An approximate estimate of the ion-activity product of calcium oxalate in rat urine

The objective of this report was to derive a simplified approximate estimate of the ion-activity product of calcium oxalate (AP_CaOx) in rat urine. The relative effect of each urine variable was assessed by means of iterative computerised approximation with the EQUIL2 program. A basic urine composition was chosen from literature and experimental data. The most pronounced influence on AP_CaOx was recorded for urinary calcium, oxalate, citrate, magnesium and volume. Based on these calculations, an AP(CaOx) index_RAT was formulated: . For a 24-h urine sample, factor A takes the value 4067 and factor F should be set to 0.015. Conclusion. A simplified approximate estimate of AP_CaOx was derived for rat urine. There was a reasonably good correspondence between AP(CaOx) index_RAT and AP_CaOx, as derived from EQUIL2 (r=0.890), provided the other urine variables do not deviate very much from that in the basic composition.     

Studies on the role of calcium phosphate in the process of calcium oxalate crystal formation

Crystals of calcium phosphate (CaP) added to solutions with a composition corresponding to that at different levels of the collecting duct (CD) and with different pH were rapidly dissolved at pH 5.0, 5.25 and 5.5. Only minor or no dissolution was observed at higher pH levels. Despite this effect, CaP crystals induced nucleation or heterogeneous crystallization of CaOx up to a pH of 6.1, whereas CaP was the type of crystalline material that precipitated at higher pH. Accordingly, small crystal volumes were recorded at pH 5.5 and great volumes at pH 6.7 4 h after the addition of CaP crystals to the solutions. Dialyzed urine appeared to counteract the dissolution of CaP and to reduce the rate of secondary crystallization. The CaP induced crystallization of CaOx was confirmed by a reduction of ¹⁴C-labeled oxalate in solution. The AP_CaOx required for a nucleation or heterogeneous crystallization of CaOx in the presence of CaP was around 1.5 × 10⁻⁸ (mol/l)². For CaP crystal formation on CaP, an AP_CaP (^aCa²⁺ × ^aPO₄ ³⁻) of approximately 50 × 10⁻¹⁴ (mol/l)² appeared to be necessary. The CaOx crystals formed were microscopically found in association with the CaP crystalline material and were most frequently of CaOx dihydrate type. Step-wise crystallization experiments comprising supersaturation with CaP (Step A), supersaturation with CaOx (Step B) and subsequently acidification (Step C) showed that CaOx crystal formation occurred when CaP crystals were dissolved and thereby served as a source of calcium. The ensuing formation of CaOx crystals is most likely the result from high local levels of supersaturation with CaOx caused by the increased concentration of calcium. These experimental studies give support to the hypothesis that crystallization of CaOx at lower nephron levels or in caliceal urine might be induced by dissolution of CaP formed at nephron levels above the CD, and that a low pH is prerequisite for the precipitation of CaOx. The observations accordingly provide additional evidence for the important role of calcium phosphate in the crystallization of calcium oxalate, that might occur both at the surface of Randall’s plaques and intratubularly at the papillary tip. Parts of these studies were presented at the Scanning Microscopy Meeting 1996, at the International Symposium on Urolithiasis, Dallas 1996 and at the Eurolithiasis meeting in Istanbul 1998.     

