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Biomedical subjects

Ralph V Clayman

Publications and source records attributed to Ralph V Clayman.

At least 37 records · Page 2Linked to original sources
PubMed2005

Effect of holmium:YAG laser pulse width on lithotripsy retropulsion in vitro.

BACKGROUND AND PURPOSE: The effect of laser pulse width on calculus retropulsion during ureteroscopic lithotripsy is poorly defined because of the limited availability of variable pulse-width lasers. We used an adjustable pulse-width Ho:YAG laser to test the effect of pulse width on in vitro phantom-stone retropulsion and fragmentation efficiency. METHODS AND MATERIALS: An Odyssey 30 Ho:YAG laser (Convergent Laser Technologies, Oakland, CA) with adjustable pulse width (350 or 700 microsec) was used to treat spherical 10-mm plaster calculi in a model ureter (N = 40) and calix (N = 16) utilizing 200- and 400-microm fibers (10 Hz, 1.0 J). Calculi were placed in a waterfilled clear polymer tube, and laser energy was applied continuously in near contact until the stone had moved 8 cm. The time (seconds) and energy (joules) needed to cause the stone to traverse this distance was recorded. Stones were also placed in a stainless-steel mesh calix model in which retropulsion was limited. Laser energy was applied for 5 minutes at each pulse width. A laser-energy meter (Molectron Detector Inc, Portland OR) was used to quantify fiber transmission efficiency after 1 minute of continuous lithotripsy for each fiber at each pulse width. RESULTS: Retropulsion was greater for stones treated at 350 microsec, indicated by a shorter time to traverse the model ureter. For the 200-microrm fiber at 350 microrsec, the average time was 11.5 seconds v 20.3 seconds at 700 microsec (P < 0.001). The average total energy delivered was 114.9 J at 350 microsec v 199.8 J at 700 microsec (P < 0.001). For the 400-microm fiber at 350 microsec, the average time was 5.8 seconds v 11.9 seconds at 700 microsec (P < 0.001). The average total energy was 57.1 J at 350 microsec v 127.3 J at 700 microsec (P < 0.001). In the caliceal model, at 350 and 700 microsec with the 200- and 400-microm fibers, mass loss was 34.9% and 33.4% (P = 0.8) and 14.6% and 21.6% (P = 0.04), respectively. The reduction in energy transmission at 350 microsec and 700 microsec with the 200- microm fiber after 60 seconds of continuous lasing was 8.82% v 9%, respectively (P = 0.95). For the 400-microm fiber, the transmission loss was 18.4% at 350 microsec v 4.4% at 700 microsec (P = 0.0002). CONCLUSION: When treating ureteral calculi, retropulsion can be reduced by using a longer pulse width without compromising fragmentation efficiency. For caliceal calculi, the longer pulse width in combination with a 400-microm fiber provides more effective stone fragmentation.

Aluminum↗
PubMed2005

Third Prize: Comparison of radical nephrectomy, laparoscopic microwave thermotherapy, cryotherapy, and radiofrequency ablation for destruction of experimental VX-2 renal tumors in rabbits.

