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Biomedical subjects

D Shemesh

Publications and source records attributed to D Shemesh.

9 recordsLinked to original sources
PubMed2003

Primary forearm arteriovenous fistula for hemodialysis access--an integrated approach to improve outcomes.

PURPOSE: Maximizing the ratio of primary arteriovenous fistula (PAVF) over bridge graft fistula (BGF) for hemodialysis access is a primary recommendation of the National Kidney Foundation published as Dialysis Outcomes Quality Initiative (DOQI). Imaging, anesthetic and surgical techniques were taken into account to achieve this and other goals, including extensive use of forearm vessels to lower immediate and early failure rates and prolong the useful life of PAVFs. DESIGN: Prospective non-randomized study. METHODS: High-resolution duplex ultrasonography (DUS) was added to careful clinical assessment in planning and follow-up of the dialysis access. Brachial plexus block, which allowed the use of an arterial tourniquet and gave a postoperative sympathectomy type effect, was used for anesthesia, and together with meticulous surgical technique, prevented spasm. Access puncture, post-operative follow-up and surgical revisions were planned in close cooperation with the nephrology team. FINDINGS: Ninety (57.3%) of the 157 fistulas constructed for new hemodialysis access between August 1998 and March 2000 were PAVFs. Seventy-three (81.1%) of these were confined to the forearm and comprise the study population, with a mean follow-up of 8.4+/-4.4 months. There were no immediate failures in the study group. The early failure rate (1 month) was 6.8% and revisions based on DUS were easily accomplished in all cases. The one year assisted primary patency rate was 81.8% and the secondary patency rate at 18 months was 98.6%. CONCLUSIONS: DUS for planning and follow-up of PAVF along with careful surgical technique under a brachial plexus blockade can achieve a PAVF/BGF ratio well above 50% with a low early failure rate and a high secondary patency rate. Algorithms are presented to achieve these goals.

Adolescent↗
PubMed2001

Influence of thoracic sympathectomy on cardiac induced oscillations in tissue blood volume.

The photoplethysmographic (PPG) signal, which measures cardiac-induced changes in tissue blood volume by light transmission measurements, shows spontaneous fluctuations. In this study, PPG was simultaneously measured in the right and left index fingers of 16 patients undergoing thoracic sympathectomy, and, from each PPG pulse, the amplitude of the pulse (AM) and its maximum (BL) were determined. The parameter AM/BL is proportional to the cardiac-induced blood volume increase, which depends on the arterial wall compliance. AM/BL increased after the thoracic sympathectomy treatment (for male patients, from 2.60+/-1.49% to 4.81+/-1.21%), as sympathetic denervation decreases arterial tonus in skin. The very low-frequency (VLF) fluctuations of BL or AM showed high correlation (0.90+/-0.11 and 0.92+/-0.07, respectively) between the right and left hands before the thoracic sympathectomy, and a significant decrease in the right-left correlation coefficient (to 0.54+/-0.22 and 0.76+/-0.20, respectively) after the operation. The standard deviation of the BL or AM VLF fluctuations also reduced after the treatment, indicating sympathetic mediation of the VLF PPG fluctuations. The study also shows that the analysis of the PPG signal and the VLF fluctuations of the PPG parameters enable the assessment of the change in sympathetic nervous system activity after thoracic sympathectomy.

Adolescent↗
PubMed2001

Dialysis access induced limb ischemia corrected using quantitative duplex ultrasound.

Dialysis access induced limb ischemia (DAILI) is a rare complication after the creation of an arteriovenous fistula in infancy but can cause irreversible ischemic limb damage in severe cases. The incidence of DAILI is higher in bridge graft fistulas than in native fistulas. DAILI patients may be managed by surgically reducing the volume flow in the fistula. However, in the pediatric age group, such a reduction of volume flow may result in thrombosis or an inadequate flow for effective dialysis. Several methods have been described to achieve the delicate balance between essential flow in the fistula and adequate limb perfusion pressure. We have developed a new method employing preoperative duplex ultrasonography to predict quantitatively the reduction in volume flow in the fistula that will allow effective dialysis while providing adequate limb perfusion. The preoperative assessment was reproduced on the operating table using intraoperative duplex. A 3-year-old girl thus treated has had resolution of her ischemic symptoms and maintains long-term patency of her dialysis access.

