Determination of 239Pu/240Pu isotopic ratio by high-resolution alpha-particle spectrometry using the ADAM program.

A novel analysis program to unfold alpha-particle energy spectra was introduced, demonstrated and validated using radiochemically processed test sources, which contained different amounts of (239)Pu and (240)Pu. A high-resolution alpha spectrometer was used for data acquisition. The software known as ADAM unfolds the spectra using nuclide-specific decay data as a constraint. The peaks can have different shapes and the software can also cope with the coincidences between alpha particles and electrons/photons. In the present paper, the (239)Pu/(240)Pu activity ratios from alpha spectrometry agreed, within the stated uncertainties, with the reference values. Number of counts in the (239,240)Pu peak group must be larger than 100 to obtain reliable values when using semiconductor detector of energy resolution FWHM=10.6 keV.

Analysis of the optical concentration curve to detect access recirculation.

The optical blood volume curve sometimes presents either a positive or a negative rapid and reversible variation (spike) during the step of the dialysate conductivity, automatically set by the monitor for the ionic dialysance (ID) measurement. We studied whether this feature was in relation with access recirculation. Firstly, we studied if the manoeuvre of reversed position of the blood lines created the same feature in the blood volume curve. Secondly, two medical teams systematically checked for the presence of spikes and measured the access recirculation by way of an ultrasound dilution technique. The manoeuvre of reversed position of the blood lines invariably reproduced the same feature on the curve of the optical blood volume measurement in case of a recirculation greater than 20%. In the normal position of the blood lines, the 16 patients with an access recirculation greater than 20% had spikes. Spikes during ID measurement were not constant for an access recirculation between 10 and 20% and did not occur for an access recirculation of less than 10% or an undetectable one. The special spike of the optical blood volume curve occurring during the ID measurement clearly detects access recirculation. The specificity is of 100% when this modification is present all along the dialysis session for all the ID measurements and the sensitivity is 100% when the access recirculation is greater than 20%.

Relationship between effective ionic dialysance and in vivo urea clearance during hemodialysis.

Effective ionic dialysance (EID) can be measured from dialyzer inlet and outlet conductivity changes following two steps of dialysate conductivity. Relationships between EID and in vivo urea clearances were studied four times per hemodialysis treatment in eight patients, each undergoing six hemodialysis treatments (192 data sets). Dialyzer blood flow was varied from 190 to 500 mL/min. Dialysate flow was constant (751 to 771 mL/min), and a standard dialyzer (700 HG; Cobe, Lakewood, CO) was used. Double samples were drawn for arterial, venous, and dialysate urea measurements. Two laboratory values were missing. Twelve unreliable laboratory values indicated by divergent results were excluded. Urea clearances were calculated by formulae converting whole-blood to blood-water urea clearances. EID was measured using Diascan (Gambro-Dasco, Medolla, Italy). Mass balance was checked by comparison of dialysate and blood-water urea clearances. Divergent results between dialysate and blood-water urea clearance values led to the exclusion of an additional three laboratory values. A small error (4.2%) in urea mass balance was found (dialysate greater than blood-water urea clearances). A total of 175 data sets were compared. EID showed excellent correlation with blood-water urea clearances (r = 0.92) over the line of identity, with a mean difference of -3.5 mL/min (-1%), and similarly with dialysate urea clearances (r = 0.92; mean difference, -13.4 mL/min; -5%). For both blood- and dialysate-side comparisons, differences increased with greater clearances. Because EID is an effective clearance and urea clearance is a measure of dialyzer clearance, the curves were corrected for cardiopulmonary recirculation; access recirculation was zero (Transonic monitor; Transonic Systems Inc, Ithaca, NY). For cardiopulmonary recirculation correction, cardiac output and access flows were assumed to be 6.4 L and 1.46 L/min. Corrected data show EID correlates with blood-side urea clearance (r = 0.92), with a mean difference of +7.3 mL/min (3.3%), and is constant over the range of clearances. EID correlated with dialysate urea clearance (r = 0.92) with virtually no difference. The difference on the blood side is consistent with the urea mass balance error found. These data indicate that EID using Diascan can provide an accurate indication of effective urea clearances obtained during hemodialysis and is of value in monitoring dialysis adequacy.

Determination of access blood flow from ionic dialysance: theory and validation.