BACKGROUND AND PURPOSE: Currently available minimally invasive renal tumor-ablation procedures include cryotherapy, radiofrequency ablation, and microwave thermotherapy. In this study, we investigated the ability of these three approaches to destroy experimental renal tumors in rabbits. The mechanism of potential tumor metastasis was also explored. MATERIALS AND METHODS: The VX-2 tumor line is an aggressive rabbit epidermoid tumor with a high metastatic potential. An initial experiment comparing cooled-tip microwave thermotherapy with cryotherapy and radical nephrectomy for treatment of small VX-2 tumors revealed that all microwave-treated rabbits had local recurrence and that several also had diffuse intraperitoneal carcinomatosis. In view of these results, a second experiment was performed in which 45 New Zealand White rabbits were implanted laparoscopically with VX-2 xenografts underneath the kidney capsule and divided into five groups of 9 each. The test groups were microwave thermotherapy with a 3.5-mm cooled-tip probe, microwave thermotherapy with a 3.5-mm noncooled- tip probe, radiofrequency ablation with a 1.5-mm cooled-tip probe, radiofrequency ablation with a 1.5- mm non-cooled tip probe, and cryotherapy with a 2.3-mm cryoprobe. The control groups were five rabbits that were not treated, five rabbits with tumors that had the tumor pierced with a probe but were untreated, and five rabbits that underwent nephrectomy after piercing of the tumor. Treatment was initiated 5 days after tumor implantation. One month later, all animals were euthanized and autopsied. RESULTS: At 5 days after tumor implantation, laparoscopic inspection revealed no visible peritoneal metastases. At 1 month, in the cooled and non-cooled microwave-thermotherapy groups, carcinomatosis occurred in five and six of nine animals, respectively. In comparison, carcinomatosis was detected in two of nine animals in the cryotherapy group at autopsy. With respect to cooled and non-cooled radiofrequency ablation, carcinomatosis was observed in four of nine rabbits in each group. In the control groups, none of the animals with unpierced tumors exhibited carcinomatosis, while carcinomatosis was seen in two of the five rabbits with tumor violated by piercing and in three of the five rabbits that underwent immediate nephrectomy after piercing of the tumor. CONCLUSION: Carcinomatosis occurred most frequently in animals treated with microwave thermotherapy, followed by radiofrequency ablation, and lastly cryoablation. The simple act of piercing a highly aggressive tumor can result in local spread. More disconcerting, and less well understood, is why certain ablative modalities appear to increase the rate of intraperitoneal spread.

Animals↗
PubMed2005

Effect of urine specific gravity on effectiveness of shockwave lithotripsy.

PURPOSE: To determine the effect of urine specific gravity (SG) and radiographic contrast medium on the efficiency of extracorporeal shockwave lithotripsy (SWL) fragmentation using a previously published in vitro model. MATERIALS AND METHODS: Artificial kidney stones (BegoStone [BEGO USA, Smithfield, RI]) of a standard size (10 x 10 mm) and weight (mean 1.90 g; range 1.89-1.91 g) were randomly allotted to one of four test media with differing SG: group 1: synthetic urine, SG 1.003; group 2: synthetic urine, SG 1.040; group 3: 50% radiographic contrast (Cysto-Conray II, Mallinckrodt Inc., Hazelwood, MO), 50% synthetic urine, SG 1.069; and group 4: 100% contrast, SG 1.121. The stones were placed in cups made of 2.2-mm screen mesh and exposed to 500 shockwaves at 20 KV from a spark-gap lithotripter (Econolith 2000; Medispec, Germantown, MD). The stone fragmentation rate (i.e., percent fragmentation) was determined by dividing the dry residual stone weight by the prelithotripsy dry weight (X 100). RESULTS: The mean fragmentation rate for the four groups was 31.7%, 37.6%, 31.8%, and 27.2%, respectively. Statistical significance was not achieved (P = 0.1). CONCLUSION: Stone breakage tends to be more effective when urine SG is about 1.040 than at higher or lower values. Hence, the recommendation for an overnight fast prior to SWL is well founded. Introduction of contrast medium may inhibit stone breakage because it increases the specific gravity.

Humans↗
PubMed2005

Impact of a double-pigtail stent on ureteral peristalsis in the porcine model: initial studies using a novel implantable magnetic sensor.

BACKGROUND AND PURPOSE: The effect of stents on ureteral peristalsis in vivo is not entirely clear. We sought to develop a minimally invasive method for its study. MATERIALS AND METHODS: In female domestic pigs, electrical potentials from the ureter were measured by bipolar steel-wire electromyography electrodes delivered laparoscopically. Mechanical movement was measured by giant magneto resistive sensors mounted on custom-made aluminum strips. After baseline values were obtained, the animals were randomized to receive silicone or polyurethane stents, and ureteral peristalsis was measured for 8 hours acutely and for 4 hours 1 week later. RESULTS: Implantation of the devices took an average of 30 minutes. A consistent correlation was found between laparoscopically observed peristaltic waves and the peristalsis detected by the two measuring devices. The devices themselves did not affect peristalsis. Stent insertion increased peristaltic activity initially but later reduced or stopped it. There was no difference in the effects of the two types of stents. CONCLUSIONS: The new technique permits close monitoring of ureteral peristalsis in vivo. Smaller stents appear to have less immediate effect than larger ones, but all type of stents tested eventually caused aperistalsis.

