Dialysate Samples Research Articles

A-032 Comparative Serum Free Thyroxine Measurements between Immunoassays and ID-LC/MS/MS Procedure Based on Equilibrium Dialysis

Abstract Background Serum free thyroxine (FT4) measurement is one of the most important clinical laboratory tests for diagnosis and classification of thyroid disorders. Currently serum FT4 is commonly measured with Immunoassays (IAs) in patient care. However, there are concerns about the accuracy of FT4 IAs. A reference measurement procedure (RMP) for FT4 based on well-defined equilibrium dialysis (ED) of serum has been established for standardization of routine FT4 IAs. As FT4 RMP is not intended for routine clinical application, in the current study, we aim to develop a high-throughput routine FT4 method based on ED-isotope dilution liquid chromatography tandem mass spectrometry (ED-ID-LC/MS/MS). FT4 RMP was used as a reference to evaluate the measurement accuracy of our ED-ID-LC/MS/MS method and an IA method, respectively. Methods FT4 in dialysate was isolated from protein-bound T4 in serum by using a commercially available micro-ED plate after 18-h ED. The 13C6 labeled T4 was added into dialysate as an internal standard. FT4 in dialysate was purified with 96-well C18 SPE plate. FT4 in the dialysate samples was analyzed by using LC/MS/MS. The T4 certified primary reference material (IRMM-468) was used for assay calibration. FT4 IA measurement was conducted in clinical analyzers (Roche e411). A set of 40 single donor sera, covering a FT4 concentration range of 11.2–32.1 pmol/L were measured by IA and our ED-ID-LC/MS/MS, respectively. Deming regression analysis was performed to compare the results obtained by these two methods with the reference values assigned by FT4 RMP. Results The described high-throughput method based on ED-ID-LC/MS/MS could simultaneously quantified T4, T3, reverse triiodothyronine (rT3) in the dialysate within 4.5 min. The linear range of the routine FT4 assay covered 1–100 pg/mL. The assay sensitivity allowed detection of 0.3 pg/mL FT4 in serum, which is sufficient for FT4 measurement in clinically relevant ranges including hypothyroid patient samples. The throughput of the ED-ID-LC/MS/MS method could be further improved by application of automated liquid handling system. Deming regression analysis showed good agreement between RMP and the routine ED-ID-LC/MS/MS method with a slope close to 1 (P > 0.05) and an intercept close to 0 (P > 0.05), indicating that the results generated from the platform of high-throughput ED-ID-LC/MS/MS could be tracible to FT4 RMP. However, proportional bias (P < 0.05) with slope of 0.74 and constant bias (P < 0.05) with intercept of 2.6 was observed between RMP and IA tested, indicating calibration bias should be addressed to standardize IA. Conclusion In summary, the accuracy, sensitivity, and throughput of ED-ID-LC/MS/MS method are appropriate for FT4 measurements in clinical laboratories and in large epidemiologic studies to establish accurate reference intervals for FT4. Population data generated by FT4 ED-ID-LC/MS/MS method will support the use of standardized FT4 measurements.

Performance characteristics of a prototype dialysate turbidity monitoring system to detect peritonitis in patients receiving peritoneal dialysis.

The risk of peritonitis has limited wider adoption of peritoneal dialysis (PD) in the United States. We developed a prototype bedside dialysate turbidity monitoring system, aiming to improve diagnostic accuracy relative to conventional approaches which depend on visual inspection and reporting of insensitive and non-specific symptoms. The prototype system was tested in a single-centre, proof-of-principle clinical study in patients receiving intermittent PD. We obtained multiple effluent dialysate samples from each consenting participant. We compared turbidity measurements with diagnostic criteria endorsed by the International Society of Peritoneal Dialysis (ISPD). Overall, we analysed 983 specimens from 65 patients, including 105 samples from patients with peritonitis and 878 samples from patients without peritonitis. An operating point derived from a previous in vitro study yielded an unadjusted sensitivity and specificity of 95.2% and 91.5%, respectively. The majority of samples that did not meet ISPD diagnostic criteria were either cases detected before criteria were met or were related to active peritonitis treatment and resolution. This proof-of-principle study demonstrates the feasibility and diagnostic accuracy of a prototype dialysate turbidity monitoring system for peritonitis surveillance.

Clinical protocol: Feasibility of evaluating abemaciclib neuropharmacokinetics of diffuse midline glioma using intratumoral microdialysis.

Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates <10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment responsivity. This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are >10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. Trial registration: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis.

Immune responses of patients on maintenance hemodialysis after infection by SARS-CoV-2: a prospective observational cohort study

BackgroundImmune dysregulation in patients with acute COVID-19 under chronic hemodialysis (CHD) is fully not elucidated. The changes of mononuclear counts and mediators before and after HD and associations with final outcome were studied.MethodIn this prospective study, hospitalized patients with moderate-to-severe COVID-19 under CHD and matched comparators under HD were analyzed for their absolute counts of lymphoid cells and circulating inflammatory mediators. Blood samples were collected before start and at the end of the first HD session; dialysate samples were also collected.ResultFifty-nine patients with acute COVID-19 under CHD and 20 uninfected comparators under CHD were enrolled. Circulating concentrations of tumor necrosis factor-alpha (TNFα), interleukin (IL)-10, interferon-γ and platelet-derived growth factor-A were increased in patients. Concentrations of mediators did not differ before and after HD. Significant decreases of CD4-lymphocytes and CD19-lymphocytes were found in patients. The decrease of the expression of HLA-DR on CD14-monocytes was associated with unfavorable outcome (defined as WHO-CPS 6 or more by day 28); increased counts of CD19-lymphocytes were associated with better outcomes.ConclusionPatients under CHD develop an inflammatory reaction to SARS-CoV-2 characterized by increase of inflammatory mediators, decrease of circulating T-lymphocytes and decrease of the expression of HLA-DR on CD14-monocytes.