BACKGROUND: Several noninvasive techniques have been recently developed for calculating blood flow rate of vascular access in hemodialyzed patients from the on-line measurement of recirculation ratio by injecting a saline bolus when the blood lines are reversed. Here we describe a new noninvasive method based on ionic dialysance measurements without the need of a saline bolus. METHODS: Mathematical modeling allows to calculate blood flow in vascular access (QA) from the recirculation ratio (Rrev) measured when the blood lines are reversed, without the need to stop ultrafiltration, by using the formula: QA = (QB - QF) 1 - Rrev/Rrev where QB is the blood flow at the dialyzer inlet and QF the ultrafiltration rate. Because the ionic dialysance takes recirculation into account, we tested a new method to assess QA from the measurement of ionic dialysance at normal (D) and reverse (Drev) positions of the blood lines for the same QB. Assuming the absence of access recirculation at normal position of the blood lines, mathematical modeling provides the following relationship: QA = (D - QF)Drev/D - Drev. The estimation of QA from measurement of ionic dialysance (QA-ID) was compared in 28 patients to the estimation of QA by ultrasound dilution technique (QA-US). RESULTS: The two methods were strongly correlated (QA-ID = 1.24 * QA-US, r2 = 0.86, P < 0.0001). The difference between QA-ID and QA-US was 107 +/- 387 ml/min (mean +/- SD). CONCLUSIONS: Our method provides a valuable estimation of the vascular access flow and is fully noninvasive, easy to perform (no need of bolus injection and of accurate measurement of QB) and totally inexpensive. Consequently this method is suitable for monitoring access blood flow in hemodialyzed patients in order to predict access thrombosis and to treat significant stenotic lesions before thrombosis.

Sodium management in dialysis by conductivity.

The determination of dialysate sodium concentration is one of the challenges of dialysis prescription, because no accurate information on the predialytic sodium overload is available. Too low dialysate sodium is responsible for intradialytic intolerance symptoms, whereas too high sodium may lead to long-term water sodium overload with cardiovascular hazards (hypertension, left heart failure). We propose here a biofeedback system based on noninvasive repeated measures of ionic dialysance and plasma water conductivity used here as a surrogate of plasma water sodium. This system achieves a stable postdialytic sodium pool and subsequently a dialysate sodium concentration adapted to the inter dialytic sodium load. This new tool in dialysate sodium prescription aims at reducing the morbidity related to patient sodium balance impairment.

Duocart biofiltration: a new method of hemodialysis.

DuoCart biofiltration (DCB) is a new hemodialysis method using a dialysate with only sodium chloride and bicarbonate obtained from two separate powder cartridges (BiCart and SelectCart, Gambro, Sweden). The ionic complement is directly reinfused in postdilution mode, using one 2 L bag of a specially designed sterile solution. The adaptation of the quantity of these infused substances to their removal through the dialysis membrane is made possible by repeated measurements of ionic dialysance (D), which are automatically performed every 30 min by the Diascan module, systematically available on the Integra dialysis monitor (Hospal, Italy), and by subsequent modification of the infusion rate (Q(R)). An appropriate kinetic model was used to determine the composition of the reinfusion solution (mM: 57 K, 47 Ca, 14.5 Mg, 180 Cl), the conductivity dialysate (set at 14.8 mS/cm) and the ratio Q(R)/D (set at 1/28). This ratio is kept constant by updating Q(R) after each measurement of D. The implementation of this technique requires an Integra dialysis monitor equipped with a two-powder-cartridge dialysate generation system. Fifteen dialysis sessions were performed (duration: 213+/-38 min; blood flow: 238+/-26 ml/min; ultrafiltration rate: 16+/-6 ml/min). The per-dialytic changes of ion plasma concentrations were monitored and found to be within the predicted range. The results substantiate the feasibility of this new hemodialysis method that presents several advantages: dialysate concentrates are in powder form, an alkaline and acetate-free dialysate is used with superior dialysate biocompatibility, no precipitation of Ca and Mg carbonate occurs in the dialysate circuit, the supply of calcium and potassium is easily adapted to individual patients' needs by change in the composition of the reinfusion solution, and a calcium-free dialysate that facilitates citrate anticoagulation is used.

Assessment of acetate free continuous veno-venous hemofiltration in acute renal failure.

