Impact of enantiomer-specific changes in pharmacokinetics between infants and adults on the target concentration of racemic ketorolac: A pooled analysis

Aims

Ketorolac is a nonsteroidal anti‐inflammatory racemic drug with analgesic effects only attributed to its S‐enantiomer. The aim of this study is to quantify enantiomer‐specific maturational pharmacokinetics (PK) of ketorolac and investigate if the contribution of both enantiomers to the total ketorolac concentration remains equal between infants and adults or if a change in target racemic concentration should be considered when applied to infants.

Methods

Data were pooled from 5 different studies in adults, children and infants, with 1020 plasma concentrations following single intravenous ketorolac administration. An allometry‐based enantiomer‐specific population PK model was developed with NONMEM 7.3. Simulations were performed in typical adults and infants to investigate differences in S‐ and R‐ketorolac exposure.

Results

S‐ and R‐ketorolac PK were best described with a 3‐ and a 2‐compartment model, respectively. The allometry‐based PK parameters accounted for changes between populations. No maturation function of ketorolac clearance could be identified. All model parameters were estimated with adequate precision (relative standard error <50%). Single dose simulations showed that a previously established analgesic concentration at half maximal effect in adults of 0.37 mg/L, had a mean S‐ketorolac concentration of 0.057 mg/L, but a mean S‐ketorolac concentration of 0.046 mg/L in infants. To match the effective adult S‐ketorolac‐concentration (0.057 mg/L) in typical infants, the EC_50‐racemic should be increased to 0.41 mg/L.

Conclusion

Enantiomer‐specific changes in ketorolac PK yield different concentrations and S‐ and R‐ketorolac ratios between infants and adults at identical racemic concentrations. These PK findings should be considered when studies on maturational pharmacodynamics are considered.

A Physiology-Based Pharmacokinetic Framework to Support Drug Development and Dose Precision During Therapeutic Hypothermia in Neonates

Therapeutic hypothermia (TH) is standard treatment for neonates (≥36 weeks) with perinatal asphyxia (PA) and hypoxic-ischemic encephalopathy. TH reduces mortality and neurodevelopmental disability due to reduced metabolic rate and decreased neuronal apoptosis. Since both hypothermia and PA influence physiology, they are expected to alter pharmacokinetics (PK). Tools for personalized dosing in this setting are lacking. A neonatal hypothermia physiology-based PK (PBPK) framework would enable precision dosing in the clinic. In this literature review, the stepwise approach, benefits and challenges to develop such a PBPK framework are covered. It hereby contributes to explore the impact of non-maturational PK covariates. First, the current evidence as well as knowledge gaps on the impact of PA and TH on drug absorption, distribution, metabolism and excretion in neonates is summarized. While reduced renal drug elimination is well-documented in neonates with PA undergoing hypothermia, knowledge of the impact on drug metabolism is limited. Second, a multidisciplinary approach to develop a neonatal hypothermia PBPK framework is presented. Insights on the effect of hypothermia on hepatic drug elimination can partly be generated from in vitro (human/animal) profiling of hepatic drug metabolizing enzymes and transporters. Also, endogenous biomarkers may be evaluated as surrogate for metabolic activity. To distinguish the impact of PA versus hypothermia on drug metabolism, in vivo neonatal animal data are needed. The conventional pig is a well-established model for PA and the neonatal Göttingen minipig should be further explored for PA under hypothermia conditions, as it is the most commonly used pig strain in nonclinical drug development. Finally, a strategy is proposed for establishing and fine-tuning compound-specific PBPK models for this application. Besides improvement of clinical exposure predictions of drugs used during hypothermia, the developed PBPK models can be applied in drug development. Add-on pharmacotherapies to further improve outcome in neonates undergoing hypothermia are under investigation, all in need for dosing guidance. Furthermore, the hypothermia PBPK framework can be used to develop temperature-driven PBPK models for other populations or indications. The applicability of the proposed workflow and the challenges in the development of the PBPK framework are illustrated for midazolam as model drug.

