Self-reporting and screening: Data with right-censored, left-censored, and complete observations

We consider survival data that combine three types of observations: uncensored, right-censored, and left-censored. Such data arises from screening a medical condition, in situations where self-detection arises naturally. Our goal is to estimate the failure-time distribution, based on these three observation types. We propose a novel methodology for distribution estimation using both semiparametric and nonparametric techniques. We then evaluate the performance of these estimators via simulated data. Finally, as a case study, we estimate the patience of patients who arrive at an emergency department and wait for treatment. Three categories of patients are observed: those who leave the system and announce it, and thus their patience time is observed; those who get service and thus their patience time is right-censored by the waiting time; and those who leave the system without announcing it. For this third category, the patients' absence is revealed only when they are called to service, which is after they have already left; formally, their patience time is left-censored. Other applications of our proposed methodology are discussed.

A novel methodology to measure waiting times for community-based specialist care in a public healthcare system

BACKGROUND

Monitoring waiting time (WT) in healthcare systems is essential, since long WT are associated with adverse health outcomes, reduced patient satisfaction and increased private financing.

OBJECTIVE

To describe a methodology developed for routine national monitoring of WT for community-based non-urgent specialist appointments, in a public healthcare system.

METHODS

The methodology is based on data from computerized appointment scheduling systems of all Health Maintenance Organizations (HMOs) in Israel. Data included first 50 available appointments for community-based specialists and actual number of visits. Five most frequent specialties: orthopedics, ophthalmology, gynecology, dermatology and otolaryngology, were included. WT offered to HMO members for non-urgent care was calculated for two scenarios: "specific" physician and "any" physician in the region. Distribution of offered WT was calculated separately for each specialty and geographical region, combined to create the nationwide distribution.

RESULTS

The methodology was tested on data extracted between December 2018-June 2019. Estimated national median WT for "specific" physician, ranged from 9 days (ophthalmology/gynecology) to 20 days (dermatology), with large variation between geographic regions. WT were 26-56 % shorter for "any" than for "specific" physician.

CONCLUSIONS

This novel method offers a solution for ongoing national WT measurement, using computerized scheduling systems. It integrates two scenarios for appointment scheduling and allows identification of differences between specialties and regions, setting the ground for interventions to strengthen public healthcare systems.

Long Term Dialysis with Low-Calcium Solution (1.0 Mmol/L) in Capd: Effects on Bone Mineral Metabolism

Objective

Peritoneal dialysate solutions with conventionally high-calcium (Ca) concentrations (1.75 mmol/L) are now widely replaced by solutions with a lower, more physiological calcium content to prevent hypercalcemia in patients treated with oral calcium-containing phosphate binders and/or calcitriol. While there is still debate on how far the dialysate calcium should be lowered (1.25 mmol/L or less), little information is available concerning the effects of a long-term treatment with low-calcium solutions on secondary hyperparathyroidism and bone mineral metabolism in general.

Design

A prospective, randomized, controlled multicenter study to compare the effects of low-calcium (LCa, dialysate calcium 1.0 mmol/L) versus standard calcium dialysate solution (SCa, dialysate calcium 1.75 mmol/L)on bone mineral metabolism in continuous ambulatory peritoneal dialysis (CAPD) patients over 2 years of treatment.

Setting

Nephrology and dialysis units of primary and tertiary hospitals in Germany and Switzerland.

Patients

All CAPD patients in the participating centers between 18 and 80 years of age, stable on CAPD for at least 1 month, free of aluminum bone disease or prior parathyroidectomy were invited to enter the study. Sixty-four patients could be randomly allotted to LCa (n = 35) or SCa (n = 29) treatment in a 2-year protocol; 34 finished the study as planned.

Interventions

Calcium carbonate (CaCO3) was given as oral phosphate binder to maintain serum phosphate <2.0 mmol/L. If hypercalcemia supervened, CaCO3 was exchanged stepwise for aluminium hydroxide (AI(OH)3)’ until normocalcemia was obtained. Patients received calcitriol (0.25 μg/day per os) if parathyroid hormone (PTH) exceeded the upper limit of normal by a factor of 2 or more.

Main Outcome Measures

We assessed total and ionized serum calcium, phosphate, serum aluminum, alkaline phosphatase, osteocalcin, PTH (intact molecule), and phosphate binder intake at regular intervals. Measurements of bone mineral density and hand skeleton x-rays were obtained at the start and after 6 months and 2 years, respectively.