Evaluation of peritoneal dialysis prescriptions in uremic rats.

Patients with end-stage kidney disease (ESKD) require dialysis or transplantation for their survival. There are few experimental animal models mimicking the human situation in which the animals are dependent on dialysis for their survival. We developed a peritoneal dialysis (PD) system for rats to enable long-term treatment under controlled conditions. Rats were chemically nephrectomised using orellanine to render them uremic. Two studies were performed, the first with highly uremic rats on PD for 5 days, and the other with moderately uremic rats on PD for 21 days. Blood and dialysate samples were collected repeatedly from the first study and solute concentrations analysed. Based on these values, dialysis parameters were calculated together with generation rates allowing for kinetic modelling of the effects of PD. In the second study, the general conditions of the rats were evaluated during a longer dialysis period. For rats with estimated glomerular filtration rate (GFR) 5-10% of normal (moderately uremic rats), five daily PD cycles kept the rats in good condition for 3 weeks. For highly uremic rats (GFR below 3% of normal), more extensive dialysis is needed to maintain homeostasis and our simulations show that a six daily and four nightly PD cycles should be needed to keep the rats in good condition. In conclusion, the PD system described in this study can be used for long-term studies of PD on uremic dialysis-dependent rats mimicking the human setting. To maintain whole body homeostasis of highly uremic rats, intense PD is needed during both day and night.

#6864 IMMUNE RESPONSES OF PATIENTS ON MAINTENANCE HEMODIALYSIS AFTER INFECTION BY SARS-COV-2: A PROSPECTIVE OBSERVATIONAL COHORT STUDY

Abstract Background and Aims We aimed to study the immune response of maintenance hemodialysis (HD) patients to Corona Virus Disease-19 (COVID-19) since it is not fully elucidated. Method In this prospective study, hospitalized HD patients with moderate-to-severe COVID-19 and matched non diseased HD comparators were analyzed for their absolute counts of lymphoid cells (flow cytometry) and circulating inflammatory mediators (ELISA). Blood samples were collected at the start and at of the end of the first in hospital HD session; dialysate samples at the end of the first half hour session. Results 59 HD patients with acute COVID-19 HD and 20 comparators were enrolled. Circulating median (range) of interferon-gamma (IFNγ) at the start of HD was 125 (125-1777) pg/ml in comparators and 810 (125-4000) pg/ml in SARS-CoV-2 (p&amp;lt;0.00001) and 125 (125-1278) pg/ml and 738 (125-4000) pg/ml at the end of HD (p&amp;lt;0.0001). Respective concentrations of platelet derived growth factor-A were 8286 (4600-28150) and 27938 (8285-99256) pg/ml (p&amp;lt;0.0001) and 7779 (5055-28128) and 27410 (6836-87887) pg/ml respectively. Similar increases were found for tumor necrosis factor-alpha (TNFα) only at the start of the HD whereas no differences were found for interleukin (IL)-6, IL-10 and IL-38. Respective mean (SD) CD4-counts were 881.3 (407.6) and 461.6 (365.4) per microliter (p&amp;lt;0.0001) and 839.4 (509.7) and 483.6 (329.9) per microliter (p&amp;lt;0.0001). Respective mean (SD) CD19-counts were 199.0 (154.5) and 76.4 (78.6) per microliter (p&amp;lt;0.0001) and 144.9 (110.3) and 98.3 (70.8) per microliter (p&amp;lt;0.0001). The respective mean (SD) MFI expression of HLA-DR on CD14-monocytes was 97.2 (28.2) and 67.4 (44.7) (p: 0.013) and 87.3 (26.7) and 63.3 (36.3) (p: 0.009). MFI of HLA-DR on CD14-monocytes before the first HD session less than 44 was associated with 100% sensitivity for unfavorable outcome (defined as respiratory failure or death) after 28 days. An absolute CD19-count more than 40 per microliter before the first HD session was associated with 8.70 odds ratio for cure favorable outcome after 28 days. Conclusion HD patients develop an inflammatory reaction to Severe Acute Respiratory Syndrome Coronavirus 2 characterized by increase of the inflammatory mediators IFN-γ, PDGF-A and TNF-a and decrease of circulating T helper lymphocytes. Decreased expression of HLA-DR on CD14-monocytes is a hallmark of unfavorable prognosis.