Monitoring of Brain Hemodynamics Coupling in Neonates using Updated Tensor Decompositions

In this paper we explore the use of updated tensor decompositions for the monitoring of brain hemodynamics in neonates. For this study, we used concomitant measurements of heart rate, mean arterial blood pressure, arterial oxygen saturation, EEG, and brain oxygenation - measured using near-infrared spectroscopy. These measurements were obtained from 22 neonates undergoing an INSURE procedure (INtubation, SURfactant and Extubation) and sedation using propofol. To develop the monitoring framework using tensors, we used radial basis kernel function (RBF) to construct a similarity matrix for consecutive segments of the signals. These matrices were concatenated forming a tensor. Updating canonical polyadic decomposition was used to evaluate the impact of propofol in the coupling between the different signals. Results indicate, as previously reported, a drop in the interaction between signals due to propofol administration. This shows that tensor decompositions can be useful in order to monitor the coupling between different physiological signals.

Nonlinear Transfer Entropy to Assess the Neurovascular Coupling in Premature Neonates

In the adult brain, it is well known that increases in local neural activity trigger changes in regional blood flow and, thus, changes in cerebral energy metabolism. This regulation mechanism is called neurovascular coupling (NVC). It is not yet clear to what extent this mechanism is present in the premature brain. In this study, we explore the use of transfer entropy (TE) in order to compute the nonlinear coupling between changes in brain function, assessed by means of EEG, and changes in brain oxygenation, assessed by means of near-infrared spectroscopy (NIRS). In a previous study, we measured the coupling between both variables using a linear model to compute TE. The results indicated that changes in brain oxygenation were likely to precede changes in EEG activity. However, using a nonlinear and nonparametric approach to compute TE, the results indicate an opposite directionality of this coupling. The source of the different results provided by the linear and nonlinear TE is unclear and needs further research. In this study, we present the results from a cohort of 21 premature neonates. Results indicate that TE values computed using the nonlinear approach are able to discriminate between neonates with brain abnormalities and healthy neonates, indicating a less functional NVC in neonates with brain abnormalities.

3 Dietary caloric normalization or restriction as preconception care strategies: Impact on metabolic health and fertility in high fat-induced obese outbred mice

Maternal metabolic disorders such as obesity and metabolic syndrome are linked to decreased oocyte and embryo quality and thus reproductive failure. Overweight and obese patients are advised to lose weight before conception to increase the chance of a healthy pregnancy. Human studies show conflicting results and are often underpowered, leading to a lack of scientifically substantiated advice. Furthermore, the effects of significant weight loss, due to caloric restriction, on oocyte quality are not known. Therefore, we aimed to feed a normal control or low-calorie diet as a preconception care strategy in high-fat-fed obese Swiss mice to improve their metabolic health and oocyte quality. Five-week-old female outbred Swiss mice (as a model for human physiology) were fed a control (CTRL; 10% fat) or a high-fat (HF; 60% fat) diet for seven weeks. Afterward, HF mice were switched to different preconception care interventions (PCCI) for six weeks, resulting in four treatment groups: (1) control diet for 13 weeks (CTRL_CTRL), (2) high fat diet for 13 weeks (HF_HF), (3) switch from a HF to an ad libitum CTRL diet (HF_CTRL), and (4) switch to a 30% caloric restriction diet (HF_CR). Change in bodyweight (twice a week, n=156 mice), metabolic health (glucose and insulin tolerance tests; n=32 mice), oocyte quality and pregnancy rates (n=32 mice) were studied. To assess oocyte quality, mature oocytes were collected after hormonal stimulation (10IU equine chorionic gonadotrophin followed by 10IU human chorionic gonadotrophin 48h later, IP injected) to evaluate oocyte lipid content (Bodipy staining; 11-12 oocytes/group) and to examine mitochondrial ultrastructure by transmission electron microscopy (4-5 oocytes/group). All data were analysed using analysis of variance and Bonferroni corrected. In comparison with the CTRL group, HF diet increased bodyweight after seven weeks (40.01±0.54g vs. 32.01±0.47 g; P&lt;0.05). After 2 weeks of PCCI, both HF_CTRL and HF_CR mice had lost weight, reaching similar weights as control mice. Overall, the deteriorated glucose tolerance and insulin sensitivity in the HF_HF group were normalized to levels similar to the CTRL_CTRL group in both PCCI. Transmission electron microscopy of HF_HF oocytes showed higher proportions of mitochondrial ultrastructural abnormalities, e.g. low electron density and rose petal appearance (Boudoures et al. 2016 Reproduction 151(3):261-270) compared with CTRL_CTRL (54.70% vs. 30.52%; P&lt;0.05). After six weeks of PCCI, the proportions of mitochondrial abnormalities were partially reduced in both HF_CTRL (39.64%) and HF_CR (44.47%) groups. The HF_HF diet increased the intracellular lipid content in oocytes with 84.41% compared with the CTRL_CTRL group (P&lt;0.05). However, both PCCI strategies failed to alleviate this effect. The HF_HF-fed mice displayed lower pregnancy rates compared with those on the CTRL_CTRL diet (12.5% vs. 100%; P&lt;0.05). Pregnancy rates were completely restored in the HF_CTRL and HF_CR group. In conclusion, both PCCI improved metabolic health (reduced weight, restored glucose tolerance and insulin sensitivity), partially improved oocyte quality, and restored pregnancy rates in HF-induced obese mice.