Results

With LCa, mean total and ionized serum calcium levels were within the normal range (total Ca: 2.0 2.6 mmol/L; ionized Ca: 1.19–1.32 mmol/L), but throughout the treatment period were significantly lower than with SCa. The incidence of hypercalcemia (>2.8 mmol/L) was three times higher in patients on SCa, despite the significantly higher amount of AI(OH)3 and less CaCO3 given in this group. In parallel, serum aluminum increased with SCa throughout the study, whereas it was slowly decreasing with LCa. Median PTH levels remained stable at about two times the upper limit of normal over the 2 years of study with LCa. However, 23% of the patients on LCa developed severe hyperparathyroidism, with PTH levels exceeding ten times the upper limit of normal compared to only 10.3% of the patients on SCa. With SCa, median PTH decreased towards near normal levels. Alkaline phosphatase and serum osteocalcin correlated positively with PTH levels. Bone mineral density was in the lower normal range in both groups a n d remained unchanged at the end of the study. Skeletal x-ray films showed only minor alterations in very few patients in both groups with no correlation to serum PTH or treatment modality.

Conclusion

In CAPD patients low-calcium dialysate solutions can be used successfully over prolonged periods of time with stable control of serum calcium. The risk of hypercalcemia resulting from calcium-containing phosphate binders and the need to use aluminum-containing phosphate binders is markedly diminished. However, there is a certain risk that severe secondary hyperparathyroidism with long-term LCa therapy will develop, even if normocalcemia is maintained. Thus, LCa dialysis requires closeand continuous monitoring of PTH and bone metabolism.

Quantifying the electronic medical record implementation to stabilization curve

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Background: The implementation of electronic medical records (EMR) has been noted to disrupt clinical workflows as providers acclimate to a new EMR. On May 30, 2015, Dana-Farber Cancer Institute (DFCI) implemented a new EMR. Using our Real Time Location System (RTLS), we sought to identify the time required to stabilize the experience for providers. We identified factors that may speed the stabilization rate to guide EMR implementations elsewhere. Methods: DFCI uses an RTLS to timestamp patient and provider locations throughout the day. To adjust for variation in appointment types, we measured the ratio of the actual exam duration (recorded by the RTLS) to the scheduled exam duration. We compared to a 3-month baseline average to quantify the immediate impact of implementation. We tracked the ratio over time to identify when stabilization occurred and compare to baseline performance. To infer influential factors, we performed a regression analysis based on RTLS data from the first 6 months post implementation. Results: The stabilization curve fits the “classical” power function model. Rapid improvement over the first ten days of clinical practice was followed by a gradual period of ongoing stabilization. The EMR impact on exam duration required approximately 30 clinical days for each provider to reach the baseline value with continued improvement over the next 30 clinical days. Factors with a potential to improve the rate of stabilization were provider type (MD, NP or PA), provider gender and provider age. Conclusions: The first ten clinical days experience a fast rate of improvement. Thus, while the initial impact is disruptive, operations improve rapidly. Initial improvement may be attributed to fixing “bugs” in the EMR and rapid learning by providers. Our presentation will explore factors that impact the rate of improvement. Understanding the stabilization rate and factors can aid organizations in training, implementation, and ongoing improvement to minimize the impact of EMR disruption. [Table: see text]

Primary unconstrained shoulder arthroplasty in patients with a fixed anterior glenohumeral dislocation

BACKGROUND

Reports of shoulder arthroplasty for the treatment of fixed glenohumeral dislocation are rare. The purpose of this study was to analyze the results following shoulder arthroplasty in patients with a fixed anterior shoulder dislocation.

METHODS

Eleven patients were evaluated at a minimum of twenty-four months after they underwent an arthroplasty for the treatment of a fixed anterior shoulder dislocation. Four patients underwent a total shoulder arthroplasty, and the remainder were treated with a hemiarthroplasty. Four shoulders had osseous reconstruction of the anterior aspect of the glenoid. The patients were evaluated with use of the Constant score, measurement of active anterior elevation and external rotation, the patient's subjective grading of the result, and a radiographic examination.

RESULTS

The mean Constant score improved from 21.1 points preoperatively to 46.0 points following the arthroplasty, and the mean active anterior elevation improved from 48.6 degrees to 90.0 degrees . The pain component of the Constant score was the most reliably improved parameter, increasing from a mean of 4.8 points preoperatively to a mean of 11.0 points postoperatively. Eight patients reported that the result was excellent or good, and the remaining three considered it to be fair. We observed seven complications in five patients, including four cases of anterior instability of the shoulder. Two of the four patients treated with a total shoulder replacement were seen to have definite loosening of the glenoid component on follow-up radiographs.

CONCLUSIONS

Shoulder arthroplasty in patients with a fixed anterior shoulder dislocation is fraught with difficulties and complications. Although arthroplasty reliably relieved shoulder pain in this population, limited functional results should be expected.