#3367 NON-INVASIVE OPTICAL ESTIMATION OF INTRADIALYTIC CONCENTRATIONS OF UREMIC TOXINS IN BLOOD OF HEMODIALYSIS PATIENTS

Abstract Background and Aims Hemodialysis (HD) adequacy is generally estimated by the dialysis adequacy marker Kt/V urea that poorly describes removal of uremic toxins with different removal kinetics, such as protein bound or middle molecule uremic toxins, which have direct effect on morbidity and mortality of end stage kidney disease (ESKD) patients. We have recently shown the feasibility of estimating an alternative dialysis adequacy marker that can be applied to dialysis sessions with varying settings and different uremic toxins, intradialytic time average concentration (TAC) of uremic toxins, such as urea, uric acid (UA), indoxyl sulfate (IS) and beta-2-microglobulin in blood of ESKD patients, from spent dialysate concentrations determined by laboratory methods [1]. The aim of this retrospective observational study was to estimate intradialytic TAC of uremic toxins UA and IS non-invasively from spent dialysate concentrations determined by optical methods. Method Twenty-two ESKD patients on chronic HD were enrolled into the study. For each patient 4 midweek dialysis sessions with different treatment settings were included (1 HD: Qb = 200 mL/min, Qd = 300 mL/min, dialyzer 1,5m2; 3 HDF: median (interquartile range) Qb = 298 (296-356) mL/min, Qd = 795 (500–800) mL/min, Vsubst = 21.8 (15–24.5) L, dialyzers 1,8 m2 and 2,2 m2). During each dialysis session, blood samples were taken at 0 min (start) and 240 min after the start from the arterial blood line and dialysate samples were taken at 7 min and 240 min after the start from the outlet of the dialysis machine. Concentrations of UA and IS in serum and spent dialysate samples were determined with HPLC. In addition, UV absorbance and fluorescence of the spent dialysate samples were measured with spectrophotometer UV-3600 and spectrofluorometer RF-6000 (both from Shimadzu Corp., Japan), after which concentrations of UA and IS in spent dialysate samples were determined based on the optical properties of samples. Stability of HD treatment settings were monitored online and dialysis sessions with unstable blood and dialysate flow rates were excluded. TAC of UA and IS were calculated from serum concentrations and evaluated from laboratory and optically estimated logarithmic mean concentrations (Mln D) of spent dialysate. Results Mean intradialytic serum TAC values of UA and IS were 198.4±44.0 μmol/L and 69.5 ± 37.8 μmol/L and strongly correlated to those estimated from optically determined Mln D 198.0±38.9 μmol/L (R2 = 0.75) and 69.5 ± 37.8 μmol/L (R2 = 0.81), respectively. Mln D of UA and IS in spent dialysate based on laboratory methods were 102.2 ± 22.8 μmol/L and 5.9 ± 3.5 μmol/L and strongly correlated with the optically determined concentrations of 102.7 ± 23.1 μmol/L (R2 = 0.97) and 6.1 ± 3.4 μmol/L (R2 = 0.97), respectively. Conclusion Intradialytic serum TAC of UA and IS can be estimated non-invasively with optical methods from their concentration in spent dialysate independent of treatment modality. Optical online monitoring of spent dialysate in real-time could therefore provide additional information about treatment adequacy regarding the removal of uremic toxins’ other than urea. In future, TAC estimation models should be optimized for each uremic toxin to establish higher accuracy, considering real-time treatment settings, recirculation etc.

#3270 TRANSPORT AND HYDROLYSIS OF ICODEXTRIN DURING PERITONEAL DIALYSIS

Abstract Background and Aims α-amylase, an enzyme present in plasma and peritoneal tissue, takes part in the process of starch digestion. During peritoneal exchange with icodextrin-based solution, polysaccharide chains are hydrolysed to shorter oligosaccharide chains, influencing osmotic properties of peritoneal dialysate. We estimated peritoneal transport parameters and compared them with hydrolytic clearances using a new model that takes into consideration absorption of icodextrin from the peritoneal cavity and its degradation by α-amylase. Method Frequent dialysate and blood samples were taken in 11 patients (8 icodextrin-naïve, 3 icodextrin-exposed) undergoing 16-hour dwell studies with icodextrin-based dialysis solution and labeled serum albumin (RISA) added as a volume marker. Using data on the intraperitoneal volume and dialysate and blood concentrations of glucose, urea, creatinine, and 7 icodextrin molecular weight (MW) fractions (glucose polymer size classes) and dialysate concentrations of α-amylase the extended three-pore model was applied to estimate individual parameters related to the peritoneal transport induced by dialysis and to hydrolysis of icodextrin by α-amylase. The following MW cut-off values were assumed for icodextrin fractions: up to 1.08, 4.44, 9.89, 21.4, 43.5, 66.7 and over 66.7 kDa, called Fractions 1–7, respectively. The hydrolytic clearances were defined as rate at which dialysate volume is cleared of the fraction by hydrolysis. The time-dependent hydrolytic clearances of icodextrin fractions were calculated and compared with diffusive ones. For the first time the extended three-pore model was validated not only with respect to the peritoneal transport of water and small solutes but also regarding concentration of icodextrin fractions. Results Mean measured and simulated dialysate to plasma concentration ratios for glucose, urea and creatinine are presented in Figure 1, left panel. The peritoneal kinetic of icodextrin (dialysate concentrations of each fraction over its initial concentration) is presented for mean measured data and numerical simulation results in Figure 1, right panel. The results showed that the model provides accurate (mean relative error less than 7%) description of individual patient peritoneal transport kinetics including that of icodextrin fractions in peritoneal dialysate. The comparison of hydrolytic clearances (H) with diffusive transport parameters for icodextrin fractions (PS, reflecting the maximal rates of their clearance by diffusion) showed that in case of shorter polymers (Fractions 1–3) diffusive clearances were higher or similar to hydrolytic ones over the whole dwell time. In case of Fractions 4 and 5, the initial domination of PS slowly decreased during the dwell time, being dominated by hydrolysis processes at the end of the exchange, at least partly due to the changes of intraperitoneal volume and α-amylase concentration. In case of polysaccharides from Fractions 6 and 7, their hydrolytic clearances remained higher than the diffusive ones during whole dwell time. Interestingly, the obtained values of H in icodextrin-exposed patients typically remained below 1.2 mL/min except for Fraction 6, for which H increased from initial value of 0.83±0.30 to 1.43±0.64 mL/min at the end of the peritoneal dwell. On the other hand, the estimated final values of H in icodextrin-naïve patients were on average higher than 1.2 mL/min in all fractions except Fractions 4 and 5. Conclusion The model provided accurate description of peritoneal transport and icodextrin hydrolysis during long icodextrin dwells. The model showed that hydrolytic processes dominate over diffusive ones during whole dwell time in case of Fractions 6 and 7, whereas diffusive processes dominate for Fractions 1–3.