Among the limitations of continuous renal replacement therapy (CRRT) in patients with severe acute renal failure (ARF) and cardiovascular instability is the use of acetate in the substitution fluid. Acetate is required to maintain acidity of the polyelectrolytic solution to avoid calcium carbonate precipitation in the presence of bicarbonate. In addition, in patients with cardiovascular instability, acetate metabolism is impaired and further compromises hemodynamics. A new CRRT technique is proposed in which bicarbonate is used as a buffer, but the acetate requirements are cancelled: acetate free veno-venous hemofiltration (AF-CVVH). This technique allows control of acid-base disturbances independent of urea removal. This preliminary report describes the feasibility of the technique based on separate infusion of water and electrolytes administered prefiltration, and isotonic sodium bicarbonate administered post filtration. The setting of the technique, adapted to the PRISMA device (Hospal, Lyon, France), was based on a model predicting the bicarbonate infusion rate for a target plasma bicarbonate level. The AF-CVVH was compared with conventional, continuous veno-venous hemofiltration (CVVH) in a crossover study that showed AF-CVVH allowed fastest control of acidosis, avoiding 70 to 80 mmol/d of acetate transfer to the patient. Urea removal was similar with both techniques. It was concluded that AF-CVVH, when compared with CVVH, has the main advantage of separately controlling urea retention and metabolic acidosis in patients with severe ARF and cardiovascular instability.

Is ionic dialysance a valid parameter for quantification of dialysis efficiency?

The on-line measurement during hemodialysis of ionic dialysance provides an estimation of urea clearance with a good and already proven correlation. Some discrepancies remain controversial, and the influence of the dialyzer membrane is still being debated. Eighty-eight measurements of ionic dialysance (ID) were performed with a Diascan module (Hospal R&D, Int., Lyon, France), 51 with cellulosic membranes, and 37 with synthetic membranes, chosen according to their surface charges. The ID was compared to the urea clearance (UK) measured from the blood (n=16) and dialysate (n=88) sides. The ID is closely correlated (r=0.91) but significantly (p < 0.01) lower than the UK by 5% (ID/UK=0.95+/-0.06). The correlation is improved by a semilogarithmic regression analysis (r=0.93). Regarding the influence of the membrane charge, a slight difference is only evidenced for UK < 180 ml/min whereby ID is closer to the urea clearance for the charged membranes (ID/UK=0.98+/-0.05 for charged membranes versus 0.95+/-0.05 for noncharged membranes, p < 0.05). The discrepancy between ID and UK could be related with the difference in the blood distribution volume of urea and that of electrolytes. The good correlation provides the major argument for ID being used as a monitoring parameter of the delivered dialysis dose. Having integrated the discrepancy between ID and UK, prescription can be guided by ID for delivering the adequate normalized dialysis dose as defined by Kt/V.

Non-invasive monitoring of effective dialysis dose delivered to the haemodialysis patient.

Assessment of normalized dialysis dose Kt/V actually delivered to the patient carries the drawback of requiring several blood or dialysate samplings and urea concentration measurements. In order to easily quantify Kt/V, we validate here the routine implementation of an original technique for the non-invasive, on-line, and fully automatic estimation of total mean urea clearance. This estimation is obtained from the measurement by a conductivity method of the effective ionic dialysance DR, which is the dialysance of electrolytes taking into account ultrafiltration and recirculation. The observed increase in DR with ultrafiltration rate and decrease in DR with elevation of access recirculation ratio show that the estimation of DR is affected by ultrafiltration and recirculation in a consistent manner. The mean value Keff of ionic dialysance DR was compared with the value Kdc of effective urea clearance obtained by dialysate collection during 12 haemodialysis sessions. The similarity (magnitude of variation 5%) between the ionic dialysance Keff and the effective urea clearance Kdc supports the validity of the equivalence between the transfer characteristics of electrolytes and urea through the dialyser membrane. Given an estimate of the urea distribution volume V, this estimation of effective urea clearance by ionic dialysance measurement allows an on-line estimation of the normalized dialysis dose Kt/V actually delivered to the patient.

A model for non-invasive estimation of in vivo dialyzer performances and patient's conductivity during hemodialysis.

On-line monitoring of hemodialysis sessions requires a non-invasive estimation of the parameters concerning the patient's status and the dialyzer performances. We describe here a model based on a new method for non-invasive dialysance and patient conductivity measurements. In this technique the same probe measures alternately the conductivity at the dialysate inlet and outlet for two different dialysate conductivity values. From these data, an appropriate model allows to determine the patient's conductivity as well as the effective dialysance of ionised solutes, that is to say the dialysance corrected for recirculation. A strong correlation is evidenced between the effective dialysance measured by this method and the urea clearance measured by conventional methods (r = 0.98 for in vitro solutions; r = 0.82 in vivo situations).

Death anxiety and job stress in hospice and medical-surgical nurses.