Multi-Project Scheduling and Control: A Process-Based Comparative Study of the Critical Chain Methodology and Some Alternatives

Critical Chain (CC) is a popular project management technique in many multi-project organizations. It applies the Theory of Constraints (TOC) to offer a practical and easy method for planning, scheduling and control of multi-project systems. While some prior studies examined CC performance for single-project management, little attention has been given to its performance in a multi-project environment. In this paper, we examine the control mechanisms of CC and some alternatives. We demonstrate that, when CC is not enough to prevent projects' lateness, such alternatives may give rise to similar and sometimes better, possibly much better performance.

Intramolecular electrophilic aromatic substitution in gas-phase-protonated difunctional compounds containing one or two arylmethyl groups

A variety of dibenzyl esters and ethers undergo a rearrangement process upon isobutane chemical ionization and collision-induced dissociation of their MH(+) ions, whereby a new bond is formed between the two benzyl groups, giving rise to abundant [C(14)H(13)](+) (m/z 181) ions. This rearrangement has been explained as an intramolecular electrophilic substitution in the gas phase occurring in an ion-neutral complex formed by the cleavage of one of the benzyl-oxygen bonds. A similar highly efficient intramolecular electrophilic substitution takes place in di-alpha- and beta-naphthylmethyl adipates affording m/z 281 [C(22)H(17)](+) ions, but not in the sterically hindered di-9-anthracylmethyl adipate. An analogous efficient rearrangement occurs in benzyl alpha- and beta-naphthylmethylcyclohexane-1,4-dicarboxylates and in benzyl alpha- and beta-phenylethylcyclohexane-1,4-dimethanol ethers. The analogous rearrangement is much less efficient in benzylallyl, benzylpropargyl and benzyl-9-anthracylmethyl derivatives, even less in benzylisopropyl and benzylacetyl analogs, and it is absent in benzyltetrahydropyranyl derivatives. The distinctive behavior of the protonated difunctional benzyl derivatives is interpreted in terms of the energy requirements of the O-R bond heterolysis of the protonated functionalities, the ability of the neutral R' groups (non-dissociated from the oxygen atom) to play the role of the nucleophile in the intramolecular electrophilic substitution processes and the electrophilicity of the R(+) ions.

Shoulder arthroplasty in patients with a prior anterior shoulder dislocation. Results of a multicenter study

BACKGROUND

Prior reports of shoulder arthroplasty performed for dislocation-induced arthropathy have included only patients who had had a prior stabilizing procedure. The purpose of this study was to report the results of shoulder arthroplasty in all patients with a prior anterior shoulder dislocation, including both those previously treated operatively and those previously treated nonoperatively.

METHODS

Fifty-five shoulders undergoing arthroplasty for arthritis following a prior anterior shoulder dislocation were evaluated. Twenty-seven of the shoulders had undergone a prior anterior stabilization procedure. The measures used to evaluate the shoulders included the Constant score, adjusted Constant score, active mobility, subjective satisfaction, radiographic result, and complications.

RESULTS

The shoulders were evaluated at a mean of 45.0 months. The Constant score improved from a mean of 30.8 points preoperatively to a mean of 65.8 points at the time of follow-up. The adjusted Constant score improved from a mean of 38.2% to a mean of 79.8%. Active forward flexion improved from a mean of 82.1 degrees to a mean of 138.9 degrees. Active external rotation improved from a mean of 4.0 degrees to a mean of 38.6 degrees. Fifty patients rated the result as good or excellent. Negative prognosticators included an older age at the time of the initial dislocation and a rotator cuff tear. No significant differences in demographic factors, pre-arthroplasty function, post-arthroplasty function, pre-arthroplasty radiographic findings, post-arthroplasty radiographic findings, complication rate, or reoperation rate were noted between the patients treated with a prior operation for the anterior instability and those treated nonoperatively.

CONCLUSIONS

This investigation documented the good results obtainable with shoulder arthroplasty for the treatment of arthritis following anterior shoulder instability. In addition, our findings suggest that capsulorrhaphy-induced arthropathy may be indistinguishable from arthritis following nonoperatively treated anterior shoulder instability.

[Shoulder arthroplasty for non-operated anterior shoulder instability with secondary osteoarthritis]

PURPOSE OF THE STUDY

The purpose of this study was to analyze the natural history of osteoarthritis of the shoulder joint secondary to non-operated anterior instability, to evaluate the clinical and radiological outcome after arthroplasty for this indication, and to compare results with data reported in the literature.

