Standardized flexible ureteroscopic technique to improve stone-free rates

OBJECTIVE

To present a unique completely standardized sequence of steps performed before, during, and after flexible ureteroscopy (FURS) that achieves superior results for FURS treatment of renal calculi.

MATERIALS AND METHODS

The "Freiburg FURS technique" includes the following steps: (a) preoperative ureteral stenting; (b) placement of 2 hydrophilic wires; (c) semirigid ureteroscopy before FURS; (d) the use of a large access sheath (14F-16F) if multiple ureteral passages are expected; (e) the use of a 2-working channel flexible endoscope; (f) a modified active flushing system; and (g) an advanced holmium laser technique with complete stone extraction. We performed a prospective analysis of 153 consecutive FURS procedures for nephrolithiasis from August 2009 to July 2011.

RESULTS

Data analysis revealed an "immediate" stone-free rate of 96.7% (as confirmed by endoscopy, fluoroscopy, and ultrasonography), a medium of 2.3 stones, and a cumulative stone size of 10.5 mm (range 3-43). The operative time was 67 minutes (range 20-160). The use of an access sheath was required in 71% of the patients and the postoperative use of a double-J stent in 57% of patients. Complications (Clavien grade II and III) developed in 9.1% of patients (including 7 with minimal perforation that required ureteral stenting for 1 month, 3 with secondary flank pain/hydronephrosis requiring double-J stenting and hospitalization, and 4 with fever or urinary tract infections requiring antibiotic therapy. Follow-up examinations after 3 months showed no late complications.

CONCLUSION

The modified FURS technique provided clinically superior results with a low complication rate. However, the approach requires the use of considerable resources, both technical and surgical and financial.

Thiazolidinedione response in familial lipodystrophy patients with LMNA mutations: a case series

Type 2 familial partial lipodystrophy (FPLD2) patients show impaired glucose and lipid metabolism resulting from lipodystrophic 'lipid pressure' and an intrinsic defect in skeletal muscle metabolism. Since mutated lamin A may interfere with peroxisome proliferator activator gamma (PPARγ) expression, we hypothesized that PPARγ stimulation improves fat distribution and metabolic abnormalities in these patients. 5 nondiabetic FPLD2 patients were treated with rosiglitazone over 12 months. We assessed body composition, body fat distribution, and skinfold thickness/subcutaneous tissue thickness. We also determined venous glucose, insulin, and free fatty acid (FFA) concentrations, and respiratory quotient (RQ) before and during oral glucose tolerance testing. Adipose tissue and muscle fasting and postprandial metabolism were studied by microdialysis. Within 12 months treatment, hip circumference increased from 93.6±2.78 cm to 96.2±2.3 cm (p<0.05). Rosiglitazone reduced fasting glucose levels and liver transaminases. Baseline and postprandial FFA concentrations were significantly lower after 12 months treatment. RQ and muscle interstitial pyruvate and lactate did not respond to treatment. We conclude that PPARγ stimulation with rosiglitazone modestly improves glucose metabolism in FPLD2 patients presumably through proximal adipose tissue expansion. The intrinsic muscular metabolic defect does not respond to rosiglitazone.

New Cs sputter ion source with polyatomic ion beams for secondary ion mass spectrometry applications

A simple design for a cesium sputter ion source compatible with vacuum and ion-optical systems as well as with electronics of the commercially available Cameca IMS-4f instrument is reported. This ion source has been tested with the cluster primary ions of Si(n)(-) and Cu(n)(-). Our experiments with surface characterization and depth profiling conducted to date demonstrate improvements of the analytical capabilities of the secondary ion mass spectrometry instrument due to the nonadditive enhancement of secondary ion emission and shorter ion ranges of polyatomic projectiles compared to atomic ones with the same impact energy.

Tyramine in the assessment of regional adrenergic function

Regional adrenergic function is difficult to assess in humans. Tyramine given through a microdialysis probe may be a useful tool in this regard. However, tyramine data is hard to interpret given the drug's complex mode of action. We characterized the response to tyramine, isoproterenol, and dopamine in adipose tissue with microdialysis probes in normal subjects. We measured glycerol concentrations to follow changes in lipolysis and monitored tissue perfusion with ethanol dilution. During perfusion with tyramine, dialysate glycerol concentration increased dose-dependently from 83+/-8 microM at baseline to 181+/-18 microM at 3.5 mM tyramine (p<0.001) followed by a fall down to 121+/-9 microM at 35 mM tyramine (p<0.001). Propranolol almost completely blocked this response. A similar lipolytic response was not observed in isolated human adipocytes. Dopamine <35 microM did not replicate the tyramine-induced lipolysis; however, dopamine >35 microM potently inhibited lipolysis. We conclude that tyramine-induced lipolysis is explained by a pre-synaptic mechanism. Tyramine applied through a microdialysis probe in concentrations up to 3.5 mM can be used to assess pre- and post-synaptic mechanisms regulating lipid mobilization.