Assessment of crystallization risk formulas in pediatric calcium stone-formers

The pathogenesis of calcium urolithiasis involves complex interactions of urinary promoters and inhibitors of crystallization. A variety of risk formulas have been established to approximate these interactions for clinical evaluation, and the aim of our study was to determine their usefulness as predictors of stone formation. The study cohort comprised 126 patients (63 boys and 63 girls) aged 6.7–18 years (mean age 14.1 ± 2.9 years) with calcium urolithiasis (61 with chemically confirmed calcium oxalate stones and 65 children with a strong clinical suspicion of this type of urolithiasis). Of these, 36 children were classified as recurrent stone-formers, whereas the remaining 90 had experienced only one stone episode. The values obtained were compared to those of a control group of 60 age- and gender- matched healthy children. A number of crystallization risk indices were calculated from analytes obtained in 24-h urine: calcium/magnesium ratio (Ca/Mg), calcium/citrate ratio (Ca/Cit), (calcium × oxalate)/(magnesium × citrate) ratio (CaOx/MgCit), relative urinary CaOx supersaturation (RS_CaOx), CaOx activity product index (AP_CaOx), and standardized CaOx activity product index (AP_{CaOx stand}). All indices, except for the AP_CaOx index, were significantly higher in stone-formers than in the controls. The Ca/Mg, Ca/Cit, CaOx/MgCit, AP_CaOx, and AP_{CaOx stand} indices were significantly higher in recurrent stone-formers than in first-episode ones. However, the determination of precise cutoffs between pathological and non-pathological values was problematic due to a considerable overlap of individual values. Based on our results, we conclude that calculation of the majority of risk indices may play a rather supplementary role in the evaluation of children with calcium urolithiasis.     

Is citrate an inhibitor of calcium oxalate crystal growth in high concentrations of urine?

The effect of citrate on calcium oxalate (CaOx) crystal growth was studied in a system in which series of samples containing [⁴⁵Ca]calcium chloride were brought to different levels of supersaturation with various concentrations of oxalate. The crystallization was assessed by measuring the amount of isotope remaining in solution 30 min after the addition of CaOx seed crystals to samples containing citrate in concentrations corresponding to those in final urine. The experiments were carried out both in pure salt solutions and in solutions with dialysed urine. Increased concentrations of citrate resulted in a reduced crystallization of CaOx in both the presence and absence of dialysed urine, but with the lowest rate of crystallization in the samples containing urine. The increased concentration of ⁴⁵Ca remaining in solution reflected a reduced crystallization, which could possibly be explained both by a reduced supersaturation and by an increased inhibition of CaOx crystal growth. The direct effects of citrate on CaOx crystal growth were assessed by calculating the ion-activity product of CaOx (AP_CaOx) at corresponding degrees of crystallization. The AP_CaOx recorded at a 30% reduction of the amount of isotope in solution increased with increasing concentrations of citrate between 1.0 and 1.5 mmol/l in samples both with and without dialysed urine. These findings indicate that citrate has a weak direct inhibitory effect on CaOx crystal growth, which adds to the reduced growth rate brought about by urinary macromolecules and a decreased supersaturation.     

Simplified estimates of ion-activity products of calcium oxalate and calcium phosphate in mouse urine

This study aimed at formulating simplified estimates of ion-activity products of calcium oxalate (AP(CaOx)) and calcium phosphate (AP(CaP)) in mouse urineto find the most important determinants in order to limit the analytical work-up. Literature data on mouse urine composition was used to determine the relative effect of each urine variable on the two ion-activity products. AP(CaOx) and AP(CaP) were calculated by iterative approximation with the EQUIL2 computerized program. The most important determinants for AP(CaOx) were calcium, oxalate and citrate and for AP(CaP) calcium, phosphate, citrate, magnesium and pH. Urine concentrations of the variables were used. A simplified estimate of AP(CaOx) (AP(CaOx)-index(MOUSE)) that numerically approximately corresponded to 10(8) × AP(CaOx) was given the following expression:[Formula: see text]For a series of urine samples with various composition the coefficient of correlation between AP(CaOx)-index(MOUSE) and 10(8) × AP(CaOx) was 0.99 (p = 0.00000). A similar estimate of AP(CaP) (AP(CaP)-index(MOUSE)) was formulated so that it approximately would correspond numerically to 10(14) × AP(CaP) taking the following form:[Formula: see text]For a series of variations in urine composition the coefficient of correlation was 0.95 (p = 0.00000). The two approximate estimates shown in this article are simplified expressions of AP(CaOx) and AP(CaP). The intention of these theoretical calculations was not to get methods for accurate information on the saturation levels in urine, but to have mathematical tools useful for rough conclusions on the outcome of different experimental situations in mice. It needs to be emphasized that the accuracy will be negatively influenced if urine variables not included in the formulas differ very much from basic concentrations.     