Catheters, Indwelling↗
PubMed1999

Management of dialysis access-associated steal syndrome: use of intraoperative duplex ultrasound scanning for optimal flow reduction.

Dialysis access-associated steal syndrome (DASS) is an uncommon complication after the creation of an arteriovenous fistula and can cause irreversible ischemic damage in severe cases. Dialysis access-associated steal syndrome has been managed with the surgical reduction of the volume flow in the fistula, but this is associated with a certain incidence of access loss. Several methods are described to achieve the delicate balance between essential flow in the fistula and an adequate limb perfusion pressure. We have developed a new method with duplex ultrasound scanning to quantitate the reduction in volume flow, which will allow effective dialysis and provide adequate limb perfusion. The preoperative assessment was reproduced on the operating table with intraoperative duplex scanning. A 65-year-old woman who underwent this treatment has had resolution of her ischemic symptoms and maintains long-term patency of her dialysis access.

Aged↗
PubMed1996

[Quantitative analysis of testicular varicocele by scintigraphy].

Testicular varcocele is the most common factor affecting male fertility. The determental effects of the varicocele on semen quality and fertility are codonsidered to be related to its severity. The aim of this study was to establish a quantitative radioisotopic method for the diagnosis and evaluation of testicular varicocele. 31 men attending our infertility clinic underwent scintigraphy with a gamma camera scanner (Apex 415) equipped with a pinhole low energy collimator (zoom factor 2). The evaluation was performed in the supine position and the collimator at 8.5 cm above the testicular area. The patients' red blood cells were labeled in-vivo by injection of SN-pyrophosphate before i.v. administration of To-99. An image of the scrotal area was obtained and the computer processing consisted of a drawing of the region of interest over the area of the varicocele, with background subtraction. The following indices were calculated: testes total count, varicocele area (in pixels) and average count per pixel (ACPP). The patients also underwent high resolution duplex sonography (HRDS) using a Multigon duplex scanner with a 7.5 Mhz transducer. Spermatic vein diameter, and reflux when present, were determined. HRDS was performed to compare and to validate the results obtained by scintigraphy. In men without varicocele mean ACPP was 2.80, in those with mild varicocele 3.76, in those with moderate varicocele 5.40 and in those with severe varicocele 7.48. A significant positive correlation was found between ACPP values and severity of the varicocele, as determined either by the diameter of the spermatic veins or by reflux of blood in the veins. We conclude that the ACPP index obtained by this new technique enables objective diagnosis and quantitative grading of testicular varicocele.

Analysis of Variance↗
PubMed1995

[Severity of testicular varicocele and sperm cell ultramorphologic characteristics].

Ultramorphologic characteristics of sperm cells found in infertile men with varicoceles were compared with the severity of the varicocele. Classification of varicoceles into mild, moderate or marked was determined by spermatic vein diameter and degree of blood reflux. These were evaluated by high resolution duplex sonography. There were no statistical differences between the 3 grades of varicocele severity with regard to abnormalities in the subcellular organelles of the acrosome, karyoplasm, and skeleton of spermatozoal heads, or in the axoneme, outer dense fiber and skeleton of sperm cell tails. The only abnormal ultramorphologic features found to be significant among the 3 groups were differences in the frequencies of karyoplasm agenesis, and of partial agenesis, malformation and degeneration of the acrosome in sperm cell heads. However, these features could not be related to grade of severity and therefore, no ultramorphologic severity pattern could be detected. Thus, no varicocele beneficial score based on grade of severity and sperm cell ultramorphology can be suggested for clinical use.

Humans↗
PubMed1991

Successful treatment of pancreatic pseudocyst with a somatostatin analogue and catheter drainage.

We report a patient with bile duct stone-induced pancreatitis who subsequently developed a large pseudocyst that became infected after endoscopic retrograde cholangiopancreatography (ERCP) was done for extraction of the stones. Percutaneous external drainage allowed control of the infection, but failed to seal the pseudocyst. We then treated the patient with a long-acting somatostatin analogue which shrunk the cyst within a week. Patients with pancreatic pseudocyst resistant to drainage should be offered a course of somatostatin before surgery is contemplated.

Aged↗