#4562 OUTBREAK OF RALSTONIA SPP AND BURKHOLDERIA SPP CATHETER-RELATED BLOODSTREAM INFECTION IN A HAEMODIALYSIS UNIT

Abstract Background and Aims Ralstonia (RB) and Burkholderia (BB) species are environmental Gram-negative bacilli responsible for several nosocomial infections in immunocompromised or frail patients. RB and BB may contaminate medical devices because of their ability to survive in a biofilm and with low nutrient requests. Reports of infection outbreaks due to RB and BB are very few and only in sporadic cases, the source of contamination was identified. We describe here: i) how we managed an outbreak of bacteremia caused by RB and BB occurred in our dialysis unit, ii) what we have done to identify the source of infection and iii) the countermeasures we adopted to reduce the risk of new events. Method From 7 to 16 April 2021, 6 out of 39 (15.4%) hemodialyzed (HD) patients with a long-term indwelling central venous catheter (CVC) developed symptoms related to infection. Blood cultures revealed the presence of RB and BB. Thus, a prompt check of the blood cultures of all HD patients with CVC was performed. Blood samples were incubated in an automated microbial detection system (VIRTUO BIOMERIEUX) and subsequently, blood positive samples were inoculated in Chocolate and Columbia blood Agar plates. In addition, a microbiological analysis of disinfectants, drugs used in dialysis unit and samples collected from the reverse osmosis water unit (ROW) and from the ROW delivery line were performed. None of the samples obtained from the ROW and from the ROW delivery line resulted positive. Thus, a microbiological analysis of the biofilm attached on the loading pipes (LP) and on the loading plastic tubes (LPT) that connect the hemodialyzer consoles (HC) to the ROW delivery line were performed. Briefly, LTP were subjected to ultrasound sonication at 30-40 KHz (BactoSonic-Bandelin), to disrupt the bacterial biofilm. The material obtained from sonication was cultured. Bacteria was identified by an automated mass spectrometry (MALDI-TOF VITEK®MS, Biomerieux). Results Bacteremia due to RB and BB was confirmed in 7 out of 39 (17.9%) of the hemodialyzed patients with a long-term indwelling CVC. 1 out of 7 was asymptomatic. Baseline characteristics of the 6 symptomatic patients were: mean age 68±16 years; mean C-reactive protein 4.48±1.3 mg/dl; mean procalcitonin 13.27±11.07 ng/ml; mean body temperature 37.9±1.4°C. The antibiotic therapy was decided according to antibiogram and included meropenem and ciprofloxacin. CVC were removed in all infected patients between 6 to 11 days from the diagnosis. Concomitantly, a new one was placed. None of the HD patients with arterio-venous fistulae developed bacteremia. RB and BB were isolated in the biofilm of 11 out of 37 LPT. Thus, we modified the ROW delivery line in order to set up a scheduled chemical and physical disinfections of the ROW delivery line with the hemodialysis consoles connected avoiding the risk of new contamination of the LPT and loading pipes. Briefly, on alternate months the whole system that include ROW delivery line (PE-Xa Medical Device, Fresenius Medical Care), loading pipes, LPT and hemodialysis consoles are disinfected by hot water (90°C) produced by a water heater (AquaB plus HF, Fresenius Medical Care) and by chemical disinfectant, 5% peracetic acid according to the protocols made by the console fabricant. In addition, we added to the reverse osmosis system a filtration module of 0.01 μm (AquaUF, Fresenius Medical Care) prior to the ROW delivery line, Figure 1. Awaiting for the modification of the ROW delivery line, the patients with CVC were dialyzed using a portable water treatment unit. After more than 14 months from the modification of the whole system for production and delivery of ROW none of the hemodialyzed patients developed infection by RB and BB. Conclusion Our experience suggests that infection outbreak by unusual bacteria such as RB and BB could be successful treated using antibiotic therapy. Nevertheless, in dialysis unit the source of infection should be investigated in order to adopt the countermeasures necessary to reduce the risk of new infections.

