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Daniel Schneditz

Publications and source records attributed to Daniel Schneditz.

8 recordsLinked to original sources
PubMed2003

Measurement of intraperitoneal volume by segmental bioimpedance analysis during peritoneal dialysis.

BACKGROUND: Currently, ultrafiltration during peritoneal dialysis is determined from direct measurement of weight differences between the initial filling and final draining volumes. A new technique based on segmental bioimpedance analysis (SBIA) has been developed to accurately measure intraperitoneal volume continuously during peritoneal dialysis. METHODS: Twenty-two peritoneal dialysis patients were studied in a supine position during peritoneal dialysis consisting of 4 tidal exchanges (TPD). For bioimpedance measurements, 4 electrodes were placed, 1 on each hand and foot, to inject an alternating current. Sensing electrodes were placed on the lower ribs and the buttocks on both sides of the body. Calibration of the SBIA method was performed by first filling a known volume of dialysate to establish the relationship between change in resistance and a known fluid volume in the peritoneal cavity. The increase of fluid volume in the peritoneal cavity during dwell time was considered to be equal to net ultrafiltration volume occurring during this period. These measurements were compared with those obtained by the difference in weight between the total filling and draining volumes. RESULTS: The change in intraperitoneal volumes measured by differences in weight (0.39 +/- 0.29 L) did not differ significantly from those established from SBIA (0.41 +/- 0.31 L). Bland-Altman analysis yielded limits of agreement of 0.12 L. CONCLUSION: The SBIA technique provides a continuous noninvasive approach to the measurement of changes in intraperitoneal fluid volume.

Adult↗
PubMed2003

Characteristics of hypotension-prone haemodialysis patients: is there a critical relative blood volume?

BACKGROUND: Intradialytic morbid events (IME, mostly hypotension) mainly due to ultrafiltration-induced hypovolaemia still are the most frequent complication during haemodialysis (HD). This study was performed to test the hypothesis that there is an individual critical relative blood volume (RBV(crit)) in IME-prone HD patients. METHODS: In this prospective international multicentre study, 60 IME-prone patients from nine dialysis centres were observed during up to 21 standard HD sessions without trial-specific intervention. The RBV was monitored continuously by an ultrasonic method (BVM; blood volume monitor). Also, the ultrafiltration rate was registered continuously. Blood pressure was measured at regular intervals, and more frequently during IME. All IME and specific therapeutic interventions were noted. RESULTS: In total, 537 IME, some with more than one symptom, were documented during 585 HD sessions. The occurrence of IME increased up to 10-fold from the start to the end of the HD session. RBV(crit) showed a wide inter-individual range, varying from 71 to 98%. However, the intra-individual RBV limit was relatively stable, with an SD of <5% in three-quarters of the patients. In patients with congestive heart failure, cardiac arrhythmia, advanced age, low ultrafiltration volume and low diastolic blood pressure, higher values of RBV(crit) were observed. While all correlations between RBV(crit) and patient characteristics alone were found to be of weak or medium strength, the combination of diastolic blood pressure, ultrafiltration volume and age resulted in a strong correlation with RBV(crit): the linear equation with these parameters allows an estimation of RBV(crit) in patients not yet monitored with a BVM. CONCLUSIONS: An individual RBV limit exists for nearly all patients. In most IME-prone patients, these RBV values were stable with only narrow variability, thus making it a useful indicator to mark the individual window of haemodynamic instabilities.

Aged↗
PubMed2003

Comparison of prescribed and delivered doses of dialysis using anthropometrically and bioelectrically measured patient volumes.