This study compared death anxiety and frequency and severity of job stress in 30 hospice and 40 medical-surgical nurses. Death anxiety was assessed through the Templer/McMordie Death Anxiety Scale, job stress through the Gray-Toft/Anderson Nursing Stress Scale. There were no significant group differences in the death anxiety scores nor in the total scores for the frequency segment of the nursing stress scale. The medical-surgical nurses scored a significantly higher total for the severity segment of the nursing stress scale. Death anxiety correlated significantly with frequency and severity of job stress for medical-surgical nurses but not for hospice nurses. Death anxiety correlated highly significantly with death and dying as a source of stress for the medical-surgical nurses.

A comparison of frequency and sources of nursing job stress perceived by intensive care, hospice and medical-surgical nurses.

This study compared the frequency and sources of nursing job stress perceived by 35 intensive care (ICU), 30 hospice and 73 medical-surgical nurses. Analysis of variance revealed no significant differences among the three groups of nurses on the overall frequency of job stress. Post-hoc Tukey tests demonstrated a significant difference in three stress subscales among the three groups. ICU and hospice nurses perceived significantly more stress than medical-surgical nurses related to death and dying; ICU and medical-surgical nurses perceived significantly more stress than hospice nurses related to floating; and medical-surgical nurses perceived significantly more stress than ICU and hospice nurses related to work-overload/staffing. Spearman-Rank Correlation revealed no significant correlations among the three groups in their rank-ordering of the eight stress subscales. Death and dying situations were the most stressful to ICU and hospice nurses, while work-overload/staffing situations were the most stressful to medical-surgical nurses. Results of the study, although not generalizable, have implications for nurse managers.

[First contact between blood and the arterial prosthesis. Study of the retention of the blood elements]. / Premier contact sang/prothèse artérielle. Etude de la rétention des éléments sanguins.

In order to characterize the nature of the interaction between arterial prostheses and their initial contact with blood, we propose the use of an in vitro test using labelled platelets and fibrinogen to measure the amount of the thrombotic matrix that is entrapped by the wall of the graft. The results have been confirmed by scanning electron microscopy. Polyester prostheses, whose healing process depends on the reorganisation of the thrombotic matrix, retains considerably more blood cells than the polytetrafluoroethylene microporous prostheses or the treated biological devices, whose fate, following implantation, maintains almost complete passivity.

[A technical stratagem to avoid skin complications in surgical repair of ruptures of the Achilles tendon]. / Un artifice technique pour éviter les ennuis cutanés dans la réparation chirurgicale des ruptures du tendon d'Achille.

The authors have advocated the longitudinal division of the anterior aspect of the tendon sheath to allow suture of the posterior aspect of the sheath in the course of repair of tendo Achillis ruptures. This technique thus allows interposition of tissue between the tendon and the skin and was used with success in 19 cases.

[Action of dydrogesterone in postpubertal menstruation disorders]. / Action de la dydrogestérone dans les troubles des règles post-pubertaires.

Seventy-four post-pubertal young women with menstrual disturbances of a functional nature were treated with 20 mg of dydrogesterone per day from the 16th to the 25th day of the cycle for three cycles. Overall efficacy was considered satisfactory, results being significantly more positive with regard to disturbances in the duration of the cycle rather than excessively heavy periods. The authors draw attention to the possibility of the restoration of luteal function in a patient treated with dydrogesterone and the validity of temperature curve and plasma progesterone levels in this context.

[Radioisotope evaluation of the interaction between blood and vascular prostheses. Preliminary results]. / Evaluation radioisotopique de l'interaction sang-prothèses vasculaires. Résultats préliminaires.

In order to illustrate the phenomena which occur at the first contact between arterial prostheses and blood, an in vitro test is suggested which may be used to quantify the retention of the cruoric matrix using labelled compounds and confirming the nature by scan electron microscopy. Reorganisation of the cruoric matrix is dependent upon the scarring of polyesters which retain considerably more blood substances than microporous polytetrafluoroethylenes or the biological models dealt with, the course of which after implantation is closer to passivation.

Diagnosis of meconium in amniotic fluids by nuclear magnetic resonance spectroscopy.

Some 40 samples of amniotic fluids were studied by nuclear magnetic resonance (NMR) spectroscopy as the first step in developing techniques for analysis of amniotic fluids in vivo without amniocentesis. It was found possible to distinguish amniotic fluids containing meconium (fetal feces) from all other kinds of amniotic fluids (hydramnios or normal fluids) by proton NMR, but precise chemical or cytological analysis seemed unavailable. Also reported are results of in vitro analysis of amniotic fluids, and of measurements performed in vivo on other biologic fluids to investigate possible in situ detection of pathological amniotic fluids.