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Background: Augmented renal clearance (ARC) holds a risk of subtherapeutic drug concentrations. Knowledge of patient-, disease-, and therapy-related factors associated with ARC would allow predicting which patients would benefit from intensified dosing regimens. This study aimed to identify ARC predictors and to describe ARC time-course in critically ill children, using iohexol plasma clearance (CL iohexol ) to measure glomerular filtration rate (GFR)., Methods: This is a retrospective analysis of data from the "IOHEXOL" study which validated GFR estimating formulas (eGFR) against CL iohexol . Critically ill children with normal serum creatinine were included, and CL iohexol was performed as soon as possible after pediatric intensive care unit (PICU) admission (CL iohexol1 ) and repeated (CL iohexol2 ) after 48-72 h whenever possible. ARC was defined as CL iohexol exceeding normal GFR for age plus two standard deviations., Results: Eighty-five patients were included; 57% were postoperative patients. Median CL iohexol1 was 122 mL/min/1.73 m 2 (IQR 75-152). Forty patients (47%) expressed ARC on CL iohexol1 . Major surgery other than cardiac surgery and eGFR were found as independent predictors of ARC. An eGFR cut-off value of 99 mL/min/1.73 m 2 and 140 mL/min/1.73 m 2 was suggested to identify ARC in children under and above 2 years, respectively. ARC showed a tendency to persist on CL iohexol2 ., Conclusions: Our findings raise PICU clinician awareness about increased risk for ARC after major surgery and in patients with eGFR above age-specific thresholds. This knowledge enables identification of patients with an ARC risk profile who would potentially benefit from a dose increase at initiation of treatment to avoid underexposure., Trial Registration: ClinicalTrials.gov NCT05179564, registered retrospectively on January 5, 2022., (© 2023. The Author(s), under exclusive licence to International Pediatric Nephrology Association.)

Accurate renal function assessment is crucial to guide intensive care decision-making and drug dosing. Estimates of glomerular filtration rate (eGFR) are routinely used in critically ill children; however, these formulas were never evaluated against measured GFR (mGFR) in this population. We aimed to assess the reliability of common eGFR formulas compared to iohexol plasma clearance (CL iohexol ) in a pediatric intensive care (PICU) population. Secondary outcomes were the prevalence of acute kidney injury (AKI) (by pRIFLE criteria) and augmented renal clearance (ARC) (defined as standard GFR for age + 2 standard deviations (SD)) within 48 h after admission based on mGFR and eGFR by the revised Schwartz formula and the difference between these two methods to diagnose AKI and ARC. In children, between 0 and 15 years of age, without chronic renal disease, GFR was measured by CL iohexol and estimated using 26 formulas based on creatinine (Scr), cystatine C (CysC), and betatrace protein (BTP), early after PICU admission. eGFR and mGFR results were compared for the entire study population and in subgroups according to age, using Bland-Altman analysis with calculation of bias, precision, and accuracy expressed as percentage of eGFR results within 30% (P30) and 10% (P10) of mGFR. CL iohexol was measured in 98 patients. Mean CL iohexol (± SD) was 115 ± 54 ml/min/1.73m 2 . Most eGFR formulas showed overestimation of mGFR with large bias and poor precision reflected by wide limits of agreement (LoA). Bias was larger with CysC- and BTP-based formulas compared to Scr-based formulas. In the entire study population, none of the eGFR formulas showed the minimal desired P30 > 75%. The widely used revised Schwartz formula overestimated mGFR with a high percentage bias of - 18 ± 51% (95% confidence interval (CI) - 29; - 9), poor precision with 95% LoA from - 120 to 84% and insufficient accuracy reflected by P30 of only 51% (95% CI 41; 61), and P10 of 21% (95% CI 13; 66) in the overall population. Although performance of Scr-based formulas was worst in children below 1 month of age, exclusion of neonates and younger children did not result in improved agreement and accuracy. Based on mGFR, prevalence