MATERIAL AND METHODS

Twenty-eight Aequalis shoulder arthroplasties were performed for osteoarthritis secondary to anterior shoulder instability in patients who had not undergone any prior stabilizing surgical procedure. This multicentric series was reviewed retrospectively at a mean follow-up of 44 months (range 24-87 month). Preoperative and last follow-up clinical status was compared using the Constant score. Standard operative technique was used and anatomic position of the implants was achieved in 27 patients. Total shoulder arthroplasty was performed in eighteen patients and simple humeral implantation in ten. Patients were divided into two sub-groups for analysis of outcome (age at first dislocation > or < 40 years).

RESULTS

There were four complications including one early loosening that required revision arthroplasty. Outcome was excellent or good in 54% of the cases. Group 1 (age at first dislocation < 40 years) included 17 patients and exhibited male predominance (13/17), young age at first dislocation (mean 28.5 years), high number of dislocations (mean 13), and a long natural history of osteoarthritis (mean 28 years). In this sub-group, imaging disclosed constructive osteoarthritis reflecting a long history. There was one case with a full-thickness tear of the supraspinatus. Outcome was excellent or good in 64% of these 17 patients (14 underwent total shoulder arthroplasty). The sub-group of 11 patients whose first dislocation occurred after the age of 40 years exhibited female predominance (9/11), a small number of dislocations (mean 1.3), and a short natural history of osteoarthritis (mean 6 years). In this sub-group, imaging disclosed six cases of basically chondrolytic osteoarthritis reflecting a short evolution. There were seven cases of full-thickness tears of the supraspinatus. Outcome was excellent or good in 36% of these 11 patients (4 underwent total shoulder arthroplasty).

DISCUSSION

The forty-year age cutoff allowed us to distinguish two populations. The first population of patients whose first dislocation had occurred before the age of 40 years was predominantly male, with a long history of constructive osteoarthritis without rotator cuff tears. Most of these patients were treated with total shoulder arthroplasty which gave results similar to those obtained with arthroplasty for primary centered osteoarthritis. The second sub-group of patients aged over 40 years at the time of the first dislocation were predominantly female with a short history of minimally constructive osteoarthritis and frequent rotator cuff tears. Humeral implants were used for most of these patients and gave less favorable results than in the former sub-group, probably due to the high rate of rotator cuff tears.

Structural assignment of isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione mono- and disulfonic acids by liquid chromatography electrospray and atmospheric pressure chemical ionization tandem mass spectrometry

Positionally isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione mono- and disulfonic acids give rise to similar electrospray ionization (ESI) and atmosphere pressure chemical ionization (APCI) mass spectra, which show very abundant MH(+) ions and negligible fragmentation. The MH(+) ions of these isomeric acids exhibit notably different behavior under collision-induced dissociation (CID) conditions. The acids with a sulfonic group at position 8' in the quinoline moiety, adjacent to the N-atom, exhibit highly abundant [MH - H(2)SO(3)](+) ions (m/z 272 for the mono- and m/z 352 for the disulfonic acids), which are of lower abundance in the CID spectra of isomers with the SO(3)H group at other positions, remote from the nitrogen atom. The latter isomers undergo efficient eliminations of SO(3) and HSO(3). The isomeric diacids with one SO(3)H group at position 4 of the indene-1,3(2H)-dione moiety, adjacent to one of the carbonyl groups, undergo highly efficient elimination of H(2)O. Mechanistic pathways, involving interactions between adjacent groups, are proposed for the above regiospecific fragmentations. Pronounced different behavior has been also observed in negative ion tandem mass spectrometric measurements of the sulfonic acids. The distinctive behavior of the isomeric acids was strongly pronounced when the measurements were performed with an ion trap mass spectrometer (LCQ), and much less so with a triple-stage quadrupole instrument (TSQ).

Intramolecular proton transfers in stereoisomeric gas-phase ions and the kinetic nature of the protonation process upon chemical ionization

The isobutane chemical ionization (CI) mass spectra of cis- and trans-1-butyl-3- and -4-dimethylaminocyclohexanols and of their methyl ethers exhibit abundant [MH - H(2)O](+) and [MH - MeOH](+) ions respectively. On the other hand, only the MH(+) ions of the cis-isomers exhibit significant [MH - H(2)O](+) and [MH - MeOH](+) ions under collision-induced dissociation (CID) conditions. The non-occurrence of water and methanol elimination in the CID spectra of the trans-isomers indicates retention of the external proton at the dimethylamino group in the MH(+) ions that survive after leaving the ion source and the first quadrupole of the triple-stage quadrupole ion separating system, and the trans-orientation of the two basic sites does not allow proton transfer from the dimethylamino group to the hydroxyl or methoxyl. Such transfer is allowed in the cis-amino alcohols and amino ethers via internal hydrogen-bonded (proton-bridged) structures, resulting in the elimination of water and methanol from the surviving MH(+) ions of these particular stereoisomers upon CID. The abundant [MH - ROH](+) ions in the isobutane-CI mass spectra of the trans-isomers indicates protonation at both basic sites, affording two isomeric MH(+) ions in each case, one protonated at the dimethylamino group and the other at the less basic oxygen function. These results show that the isobutane-CI protonation of the amino ethers and amino alcohols is a kinetically controlled process, occurring competitively at both basic sites of the molecules, despite the large difference between their proton affinities ( approximately 25 and approximately 35 kcal mol(-1); 1 kcal = 4.184 kJ). Copyright 1999 John Wiley & Sons, Ltd.