Animals↗
PubMed2005

What happens to hemostatic agents in contact with urine? An in vitro study.

BACKGROUND AND PURPOSE: As the indications for topical hemostatic agents increase in urology, the question arises: what happens to these agents when they enter the urinary collecting system? To answer this question, we performed a series of in-vitro experiments mixing three hemostatic agents with normal and sanguineous urine. MATERIALS AND METHODS: Four commercially available topical hemostatic products: oxidized regenerated cellulose (Surgicel; Ethicon, Somerville, NJ), fibrin sealant (Tisseel VH Kit; Baxter Health Care Corporation, Irvine, CA), gelatin matrix hemostatic sealant (FloSeal; Baxter Health Care), and polyethylene glycol (CoSeal; Cohesion Technologies, Palo Alto, CA) were studied. Human urine (10 mL) was added to samples of each substance; this was done in triplicate. The 12 sample tubes were then capped and placed on a tube shaker at slow speed and 37 degrees C. Observations regarding consistency of the material were made at 6, 12, 24, 48, 72, 96, and 120 hours (5 days). Gelatin matrix hemostatic sealant was further tested in urine with various amounts of blood or blood clot; observations were again recorded out to 5 days. RESULTS: Surgicel maintained its solid form when it initially came in contact with urine, but over a period of 5 days, it transformed into a mucoid substance with visible free-floating fibers. It did not dissolve completely in urine within 5 days. Gelatin matrix was immediately transformed by urine into a fine colloidal suspension that did not change over the 5 days of the study. Fibrin glue, after mixing of the two components (fibrinogen and thrombin) directly in the urine, and polyethylene glycol immediately formed a solid clot at the bottom of the test tube on contact with the urine. When the mixture of fibrin sealant was allowed to form for 15 minutes and then added to urine, it again maintained a solid form. After 72 hours, the fibrin glue became a semisolid gelatinous plug. On analysis at 5 days, the fibrin sealant clot had transformed into a cohesive mucoid gel, and the polyethylene glycol clot had not changed. The gelatin matrix hemostatic sealant, when in contact with blood or blood clot, appeared to either become part of a clot or to remain in a colloidal suspension. At 5 days, all clots had dissolved to fine particulate suspensions, and the gelatin matrix appeared as a fine suspension. CONCLUSION: Fibrin glue and oxidized regenerated cellulose maintain a solid form when initially placed in direct contact with urine and then assume a semisolid gelatinous state, which is still present at 5 days. Polyethylene glycol forms a solid clot initially and does not change after 5 days. Only hemostatic gelatin matrix remained as a fine particulate suspension in both normal and sanguineous urine. The implications of these findings with regard to sealing the renal parenchyma or small violations of the collecting system after percutaneous or laparoscopic surgery await in-vivo testing.

Blood Loss, Surgical↗
PubMed2005

Initial impact of a dedicated postgraduate laparoscopic mini-residency on clinical practice patterns.

BACKGROUND AND PURPOSE: Laparoscopic surgical techniques are difficult to master, especially for surgeons who did not receive this type of training during their residencies. We have established a 5-day mentor-preceptor- proctor-guided postgraduate "mini-residency" (M-R) experience in minimally invasive surgery. The initial results from the first 16 participants in the laparoscopic M-R modules are presented. PARTICIPANTS AND METHODS: On the first and the last day of the M-R, all participants underwent surgical skills testing using an open-surgery, standard laparoscopic, and robot-assisted laparoscopic format. A written examination was also administered on the last day. The influence of M-R on the participants' practice pattern was then assessed by a follow-up questionnaire survey 1 to 7 months after their attendance. RESULTS: Data from the first 16 participants were analyzed. Of note, the score was significantly improved for only one of the four tested laparoscopic skills (i.e., threading a suture through loops). Nonetheless, on the follow-up survey, of the 15 respondents, two laparoscopically naïve participants had performed laparoscopic nephrectomy, and of the eight participants who had prior renal-ablative laparoscopic experience, four had performed advanced reconstructive laparoscopic cases. CONCLUSIONS: A 5-day dedicated postgraduate M-R in laparoscopy appears to be helpful for urologists wishing to incorporate this surgical approach into their practices. The "take rate" among participants is initially at the 40% level, similar to what has been previously reported after a 1 to 2-day hands-on didactic laparoscopy course.