#4452 ICODEXTRIN EFFICIENCY IN FLUID AND SODIUM REMOVAL REMAINS STABLE DURING LONG PERITONEAL DWELLS

Abstract Background and Aims Inadequate fluid and sodium removal has been shown to increase risk of overhydration and hypertension. In peritoneal dialysis, icodextrin-based solution provides sustained ultrafiltration, and therefore can be used for the long exchanges, especially in patients with fast solute transport rates in whom the effective ultrafiltration period is shortened. We investigated to which extent the efficiency of icodextrin in fluid and sodium removal is changing during 16-hour peritoneal dwells. Method Data on intraperitoneal volume, and concentrations of icodextrin and sodium in dialysate during 16 hours of peritoneal dwells with icodextrin-based solution were analysed in 11 clinically stable patients. Labeled serum albumin (RISA) was used as a volume marker and dialysate samples of 12 mL were collected at 8, 12, and 16 hours of peritoneal dwell. Residual volume was evaluated from marker dilution after 16 hours by rinsing peritoneal cavity with 2 L of fresh 1.36% glucose dialysis fluid. Ultrafiltration (UF) was calculated for each patient and each sampling time as the difference between drained and initially infused volume corrected for the sample volume. The total absorption of icodextrin-derived carbohydrates (AbsCHO) was calculated for each patient as the difference between initially infused and drained carbohydrates mass. The icodextrin ultrafiltration efficiency (UFE) was calculated for each sampling time as the ultrafiltration divided by the amount of icodextrin mass absorbed (AbsCHO). The efficiency of icodextrin in sodium removal (NaRE) was calculated for each sampling time as the sodium mass removed (difference between drained and initially infused sodium mass) divided by the corresponding icodextrin mass absorbed (AbsCHO). Correction for the residual volume and samples collections were applied for AbsCHO, UFE and NaRE calculations. Results After 16-hour dwell with icodextrin-based solution the ultrafiltration was positive in all except one patient, being on average (mean±SD) 669±369 mL. During the dwell, icodextrin was slowly absorbed from the peritoneal cavity, see Figure 1, left panel. At 16 hours, the mean cumulative CHO absorption (AbsCHO) reached 68.0±20.7 g (44±13% of initial CHO mass) while 56% of initial icodextrin mass infused still remained in dialysate, Figure 1, left panel. Icodextrin UF efficiency (UFE) calculated at 8, 12, and 16 hours remained stable (p = 0.6, ANOVA repeated measures) and was on average 9.9±5.8 mL/g, Figure 1, right panel. Moreover, icodextrin sodium removal efficiency (NaRE) also remained stable after 8 hours (p = 0.6, ANOVA repeated measures) and was on average 1.2±0.7 mmoL/g, Figure 1, right panel. Conclusion During 16 hours of peritoneal dialysis dwells with icodextrin-based solution, icodextrin was slowly absorbed with 56% of the osmotic agent remaining in the dialysate after 16 hours. The efficiency of icodextrin in terms of fluid (UFE) and sodium (NaRE) removal remained stable and did not subside from 8 to 16 hours of the dwell.

Pursuing the Real Vancomycin Clearance during Continuous Renal Replacement Therapy in Intensive Care Unit Patients: Is There Adequate Target Attainment?

Introduction: Vancomycin is used in intensive care unit (ICU) patients for the treatment of infections caused by gram-positive bacteria. The vancomycin pharmacokinetic/pharmacodynamic index is a ratio of the area under the concentration to the minimum inhibitory concentration ≥400–600 h*mg/L. This target can generally be achieved by a plasma concentration of 20–25 mg/L. Together with the pathophysiological alterations and pharmacokinetic variability associated with critical illness, the use of continuous renal replacement therapy (CRRT) may complicate the attainment of adequate vancomycin concentrations. The primary objective was the prevalence of attainment of vancomycin concentrations 20–25 mg/L after 24 h in adult ICU patients receiving CRRT. Secondary outcomes were to evaluate target attainment at days 2 and 3 and to calculate vancomycin clearance (CL) by CRRT and residual diuresis. Methods: We performed a prospective observational study in adult ICU patients on CRRT, which received at least 24 h continuous infusion of vancomycin. Between May 2020 and February 2021, daily vancomycin residual blood gas and dialysate samples were collected from 20 patients, every 6 h and if possible vancomycin urine samples. Vancomycin was analysed with an immunoassay method. The CL by CRRT was calculated by a different approach correcting for the downtime and providing insight into the degree of filter patency. Results: The proportion of patients with vancomycin concentrations <20 mg/L was 50% 24 h after starting vancomycin (n = 10). No differences were observed in patient characteristics. The target vancomycin concentration 20–25 mg/L was only achieved in 30% of the patients. On days 2 and 3, despite the use of TDM and albeit in lower percentages, sub- and supratherapeutic levels were still observed. Taking downtime and filter patency into account resulted in lower vancomycin CL. Conclusions: 50% of the studied ICU patients on CRRT showed subtherapeutic vancomycin concentrations 24 h after starting therapy. The results reveal that optimization of vancomycin dosage during CRRT therapy is needed.