A model for assuring clamping success during laparoscopic partial nephrectomy with segmental renal artery clamping

Objectives

A model for assuring clamping success was established for laparoscopic partial nephrectomy (LPN) with segmental renal artery clamping (SRAC).

Materials and methods

Patients (n = 107; December 2009–September 2011) who underwent LPN with SRAC dependent on the experience of the surgeon and CTA were retrospectively reviewed to determine the optimal characteristics of target arteries. After multiple logistic regression analysis, variables used to build a nomogram were selected using a backward elimination scheme. A model for a clamping program customized to the patient was designed. The surgical outcomes of patients (n = 141; October 2011–June 2014) who subsequently underwent LPN-SRAC with the applied model were compared with those of the first group of patients.

Results

Five potential predictors were initially assessed: segmental renal artery angle, target artery diameter, and distance (d) to the abdominal aorta, renal hilum (d _RH), and kidney midline (d _KML). The regression equation was set up as:

$${\text{Clamping assurance}} = \frac{{{\text{e}}^{x} }}{{1 + {\text{e}}^{x} }},\quad {\text{where}}\,x = 12.360 + 4.863\left( {d_{\text{RH}} } \right) - 8.848\left( {d_{\text{KML}} } \right).$$

Comparing the patient groups, those for whom the new SRAC model was applied had a significantly better success rate of clamping (P < 0.001), less total operative time (P < 0.001), and less operative blood loss (P = 0.042). No obvious differences were observed in time of warm ischemia, postoperative hospitalization, RENAL nephrometry score, or number of final clamped branches.

Conclusions

The model for assuring clamping success was helpful in designing an SRAC program and thus benefiting the LPN procedure.

     

Creatinine-based equation to estimate the glomerular filtration rate in Japanese children and adolescents with chronic kidney disease

Background

Renal inulin clearance is the gold standard for evaluation of kidney function, but cannot be measured easily in children. Therefore, we utilize the serum creatinine (Cr)-based estimated GFR (eGFR) measuring serum Cr by the enzymatic method, and we have reported simple serum Cr-based eGFR in Japanese children aged between 2 and 11 years old. Furthermore, we should use serum Cr-based eGFR in Japanese adolescents as well as children with chronic kidney disease for evaluation of renal function.

Methods

The inulin clearance and serum Cr level determined by an enzymatic method were measured in 131 pediatric chronic kidney disease (CKD) patients between the ages of 2 and 18 years old with no underlying disease affecting renal function except CKD to determine the serum Cr-based eGFR in Japanese children and adolescents.

Results

We offer the complex estimated GFR equation using polynomial formulae for reference serum creatinine levels with body length in Japanese children except infants, resulting in the following equation: $$ {\text{eGFR}} = 110.2 \times ({\text{reference serum Cr}}/{\text{patient's serum Cr}}) + 2.93 $$ Reference serum Cr levels (y) are shown by the following two equations of body length (x): $$ \begin{aligned} {\text{Males}}:\quad \, y = & -1.259x^{5} + 7.815x^{4} -18.57x^{3} + 21.39x^{2} -11.71x + 2.628 \\ {\text{Females}}:\quad \, y = & -4.536x^{5} + 27.16x^{4} -63.47x^{3} + 72.43x^{2} -40.06x + 8.778 \\ \end{aligned} $$

Conclusion

The new polynomial eGFR formula showing the relationship with body length and serum Cr level may be applicable for clinical screening of renal function in Japanese children and adolescents aged between 2 and 18 years.     