of AKI and ARC within 48 h was 17% and 45% of patients, respectively. There was poor agreement between revised Schwartz formula and mGFR to diagnose AKI (kappa value of 0.342, p < 0.001; sensitivity of 30%, 95% CI 5; 20%) and ARC (kappa value of 0.342, p < 0.001; sensitivity of 70%, 95% CI 33; 58)., Conclusion: In this proof-of-concept study, eGFR formulas were found to be largely inaccurate in the PICU population. Clinicians should therefore use these formulas with caution to guide drug dosing and therapeutic interventions in critically ill children. More research in subgroup populations is warranted to conclude on generalizability of these study findings., Clinicaltrials: gov NCT05179564, registered retrospectively on January 5, 2022., What Is Known: • Both acute kidney injury and augmented renal clearance may be present in PICU patients and warrant adaptation of therapy, including drug dosing. • Biomarker-based eGFR formulas are widely used for GFR assessment in critically ill children, although endogenous filtration biomarkers have important limitations in PICU patients and eGFR formulas have never been validated against measured GFR in this population., What Is New: • eGFR formulas were found to be largely inaccurate in the PICU population when compared to measured GFR by iohexol clearance. Clinicians should therefore use these formulas with caution to guide drug dosing and therapeutic interventions in critically ill children. • Iohexol plasma clearance could be considered an alternative for accurate GFR assessment in PICU patients., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: In critically ill children, severely altered pharmacokinetics may result in subtherapeutic β-lactam antibiotic concentrations when standard pediatric dosing regimens are applied. However, it remains unclear how to recognize patients most at risk for suboptimal exposure and their outcome. This study aimed to: 1) describe target attainment for β-lactam antibiotics in critically ill children, 2) identify risk factors for suboptimal exposure, and 3) study the association between target nonattainment and clinical outcome., Design: Post hoc analysis of the "Antibiotic Dosing in Pediatric Intensive Care" study (NCT02456974, 2012-2019). Steady-state trough plasma concentrations were classified as therapeutic if greater than or equal to the minimum inhibitory concentration of the (suspected) pathogen. Factors associated with subtherapeutic concentrations and clinical outcome were identified by logistic regression analysis., Setting: The pediatric and cardiac surgery ICU of a Belgian tertiary-care hospital., Patients: One hundred fifty-seven patients (aged 1 mo to 15 yr) treated intravenously with amoxicillin-clavulanic acid, piperacillin-tazobactam, or meropenem., Interventions: None., Measurements and Main Results: Three hundred eighty-two trough concentrations were obtained from 157 patients (median age, 1.25 yr; interquartile range, 0.4-4.2 yr). Subtherapeutic concentrations were measured in 39 of 60 (65%), 43 of 48 (90%), and 35 of 49 (71%) of patients treated with amoxicillin-clavulanic acid, piperacillin-tazobactam, and meropenem, respectively. Estimates of glomerular filtration rate (eGFR; 54% increase in odds for each sd increase in value, 95% CI, 0.287-0.736; p = 0.001) and the absence of vasopressor treatment (2.8-fold greater odds, 95% CI, 1.079-7.253; p = 0.034) were independently associated with target nonattainment. We failed to identify an association between antibiotic concentrations and clinical failure., Conclusions: Subtherapeutic β-lactam concentrations are common in critically ill children and correlate with renal function. eGFR equations may be helpful in identifying patients who may require higher dosing. Future studies should focus on the impact of subtherapeutic concentrations on clinical outcome., Competing Interests: Dr. Van Der Heggen received funding from Clinical Research Fund Ghent University Hospital, Belgium. Dr. De Cock received funding from a Clinical Research fund. The remaining authors have disclosed that they do not have any potential conflicts of interest., (Copyright © 2022 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies.)