Role of thromboxane in the altered vascular reactivity of pregnant rats with adriamycin nephropathy

BACKGROUND

Pregnant rats with adriamycin nephropathy (ADRP rats) develop hypertension and have an increased vascular reactivity to noradrenaline in the isolated mesenteric bed in vitro. We have shown previously that the administration of daltroban, a specific thromboxane receptor antagonist, prevented hypertension in ADRP rats.

METHODS

We measured the effect of daltroban (10(-5) mol/l) on the vasoconstrictory response to noradrenaline (1-10 micromol/l) in the isolated mesenteric bed of ADRP rats at the end of pregnancy, as compared with normal pregnant and adriamycin-treated virgin rats. In further experiments, we measured the changes of flow induced by increasing concentrations of the thromboxane analogue, U46619 (10(-7)-10(-6) mol/l). Finally, changes of flow were assessed in arteries maximally constricted with U46619 (10(-6) mol/l), during perfusion in the presence of increasing concentrations of daltroban (10(-7)-10(-5) mol/l).

RESULTS

Daltroban diminished the response to noradrenaline in all groups, shifting the concentration-effect curve to the right. However, at maximal concentrations of noradrenaline, daltroban was ineffective in all rats, except in ADRP animals. The vasoconstrictory response to U46619 was significantly reduced in all pregnant rats, both normal and adriamycin-treated. Daltroban progressively released the vasoconstriction induced by U46619 in all groups. However, this vasodilator response was attenuated in the adriamycin-treated rats, the slopes of their curves being smaller than those of the respective untreated groups (0.038 +/- 0.006 in virgin rats vs 0.063 +/- 0.011 in controls, P < 0.05; and 0.015 +/- 0.005 in ADRP vs 0.028 +/- 0.008 in normal pregnancy, P < 0.05).

CONCLUSIONS

The findings could be explained by enhanced occupancy of thromboxane receptors by an endogenous agonist, possibly PGH2, as a consequence of either increased levels of the autacoid or increased number of affinity receptors.

P-glycoprotein expression is not a useful predictor of acute or chronic kidney graft rejection

Because of the role of P-glycoprotein (P-gp) in multidrug resistance (MDR), it has been suggested that P-gp might play a role in acute and chronic rejection after organ transplantation. The purpose of the present work was to investigate a possible relationship between graft outcome and P-gp expression on peripheral mononuclear cells of renal transplant recipients. We determined P-gp expression in 27 patients with long-term, stable graft function (ST) and in 15 patients with chronic deterioration of graft function (CR). In addition, 40 patients were studied prior to, and at intervals after, transplantation with 21 healthy individuals serving as controls. P-gp values were highest in healthy controls and in ST patients. We found no correlation between P-gp values and acute rejection. CR patients tended to have lower levels of P-gp expression. Our results contradict the opinion that an overexpression of P-gp induces acute or chronic rejection by inhibiting the efficacy of immunosuppressive treatment.

Altered vascular reactivity following partial nephrectomy in the rat: a possible mechanism of the blood-pressure-lowering effect of heparin

BACKGROUND

This study was designed to assess whether the antihypertensive effect of heparin in rats after renal mass reduction (RMR) is related to changes in nitric oxide activity, and to study in vitro the altered behaviour of resistance-sized arteries induced by chronic administration of heparin.

METHODS

Male Wistar rats were assigned to one of two experimental protocols. In the first protocol, RMR rats received heparin (250 units/day s.c.) and tail systolic blood pressure (SBP) was measured weekly for 4 weeks. In a subgroup, urinary nitrate excretion (UNO3) and in vitro vascular reactivity of isolated perfused mesenteric arterial beds were measured 2 weeks after RMR. The second protocol assessed whether inhibition of NO synthesis with L-NAME (70 mg/l added to the drinking water) prevents the blood-pressure-lowering effect of heparin.