BACKGROUND: One of the uncertainties in the prescription of dialysis dose, measured as Kt/V for urea (Kt/Vu), is the volume of urea distribution (V). The aim of our study was to compare two different approaches to estimating V and Kt/V, respectively, and to compare the predicted (prescribed) dose with the actually delivered dose, measured by urea kinetics. MATERIAL/METHODS: V was estimated using anthropometric measures with the Watson formula (VWatson), and also by multi-frequency bioimpedance analysis (VBIS). Both volumes were determined for the state at the end of dialysis and ultrafiltration, and then used to predict (prescribe) Kt/VWatson and Kt/VBIS, respectively. The delivered Kt/Vu was determined from pre- and postdialysis urea concentrations. RESULTS: 209 patients were studied in 254 measurements. VWatson and VBIS correlated significantly (VBIS=0.64*VWatson+15.03, r2=0.67) but VWatson (36.0 +/- 6.4 L) was higher than VBIS (32.5 +/- 8.1 L). The bias between techniques was 3.5 +/- 4.6 L. As a consequence of volume underestimation, Kt/VBIS was overestimated (1.44 +/- 0.38) when compared to the actually delivered Kt/Vu (1.28 +/- 0.32). However, Kt/VWatson (1.27 +/- 0.25) based on VWatson was almost identical to the actually delivered treatment dose. CONCLUSIONS: The close correspondence between the delivered and predicted (prescribed) dose of dialysis using anthropometric volumes leads to the conclusion that in this study kinetic distribution volume was best described by VWatson. The overestimation of prescribed dialysis dose based on bioimpedance analysis suggests caution in the use of bioimpedance volumes, because of the risk of prescribing inadequate dialysis.

Adult↗
PubMed2002

Heat accumulation with relative blood volume decrease.

BACKGROUND: Both hypovolemia and heat accumulation act as powerful perturbations of blood pressure control. In hemodialysis, hypovolemia and heat accumulation often develop simultaneously, and the question arises of whether and to what extent these perturbations are linked. METHODS: Heat accumulation was measured by the amount of thermal energy (E) removed from a patient during prescribed ultrafiltration under isothermic hemodialysis conditions, ie, constant patient temperature. Measurement and control of temperatures and thermal energies were performed using the blood temperature monitor. Relative blood volume (RBV) was measured using the blood volume monitor. RESULTS: Thirty-eight treatments were analyzed in 12 patients (3 women). During treatments lasting 189 +/- 28 minutes, 5.1% +/- 1.3% of postdialysis body weight were removed from patients by ultrafiltration at a mean rate of 1.1 +/- 0.3 L/h. Blood volumes decreased to 85% +/- 7% of initial values, and 229 +/- 106 kJ of E were removed from patients at a cooling rate (J) of 20 +/- 8 W, corresponding to 28% +/- 11% of estimated energy expenditure (H%). E, J, and H% significantly increased as RBV decreased (P < 0.05). Linear regression analysis between J and RBV showed that approximately 1 W had to be removed from the patient for each percentage of change in blood volume (J = -102.38 + 0.97* RBV; r2 = 0.63). CONCLUSION: Results show that the probability for the effect of heat stress during hemodialysis increases with ultrafiltration-induced blood volume changes. Temperature control is an important aspect of hemodialysis treatment.

Adaptation, Physiological↗
PubMed2002

Online monitoring of cerebral hemodynamics during hemodialysis.

BACKGROUND: Several factors, including anemia, diabetes, and hypertension, potentially could disturb the cerebral autoregulation mechanism in hemodialysis (HD) patients. This study examined the effect of hemodynamic and rheological changes on mean cerebral blood flow (CBF) velocity (MV) during HD. METHODS: Continuous online monitoring of MV and pulsatility index in the middle cerebral artery were performed in 18 HD patients by transcranial Doppler ultrasound during the entire HD period (range, 3 to 4 hours). In addition, blood pressure, hematocrit (Hct), and relative decrease in blood volume were continuously monitored. Blood samples were obtained at the beginning and end of HD to measure hemorheological variables. RESULTS: After HD, Hct increased significantly from 33.6% +/- 5.9% to 41.4% +/- 5.7% (P < 0.001). Blood and plasma viscosity increased significantly from 3.33 +/- 0.77 to 4.36 +/- 1.3 mPa.s (P < 0.001) and from 1.35 +/- 0.29 to 1.54 +/- 0.38 mPa.s (P < 0.001), respectively. The change in MV (DeltaMV) was not significantly different from zero and correlated significantly with change in Hct. During HD, mean arterial pressure (MAP) in 15 patients changed within the normal range (group I), whereas 3 patients developed hypotension (group II) and their MAP decreased from 99 +/- 5 to 60 +/- 8 mm Hg (P < 0.05). In both groups, DeltaMV were not significant. CONCLUSION: Results of this study suggest that CBF does not appear to be diminished significantly during HD.