The effect of oral glucose loads on tissue metabolism during angiotensin II receptor and beta-receptor blockade in obese hypertensive subjects

AT1 receptor blockers and ACE inhibitors decrease the risk for new onset diabetes mellitus. The phenomenon could be related to a direct angiotensin II effect on tissue metabolism. To address the issue, we recruited eighteen obese hypertensive patients. Patients were randomized to double-blind treatment with either valsartan (n = 8) or atenolol (n = 10) for thirteen weeks. They underwent an oral glucose tolerance test before and during active treatment, while metabolism was monitored through subcutaneous and intramuscular microdialysis and indirect calorimetry. After glucose ingestion, venous glucose and insulin concentrations increased rapidly while systemic free fatty acid concentrations were suppressed. Dialysate glucose and lactate concentrations increased briskly in adipose tissue and in skeletal muscle. Dialysate glycerol decreased profoundly in both tissues. Respiratory quotient increased markedly after glucose ingestion. These responses were identical at baseline and during active treatment either drug. We conclude that AT1 receptor blockade in obese hypertensive patients has no effect on interstitial glucose supply, lipolysis, and substrate oxidation. One possible explanation is that angiotensin II levels in obese hypertensives are not sufficient to elicit the metabolic changes that have been observed after direct angiotensin II application. The exact mechanism by which inhibition of the renin-angiotensin-aldosterone system decreases the diabetes risk remains unresolved and requires further study.

Blood flow in subcutaneous adipose tissue depends on skin-fold thickness

Blood flow in subcutaneous adipose tissue is reduced in obese compared to lean subjects. Limitations in vascular supply might interfere with adipose tissue function as a metabolic and endocrine organ. We tested the hypothesis that nutritive blood flow and tissue metabolism depends on subcutaneous adipose tissue thickness even in normal-weight subjects. Sixteen young, healthy, normal-weight subjects (8 men, 8 women) were included in the study. Abdominal subcutaneous adipose thickness was assessed by skin-fold measurements. The microdialysis technique was applied for monitoring basal adipose tissue blood flow (ethanol dilution technique) and metabolism. An increase in skin-fold thickness from 15 to 45 mm and from 8 to 37 mm was associated with a linear increase in basal ethanol ratio from 0.19 to 0.63 and 0.25 to 0.75 and linear decreases in dialysate glucose concentrations from 1.95 to 0.24 mM and 1.68 to 0.29 mM, and 152 to 42 microM and 172 to 49 microM for glycerol concentrations in men and women, respectively (p < 0.05). Isoproterenol-stimulated blood flow also inversely correlated to skin-fold thickness (p < 0.05). We conclude that increased adipose tissue thickness is associated with reduced tissue perfusion and metabolism, even in lean subjects. Skin-fold thickness is an important confounding variable in metabolic studies, particularly in microdialysis experiments.

Impact of increasing parenteral protein loads on amino acid levels and balance in critically ill anuric patients on continuous renal replacement therapy

OBJECTIVES

We wanted to establish optimum protein and glucose intakes during total parenteral nutrition by using a constant caloric but changing protein intake in critically ill, ventilated, anuric patients on continuous renal replacement therapy and measuring amino acid and glucose losses across the hemofilter.

METHODS

Eleven consecutive, critically ill patients (eight male, age, 43.5 +/- 21.8 y; Acute Physiology and Chronic Health Evaluation II score, 20.5 +/- 7.0; Acute Physiology and Chronic Health Evaluation risk of death: 36.5% +/- 23.0 and 6 +/- 1 impaired organ systems) entered this study. Patients were fed by continuous infusion of a total parenteral mixture consisting of Synthamin (a mixture of essential and non-essential amino acids), 50% dextrose, and intralipid (long-chain triglycerides) to meet caloric requirements as predicted by Schofield's equation corrected by stress factors. The amount of protein infused was varied (1 to 2.5 g. kg(-1). d(-1)) by increments of 0.25 g. kg(-1). d(-1). Patients were stabilized on each feeding regimen for at least 24 h before paired samples of blood and dialysate were taken for amino acid and glucose measurements. Continuous renal replacement therapy was performed by using a blood pump with a blood flow of 100 to 175 mL/min. Dialysate was pumped in and out counter-currently to the blood flow at 2 L/h. A biocompatible polyacrylonitrile hemofilter was used in all cases.

RESULTS

With protein intakes below 2.5 g. kg(-1). d(-1), blood levels of 14% to 57% of the measured amino acids were below the lower limits of the normal range. At 2.5 g. kg(-1). d(-1), all measured amino acids were within the normal range. Amino acid balance became more positive as protein input increased (P = 0.0001). Glucose and amino acid losses were dependent on blood concentration. Overall, 17% (range, 13% to 24%) of infused amino acids and 4% of infused glucose were lost in the dialysate.