Fourier transform raman spectroscopy of synthetic and biological calcium phosphates

Fourier-transform (FT) Raman spectroscopy was used to characterize the organic and mineral components of biological and synthetic calcium phosphate minerals. Raman spectroscopy provides information on biological minerals that is complimentary to more widely used infrared methodologies as some infrared-inactive vibrational modes are Raman-active. The application of FT-Raman technology has, for the first time, enabled the problems of high sample fluorescence and low signal-to-noise that are inherent in calcified tissues to be overcome. Raman spectra of calcium phosphates are dominated by a very strong band near 960 cm^–1 that arises from the symmetric stretching mode of the phosphate group. Other Raman-active phosphate vibrational bands are seen at approximately 1075 , 590 , and 435 cm^–1 . Minerals containing acidic phosphate groups show additional vibrational modes. The different calcium phosphate mineral phases can be distinguished from one another by the relative positions and shapes of these bands in the Raman spectra. FT-Raman spectra of nascent, nonmineralized matrix vesicles (MV) show a distinct absence of the phosphate band even though these structures are rich in calcium and phosphate. Similar results were seen with milk casein and synthetic Ca-phosphatidyl-serine-PO₄ complexes. Hence, the phosphate and/or acidic phosphate ions in these noncrystalline biological calcium phosphates is in a molecular environment that differs from that in synthetic amorphous calcium phosphate. In MV, the first distinct mineral phase to form contained acidic phosphate bands similar to those seen in octacalcium phosphate. The mineral phase present in fully mineralized MV was much more apatitic, resembling that found in bones and teeth. These findings are consistent with formation of an OCP-like precursor during MV mineral formation that subsequently hydrolyzes to form hydroxyapatite.     

Early diastolic function during exertion influences exercise intolerance in patients with hypertrophic cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction (LVEF) often develop dyspnea and exercise intolerance. Diastolic dysfunction may contribute to exercise intolerance in these patients. This study aimed to clarify our hypothesis as to whether diastolic function rather than systolic function would be associated with exercise intolerance in HCM using two-dimensional (2D) speckle tracking echocardiography during exercise.

Methods

Thirty-three HCM patients (mean age 59.3 ± 15.7 years) underwent 2D speckle tracking echocardiography at rest and during submaximal semi-supine bicycle exercise. Global longitudinal strain (LS), LS rate during systole (LSRs), early diastole (LSRe), and late diastole (LSRa) were measured. The symptom-limited cardiopulmonary exercise testing was performed using a cycle ergometer for measuring the peak oxygen consumption (peak $ \dot{V}_{{{\text{O}}_{2} }} $ ).

Results

In the multivariate linear regression analysis, peak $ \dot{V}_{{{\text{O}}_{2} }} $ did not associate with strain or strain rate at rest. However, peak $ \dot{V}_{{{\text{O}}_{2} }} $ correlated with LS (β = ?0.403, p = 0.007), LSRe (β = 6.041, p = 0.001), and LSRa (β = 5.117, p = 0.021) during exercise after adjustment for age, gender, and heart rate. The first quartile peak $ \dot{V}_{{{\text{O}}_{2} }} $ (14.2 mL/min/kg) was assessed to predict exercise intolerance. The C-statistic of delta LSRe was 0.74, which was relatively greater than that of delta LS (0.70) and delta LSRa (0.58), indicating that early diastolic function rather than systolic and late diastolic function affects exercise intolerance.

Conclusions

LSRe during exercise is closely associated with the peak $ \dot{V}_{{{\text{O}}_{2} }} $ . Early diastolic function during exercise is an important determinant of exercise capacity in patients with HCM.     

Creatinine-based equations to estimate glomerular filtration rate in Japanese children aged between 2 and 11 years old with chronic kidney disease

Background

Renal inulin clearance is the gold standard for glomerular filtration rate (GFR), but is compromised by problems of collecting urine samples in children, especially those <6 years of age or with a bladder dysfunction. Therefore, we should utilize the serum creatinine (Cr)-based estimated GFR (eGFR), measuring serum Cr by enzymatic method. The updated Schwartz formulae were reported by enzymatic Cr instead of by the Jaffe method in American children aged 1–16 years old. We believe it would be better to determine serum Cr-based eGFR by the enzymatic method in Japanese children for evaluation of renal function.

Methods

Serum Cr-based eGFR was determined by measuring inulin clearance and serum Cr level in 76 pediatric chronic kidney disease (CKD) patients (49 males and 27 females) aged 2–11 years with no underlying disease that would affect renal function.