TRLS-02. FEASIBILITY OF EVALUATING ABEMACICLIB NEUROPHARMACOKINETICS OF DIFFUSE MIDLINE GLIOMA USING INTRATUMORAL MICRODIALYSIS

Abstract BACKGROUND Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates &amp;lt;10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment response. METHODS This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are &amp;gt;10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. DISCUSSION The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. TRIAL REGISTRATION: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis; https://clinicaltrials.gov/ct2/show/NCT05413304?term=22c0003&amp;draw=2&amp;rank=1

Removal of Middle Molecules and Dialytic Albumin Loss: A Cross-over Study of Medium Cutoff and High-Flux Membranes with Hemodialysis and Hemodiafiltration.

Key Points HDF and MCO have shown greater clearance of middle-size uremic solutes in comparison with HF dialyzers; MCO has never been studied in HDF.MCO in HDF does not increase the clearance of B2M and results in a higher loss of albumin. Background Middle molecule removal and albumin loss have been studied in medium cutoff (MCO) membranes on hemodialysis (HD). It is unknown whether hemodiafiltration (HDF) with MCO membranes provides additional benefit. We aimed to compare the removal of small solutes and β2-microglobulin (B2M), albumin, and total proteins between MCO and high-flux (HFX) membranes with both HD and HDF, respectively. Methods The cross-over study comprised 4 weeks, one each with postdilutional HDF using HFX (HFX-HDF), MCO (MCO-HDF), HD with HFX (HFX-HD), and MCO (MCO-HD). MCO and HFX differ with respect to several characteristics, including membrane composition, pore size distribution, and surface area (HFX, 2.5 m2; MCO, 1.7 m2). There were two study treatments per week, one after the long interdialytic interval and another midweek. Reduction ratios of vitamin B12, B2M, phosphate, uric acid, and urea corrected for hemoconcentration were computed. Dialysis albumin and total protein loss during the treatment were quantified from dialysate samples. Results Twelve anuric patients were studied (six female patients; 44±19 years; dialysis vintage 35.2±28 months). The blood flow was 369±23 ml/min, dialysate flow was 495±61 ml/min, and ultrafiltration volume was 2.8±0.74 L. No significant differences were found regarding the removal of B2M, vitamin B12, and water-soluble solutes between dialytic modalities and dialyzers. Albumin and total protein loss were significantly higher in MCO groups than HFX groups when compared with the same modality. HDF groups had significantly higher albumin and total protein loss than HD groups when compared with the same dialyzer. MCO-HDF showed the highest protein loss among all groups. Conclusions MCO-HD is not superior to HFX-HD and HFX-HDF for both middle molecule and water-soluble solute removal. Protein loss was more pronounced with MCO when compared with HFX on both HD and HDF modalities. MCO-HDF has no additional benefits regarding better removal of B2M but resulted in greater protein loss than MCO-HD.

BIOPHARMACEUTICAL INVESTIGATION OF ANTIOXIDANT GEL

Introduction: With the recognized association between oxidative stress and skin diseases, incorporating antioxidants into treatment strategies has gained importance. However, dermatological dosage forms containing antioxidants are underrepresented on the pharmaceutical market. The search for delivery systems that ensure antioxidant stability and enhance antioxidant effects on the skin remains is quite relevant. Among the various dosage forms, gels have gained significant interest in recent times.&#x0D; The purpose of this study work is to conduct a comparative biopharmaceutical investigation of gels containing the synthetic antioxidant ethylmethylhydroxypyridine succinate (EMHPS) at different concentrations of the active ingredient.&#x0D; Materials and methods: The study utilized gel compositions containing EMHPS at concentrations ranging from 2.5% to 7.5%. Synthetic polymer compounds were employed as gelling agents, and the gels were prepared under laboratory conditions according to the technological scheme developed by the author. The obtained samples were assessed for thermal, colloidal, and mechanical stability. The release rate of EMHPS from the gels was determined by the dialysis method using a semipermeable membrane according to Kruchinsky. Dialysate samples were collected over a 5-hour period and analyzed spectrophotometrically at 297 nm. The data obtained were checked for normal distribution and statistically processed using Excel tables.&#x0D; Results: The studied gels exhibited thermal and colloidal stability, no delamination occurred under elevated temperature and centrifugation conditions. The gels and their bases demonstrated mechanical stability, with respective values ranging from 1 to 2. Analysis of the dialysis results revealed that the release of the active substance from all three gel samples commenced after 15 minutes, exhibited intensive increase within the first 60 minutes, and continued to gradually increase from 1 to 4 hours. Although the fraction of released active substance remained consistent across the three gels at each time interval, the absolute EMHPS amount in the dialysate depended on the drug concentration&#x0D; In conclusion, synthetic-based gels containing EMHPS can be successfully formulated, meeting the criteria of thermal, colloidal, and mechanical stability. These gels demonstrated the ability to release 47-49% of the active substance within the first 30 minutes, proportional to its concentration

Comparison of Intravenous Microdialysis and Standard Plasma Sampling for Monitoring of Vancomycin and Meropenem Plasma Concentrations-An Experimental Porcine Study.