RESULTS

In untreated RMR rats SBP increased from 111+/-3 mmHg to 127+/-5 mmHg at 2 weeks and 139+/-5 mmHg at 4 weeks. In contrast, in RMR rats treated with heparin, SBP was 114 +/-3 mmHg at 2 weeks and 115+/-4 mmHg at 4 weeks (P<0.05 for both). Treatment with L-NAME increased SBP both in untreated and heparin-treated RMR groups. Two weeks after nephrectomy daily urinary nitrate increased significantly more in RMR rats treated with heparin than in untreated RMR rats (22+/-2 vs 14.2+/-2.3 micromol/day, P<0.05). In vitro studies performed at 2 weeks showed that vessels of untreated RMR rats had a blunted vasodilator response to acetylcholine that was restored to levels similar to that of controls in the heparin-treated group.

CONCLUSIONS

These results suggest that, in rats after renal ablation, heparin may exert its antihypertensive effect, at least in part, by affecting the altered behaviour of resistance vessels during the development phase of hypertension. Increased NO production may contribute to this effect.

Hypertension in the transplanted patient

Hypertension is a common finding after renal transplantation, and it has a variety of underlying mechanisms. One reason is the type of immunosuppressive therapy, with a higher prevalence of hypertension in cyclosporine-treated patients. Cyclosporine interferes with several humoral and neural systems which are involved in blood pressure regulation such as the renin-angiotensin system, endothelins, nitric oxide, prostaglandins and the sympathetic nervous system. Other pathomechanisms for posttransplant hypertension are uncontrolled renin secretion of the native kidneys, polycythemia, recurrence of renal disease in the graft and renal failure. Renal transplant artery stenosis is a potentially treatable cause of post-transplant hypertension and several techniques such MRT angiography, Doppler sonography and conventional angiography are available. The diagnosis and treatment of hypertension are of high importance in general for the transplanted patient, and especially for the long-term prognosis of graft function.

Pharmacokinetics of mycophenolic acid (MPA) and determinants of MPA free fraction in pediatric and adult renal transplant recipients. German Study group on Mycophenolate Mofetil Therapy in Pediatric Renal Transplant Recipients

Dosage guidelines for mycophenolate mofetil (MMF), an ester prodrug of the immunosuppressant mycophenolic acid (MPA), are still preliminary in children. This study compares the pharmacokinetics of MPA and its major metabolite MPA glucuronide (MPAG) in pediatric renal transplant recipients receiving 600 mg MMF/m2 body surface area twice a day to those of adults on the currently recommended oral dose of 1 g of MMF twice a day. Concentration-time profiles of 18 children (age, 10.7+/-0.72 yr; range, 5.9 to 15.3 yr) and 10 adults were investigated 1 and 3 wk after transplantation. Plasma concentrations of MPA and MPAG were measured by reverse-phase HPLC. Because MPA is extensively bound to serum albumin and only the free fraction is presumed to be pharmacologically active, the MPA free fraction was also analyzed by HPLC after separation through ultrafiltration. The areas under the concentration-time curves (AUC0-12) of total and free MPA throughout the 12-h dosing interval in children were, in general, comparable to the corresponding data in adult patients. The mean AUC0-12 of MPA and free MPA did not change significantly over the first 3 wk after transplantation, but there was substantial intra- and interindividual variation. MPAG-AUC0-12 values in children with primary renal transplant dysfunction were threefold higher than in those with functioning transplants. Renal impairment had no consistent effect on total MPA-AUC0-12 values, but the MPA free fraction in children (median, 1.65%; range, 0.40 to 13.8%) was significantly (r2=0.46) modulated by renal transplant function and serum albumin levels. In conclusion, concentration-time profiles of pediatric renal transplant recipients administered 600 mg MMF/m2 body surface area twice a day are comparable to those in adults on 1 g MMF twice a day in the first 3 wk after transplantation. Renal impairment and decreased serum albumin levels led to an increase in the free fraction of MPA and the free MPA-AUC0-12 values. Because the pharmacologic activity of MPA is a function of unbound drug concentration, these findings might be relevant for the pharmacodynamic effects of MPA.

Exercise activates renal dysfunction in hypertension

A bilateral, exercise-mediated renal functional abnormality was first described more than a decade ago. The disturbance is specific for hypertension, is seen in different forms of hypertension, and has been studied most extensively in hypertensives with renovascular disease. The bilateral-abnormal exercise renogram identifies the disturbance. Hypertensives with unilateral renovascular disease were studied in the continuing evaluation of the bilateral function disturbance. We examined 31 hypertensives with documented unilateral renovascular disease, all of whom had renography at rest and during 60 to 80 W ergometric exercise. An additional seven normotensives and 17 essential hypertensives served as controls, and had the same sequence of studies. All patients reported upon continued on to an infusion clearance with 131I-hippurate and 111In-diethylenetriamine pentaacetic acid to determine glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) at rest, and during 25 W ergometric exercise. Eighteen of 31 hypertensives with unilateral renovascular disease were found to have a bilateral-abnormal exercise renogram. Clearance examinations in these identified a prominent reduction of the GFR and a lesser decrease in the ERPF during exercise. Hypertensives with normal exercise renograms did not have the exercise mediated abnormal clearance pattern. Similar results were observed in the control population of essential hypertensives, 65% of whom developed the functional disturbance. The seven normotensives controls did not exhibit the exercise mediated function changes. We conclude that an exercise-mediated bilaterally occurring functional disturbance exists in certain hypertensives, who then have a bilateral-abnormal exercise renogram. Associated with this is a distinctly abnormal clearance during exercise which is characterized by a low filtration fraction.