Results

We showed the inulin clearance by expression of the body length/serum Cr ratio in pediatric CKD patients, which resulted in the equation: $ {\text{inulin}}\;{\text{GFR}} = 0. 3 4 2 \times {\text{body length}}\;({\text{cm}})/{\text{serum}}\;{\text{Cr}}\;({\text{mg}}/{\text{dL}}) \pm 2. 7 5 $ . Additionally, we suggest the following serum Cr-based eGFR formula passing through the origin: $ {\text{eGFR}}\; ( {\text{mL}}/{ \hbox{min} }/ 1. 7 3 \,{\text{m}}^{ 2} )= 0. 3 5 \times {\text{body}}\;{\text{length}}\; ( {\text{cm)/serum}}\;{\text{Cr}}\; ( {\text{mg}}/{\text{dL)}} $ , because it is simple and easy to remember, thus making it clinically useful.

Conclusion

The new eGFR formula derived from body length and serum Cr level is applicable for clinical screening of renal function in Asian as well as Japanese children aged between 2 and 11 years old.     

Quantitative analysis of pathological nails using laser-induced breakdown spectroscopy (LIBS) technique

Laser-induced breakdown spectroscopy (LIBS) has been used as a potential method for simultaneous measurement of the elements Ca, Na, and K, for normal and pathological nails. We compared the measured LIBS spectra of these elements for normal and pathological nails. The \( B^{2} \sum ^{ + } \to {\text{X}}^{2} \sum ^{ + } \) violet band emission spectrum of CN was used for the estimation of the transient temperature of the plasma plume and consequently of the sample surface considering thermodynamic equilibrium.     

Global longitudinal strain by two-dimensional speckle tracking imaging predicts exercise capacity in patients with chronic heart failure

Background

Left ventricular ejection fraction (LVEF) predicts mortality in patients with chronic heart failure (CHF). However, a weak correlation was found between LVEF and peak oxygen uptake ( $ \dot{V}{\text{O}}_{2} $ ) in CHF patients. Global longitudinal strain measured by two-dimensional (2D) strain is regarded as a more useful predictor of cardiac events than LVEF. We investigated whether 2D strain obtained at rest could predict peak $ \dot{V}{\text{O}}_{2} $ in patients with CHF.

Methods

Fifty-one patients (mean age of 54.0 ± 12.0 years, 14 females, LVEF 46.0 ± 15.0%) with stable CHF underwent resting echocardiography and cardiopulmonary exercise testing. Leg muscle strength was measured for the evaluation of peripheral factors. Global longitudinal strain (GLS) in the apical 4-, 3-, and 2-chamber views and global circumferential strain (GCS) in the parasternal mid short-axis view were measured.

Results

In all patients, peak $ \dot{V}{\text{O}}_{2} $ correlated with leg muscle strength (r = 0.55, p < 0.0001), LVEF (r = 0.46, p < 0.001), GLS (r = ?0.45, p < 0.001), and GCS (r = ?0.41, p = 0.005), respectively. No significant correlation was found between the ratio of early transmitral velocity to peak early diastolic mitral annulus velocity (E/E′) and peak $ \dot{V}{\text{O}}_{2} $ . In the patients with heart failure and reduced LVEF, a multiple stepwise linear regression analysis based on leg muscle strength, LVEF, E/E′, GLS, and GCS was performed to identify independent predictors of peak $ \dot{V}{\text{O}}_{2} $ , resulting in leg muscle strength and GLS (R ² = 0.888) as independent predictors of peak $ \dot{V}{\text{O}}_{2} $ .

Conclusion

Global longitudinal strain at rest could possibly predict exercise capacity, which appeared to be more useful than LVEF, E/E′, and GCS in CHF patients with reduced LVEF.     