Renal Precision Medicine in Neonates and Acute Kidney Injury: How to Convert a Cloud of Creatinine Observations to Support Clinical Decisions

Renal precision medicine in neonates is useful to support decision making on pharmacotherapy, signal detection of adverse (drug) events, and individual prediction of short- and long-term prognosis. To estimate kidney function or glomerular filtration rate (GFR), the most commonly measured and readily accessible biomarker is serum creatinine (S_cr). However, there is extensive variability in S_cr observations and GFR estimates within the neonatal population, because of developmental physiology and superimposed pathology. Furthermore, assay related differences still matter for S_cr, but also exist for Cystatin C. Observations in extreme low birth weight (ELBW) and term asphyxiated neonates will illustrate how renal precision medicine contributes to neonatal precision medicine. When the Kidney Disease Improving Global Outcome (KDIGO) definition of acute kidney injury (AKI) is used, this results in an incidence up to 50% in ELBW neonates, associated with increased mortality and morbidity. However, urine output criteria needed adaptations to broader time intervals or weight trends, while S_cr and its trends do not provide sufficient detail on kidney function between ELBW neonates. Instead, we suggest to use assay-specific centile S_cr values to better describe postnatal trends and have illustrated its relevance by quantifying an adverse drug event (ibuprofen) and by explaining individual amikacin clearance. Term asphyxiated neonates also commonly display AKI. While oliguria is a specific AKI indicator, the majority of term asphyxiated cases are non-oliguric. Asphyxia results in a clinical significant-commonly transient-mean GFR decrease (-50%) with a lower renal drug elimination. But there is still major (unexplained) inter-individual variability in GFR and subsequent renal drug elimination between these asphyxiated neonates. Recently, the Baby-NINJA (nephrotoxic injury negated by just-in-time action) study provided evidence on the concept that a focus on nephrotoxic injury negation has a significant impact on AKI incidence and severity. It is hereby important to realize that follow-up should not be discontinued at discharge, as there are concerns about long-term renal outcome. These illustrations suggest that integration of renal (patho)physiology into neonatal precision medicine are an important tool to improve contemporary neonatal care, not only for the short-term but also with a positive health impact throughout life.

Creatinine at Birth Correlates with Gestational Age and Birth Weight: Another Factor of the Imbroglio in Early Neonatal Life

BACKGROUND

Serum creatinine (Scr) in early neonatal life (first week of life) displays extensive variability; hence, a better understanding is needed to use Scr as a diagnostic biomarker for acute kidney injury (AKI).

OBJECTIVE

The objective of this study was to explore Scr trends and its covariates in early neonatal life.