CONCLUSIONS

This study of critically ill, ventilated, anuric patients on continuous renal replacement therapy suggested that increases in protein and glucose are required to account for the increased losses across the hemofilter. A protein intake of 2.5 g. kg(-1). d(-1) appeared to optimize nitrogen balance and correct amino acid deficiencies.

Study of the microgeometry of porous materials using synchrotron computed microtomography

A series of measurements of the structure of a variety of porous materials has been made using synchrotron computed microtomography (SCMT). The work was carried out at the Brookhaven National Synchrotron Light Source (NSLS), the Argonne Advanced Photon Source (APS) and the European Synchrotron Radiation Facility (ESRF). The experiments at Brookhaven and Argonne were carried out on bending magnet beam lines using area detectors to obtain CT images based on determination of X-ray absorption coefficients. The work at the ESRF used an undulator beam line, a 13 KeV pencil X-ray beam of 2 µm and an energy dispersive X-ray detector to make tomographic sections of trace element distributions by X-ray fluorescence tomography. Most of the work was done with a pixel/voxel size ranging from 0.002 to 0.010 mm. We examined the structure of unconsolidated estuarine sediments, whose structure is relevant to transport of contaminants in rivers and estuaries. Fluorescent tomography with 2–3 µm resolution was used to ascertain whether or not metals were concentrated on the surface or throughout the volume of a single sediment particle. Sandstone samples were investigated to obtain a set of values describing their microstructures that could be useful in fluid flow calculations relevant to petroleum recovery or transport of environmental contaminants. Measurements were also made on sandstone samples that had been subjected to high-pressure compression to investigate the relation between the microgeometry and the magnitude of the applied pressure. Finally, a Wood’s metal-filled sample was scanned for demonstration of resolution enhancement and fluid flow studies.

Age-related changes of Renin-Angiotensin system genes in white adipose tissue of rats

The adipose tissue renin-angiotensin system has been implicated in the regulation of adipocyte growth and differentiation. We studied the influence of age, body weight, total body fat content, anatomical localization, and diet on the expression of angiotensinogen (AGT) and angiotensin II type 1 (AT 1 )-receptor genes in white adipose tissue of normal and postnatal overfed rats. Relative gene expression was measured in epididymal adipose tissue and liver of control and postnatal overfed (PNO) rats at the age of 4, 8, and 12 weeks using real time RT-PCR. Body fat content was determined by carcass analysis. Body weight and body fat content were only significantly greater in PNO rats when compared to control rats at the age of 4 weeks. At the age of 12 weeks, AGT expression was significantly decreased in both tissues. Furthermore, expression of the AT 1 -receptor gene was significantly decreased in liver but not in adipose tissue at 12 weeks of age. Postnatal overfeeding did not influence the expression levels of either gene at any time-point in either liver or adipose tissue. At the age of 24 weeks, AGT expression was significantly greater in epididymal than in subcutaneous adipose tissue, whereas no site-specific differences could be found for the AT 1 -receptor. We conclude that age and depot-specific mechanisms are of more importance for the expression of AGT and AT 1 -receptor genes during the first 12 weeks of age than a short period of overfeeding.

Gender-specific response to interstitial angiotensin II in human white adipose tissue

Angiotensin II is synthesized locally in various tissues. However, the role of interstitial angiotensin II in the regulation of regional metabolism and tissue perfusion has not as yet been clearly defined. We characterized the effect of interstially applied angiotensin II in abdominal subcutaneous adipose tissue of young, normal-weight, healthy men (n = 8) and women (n = 6) using the microdialysis technique. Adipose tissue was perfused with 0.01, 0.1, and 1 micro M angiotensin II. Dialysate concentrations of ethanol, glycerol, glucose, and lactate were measured to assess changes in blood flow (ethanol dilution technique), lipolysis, and glycolysis, respectively. Baseline ethanol ratio and dialysate lactate were both significantly higher, whereas dialysate glucose was significantly lower in men vs. women. In men, ethanol ratio and dialysate glucose, lactate and glycerol did not change significantly during perfusion with angiotensin II. In women, however, angiotensin II induced a significant increase in ethanol ratio and dialysate lactate and a decrease in dialysate glucose close to values found for men and this response was almost maximal at the lowest angiotensin II concentration used. Dialysate glycerol did not change significantly. We conclude that baseline blood flow and glucose supply and metabolism is significantly higher in women than in men. In men, interstitial Ang II has only a minimal effect on adipose tissue blood flow and metabolism. In women, however, a high physiological concentration of interstitial angiotensin II can reduce blood flow down to values found in men. This is associated with an impaired glucose supply and metabolism. Additionally, Ang II inhibits lipolysis.