Background Correct dosing and therapeutic drug monitoring (TDM) practices are essential when aiming for optimal vancomycin treatment. Objective To assess target attainment after initial dosing and dose adjustments, and to determine compliance to dosing and TDM guidelines. Setting Tertiary care university hospital in Belgium. Method A chart review was performed in 150 patients, ranging from preterm infants to adults, treated intravenously with vancomycin. Patient characteristics, dosing and TDM data were compared to evidence-based hospital guidelines. Main outcome measures Target attainment of vancomycin after initial dosing and dose adjustments. Results Subtherapeutic concentrations were measured in 68% of adults, in 76% of children and in 52% of neonates after treatment initiation. Multiple dose adaptations (median 2, Q1 1-Q3 2) were required for target attainment, whilst more than 20% of children and neonates never reached targeted concentrations. Regarding compliance to the hospital guideline, some points of improvement were identified: omitted dose adjustment in adults with decreased renal function (53%), delayed sampling (16% in adults, 31% in children) and redundant sampling (34% of all samples in adults, 12% in children, 13% in neonates). Conclusion Target attainment for vancomycin with current dosing regimens and TDM is poor in all age groups. Besides, human factors should not be ignored when aiming for optimal treatment. This study reflects an ongoing challenge in clinical practice and highlights the need for optimization of vancomycin dosing strategies and improvement of awareness of all health care professionals involved., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Many critically ill patients display a supraphysiological renal function with enhanced renal perfusion and glomerular hyperfiltration. This phenomenon described as augmented renal clearance (ARC) may result in enhanced drug elimination through renal excretion mechanisms. Augmented renal clearance seems to be triggered by systemic inflammation and therapeutic interventions in intensive care. There is growing evidence that ARC is not restricted to the adult intensive care population, but is also prevalent in critically ill children. Augmented renal clearance is often overlooked due to the lack of reliable methods to assess renal function in critically ill children. Standard equations to calculate glomerular filtration rate (GFR) are developed for patients who have a steady-state creatinine production and a stable renal function. Those formulas are not reliable in critically ill patients with acutely changing GFR and tend to underestimate true GFR in patients with ARC. Tools for real-time, continuous, and non-invasive measurement of fluctuating GFR are most needed to identify changes in kidney function during critical illness and therapeutic interventions. Such devices are currently being validated and hold a strong potential to become the standard of practice. In the meantime, urinary creatinine clearance is considered the most reliable method to detect ARC in critically ill patients. Augmented renal clearance is clearly associated with subtherapeutic antimicrobial concentrations and subsequent therapeutic failure. This warrants the need for adjusted dosing regimens to optimize pharmacokinetic and pharmacodynamic target attainment. This review aims to summarize current knowledge on ARC in critically ill children, to give insight into its possible pathophysiological mechanism, to evaluate screening methods for ARC in the pediatric intensive care population, and to illustrate the effect of ARC on drug exposure, therapeutic efficacy, and clinical outcome.

Background: Augmented renal clearance (ARC), an increase in kidney function with enhanced elimination of circulating solute, has been increasingly recognized in critically ill adults. In a pediatric intensive care setting, data are scarce. The primary objective of this study was to investigate the prevalence of ARC in critically ill children. Secondary objectives included a risk factor analysis for the development of ARC and a comparison of two methods for assessment of renal function., Methods: In 105 critically ill children between 1 month and 15 years of age, glomerular filtration rate (GFR) was measured by means of a daily 24-h creatinine clearance (24 h Cl Cr ) and compared to an estimated GFR using the revised Schwartz formula. Logistic regression analysis was used to identify risk factors for ARC., Results: Overall, 67% of patients expressed ARC and the proportion of ARC patients decreased during consecutive days. ARC patients had a median Cl Cr of 142.2 ml/min/1.73m 2 (IQR 47.1). Male gender and antibiotic treatment were independently associated with the occurrence of ARC. The revised Schwartz formula seems less appropriate for ARC detection., Conclusions: A large proportion of critically ill children develop ARC during their stay at the intensive care unit. Clinicians should be cautious when using Schwartz formula to detect ARC. Our findings require confirmation from large study cohorts and investigation of the relationship with clinical outcome.

Introduction: Arachnoid cysts are lesions present in 1% of the population and usually found in the temporal fossa. Clinical and radiologic presentations can differ greatly. Despite intensive research, it is still debatable which patients will benefit from surgery., Objective: This study aims to investigate the pretreatment parameters influencing the outcome after neuroendoscopic treatment of temporal arachnoid cysts., Materials and Methods: A retrospective analysis of 34 patients who underwent an endoscopic fenestration of a temporal arachnoid cyst between July 1991 and December 2013 was performed., Results: In symptomatic patients, there was a clinical improvement in 76.4% of cases. The best results were found in treating symptoms related to intracranial hypertension, acute neurologic defects, and macrocrania. Patients with temporal lobe epilepsy improved after cyst fenestration in 33.3% of cases. Behavioral problems and psychomotor retardation remained largely unchanged. Patients with a complex neurologic presentation, often from a congenital syndrome and combined with an intellectual disability, had the least benefit from endoscopic surgery. Radiologic follow-up showed a cyst volume decrease in 91.2% of cases. Complications were present in 29.4%, but were mostly minor and transient., Conclusion: This study demonstrates that patients with symptoms related to intracranial hypertension, acute neurologic deficits, and macrocrania have the best postoperative outcome. Also, patients with ipsilateral temporal lobe epilepsy seem to be good candidates for endoscopic arachnoid cyst fenestrations. In complex neurologic disorders without one of the previously mentioned symptoms, endoscopy remains less successful., (Copyright © 2015 Elsevier Inc. All rights reserved.)