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Biomedical subjects

Jamil Rehman

Publications and source records attributed to Jamil Rehman.

31 records · Page 2Linked to original sources
PubMed2003

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: determination of optimal parameters for in vitro stone fragmentation.

PURPOSE: The Twinheads extracorporeal shock wave lithotriptor (THSWL) is composed of 2 identical shock wave generators and reflectors. One reflector is under the table and the other is over the table with a variable angle between the axes of the 2 reflectors. The 2 reflectors share a common second focal point, making it possible to deliver an almost synchronous twin pulse to the targeted stone. We studied the optimal parameters for in vitro stone fragmentation. MATERIALS AND METHODS: Two types of 1 cm artificial stones were used, namely Bon(n)-stones of 3 compositions (75% calcium oxalate monohydrate [COM] plus 25% uric acid, struvite and cystine) and plaster of Paris. The parameters tested were shock wave number (100, 500 and 1,000), shock wave power (8, 11 and 14 kV) and angle between the reflector axes (67, 90 and 105 degrees). After the optimal parameters were determined we studied the disintegrative efficacy of THSWL for 3 types of human urinary calculi, including COM, calcium hydrogen phosphate (brushite) and cystine. Each stone received 1,000 twin shock waves at 14 kV with an angle of 90 degrees between the reflectors. All experiments were done using a rate of 60 twin shock waves per minute. Following lithotripsy stone fragments were processed and sized. The ratio of the weight of fragments greater than 2 mm-to-total weight of all fragments was calculated. RESULTS: Optimal stone fragmentation results for THSWL were obtained with the maximum number of shock waves (1,000) and full power (14 kV). There was no significant statistical difference in fragment size or the ratio of fragments greater than 2 mm with the use of different angles except for cystine and plaster of Paris calculi, for which the right angle was most effective. At application of the optimal parameters to human stones THSWL produced small fragment size for COM and cystine stones, while brushite stones were not fragmented to the same extent. CONCLUSIONS: The efficacy of synchronous twin pulse technology improves as the number of shock waves and power increase. A 90-degree angle between the shock wave reflectors is advantageous for certain stones (that is cystine and plaster of Paris) but it is not a factor for other stone compositions. THSWL has satisfactory disintegrative efficacy for human stones, especially COM and cysteine calculi.

Calcium Oxalate↗
PubMed2002

Comparison of intrarenal pressure and irrigant flow during percutaneous nephroscopy with an indwelling ureteral catheter, ureteral occlusion balloon, and ureteral access sheath.

OBJECTIVES: To determine the differential effects on renal pressures and irrigation flow associated with the application of different ureteral catheters during percutaneous nephrolithotomy. METHODS: Using ex vivo fresh cadaveric tissue, we established a percutaneous nephrolithotomy model. After obtaining lower pole percutaneous access, we recorded the pressure and irrigant flow measurements. Measurements were made with an empty ureter, 6F ureteral catheter, occlusion balloon catheter, and ureteral access sheaths (10/12F and 12/14F). Three 1-minute trials for each condition were recorded in each of four kidneys. RESULTS: Ureteral catheterization with both the 10/12F and the 12/14F ureteral access sheaths resulted in significantly decreased intrarenal pressures in the pressure range tested compared with an empty ureter, a ureteral catheter, or an occlusion balloon application. Total irrigant flow for the 12/14F ureteral access sheath was significantly higher than for the empty ureter, ureteral catheter, or occlusion balloon in the entire pressure range evaluated. CONCLUSIONS: In this in vitro cadaveric model, application of the ureteral access sheath during percutaneous nephrolithotomy resulted in decreased intrarenal pressures and increased irrigant flow.

Catheterization↗
PubMed2002

Effect of argon-beam coagulation on the integrity of suture material.

PURPOSE: To evaluate the effect of argon-beam coagulator (ABC) energy on suture materials. MATERIALS AND METHODS: Six absorbable and nonabsorbable suture materials (polyglactin, chromic catgut, polydioxanone, silk, poliglecaprone, and Gore-Tex) were placed under tension and exposed to ABC energy to determine breaking times. Subsequently, all suture materials were exposed to limited ABC energy, and tensiometry was used to determine decreases in breaking strengths. RESULTS: Among the suture materials tested, Gore-Tex was the most resistant to ABC energy. Although absorbable suture materials were less resistant than nonabsorbable suture materials, 2-0 polyglactin manifested the greatest resiliance to deterioration with ABC energy exposure. CONCLUSIONS: The ABC has differential effects on suture materials. Larger-gauge suture materials are more resistant to ABC than smaller materials. Similarly, nonabsorbable sutures are generally more resilient to ABC energy than absorbable materials. Among the suture materials evaluated in our in vitro model, 2-0 Gore-Tex was best suited for vascular ligation, and 2-0 polyglactin is optimal for renal collecting system closure if ABC is anticipated as an adjunct for hemostasis.

