tract endoscopy. When combined with new intracorporeal lithotripsy devices such as the Holmium:YAG laser, urologists have an effective alternative to ESWL for many stone problems. In this article we review our technique of flexible ureteroscopy combined with Holmium:YAG laser lithotripsy.

Equipment Design↗
PubMed1999

Biomaterials in Urology II: future usage and management.

It seems likely, and indeed inevitable, that medical device usage will continue its rapid increase over the next 10 to 20 years and beyond. For surgeons, these new inventions will come in many forms but should take into account biocompatibility and resistance to encrustations and to microorganisms. This review focuses on research under way at present in vitro and in vivo on materials and coatings, use of bioelectrics, use of artificial organs and tissues, application of indigenous bacteria, and other alternative device management techniques, which could well become part of clinical practice in the future. By necessity, some of these citations are speculative, but supporting documentation for their inclusion is presented.

Animals↗
PubMed1998

XPS and SEM detection of surface changes on 64 ureteral stents after human usage.

Ureteral stents are commonly implanted to assist the postsurgery flow of urine from the kidney to the bladder. We hypothesized that different surface compositions of stent material could result in different conditioning film depositions and potentially altered receptivity to bacterial biofilms. Using XPS, three types of ureteral stents recovered from 64 patients were found to have adsorbed conditioning films that altered the surface composition of the devices. Elements associated with encrustation (calcium, magnesium and phosphorus) were found on 69% of the silicone latex stents, 44% of the low surface energy (LSe) devices, and 38% of the carbon-rich stents. No statistical difference was found in relation to patient gender, stent type, duration of implantation, and encrustation deposition. The composition of the film suggested that the nature of the underlying material did not significantly alter the elements that adsorbed. Thus, devices may take on a similar surface coat within days, and perhaps hours, of exposure to the host. With respect to dense encrustations, fewer appeared on the LSe devices. SEM confirmed the presence and nature of the film crystals and showed bacterial biofilms adherent to devices and encrustations in three patients who had received prophylactic trimethoprim compared to one on ciprofloxacin. In conclusion, although encrustation deposition and biofilm formation on ureteral stents is not unique to Cook devices, the human model and surface science test systems described here are invaluable to evaluate biomaterials used in patients. Unless biomaterials undergo rigorous analysis in vivo, including true assessment of the outcome of prophylactic antibiotic usage, clinicians will be unable to accurately select the best device and management strategy for a given patient.

Adult↗
PubMed1998

Conditioning film deposition on ureteral stents after implantation.

Three types of ureteral stents were used in a study of 53 patients. Following extracorporeal shock wave lithotripsy, the stents were implanted and retained for periods of between 3 and 40 days. Each patient received daily antibiotic therapy with either ciprofloxacin or trimethoprim. After removal, the devices were analyzed for adherent bacteria and encrustations. The study showed that a conditioning film became deposited onto the stents upon implantation, changing the surface characteristics of the biomaterials. Dense encrustations were found to be least on a low surface energy device. No differences were found related to patient age and gender or duration of stent insertion. Flakiness and apparent sloughing of the stent surfaces was observed in some devices, raising concerns as to what actually happens to medical devices when exposed to the host urinary tract. Bacteria were recovered from the urine of three patients and the stents of four patients treated with trimethoprim. Five stents had bacterial biofilms detected by SEM. The actual clinical end-point was not the focus of this study, but no patients became septic. Our goal was to demonstrate conclusively in humans that medical devices do develop conditioning films upon implantation, and that they can be susceptible to bacterial colonization even during antibiotic treatments. The kidneys of stented patients are clearly at risk of infection, and only by proper selection of a stent type and appropriate antibiotic coverage can this risk be significantly reduced.

Adolescent↗
PubMed1998

Microwave thermotherapy for benign prostatic hyperplasia with the Dornier Urowave: results of a randomized, double-blind, multicenter, sham-controlled trial.