Evaluation of urine composition and calcium salt crystallization properties in standardized volume-adjusted 12-h night urine from normal subjects and calcium oxalate stone formers

The volume of 12-h night urine from ten normal men (NM), ten normal women (NW) and 31 male calcium stone formers (SFM) was adjusted to 750 ml and analysed with respect to supersaturation with calcium oxalate (CaOx) and calcium phosphate (CaP), inhibition of CaOx crystal growth and aggregation, as well as the CaOx and CaP crystallization propensity. Concentrations of oxalate and glycosaminoglycans and AP(CaOx) index, an estimate of the CaOx ion-activity product, were higher and the concentration of citrate lower in NM than in NW. In SFM the directly assessed risk of CaOx crystallization was higher and the inhibition of CaOx crystal growth lower than in NM. There were no differences between the groups regarding inhibition of CaOx crystal growth by 74% dialysed urine or inhibition of CaOx crystal aggregation. SFM with mixed CaOxCaP stones had a higher concentration of phosphate and a higher AP(CaP) index at pH 7.0 than SFM with CaOx stones.     

Acute obstructive jaundice and chronic cirrhosis protect against the adverse renal effects of pneumoperitoneum: role of nitric oxide

Background

Obstructive jaundice and cirrhosis are associated with impaired renal function. Previously we demonstrated that increased intra-abdominal pressure (IAP, pneumoperitoneum) in normal rats induced renal dysfunction. This study investigated the renal effects of pneumoperitoneum in rats with acute jaundice and cirrhotic rats.

Methods

Following a baseline period, rats with obstructive jaundice or cirrhosis induced by acute or chronic bile duct ligation (BDL), respectively, and their sham-controls were subjected to consecutive IAPs of 10 and 14 mmHg for 45 min each. Urine flow (V), Na⁺ excretion (U_NaV), glomerular filtration rate (GFR), renal plasma flow (RPF), and urinary NO metabolites ( $ {\text{U}}_{{{\text{NO}}_{ 2} + {\text{NO}}_{ 3} }} $ ) and cGMP (U_cGMP) were determined.

Results:

Elevating IAP from 0 to 10 and 14 mmHg in normal rats caused IAP-dependent reductions in V, U_NaV, GFR, RPF, $ {\text{U}}_{{{\text{NO}}_{ 2} + {\text{NO}}_{ 3} }} , $ and U_cGMP. Basal renal function and hemodynamics were lower in rats with obstructive jaundice. In contrast to normal rats, application of elevated IAP of 10 and 14 mmHg significantly improved V, U_NaV, GFR, RPF, and MAP along with increased $ {\text{U}}_{{{\text{NO}}_{ 2} + {\text{NO}}_{ 3} }} $ and preserved U_cGMP. Similarly, when identical IAP conditions were applied to cirrhotic rats, no deleterious changes in V, U_NaV, GFR or RPF were observed.

Conclusions

Application of pneumoperitoneum to rats with acute BDL improves kidney function and renal hemodynamics. Likewise, increased IAP does not exert adverse renal effects in cirrhotic rats. These effects are distinct from the deleterious renal consequences of increased IAP in normal rats. Perturbations in the generation of NO/cGMP during IAP in normal rats but not in rats with BDL or cirrhosis may contribute to these differences.     

Developmental changes in the left ventricular diastolic wall strain on M-mode echocardiography

Background

The diastolic wall strain (DWS) of the left ventricle has been proposed as an indicator of left ventricular (LV) wall stiffness. The DWS is calculated as follows using M-mode echocardiography:

$${\text{DWS}} = \left[ {\left( {\text{LV posterior wall thickness at end-systole}} \right) - \left( {\text{LV posterior wall thickness at end-diastole}} \right)} \right]/\left( {\text{LV posterior wall thickness at end-systole}} \right)$$

Although this index is simple and clinically useful, normal values for children, including neonates, have not been reported.

Methods

The DWS was measured in 235 healthy people, ranging from neonates to adults. They were classified into 8 subgroups according to their age. The DWS was compared with conventional echocardiographic parameters for left ventricle function, including shortening fraction of the left ventricle, the Tei index, E/A of mitral flow, mitral annular tissue Doppler velocity during systole (s′) and during early diastole (e′), and the E/e′ ratio.