Absorbable Implants↗
PubMed2002

Current management of urolithiasis: progress or regress?

PURPOSE: To assess the impact of the development of less powerful second- and third-generation shockwave lithotripters on surgical stone therapy in light of recent advances in ureteroscopy and laser lithotripsy. As such, we sought to identify current trends in the treatment of stone disease, both at our university medical center and nationally, and to contrast them with the corresponding data from 1990. PATIENTS AND METHODS: All urolithiasis procedures (ureteroscopy, SWL, open surgery, and percutaneous stone removal) performed in 1998 were compared with all urolithiasis procedures performed 8 years earlier (1990) at a single institution (Washington University, St. Louis). In addition, Medicare data for each year from 1988 through 2000 were collected from the Health Care Financing Administration to assess the national trends for open stone surgery, ureteroscopic stone removal, SWL, and percutaneous nephrolithotomy. RESULTS: At Washington University, the number of percutaneous stone removals remained stable; however, the overall number of ureteroscopies increased by 53%, while the number of SWLs, decreased by 15%. The Medicare data likewise reflect a marked decrease in open stone surgery and a marked increase in ureteroscopic stone surgery with a slight increase in SWL. Utilization of percutaneous nephrolithotomy remained unchanged. CONCLUSIONS: We believe this trend toward ureteroscopy is attributable to several factors: improved, smaller rigid and flexible ureteroscopes; the availability of more effective intracorporeal lithotripters (e.g., pneumatic and holmium laser), and the lack of development of lower cost, more effective SWL. This is an unfortunate trend, as we are moving away from the noninvasive treatment that was the hallmark of urolithiasis therapy at the beginning of the last decade toward more invasive endoscopic therapy. Increased research efforts in SWL technology are sorely needed.

Female↗
PubMed2002

Renal hypothermia achieved by retrograde intracavitary saline perfusion.

BACKGROUND AND PURPOSE: Hypothermia during vascular clamping protects the kidney from ischemia-induced nephron loss. Traditionally, cooling is achieved by packing the kidney in ice, which lowers the temperature of the rest of the surgical field as well, and the method cannot be used during laparoscopy. We evaluated the utility of a newly developed ureteral access system for circulating ice-cold saline. MATERIALS AND METHODS: Domestic pigs underwent retrograde endoscopic cooling through an access sheath without (N = 2) or with (N = 3) renal artery occlusion, traditional ice-slush cooling with renal artery occlusion (N = 3), or occlusion without hypothermia (N = 3). Five days later, the pigs were sacrificed and the kidneys and ureters examined histologically. RESULTS: Endoscopic cooling with renal artery occlusion and ice-slush cooling both produced renal hypothermia. The former produced medullary and cortical temperatures of 21.3 degrees C and 27.3 degrees C, respectively, and the latter medullary and cortical temperatures of 28.8 degrees C and 23.7 degrees C, respectively. Histologically, there were minimal changes in the first three groups, whereas venous congestion, multifocal chronic inflammation, and periarteriolar hemorrhage were seen after renal artery occlusion without hypothermia. CONCLUSION: Retrograde endoscopic renal hypothermia is effective and requires no novel equipment or special surgical skills. Clinical application has not yet been attempted.

Animals↗
PubMed2002

Ferromagnetic self-regulating reheatable thermal rod implants for in situ tissue ablation.

BACKGROUND AND PURPOSE: Ferromagnetic compounds, when placed in a radiofrequency magnetic field, develop an electrical current. When placed in tissue, resistance to the transmission of the electrical current leads to heating of the tissues next to the ferromagnetic compound. The Curie temperature is a transition point at which the development of a particular temperature within the material results in loss of its magnetic properties; as such, when this temperature is reached, there is cessation of current, and thus heat production stops. Our goal was to examine the ablative impact of permanently implanted palladium and cobalt self-regulating temperature rods on solid abdominal and pelvic organs. These rods were designed to develop a maximum temperature of 70 degrees C. MATERIALS AND METHODS: In 16 pigs, renal, hepatic, uterine, and pancreatic ferromagnetic rods were placed using a template. The rods were delivered in 1-cm parallel rows of two rods each in order to ablate 7 g of tissue. The animals were subsequently treated in an extracorporeal magnetic field of 50 gauss rms at a frequency of 50 kHz. The position of the rods was confirmed by fluoroscopy before the animal was put in the magnetic field. The animals received one or two treatment sessions. Intralesional and extralesional temperatures were measured continuously. Serum chemistry was analyzed before surgery, after each treatment, and at the time of harvest. Two weeks following therapy, the treated tissues were harvested and examined histopathologically. RESULTS: In all tissues with properly aligned rods, the temperature of the tissue surrounding the rods exceeded 50 degrees C. Histologic review showed confluent tissue necrosis in 7 of 9 kidneys (78%), 6 of 9 livers (67%), 1 of 3 pancreases (33%), and 1 of 3 uterine specimens (33%). Necrosis extended for 2 mm beyond the periphery of the rods. All failures were secondary to technical misalignment of the rods, which occurred because of our attempt to treat more than one organ in each animal. CONCLUSIONS: Ferromagnetic rods, when properly aligned in a magnetic field, create well-defined areas of necrosis. There are no skip areas of viable tissue within the treated area, and there is a precipitous fall-off of injury just outside the area of treatment. Also, because the rods can be reactivated at any time, recurrent lesions within the same site can be treated. This form of minimally invasive in situ ablative therapy appears promising. Clinical trials in the kidney and in other abdominal and pelvic organs are pending.