Microdialysis is a catheter-based method suitable for dynamic sampling of unbound antibiotic concentrations. Intravenous antibiotic concentration sampling by microdialysis has several advantages and may be a superior alternative to standard plasma sampling. We aimed to compare concentrations obtained by continuous intravenous microdialysis sampling and by standard plasma sampling of both vancomycin and meropenem in a porcine model. Eight female pigs received 1 g of both vancomycin and meropenem, simultaneously over 100 and 10 min, respectively. Prior to drug infusion, an intravenous microdialysis catheter was placed in the subclavian vein. Microdialysates were collected for 8 h. From a central venous catheter, plasma samples were collected in the middle of every dialysate sampling interval. A higher area under the concentration/time curve and peak drug concentration were found in standard plasma samples compared to intravenous microdialysis samples, for both vancomycin and meropenem. Both vancomycin and meropenem concentrations obtained with intravenous microdialysis were generally lower than from standard plasma sampling. The differences in key pharmacokinetic parameters between the two sampling techniques underline the importance of further investigations to find the most suitable and reliable method for continuous intravenous antibiotic concentration sampling.

Effect of Different Dialysis Membranes on Protein Loss During Hemodialysis

Objective: To compare the loss of proteins with high and low flux hemodialysis membranes.&#x0D; Study Design: Cross-sectional analytical study.&#x0D; Place and Duration of Study: Department of Nephrology, Pak Emirates Military Hospital, Rawalpindi Pakistan, from Nov 2019 to Feb 2020.&#x0D; Methodology: This study was conducted on patients with end-stage renal disease on maintenance haemodialysis. We excluded patients on haemodialysis for less than one month, those with poor compliance to hemodialysis, those undergoing hemodialysis for less than four hours per session and unwilling patients. Patients were divided into two groups: one was dialyzed with high flux membranes, whereas low flux membranes were used for the other group. Dialysate samples were collected during the first hour and then during the last hour of each haemodialysis session to estimate protein losses in each group.&#x0D; Results: Data were recorded during 133 hemodialysis sessions, the patients underwent. There were 22 patients, including 12 (54.55%) males, having a mean age of 46.45±13.99 years. Most patients (17, 77.27%) were on twice-a-week dialysis, whereas the rest were dialyzed thrice weekly. Protein loss was 0.45± 0.23g/L with low flux membranes and 1.20±0.60g/L with high flux membranes. This difference was statistically significant (p= &lt;0.001).&#x0D; Conclusion: High flux dialysis membranes are associated with greater protein loss during hemodialysis.

Combined In Vivo Microdialysis and PET Studies to Validate [11C]Yohimbine Binding as a Marker of Noradrenaline Release.

The noradrenaline system attracts attention for its role in mood disorders and neurodegenerative diseases but the lack of well-validated methods impairs our understanding when assessing its function and release in vivo. This study combines simultaneous positron emission tomography (PET) and microdialysis to explore if [11C]yohimbine, a selective antagonist radioligand of the α2 adrenoceptors, may be used to assess in vivo changes in synaptic noradrenaline during acute pharmacological challenges. Anesthetised Göttingen minipigs were positioned in a head holder in a PET/CT device. Microdialysis probes were placed in the thalamus, striatum and cortex and dialysis samples were collected every 10 min. Three 90 min [11C]yohimbine scans were acquired: at baseline and at two timepoints after the administration of amphetamine (1-10 mg/kg), a non-specific releaser of dopamine and noradrenaline, or nisoxetine (1 mg/kg), a specific noradrenaline transporter inhibitor. [11C]yohimbine volumes of distribution (VT) were obtained using the Logan kinetic model. Both challenges induced a significant decrease in yohimbine VT, with time courses reflecting their different mechanisms of action. Dialysis samples revealed a significant increase in noradrenaline extracellular concentrations after challenge and an inverse correlation with changes in yohimbine VT. These data suggest that [11C]yohimbine can be used to evaluate acute variations in synaptic noradrenaline concentrations after pharmacological challenges.

Accelerated bacteriological examination of urine and dialysate in the diagnosis of urinary tract infections in children

Aim. To evaluate the feasibility of an accelerated method for determining the etiology of infections in urine, dialysate and residual antimicrobial activity by using laser light scattering technology.Materials and methods. From January to September 2019, 106 urine samples and 42 dialysate samples from children aged 1–16 with various urinary pathologies and those on peritoneal dialysis underwent culture-based examination on an ALIFAX HB&amp;L LIGHT analyzer (Alifax, Italy) using laser light scattering technology.Results. Three hours after inoculation, 81 samples (76.4%) appeared to be negative and 25 samples (23.6%) proved to be positive. No microorganisms were detected in 38 dialysate samples (90.5%), two samples had Staphylococcus aureus (104 CFU/ml), and one dialysate sample had Corynebacterium sp. and associations of Escherichia coli + Candida albicans + Staphylococcus haemolyticus, associated with peritoneal catheter colonization. Bacteriuria was caused by Enterobacterales in 39.3% (E. coli, Morganella morganii, Citrobacter amalonaticus, Enterobacter cloacae), non-fermenting gram-negative bacteria – in 14.3% (Pseudomonas aeruginosa, Ralstonia picketii, Oligella sp., Acinetobacter baumannii), Enterococcus sp. – 21.4%, S. haemolyticus, Staphylococcus epidermidis – 10.7%, Candida albicans – 3.6%, contamination: Streptococcus viridians, Corynebacterium sp. – 7.1%. Residual antimicrobial activity in urine was detected in 30.1% of patients.Conclusion. The laser light scattering technology enables a minimal concentration of microorganisms to be detected in a smaller amount of urine or dialysate, which is very important for accelerated diagnosis of urinary tract infections and complications of peritoneal dialysis in children.