Adult↗
PubMed2005

Fibrin glue-oxidized cellulose sandwich for laparoscopic wedge resection of small renal lesions.

PURPOSE: We present our experience with standard laparoscopic wedge resection of small renal tumors using a fibrin glue-oxidized cellulose sandwich for hemostasis. MATERIALS AND METHODS: From May 2002 to December 2003, 15 patients underwent laparoscopic wedge resection for a total of 15 nonhilar renal masses. Renal hilar clamping was performed in 1 patient and no sutures were placed. We used ultrasonic shears and an argon beam coagulator to resect and then coagulate the tumor bed. Tisseel (Baxter Corp., Deerfield, Illinois) was applied to the resection bed, followed by a layer of oxidized, regenerated cellulose (Surgicel, Ethicon, Somerville, New Jersey) and a final layer of Tisseel. RESULTS: Mean preoperative tumor size was 2.2 x 2.2 x 2.1 cm. Lesions were subdivided based on the percent of the lesion that extended beyond the renal parenchymal border on computerized tomography as exophytic-greater than 60% in 6 cases, endophytic-less than 40% in 4 and mesophytic-40% to 60% in 5. Mean operative time was 3.8 hours (range 3 to 5). Mean blood loss was 108 ml (range 20 to 300). No patient required blood transfusion. There was no significant difference in blood loss or change in creatinine among the endophytic, exophytic and mesophytic groups (150, 121 and 93 ml, and 0.03, 0.07 and 0.04 mg/dl, respectively). Margin status was negative in all cases (mean thickness 3.2 mm). Average hospital stay and time to the resumption of oral intake were 2.7 and 1.4 days, respectively. CONCLUSIONS: Small exophytic or mesophytic renal lesions can be safely excised laparoscopically without vessel clamping. Excellent hemostasis was achieved in each case with the newer hemostatic agents.

Aged↗
PubMed2005

Comparison of flexible ureteroscopes: deflection, irrigant flow and optical characteristics.

PURPOSE: We measured and compared the deflection, irrigation flow rates, distortion, resolution and light transmission of new generation flexible ureteroscopes. MATERIALS AND METHODS: Multiple characteristics of 5 flexible ureteroscopes (ACMI DUR-8 Elite, Olympus URF-P3, Storz 11278AU1 [Flex-X], Wolf 7330.072 and Wolf 7325.172) commonly available in the market were measured and compared. Measured data included active deflection, irrigation flow rates and optical characteristics. Each ureteroscope was evaluated with an empty working channel and with various accessories. Optical characteristics, specifically resolution and distortion, were measured using test targets (Edmund Optics, Barrington, New Jersey). Light transmission was also measured from the ureteroscope tip at 50% and 100% intensity. All 5 flexible ureteroscopes were tested in a laboratory setting using a Storz OR 1 system to capture the images. RESULTS: For all 5 ureteroscopes the angle of deflection was most impaired by a 365 microm laser fiber probe and least impaired by a 2.2Fr nitinol basket. Among all 5 ureteroscopes irrigation flow rate was most impaired with a 3.0Fr basket and least impaired with 200 microm laser fiber. The Wolf 7325.172 had the highest observed resolution of 25.39 lines per mm and the Wolf 7330.072 had the lowest distortion at 11.9%. The Karl Storz Flex-X and the ACMI DUR-8 Elite had the highest light output at 374 and 364 mV, respectively. CONCLUSIONS: The various flexible ureteroscopes differ with regard to flow rates as well as degree of deflection with either an empty or an occupied working channel. The Wolf flexible ureteroscope with a slightly larger working channel and a fused quartz bundle provided for superior flow and better optical performance. However, the greatest amount of tip deflection and highest light output were found in the ACMI and Karl Storz flexible ureteroscopes.

Artifacts↗