OBJECTIVES: To study the efficacy and safety of a new transurethral microwave thermotherapy device (the Urowave) in the treatment of men with clinical benign prostatic hyperplasia (BPH) in a randomized, double-blind, sham-controlled trial. METHODS: A total of 220 patients (mean age 66.2 years) with clinical BPH, an American Urological Association symptom index (AUA SI) of 13 points or more, and a peak flow rate of 12 mL/s or less were enrolled and randomized 2:1 for active versus sham treatment. All treatments were conducted as an outpatient procedure under local anesthesia, with oral sedation and analgesia only. Patients were followed up at 1 week and 1, 3, and 6 months after treatment. RESULTS: The treatments were well tolerated, and no patient received general or spinal anesthesia. The AUA SI dropped from 23.6 to 12.7 points at 6 months (P < 0.05) in the active group and from 23.9 to 18.0 points in the sham-treated group (P < 0.05, between-group difference). Statistically significant improvements were also noted for peak flow rate (7.7 to 10.7 mL/s at 6 months for active treatment, 8.1 to 9.8 mL/s for sham treatment, P < 0.05, between-group difference) and for average flow rate. A decrease in AUA SI of more than 30% was achieved in 72% versus 38% of patients (active versus sham treatment, respectively) and more than 50% in 50% versus 19% of patients. In general, active Urowave-treated patients perceived "a lot" of improvement, whereas sham-treated patients perceived "a little" to "some" improvement. More of the actively treated patients had dysuria and urgency after treatment, and ejaculatory dysfunction (e.g., hematospermia) was more common in actively treated patients as well. Secondary urinary retention after removal of the catheter occurred in 8 patients (5.4%). CONCLUSIONS: The Dornier Urowave transurethral microwave thermotherapy device for treatment of clinical BPH is effective in decreasing symptoms and bother and improving quality of life and flow rate and is superior to sham treatment. Patients perceive a great deal of improvement, independent of their baseline symptom severity. Adverse events are in general transient and mild in nature. Extended follow-up is necessary to document long-term durability of improvements.

Aged↗
PubMed1996

Low-molecular-weight variants of osteopontin generated by serine proteinases in urine of patients with kidney stones.

Osteopontin (OPN) is a multifunctional glycosylated phosphoprotein found in body fluids, including urine, and has been implicated in urinary stone formation. We tested the hypothesis that OPN levels in urine of patients with kidney stones differed from normal individuals. To quantify OPN levels in the urine, we developed an ELISA using a combination of a mouse monoclonal and rabbit polyclonal antibodies raised against a recombinant glutathione-S-transferase-human OPN fusion protein. In a group of 34 patients diagnosed with kidney stones compared with a control group of 23 normal individuals, we found that OPN levels in urine of the patient and control groups ranged from 0.01 to 2.7 micrograms/ml, with no significant difference in their medians (P > 0.8, Mann-Whitney test). OPN in urine was qualitatively assessed by Western blotting using a biotinylated monoclonal antibody to detect various molecular forms. The urine of most individuals contained OPN species within in the 55- to 66-kDa electrophoretic mobility range. However, a significantly higher proportion of individuals in the patient group (13 of 34) was found to have aberrant urine OPN species (< or = 40 kDa) compared to 2 of 23 for the control group (P < 0.03, chi 2 test). Mixing experiments indicated that urine samples with aberrant OPN contain proteases inhibitable with phenylmethylsulfonyl fluoride. Such proteases could break down normal urine OPN in vitro. Therefore, urine from a high frequency of kidney stone patients contains serine proteases that contribute to proteolytic cleavage of OPN.

Adult↗
PubMed1996

Urine culture screening in lithotripsy compared with traditional methods.

The authors compare biochemical screening tests with microscopy, cultures, and patient symptoms in 257 patients who visited the Urology-Lithotripsy Unit. They conclude that strip screening and microscopy were poor methods to screen for UTI in patients with stents and raise the question whether all stent patients or just symptomatic stent patients should have urine cultures. The authors also suggest that UTI can be eliminated as a diagnosis in 45% of non-stent patients by using strip screening and not doing further testing. These recommendations have quality improvement and cost effectiveness implications.

Acute Disease↗
PubMed1991

A comparison of renal damage induced by varying modes of shock wave generation.

To evaluate for the possible differences in the extent of pathologic injury occurring following treatment with various lithotripsy modalities, we subjected rabbits to treatment on either an electrohydraulic, electromechanical, or piezoelectric lithotripter. Functional evaluations by enzymuria failed to reveal any difference in the extent of damage between the lithotripters. Pathologic evaluation of the kidneys revealed that both electrohydraulic and electromechanical lithotripsy resulted in an increased instance of acute subcapsular hematoma and fibrosis when compared to piezoelectric treated kidneys (p less than 0.001). Despite the definitive differences noted in the acute animals, there was no significant variation in the area of permanent renal damage that occurred between the various lithotripters.

Acetylglucosaminidase↗