Effect of haemodialysis on the pharmacokinetics and pharmacodynamics of evogliptin.

To investigate the possible effect of haemodialysis (HD) on the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of evogliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor. A single-dose, open-label, parallel-group study of eight end-stage renal disease (ESRD) patients and eight matched healthy subjects was conducted. ESRD patients received a single oral dose of evogliptin 5mg after and before HD with a 2-week washout between each dose, and healthy subjects received a single oral dose of evogliptin 5mg. Serial blood, dialysate, and urine samples were collected to assess the PK and PD profiles of evogliptin. To compare PK parameters before and after HD, geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were calculated. The GMRs for the maximum concentration and area under the concentration-time curve from time 0 to the last measurable timepoint (AUClast ) of evogliptin when administered before HD compared with after HD were 0.7293 (90% CI 0.6171-0.8620) and 0.9480 (90% CI 0.8162-1.1010), respectively. The maximum DPP-4 inhibitory effect, area under the DPP-4 inhibitory effect-time curve, and time duration of more than 80% DPP-4 inhibition were comparable when evogliptin was administered before and after HD. Compared with healthy subjects, the mean AUClast of evogliptin was approximately 1.4-fold greater in ESRD patients, but the difference is unlikely to affect the safety and efficacy of evogliptin. The effect of HD on the PK and PD characteristics of evogliptin was not clinically significant; therefore, dose adjustment according to HD status is not necessary.

Viloxazine Increases Cortical Serotonin Without Inhibiting Serotonin Reuptake at Doses Used to Treat ADHD

AbstractBackgroundMost FDA-approved ADHD treatments increase norepinephrine (NE) and dopamine (DA); however, our prior preclinical studies of the non-stimulant ADHD treatment viloxazine ER (Qelbree®) demonstrated that viloxazine also increases serotonin (5-HT). A prior microdialysis study showed increases in NE, DA, and 5-HT in the rat prefrontal cortex (PFC); however, the 50 mg/kg dose resulted in supratherapeutic plasma concentrations. Viloxazine is a moderate affinity selective NE reuptake inhibitor, structurally different than traditional SSRI antidepressants. Viloxazine has negligible activity at the serotonin reuptake transporter (SERT), suggesting viloxazine has a different mechanism of 5-HT PFC elevation than SSRIs. The current microdialysis study was undertaken to further characterize if viloxazine affects 5-HT and its 5-HIAA metabolite at therapeutically relevant plasma concentrations. Results are compared to similar microdialysis studies of SSRIs.MethodsRats were implanted with I-shaped microdialysis probes connected to a microperfusion pump, delivering artificial cerebrospinal fluid, in the PFC. After a 2-hour baseline period, viloxazine (1, 3, 10, or 30 mg/kg) was administered (ip). Dialysate samples were collected from the interstitial fluid (ISF) of the PFC before and after dosing. LC-MS/MS was used to determine the dialysate concentrations of viloxazine and viloxazine-induced changes in NE, 5-HT, and their respective metabolites, DHPG and 5-HIAA. Viloxazine plasma concentrations were also measured.Animal research was approved by the Institutional Animal Care and Use Committee and conducted in accordance with the National Research Council’s Guide for the Care and Use of Laboratory Animals.ResultsViloxazine administration resulted in significant dose-dependent increases in ISF NE levels and corresponding decreases in DHPG (NE metabolite) at all doses tested, reflecting viloxazine’s activity as a NET inhibitor. Viloxazine treatment also resulted in a dose-dependent elevation of ISF 5-HT levels in the PFC. Of the doses tested, 30 mg/kg was found to be clinically relevant as it induced ISF concentrations approximating unbound plasma concentrations in pediatric ADHD patients. At this dose, 5-HT levels were significantly increased over baseline and higher than vehicle levels. Coincident changes in 5-HIAA concentrations were not observed, reaffirming viloxazine’s lack of activity as a SERT inhibitor.ConclusionViloxazine induced dose-dependent increases in NE and 5-HT in the PFC, a critical target region for ADHD therapies. At clinically relevant viloxazine plasma concentrations, 5-HT was increased in the PFC. Unlike SSRIs, which correspondingly decrease the 5-HT metabolite in the PFC (indicating serotonin reuptake inhibition), viloxazine did not affect 5-HIAA levels. Thus, viloxazine increases cortical 5-HT levels by a different mechanism than SSRIs. Whether 5-HT effects aid in viloxazine therapeutic efficacy in ADHD is yet unknown.FundingSupernus Pharmaceuticals, Inc.