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Abstract Background Critically ill patients, particularly those treated with extracorporeal devices or at extremes of weight, experience pharmacokinetic variability which can compromise beta-lactam (BL) antibiotic target attainment and treatment response. Therapeutic drug monitoring (TDM) for BL antibiotics can improve precision pharmacotherapy but has had limited implementation. The objective of this study was to evaluate the frequency of BL target attainment among adult intensive care unit (ICU) patients who underwent TDM. Methods This observational study evaluated adults treated with cefepime, piperacillin/tazobactam or meropenem in ICUs at the Mayo Clinic in Rochester, Minnesota who underwent TDM from June-September 2022. During the study timeframe, multidisciplinary teams were encouraged to perform BL TDM on patients requiring extracorporeal membrane oxygenation, continuous kidney replacement therapy, or at an extreme of body weight (weight < 40 kg or >120 kg or BMI < 18 kg/m2 or > 40 kg/m2). Percentage of patients with initial serum trough concentrations within the therapeutic range was calculated (Table 1). Results During the study timeframe, 59 trough concentrations were performed on critically ill patients, of which 5 were excluded due to uninterpretable results. Of the remaining 54 BL trough concentrations analyzed, 49 (91%) were initial troughs during the antibiotic course, and 5 (9%) were repeat troughs. Thirty-six (73%) of the initial trough concentrations were within the therapeutic range. Among the trough concentrations outside the therapeutic range, 10 (77%) were too high, and 3 (23%) were too low (Table 2). Dose adjustment occurred in 19 (39%) of initial trough evaluations, including 6 which were adjusted despite a level within the therapeutic range. All of the repeat trough concentrations drawn during the same antibiotic course were within the therapeutic range (n = 5/5; 100%). Conclusion One-fourth of initial BL trough concentrations were outside of the therapeutic range. BL levels outside the therapeutic range prompted dose adjustment to improve the potential for effectiveness or limit the potential for toxicity. BL TDM appears to be a promising strategy to enhance precision pharmacotherapy in the critically ill. Disclosures Sara Ausman, PharmD, Gilead: Honoraria Christina G. Rivera (O'Connor), Pharm.D, Gilead Sciences: Advisor/Consultant|Gilead Sciences: Board Member|Gilead Sciences: Grant/Research Support|Gilead Sciences: Honoraria

Key Points Using multiple markers may improve GFR estimation especially in settings where creatinine and cystatin C are known to be limited. Panel eGFR is a novel multimarker eGFR equation consisting of age, sex, cystatin C, and nuclear magnetic resonance–measured creatinine, valine, and myo-inositol. eGFR-Cr and eGFR-Cr-CysC may underestimate measured GFR, while panel eGFR was unbiased among younger Black male individuals. Background Using multiple markers may improve accuracy in GFR estimation. We sought to externally validate and compare the performance of a novel multimarker eGFR (panel eGFR) equation among Black and White persons using the Genetic Epidemiology Network of Arteriopathy cohort. Methods We included 224 sex, race/ethnicity, and measured GFR (mGFR) category–matched persons, with GFR measured using urinary clearance of iothalamate. We calculated panel eGFR using serum creatinine, valine, myo-inositol, cystatin C, age, and sex. We compared its reliability with current eGFR equations (2021 CKD Epidemiology Collaboration creatinine [eGFR-Cr] and creatinine with cystatin C [eGFR-Cr-CysC]) using median bias, precision, and accuracy metrics. We evaluated each equation's performance in age, sex, and race subgroups. Results In the overall cohort, 49% were Black individuals, and mean mGFR was 79 ml/min per 1.73 m 2 . Panel eGFR overestimated mGFR (bias: −2.4 ml/min per 1.73 m 2 ; 95% confidence interval [CI], −4.4 to −0.7), eGFR-Cr-CysC underestimated mGFR (bias: 4.8 ml/min per 1.73 m 2 ; 95% CI, 2.1 to 6.7), while eGFR-Cr was unbiased (bias: 2.0 ml/min per 1.73 m 2 ; 95% CI, −1.1 to 4.6). All equations had comparable accuracy. Among Black male individuals younger than 65 years, both eGFR-Cr (bias: 17.0 ml/min per 1.73 m 2 ; 95% CI, 8.6 to 23.5) and eGFR-Cr-CysC (bias: 14.5 ml/min per 1.73 m 2 ; 95% CI, 6.0 to 19.7) underestimated mGFR, whereas panel eGFR was unbiased (bias: 1.7 ml/min per 1.73 m 2 ; 95% CI, −3.4 to 10.0). Metrics of accuracy for all eGFRs were acceptable in all subgroups except for panel eGFR in Black female individuals younger than 65 years (P30: 73.3%). Conclusions Panel eGFR can be used to estimate mGFR and may have utility among Black male individuals younger than 65 years where current CKD Epidemiology Collaboration equations are biased.