Results

The DWS in the just after birth group was 0.28 ± 0.11, which was significantly lower than that of the remaining groups (p < 0.05), except for the neonate group at 5–10 days after birth. The DWS was highest in the 1–9 years of age group, and then gradually decreased with age. Stepwise regression of various echocardiographic parameters showed that e′ was the most relevant parameter for the DWS (β = 0.64).

Conclusions

Normal values for the DWS of the left ventricle change with age. The data reported in this study can be used as normal values for the DWS of the left ventricle determined by M-mode echocardiography.

     

The potential of at-home prediction of the formation of urolithiasis by simple multi-frequency electrical conductivity of the urine and the comparison of its performance with urine ion-related indices,color and specific gravity

It is important to control daily diet, water intake and life style as well as monitor the quality of urine for urolithiasis prevention. For decades, many ion-related indices have been developed for predicting the formation of urinary stones or urolithiasis, such as EQUILs, relative supersaturation (RSS), Tiselius indices (TI), Robertson risk factor algorithms (RRFA) and more recently, the Bonn risk index. However, they mostly demand robust laboratory analysis, are work-intensive, and even require complex computational programs to get the concentration patterns of several urine analytes. A simple and fast platform for measuring multi-frequency electrical conductivity (MFEC) of morning spot urine (random urine) to predict the onset of urolithiasis was implemented in this study. The performance thereof was compared to ion-related indices, urine color and specific gravity. The concentrations of relevant ions, color, specific gravity (SG) and MFEC (MFEC tested at 1, 10, 100, 5001 KHz and 1 MHz) of 80 random urine samples were examined after collection. Then, the urine samples were stored at 4 °C for 24 h to determine whether sedimentation would occur or not. Ion-activity product index of calcium oxalate (AP(CaOx) EQ2) was calculated. The correlation between AP(CaOx) EQ2, urine color, SG and MFEC were analyzed. AP(CaOx) EQ2, urine color and MFEC (at 5 frequencies) all demonstrated good prediction (p = 0.01, 0.01, 0.01, respectively) for stone formation. The positive correlation between AP(CaOx) EQ2 and MFEC is also significant (p = 0.01). MFEC provides a good metric for predicting the onset of urolithiasis, which is comparable to conventional ion-related indices and urine color. This technology can be implemented with much ease for objectively monitoring the quality of urine at points-of-care or at home.     

On the relationship between glomerular filtration rate and serum creatinine in children

The Schwartz formula (eGFR?=?kL/Scr, with k?=?0.55) to determine the estimated glomerular filtration rate (eGFR) in children with chronic kidney disease (CKD), based on length (L) and serum creatinine (Scr) has recently been updated for enzymatic serum creatinine concentrations, resulting in k?=?0.413. Based on a meta-analysis, we evaluated the validity of this updated equation and other published equations for healthy children. This is the first time that publicly available data for healthy children of uncorrected and body surface area (BSA)-corrected median GFR have been combined with median serum creatinine values and median lengths and weights from different sources in the literature to evaluate several statistical models to estimate GFR in children. For enzymatic serum creatinine, we show that the simple model for uncorrected GFR (uGFR?=?k′L³/Scr, with k′?=?1.32?×?10^?5) and the BSA-corrected GFR (cGFR?=?kL/Scr, analogous to the Schwartz formula), with an important age-dependent adaptation for k ( $ {\text{k}} = 0.0{\text{414}} \times { \ln }\left( {\text{Age}} \right) + 0.{\text{3}}0{\text{18}} $ ), correlate extremely well with chromium-51–ethylenediamine tetra-acetic acid (⁵¹Cr-EDTA) data for children between 1 month and 14 years of age. With this age-dependent modification for k, presented here, the simple bedside calculation tool derived by Schwartz can be used for screening all children for CKD. When height information is not available, the Lund–Malmö equation is an excellent alternative.     