Animals↗
PubMed2002

Hydrophilic guide wire technique to facilitate organ entrapment using a laparoscopic sack during laparoscopy.

PURPOSE: Morcellation of the kidney in a LapSac (Cook Surgical, Spencer, Indiana) is reportedly safe and effective during laparoscopic nephrectomy. However, organ entrapment in a LapSac can be difficult, especially during early surgeon experience. A technique to facilitate organ entrapment is described. MATERIALS AND METHODS: We have recently used a simple technique to facilitate deployment of the LapSac in the abdomen using a hydrophilic nitinol guide wire passed through the holes in the mouth of the sack beside its drawstring. The inherent elasticity of the guide wire helps to spring open the mouth of the sack, while facilitating appropriate orientation of the sack mouth. RESULTS: This technique appears to decrease the time needed for organ entrapment because it eliminates the need to triangulate the sack to achieve organ entrapment. An additional port is usually not required during the procedure. CONCLUSIONS: The hydrophilic guide wire technique is inexpensive and effective for LapSac deployment and organ entrapment.

Humans↗
PubMed2002

Bare naked baskets: ureteroscope deflection and flow characteristics with intact and disassembled ureteroscopic nitinol stone baskets.

PURPOSE: Lower pole renal access during flexible ureterorenoscopy is often limited by the active deflection capabilities of the ureteroscope. Deterioration in the deflection and flow capabilities of ureteroscopes occurs with the passage of instrumentation through the working channel. We performed in vitro evaluation of a novel technique using unsheathed nitinol baskets to minimize the deterioration in deflection and maximize the irrigant flow associated with instrument passage through the working channel during flexible ureterorenoscopy. MATERIALS AND METHODS: Alterations in the irrigant flow and active deflection of 4 ureteroscopes from different manufacturers were evaluated. Each ureteroscope was evaluated with an empty working channel, and then with sheathed and unsheathed 2.2, 3 and 3.2Fr (Cook Urological, Inc., Indianapolis, Indiana), 2.4 and 3Fr (Microvasive Urology, Natick, Massachusetts) nitinol baskets in the working channel. RESULTS: With all baskets tested and in all ureteroscopes the deterioration in active deflection and irrigant flow was improved with the unsheathed baskets. The disassembled basket within the working channel allowed an additional 15 to 20 degrees of active deflection. In addition, the disassembled basket allowed for a 2 to 30-fold increase in irrigant flow compared with an intact basket. CONCLUSIONS: The combination of improved deflection and irrigant flow with this technique may improve ureteroscopic access to lower pole renal calculi.

Alloys↗
PubMed2002

Comparison of hand assisted and standard laparoscopic radical nephroureterectomy for the management of localized transitional cell carcinoma.

PURPOSE: Hand assisted laparoscopy affords the surgeon tactile sensation and blunt dissection, which are currently limited using the standard laparoscopic technique. Therefore, we compared standard and hand assisted laparoscopic radical nephroureterectomy for localized upper tract transitional cell carcinoma. MATERIALS AND METHODS: The medical records of 27 patients who underwent standard (11) or hand assisted (16) laparoscopic radical nephroureterectomy between April 1998 and January 2001 were retrospectively reviewed. The parameters of efficacy, efficiency, safety and convalescence were compared. RESULTS: Mean patient age was 64 and 66 years (p = 0.72) in the standard and hand assisted groups, and the mean American Society of Anesthesiologists score was 2.5 and 2.7 (p = 0.64), respectively. All standard and 15 of the 16 hand assisted (94%) procedures were successfully completed via laparoscopy. Total operative time was more than 1 hour shorter for hand assisted than for laparoscopic radical nephroureterectomy (4.9 versus 6.1 hours, p = 0.055). Mean estimated blood loss was similar in the standard and hand assisted groups (190 and 201 ml., p = 0.78). In each group 1 patient required blood transfusion. Mean specimen weight was significantly higher in hand assisted cases (576 versus 335 gm., p = 0.036). Mean time to oral intake was similar in patients who underwent standard and hand assisted laparoscopic radical nephroureterectomy (13 and 20 hours, respectively, p = 0.45). The mean analgesic requirement was also similar (29 and 33 mg. morphine sulfate, respectively, p = 0.83). Mean hospital stay in uncomplicated cases was similar for standard and hand assisted surgery (2.9 and 2.5 days, respectively). Overall hospital stay in the 2 cohorts was also similar (3.3 and 4.5 days, respectively, p = 0.59). Four patients per group experienced postoperative complications. There were no deaths in the standard group but 1 patient (6%) in the hand assisted group died postoperatively. Mean time to partial and complete convalescence in the standard and hand assisted groups was 2.4 and 5.2, and 3.5 and 8.0 weeks, while mean followup was 27.4 and 9.6 months, respectively. CONCLUSIONS: Compared with standard laparoscopy hand assisted laparoscopy decreases operative time without significantly altering short-term parameters of convalescence. However, long-term convalescence after hand assisted laparoscopic radical nephroureterectomy is 1 to 3 weeks longer (p = 0.27). Longer followup in the hand assisted cohort is necessary to determine whether there are any differences in the 2 methods in regard to cancer control.