As the population in many industrial countries is aging, the risk, incidence, and prevalence of CKD increases. In the kidney, advancing age results in a progressive decrease in nephron number and an increase in glomerulosclerosis. In this review, we focus on the effect of aging on glomerular podocytes, the post-mitotic epithelial cells critical for the normal integrity and function of the glomerular filtration barrier. The podocytes undergo senescence and transition to a senescence-associated secretory phenotype typified by the production and secretion of inflammatory cytokines that can influence neighboring glomerular cells by paracrine signaling. In addition to senescence, the aging podocyte phenotype is characterized by ultrastructural and functional changes; hypertrophy; cellular, oxidative, and endoplasmic reticulum stress; reduced autophagy; and increased expression of aging genes. This results in a reduced podocyte health span and a shortened life span. Importantly, these changes in the pathways/processes characteristic of healthy podocyte aging are also often similar to pathways in the disease-induced injured podocyte. Finally, the better understanding of podocyte aging and senescence opens therapeutic options to slow the rate of podocyte aging and promote kidney health.

AbstractStudy ObjectiveTo develop and validate a model for predicting acute kidney injury (AKI) after high‐dose methotrexate (HDMTX) exposure.DesignRetrospective analysis.SettingMultisite integrated health system throughout Minnesota and Wisconsin.PatientsAdult patients with lymphoma who received HDMTX as a 4‐h infusion.Measurements and Main ResultsLASSO methodology was used to identify factors available at the outset of therapy that predicted incident AKI within 7 days following HDMTX. The model was then validated in an independent cohort. The incidence of AKI within 7 days following HDMTX was 21.6% (95% confidence interval (CI) 18.4%‐24.8%) in the derivation cohort (435 unique patients who received a total of 1642 doses of HDMTX) and 15.6% (95% CI 5.3%‐24.8%) in the validation cohort (55 unique patients who received a total of 247 doses of HDMTX). Factors significantly associated with AKI after HDMTX in the multivariable model included age ≥ 55 years, male sex, and lower HDMTX dose number. Other factors that were not found to be significantly associated with AKI on multivariable analysis, but were included in the final model, were body surface area, Charlson Comorbidity Index, and estimated glomerular filtration rate. The c‐statistic of the model was 0.72 (95% CI 0.69‐0.75) in the derivation cohort and 0.72 (95% CI 0.60‐0.84) in the validation cohort.ConclusionThis model utilizing identified sociodemographic and clinical factors is predictive of AKI following HDMTX administration in adult patients with lymphoma.

ABSTRACT Cefepime exhibits highly variable pharmacokinetics in critically ill patients. The purpose of this study was to develop and qualify a population pharmacokinetic model for use in the critically ill and investigate the impact of various estimated glomerular filtration rate (eGFR) equations using creatinine, cystatin C, or both on model parameters. This was a prospective study of critically ill adults hospitalized at an academic medical center treated with intravenous cefepime. Individuals with acute kidney injury or on kidney replacement therapy or extracorporeal membrane oxygenation were excluded. A nonlinear mixed-effects population pharmacokinetic model was developed using data collected from 2018 to 2022. The 120 included individuals contributed 379 serum samples for analysis. A two-compartment pharmacokinetic model with first-order elimination best described the data. The population mean parameters (standard error) in the final model were 7.84 (0.24) L/h for CL1 and 15.6 (1.45) L for V1. Q was fixed at 7.09 L/h and V2 was fixed at 10.6 L, due to low observed interindividual variation in these parameters. The final model included weight as a covariate for volume of distribution and the eGFR cr-cysC (mL/min) as a predictor of drug clearance. In summary, a population pharmacokinetic model for cefepime was created for critically ill adults. The study demonstrated the importance of cystatin C to prediction of cefepime clearance. Cefepime dosing models which use an eGFR equation inclusive of cystatin C are likely to exhibit improved accuracy and precision compared to dosing models which incorporate an eGFR equation with only creatinine.