Measurement of the risk of calcium phosphate crystallization in urine

Summary A method is described for analysis of the risk of calcium phosphate (CaP) crystallization in urine samples. The pH required for formation of 500 crystals in the size range 3.5 to 5 m (pH_CaP) was determined in a Coulter Counter following addition of sodium hydroxide. The risk of CaP crystallization (CaP-CR) was defined as: 1/(pH_CaP–5.8). CaP-CR was determined in 24 h urine collections from 25 patients with calcium stone disease and 26 normal subjects, each urine diluted to a creatinine concentration of 5 mol per ml. The mean (±SD) CaP-CR was 0.71±0.18 and 0.63±0.14 respectively and did not differ significantly. This method might be useful for evaluations and follow-up of stone formers with respect to the risk of CaP precipitation and stone formation.     

Nichtinvasive Bestimmung des Herzzeitvolumens bei beatmeten Patienten

Objective

This study was performed to evaluate a new simplified rebreathing method to determine cardiac output (CO) in mechanically ventilated patients.

Methods

Using a rebreathing system (AMIS 2001, Innovision, Dänemark), effective pulmonary blood flow (PBF) and oxygen consumption ( ${\dot{V}O_2}$ ) were determined non-invasively in 40 patients. After estimation of arterial (CaO₂) and capillary oxygen (CcO₂) content from the results of an arterial blood gas analysis, intrapulmonary shunt was calculated as ${Q_s/Q_t{\rm{ }} = {\rm{ }}[CcO_2{\rm{ }}CaO_2]{\rm{ }}*{\rm{ }}PBF/\dot{V}O_2}$ . Cardiac output was determined by the rebreathing method as ${CO_{rb} = PBF/(1-Q_s/Q_t)}$ . The cardiac output measured by thermodilution (CO_thd) was used to determine reference values, which were calculated as mean value of CO_thd and CO_rb. Intrapulmonary shunt calculated from arterial and mixed-venous blood gas analyses served as reference for the non-invasive determination. In addition, reproducibility of the new method was determined in 15 patients.

Results

CO_thd varied from 3.7–9.5 l/min (6.1 ± 1.6 l/min; mean ±SD). Bias and precision of CO_rb determination accounted for 0.18 l/min (2.9%) and ± 0.61 l/min (10%), respectively. Precision of intrapulmonary shunt measurement accounted for ±2.1%. Reproducibility of the CO measurements accounted for 0.24 l/min or 3.9%.

Conclusion

The rebreathing system evaluated in the present study allows the noninvasive determination of cardiac output with rather high accuracy and good reproducibility. However, technical improvement and further investigation in patients with extremely high cardiac output and shunt values will be needed before its routine clinical use.     

The role of pharmacological steroid therapy in preservation of renal function in severely injured patients requiring massive transfusion

Purpose

Glucocorticoids (GC) attenuate the post-insult inflammatory response and have been observed to confer end-organ protection following a variety of ischemic insults. We aim to assess this benefit on renal perfusion and function in injured patients requiring massive transfusion.

Methods

The effect of pharmacologic methylprednisolone (MP) therapy was studied in 118 patients (pts), of whom 60, by random, received 1 g MP intraoperatively and 15 mg/kg for an additional 3 days. Postoperative measurements were made of effective renal plasma flow (ERPF), glomerular filtration by inulin (C_In), creatinine clearance (C_Cr) and clearances of osmoles (C_Cosm), sodium (C_Na), and free water (\({\text{C}}_{{{\text{H}}_{ 2} {\text{O}}}}\)). Continuous variables were compared between the two groups using the student’s t test.

Results

Enrolled pts on average received 13.5 units of PRBCs with no differences in the resuscitation regimen. There were no statistically significant differences in the postoperative renal function as measured by ERPF (p = 0.57), C_In (p = 0.84), C_Cr (p = 0.99), C_Na (p = 0.07), C_Osm (p = 0.95), and \({\text{C}}_{{{\text{H}}_{ 2} {\text{O}}}}\) (p = 0.33). The incidence of renal compromise, as determined by an inulin clearance of <25 mL/min or serum creatinine greater than 3.0 mg/dL, was also similar. Three patients in the MP treatment group had renal compromise compared to one in the control group.

Conclusions

In the absence of larger studies, this study demonstrates that GC likely have no role in preserving renal function in severely injured patients.