Aged↗
PubMed2002

Estimating phosphate removal in haemodialysis: an additional tool to quantify dialysis dose.

BACKGROUND: Half of the dialysis population suffers from hyperphosphataemia, which is now recognized as a major factor of haemodialysis (HD) morbidity and mortality. Current control is focussed on reducing dietary phosphate intake and diminishing absorption using phosphate binders, whereas control and quantification of phosphate removal by HD is undervalued. The aim of this prospective study was to develop a simple, bedside formula to estimate dialytic phosphate removal in stable HD patients. METHODS: This was a prospective, randomized trial. Phosphate and urea elimination were assessed in a representative group of patients at two dialysis centres using randomly different dialysers (1.3-2.4 m(2)). Quantification was performed by partial dialysate collection, concentration measurements in blood and effluent dialysate spot samples, and Kt/V(urea) during standard high-flux HD. Multiple linear regression analyses were used in 77% of all data sets to generate an equation to predict phosphate removal. The formula was validated in the remaining 23% of data sets, in the same group of patients using a large capillary filter, and in diabetic patients treated with a small dialyser at different blood flows (200, 250, and 300 ml/min). RESULTS: A formula allowing quantification of phosphate removal within one HD session was developed in 18 of 74 patients during 41 treatments (137 out of 177 data sets) and was determined as: M(PO4pred)=0.1t -17+50c(ds60)+11c(b60), where t is treatment time in min, c(ds60) and c(b60) are phosphate concentrations in dialysate and plasma measured 60 min into HD in mmol/l, and M(PO4pred) is estimated phosphate removed in mmol. The precision was remarkable (r(2)=0.92-0.94). The comparison of phosphate and Kt/V(urea) showed a significant association (r(2)=0.28), albeit with remarkable scatter. CONCLUSIONS: We present the first approach to quantify phosphate removal during high-flux HD by a bedside formula. Only 28% of the variation in phosphate removal was explained by Kt/V(urea). It appears that other factors not adequately accounted for by Kt/V(urea) affect phosphate removal. Therefore, we propose an individual control and quantification of phosphate removal in HD.

Aged↗
PubMedDate not supplied

Surveillance of fistula function by frequent recirculation measurements during high efficiency dialysis.

Native fistulae are assumed to remain patent even with low access flows and are likely to cause access recirculation in high efficiency treatments done with high extracorporeal blood flows. We tested whether frequent recirculation measurements could be used to identify fistulae at risk to fail because of low access flow. High efficiency hemodialysis was delivered by 2008H machines equipped with blood temperature monitors (BTM) to measure recirculation within the first hour of every hemodialysis treatment. Access flow was measured when two consecutive BTM recirculation measurements exceeded a threshold of 15%. If access flow was < 500 ml/min, patients were referred for fistula revision. Eighty patients with native AV fistulae were studied for a period of 6 months. Nine of 11 interventions performed during the whole observation period were triggered by a BTM recirculation above the threshold. Two fistulae thrombosed in spite of a BTM recirculation below the threshold. One fistula with a BTM recirculation above the threshold had an access flow of 1,550 ml/min and was not referred for revision. BTM recirculation to detect fistulae for revision is sensitive (81.8%) and specific (98.6%) in the presence of cardiopulmonary recirculation and can be done with minimum intervention and without loss of efficient treatment time.

Adult↗