Significance Statement Segmentation of multiple structures in cross-sectional imaging is time-consuming and impractical to perform manually, especially if the end goal is clinical implementation. In this study, we developed, validated, and demonstrated the capability of a deep learning algorithm to segment individual medullary pyramids in a rapid, accurate, and reproducible manner. The results demonstrate that cortex volume, medullary volume, number of pyramids, and mean pyramid volume is associated with patient clinical characteristics and microstructural findings and provide insights into the mechanisms that may lead to CKD. Background The kidney is a lobulated organ, but little is known regarding the clinical importance of the number and size of individual kidney lobes. Methods After applying a previously validated algorithm to segment the cortex and medulla, a deep-learning algorithm was developed and validated to segment and count individual medullary pyramids on contrast-enhanced computed tomography images of living kidney donors before donation. The association of cortex volume, medullary volume, number of pyramids, and mean pyramid volume with concurrent clinical characteristics (kidney function and CKD risk factors), kidney biopsy morphology (nephron number, glomerular volume, and nephrosclerosis), and short- and long-term GFR <60 or <45 ml/min per 1.73 m 2 was assessed. Results Among 2876 living kidney donors, 1132 had short-term follow-up at a median of 3.8 months and 638 had long-term follow-up at a median of 10.0 years. Larger cortex volume was associated with younger age, male sex, larger body size, higher GFR, albuminuria, more nephrons, larger glomeruli, less nephrosclerosis, and lower risk of low GFR at follow-up. Larger pyramids were associated with older age, female sex, larger body size, higher GFR, more nephrons, larger glomerular volume, more nephrosclerosis, and higher risk of low GFR at follow-up. More pyramids were associated with younger age, male sex, greater height, no hypertension, higher GFR, lower uric acid, more nephrons, less nephrosclerosis, and a lower risk of low GFR at follow-up. Conclusions Cortex volume and medullary pyramid volume and count reflect underlying variation in nephron number and nephron size as well as merging of pyramids because of age-related nephrosclerosis, with loss of detectable cortical columns separating pyramids.

Significance Statement Glomerular size differs by cortex depth. Larger nephrons are prognostic of progressive kidney disease, but it is unknown whether this risk differs by cortex depth or by glomeruli versus proximal or distal tubule size. We studied the average minor axis diameter in oval proximal and distal tubules separately and by cortex depth in patients who had radical nephrectomy to remove a tumor from 2019 to 2020. In adjusted analyses, larger glomerular volume in the middle and deep cortex predicted progressive kidney disease. Wider proximal tubular diameter did not predict progressive kidney disease independent of glomerular volume. Wider distal tubular diameter showed a gradient of strength of prediction of progressive kidney disease in the more superficial cortex than in the deep cortex. Background Larger nephrons are prognostic of progressive kidney disease, but whether this risk differs by nephron segments or by depth in the cortex is unclear. Methods We studied patients who underwent radical nephrectomy for a tumor between 2000 and 2019. Large wedge kidney sections were scanned into digital images. We estimated the diameters of proximal and distal tubules by the minor axis of oval tubular profiles and estimated glomerular volume with the Weibel–Gomez stereological model. Analyses were performed separately in the superficial, middle, and deep cortex. Cox proportional hazard models assessed the risk of progressive CKD (dialysis, kidney transplantation, sustained eGFR <10 ml/min per 1.73 m 2 , or a sustained 40% decline from the postnephrectomy baseline eGFR) with glomerular volume or tubule diameters. At each cortical depth, models were unadjusted, adjusted for glomerular volume or tubular diameter, and further adjusted for clinical characteristics (age, sex, body mass index, hypertension, diabetes, postnephrectomy baseline eGFR, and proteinuria). Results Among 1367 patients were 62 progressive CKD events during a median follow-up of 4.5 years. Glomerular volume predicted CKD outcomes at all depths, but only in the middle and deep cortex after adjusted analyses. Proximal tubular diameter also predicted progressive CKD at any depth but not after adjusted analyses. Distal tubular diameter showed a gradient of more strongly predicting progressive CKD in the superficial than deep cortex, even in adjusted analysis. Conclusions Larger glomeruli are independent predictors of progressive CKD in the deeper cortex, whereas in the superficial cortex, wider distal tubular diameters are an independent predictor of progressive CKD.