Fragmentation of isomeric N-quinolinylphthalimides on electron impact ionization

The isomeric 2-, 3-, 5-, 6- and 8-quinolinylphthalimides give rise to different electron impact ionization mass spectra, which permit easy distinction. The specific fragmentation process are rationalized in terms of proximity effects and stabilization of cyclic ion structures. Collision-induced dissociation spectra were used to support the proposed ion structures of major fragment ions.

Vena cava diameter measurement for estimation of dry weight in haemodialysis patients

A correct estimation of volume status and so-called dry weight in dialysis patients remains a difficult clinical problem. Clinical status and chest X-ray are not sensitive enough, while invasively measured central venous pressures are not routinely available. Recently, the sonographic determination of the diameter and collapse of the inferior vena cava (IVC) has been proposed as a noninvasive method for estimating intravascular volume. We tried to evaluate the clinical relevance of this method in dialysis patients by comparing it with central venous pressures (CVP) and atrial natriuretic peptide (ANP). To establish a normal range and to control for confounding variables, we examined a large number of healthy controls. Furthermore, the influence of tricuspid insufficiency was examined echocardiographically. Measurements of the IVC diameters were well reproducible, with a coefficient of variation for interobserver error of 2.2%, and a coefficient of variation of 1.4% for intraobserver error. The collapse index was less well reproducible and therefore not used for further analysis. In 86 normal controls (age 18 to 76 years), IVC diameters showed a wide variation, and they were not correlated to age, height, weight, or body surface area. However, there was a significant correlation of IVCex to heart rate (r = 0.63, P < 0.001). Therefore, we calculated percentiles of the heart rate-IVCex relation in normals, and compared the results in patients to these. In 10 overhydrated haemodialysis patients, CVP was closely correlated to IVCex (r = 0.72, P < 0.001), but there was a wide interindividual variation of the slope of this relation. An IVCex above the 95th percentile of normal was a good predictor of an elevated CVP (i.e. > 12 cmH2O). In another 39 stable, chronic haemodialysis patients, there was a significant correlation of the intradialytic decrease of ANP and IVCex (r = 0.69, P < 0.001). However, this correlation existed only in patients without tricuspid insufficiency. In summary, sonography of the inferior vena cava is a valuable tool for estimating dry weight in dialysis patients, provided that some caveats are kept in mind: (i) there is a wide variation of IVC diameters in normals, and single measurements are not helpful in individual patients; (ii) there is a significant, inverse correlation between IVC diameters and heart rate, and the precision of intravascular volume assessment is enhanced by interpreting heart rate corrected diameters; (iii) the presence of tricuspid insufficiency leads to unreliable results, as it influences IVC diameters per se. Intravascular volume changes are reflected by IVC measurements, as shown by the correlation to other indices of intravascular volume, such as CVP and alpha-hANP. IVC sonography is noninvasive and easily available; serial measurements allow an estimation of changes of intravascular volume in patients without cardiac filling impairment. However, unlike with body impedance, interstitial volume is not reflected by IVC diameters.

Repeat exercise renograms in hypertension identify persistent renal dysfunction

BACKGROUND

Hypertensives may develop bilateral trapping of para-aminohippurate analogues in the tissue of the kidneys during light exercise, as can be demonstrated using radioactively labelled [131I]-hippurate or [99mTc]-mercaptoacetyl-triglycine. Tracer accumulation in the kidneys during exercise results in a typical renographic pattern, the bilateral-abnormal exercise renogram. The disturbance is common during exercise, being found in almost 60% of all hypertensives, regardless of aetiology.

OBJECTIVE

To determine whether bilateral-abnormal exercise renograms are spurious phenomena, or whether the results of exercise renography are reproducible.

DESIGN

We reviewed the renographic examinations of 27 hypertensive patients, each of whom had undergone at least one resting and two [131I]-hippurate or [99mTc]-mercaptoacetyl-triglycine gamma-camera exercise renograms. The status of the renal artery at the time of scintigraphy was documented, using available arteriograms. The causes of vascular lesions were noted, as were revascularization procedures and the antihypertensive medication being taken at the time of scintigraphy.