Aged↗
PubMed2002

Hand assisted laparoscopic radical nephrectomy for renal cell carcinoma with inferior vena caval thrombus.

PURPOSE: To our knowledge we present the initial clinical report of hand assisted laparoscopic radical nephrectomy for renal cell carcinoma with tumor thrombus extending into the inferior vena cava. MATERIALS AND METHODS: A 76-year-old man was referred to our medical center with a 12.5 x 10 cm. stage T3b right renal tumor extending into the inferior vena cava. The caval thrombus was limited and completely below the level of the hepatic veins. After preoperative renal embolization via the hand assisted transperitoneal approach the right kidney was completely dissected with the renal hilum. Proximal and distal control of the inferior vena cava was obtained with vessel loops and a single lumbar vein was divided between clips. An endoscopic Satinsky vascular clamp was placed on the inferior vena cava just beyond its juncture with the right renal vein, thereby, encompassing the caval thrombus. The inferior vena cava was opened above the Satinsky clamp and a cuff of the inferior vena cava was removed contiguous with the renal vein. The inferior vena cava was repaired with continuous 4-zero vascular polypropylene suture and the Satinsky clamp was then removed. A literature search failed to reveal any similar reports of laparoscopic radical nephrectomy for stage T3b renal cell cancer. RESULTS: Surgery was completed without complication with an estimated 500 cc blood loss. Pathological testing confirmed stage T3b grade 3 renal adenocarcinoma with negative inferior vena caval and soft tissue margins. CONCLUSIONS: The introduction of vascular laparoscopic instrumentation and the hand assisted approach enabled us to extend the indications for laparoscopic radical nephrectomy to patients with minimal inferior venal caval involvement.

Aged↗
PubMedDate not supplied

Determination of cell viability after laparoscopic tissue stapling in a porcine model.

BACKGROUND AND PURPOSE: Surgical stapling devices are often used to secure the distal ureter along with a cuff of bladder during laparoscopic nephroureterectomy. As the viability of cells within the stapled tissue would be important in patients with upper urinary-tract transitional-cell carcinoma, we determined the viability of cells within the lines of various commercially available staplers in a porcine model. MATERIALS AND METHODS: Four laparoscopic stapling devices were used: two vascular and two tissue designs (US Surgical, Norwalk, CT, and Ethicon, Cincinnati, OH). The devices were deployed across a portion of the bladder, much as they would be during a nephroureterectomy to create a bladder cuff while excising the distal ureter. The animals were sacrificed 6 weeks later, and the stapled sites were harvested for histopathologic examination by an experienced genitourinary pathologist (PH). RESULTS: Grossly, there were no visible staples at harvest of the stapled bladder and the ureterovesical junction, with a completely healed bladder being seen in all four animals. On histologic examination with hematoxylin and eosin staining, there were distinctly viable cells within the staple lines of the ureterovesical junction and the bladder wall, similar to the unstapled control tissue. There were viable cells in all samples of tissues stapled by either vascular or tissue staplers. CONCLUSIONS: Deployment of both vascular and tissue staplers resulted in viable cells within the staple lines at the ureterovesical junction and bladder wall in this porcine model. There is a potential risk of tumor recurrence at the stapled site in patients who have the ureter and bladder cuff secured with these devices during laparoscopic nephroureterectomy for upper-tract transitional-cell carcinoma. Despite this concern, to date, over a period of 13 years, clinical experience has not revealed a single case of tumor recurrence within the stapled cuff of bladder. Careful endoscopic evaluation of the stapled bladder-cuff site after laparoscopic nephroureterectomy should minimize the potential for local tumor recurrence.

Animals↗