Abstract Background and Aims The use of multiple markers may improve the accuracy in glomerular filtration rate (GFR) estimation especially when the interpretation of creatinine and cystatin C is limited. We sought to externally validate a recently developed multi-marker nuclear magnetic resonance (NMR)-based estimated GFR equation (eGFR-NMR) using the biracial Genetic Epidemiology Network of Arteriopathy cohort. Method We included 224 sex, race/ethnicity, and mGFR-category-matched participants. GFR was measured using urinary clearance of iothalamate (mGFR). We calculated eGFR-NMR using serum creatinine, valine, myo-inositol, and cystatin C, age, and sex. We compared the reliability of eGFR-NMR with current eGFR equations (2021 Chronic Kidney Disease Epidemiology Collaboration equations for creatinine [eGFR-Cr] and creatinine with cystatin C [eGFR-Cr-CysC]) using median bias, precision, and accuracy metrics. In particular, we evaluated its performance in age, sex, and race subgroups. Results In the overall cohort, mean age was 63 (±8) years, 54% were females, 49% were Black individuals, and mean mGFR was 78.7 (±24.3) ml/min/1.73 m2. eGFR-NMR overestimated mGFR by 2 mL/min/1.73 m2 (95% CI, 4 to 0.7) while eGFR-Cr-CysC underestimated mGFR by −5 mL/min/1.73 m2 (95% CI, −2 to −7). All equations had acceptable accuracy metrics. When stratified by age, sex, and race, eGFR-NMR performed the best among Black males age &lt;65 years compared to current equations (Figure 1). In this subgroup, eGFR-NMR was unbiased (bias, 2mL/min/1.73 m2 [95% CI, -3 to 10]) compared to substantial biases of eGFR-Cr (bias, 17 mL/min/1.73 m2 [95% CI, 9 to 24]) and eGFR-Cr-CysC (bias, 15 mL/min/1.73 m2 [95% CI, 6 to 20]). In other subgroups, measures of accuracy for eGFR-NMR, eGFR-Cr, eGFR-Cr-CysC were generally similar. Conclusion eGFR-NMR can be used to estimate mGFR and was more accurate than CKD-EPI equations among Black males age &lt;65 years.

Abstract Background and Aims At least 30% of acute kidney injury (AKI) survivors lack appropriate follow up after hospital discharge. AKI survivors have highly dynamic posthospital course which warrants close monitoring to prevent adverse outcomes. Digital health solutions like remote patient monitoring (RPM) could be used to improve quality and efficiency of AKI survivor care. The purpose for this study was to assess the feasibility and effectiveness of the Mayo Clinic AKI RPM program, launched in October 2021. Method The Mayo Clinic AKI RPM program enrolled individuals who experienced AKI during a hospitalization and underwent nephrology consultation (Figure 1). Feasibility was assessed as the proportion of individuals approached for AKI RPM enrollment during the first year of the program who submitted at least one set of vital signs after discharge. An effectiveness analysis compared stage 3 AKI survivors enrolled in AKI RPM with at least 30-days of follow-up to matched historical controls (3:1) sampled from before RPM was available (2018-2021). The primary endpoint was hospital readmission or emergency department (ED) visit within 30-days, assessed with the Chi-square test. Secondarily we explored time to first readmission or ED visit with a Kaplan-Meier survival curve with a non-parametric comparison between groups, as well as readmission length of stay with the Wilcoxon Rank Sum test due to right skewed data distribution. Results Of the 50 individuals approached for AKI RPM participation, 45 (90%) submitted at least one set of vitals. Among AKI RPM patients, 34 patients with stage 3 AKI were matched to 102 controls based on baseline characteristics and demographics. Dialysis during hospitalization (liberated by discharge) was used in 36 (27%) of patients. Sixty (44%) individuals required ICU level of care. Median (IQR) discharge estimated glomerular filtration rate was 15 (11, 27) mL/min/1.73m2. Through matching, groups were well balanced with respect to pertinent baseline demographics. Hospital readmission or ED visit occurred in 17 (50%) of AKI RPM patients within 30-days compared to 39 (38%) of controls within 30-days (P = .23). The endpoint appeared driven by ED visits within 30-days, not readmissions [At least one ED visit: 13 (38%) vs 21 (21%), respectively (P = .04); At least one hospital readmission: 7 (21%) vs 26 (26%), respectively (P = .56)]. Time to first readmission or ED visit within 30-days was similar between groups (P = .35; Figure 2). Among the 33 patients who were readmitted to the hospital within 30-days, readmission length of stay was similar in the AKI RPM group compared to controls [Median (IQR) 76 (10.6, 121) hours vs 108 (70, 165) hours); P = 0.33]. Conclusion In conclusion, AKI RPM was a feasible program when used to bridge the care continuum (hospital to home) in non-dialysis dependent AKI survivors. Incidence of at least one hospital readmission or ED visit within 30-days was statistically similar between AKI RPM patients and controls. More AKI RPM patients experienced ED encounters in the 30-days after discharge, but frequency of hospital readmission was similar. Digital health solutions such as RPM offer a unique opportunity to address the important gap in AKI care after discharging from the hospital. Additional research is needed to explore the impact of AKI RPM on patient outcomes.