RESULTS

The average time between exercise renograms was 15.5 months, and 24 of the 27 hypertensive patients had comparable results in the first and the follow-up exercise renogram, divergent results being noted for the other three patients. Re-evaluation of the scintigrams of the three hypertensive patients with divergent results suggested that intermittent pelvic retention might have caused errors of interpretation in two. We found it notable that neither revascularization nor a change in antihypertensive drug therapy influenced the results of exercise renography. Exercise renograms were reproducible over long periods, and potential extraneous influences on blood flow, such as antihypertensive drugs or revascularization, failed to alter the results.

CONCLUSION

The results are considered relevant, because a direct relationship appears probable between hypertension and the disturbance investigated. Reproducible results suggest that the exercise-mediated disturbance is fixed to the kidneys, that it can be reactivated repeatedly and that it may play a role in maintaining hypertension.

Preparative separation of stereoisomeric 1-methyl-4-methoxymethylcyclohexanecarboxylic acids by pH-zone-refining counter-current chromatography

The application of pH-zone-refining counter-current chromatography (CCC) to the preparative separation of stereoisomeric acids is described. The separation was accomplished on the basis of the difference in acidity of the two stereoisomers. pH-Zone-refining CCC of 400 mg of a crude synthetic mixture of stereoisomeric 1-methyl-4-methoxymethylcyclohexanecarboxylic acids yielded 49.5 and 40 mg of the pure Z- and E-stereoisomers respectively. The two-phase solvent system consisted of hexane-ethyl acetate-methanol-water (1:1:1:1). Trifluoro acetic and octanoic acids were used as retainer acids. The eluent base was aqueous ammonia. The eluted fraction were monitored by gas chromatography-mass spectrometry.

[Vena cava ultrasonography for the assessment of hydration status in kidney insufficiency]

Vena cava diameter (VCD) was measured by ultrasonography in 10 acutely hypervolemic dialysis patients (6 men, 4 women; mean age 61.3 +/- 15.4 years), results being compared with the level of the central venous pressure (CVP) and, in 39 long-term dialysis patients (18 men, 21 women; mean age 56 +/- 15 years), with the plasma concentration of atrial natriuretic peptide (ANP). In 86 subjects without renal disease (43 men, 43 women; mean age 39.4 +/- 14.6 years) there was a statistically highly significant correlation between the end-expiratory VCD and heart rate (r = -0.63; P < 0.001). These data were used to construct a VCD/heart rate (HR) nomogram. In the ten dialysis patients HR-adjusted VCD correlated significantly at various hydration states (54 measurements) with the CVP (r = 0.72; P < 0.001). The steep slope for the relationship between CVP and VCD showed marked interindividual variations. However, in all patients (except one) with a raised CVP (> 12 cm H2O) the HR-adjusted VCD was above the 95th percentile. In the 39 patients on long-term dialysis (13 with, 25 without predialysis tricuspid regurgitation [TR] there occurred a parallel decrease in VCP and ANP during removal of fluid. In the 25 patients without TR, the fall in ANP concentration and VCD correlated significantly (r = 0.70; P < 0.001). These results indicate that, in patients with renal failure but normal cardiac function, measurement of the VCD by ultrasonography provides an adequate index of hydration.

Elevated blood pressure profile and left ventricular mass in children and young adults with autosomal dominant polycystic kidney disease

Twelve children (< 15 yr) and 12 young adults with autosomal dominant polycystic kidney disease (ADPKD) confirmed by ultrasonography and 24 nonaffected individuals matched for age, sex, and body surface area were examined with ambulatory blood pressure monitoring and echocardiography. All patients and controls had normal renal function (median serum creatinine, 0.85 mg/dL; range, 0.5 to 1.1). In children, daytime and nighttime blood pressures were not significantly different from those of controls; the median left ventricular mass index (in grams per square meter) was higher in patients (66.6 g/m2) than in controls (61.3 g/m2; P < 0.002), although all values remained within the normal range. In young adults with ADPKD, mean arterial blood pressure was significantly higher than that in controls both during daytime (98.3 mm Hg; range, 74 to 126 versus 90.6 mm Hg; range, 73 to 116; P < 0.006) and during nighttime (83.2 mm Hg; range, 66.5 to 125 versus 79.0 mm Hg; range, 63 to 91; P < 0.05). In parallel, the median left ventricular mass index was significantly higher in young adults (81.8 g/m2; range, 62 to 174 versus 64.3 g/m2; range, 52 to 102; P < 0.02). The results document that ambulatory daytime and nighttime blood pressures and left ventricular mass indices are higher in asymptomatic carriers of the ADPKD trait compared with controls, although most values are still within the normal range.