METHODS

Analysis of a rich, pooled Scr dataset (enzymatic assay) of 4,509 Scr observations in 1,181 neonates in the first week of life with birth weight, gestational age (GA), and postnatal age as covariates was conducted. Descriptive data were summarized as median and range. The Spearman rank correlation test was used to examine Scr, while the Mann-Whitney U test was used to determine the differences between the different GA (≤32, 33-36, or ≥37 weeks) categories.

RESULTS

The median Scr at delivery was 55.7 (range 28.3-194.5) µmol/L, correlating with birth weight (r = 0.088) or GA (r = 0.183) for the full dataset. At birth, the median Scr was highest in term (≥37-week) neonates. In early neonatal life (median Scr values), there was a gradual increase to attain a peak Scr by day 2-3, highest and most delayed in neonates ≤32 weeks GA. This is followed by a blunted decrease when ≤32-week neonates were compared to those of 33-36 or ≥37 weeks GA.

CONCLUSIONS

The Scr pattern in early neonatal life is complex, with the highest Scr at birth in full-term neonates, while those ≤32 weeks GA displayed the highest and delayed peak Scr with a subsequent blunted decrease. Knowledge of these patterns is crucial to explore the utility of Scr as an AKI biomarker.

EAU-ESMO consensus statements on the management of advanced and variant bladder cancer-an international collaborative multi-stakeholder effort: under the auspices of the EAU and ESMO Guidelines Committees†

BACKGROUND

Although guidelines exist for advanced and variant bladder cancer management, evidence is limited/conflicting in some areas and the optimal approach remains controversial.

OBJECTIVE

To bring together a large multidisciplinary group of experts to develop consensus statements on controversial topics in bladder cancer management.

DESIGN

A steering committee compiled proposed statements regarding advanced and variant bladder cancer management which were assessed by 113 experts in a Delphi survey. Statements not reaching consensus were reviewed; those prioritised were revised by a panel of 45 experts before voting during a consensus conference.

SETTING

Online Delphi survey and consensus conference.

PARTICIPANTS

The European Association of Urology (EAU), the European Society for Medical Oncology (ESMO), experts in bladder cancer management.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Statements were ranked by experts according to their level of agreement: 1-3 (disagree), 4-6 (equivocal), 7-9 (agree). A priori (level 1) consensus was defined as ≥70% agreement and ≤15% disagreement, or vice versa. In the Delphi survey, a second analysis was restricted to stakeholder group(s) considered to have adequate expertise relating to each statement (to achieve level 2 consensus).

RESULTS AND LIMITATIONS

Overall, 116 statements were included in the Delphi survey. Of these, 33 (28%) statements achieved level 1 consensus and 49 (42%) statements achieved level 1 or 2 consensus. At the consensus conference, 22 of 27 (81%) statements achieved consensus. These consensus statements provide further guidance across a broad range of topics, including the management of variant histologies, the role/limitations of prognostic biomarkers in clinical decision making, bladder preservation strategies, modern radiotherapy techniques, the management of oligometastatic disease and the evolving role of checkpoint inhibitor therapy in metastatic disease.

CONCLUSIONS

These consensus statements provide further guidance on controversial topics in advanced and variant bladder cancer management until a time where further evidence is available to guide our approach.

A sensitive liquid chromatography method for analysis of propofol in small volumes of neonatal blood

WHAT IS KNOWN AND OBJECTIVE

Sampling volumes of blood from neonates is necessarily limited. However, most of the published propofol analysis assays require a relatively large blood sample volume (typically ≥0.5 mL). Therefore, the aim of the present study was to develop and validate a sensitive method requiring a smaller sample volume (0.2 mL) to fulfill clinically relevant research requirements.

METHODS

Following simple protein precipitation and centrifugation, the supernatant was injected into the HPLC-fluorescence system and separated with a reverse phase column. Propofol and the internal standard (thymol) were detected and quantified using fluorescence at excitation and emission wavelengths of 270 nm and 310 nm, respectively. The method was validated with reference to the Food and Drug Administration (FDA) guidance for industry. Accuracy (CV, %) and precision (RSD, %) were evaluated at three quality control concentration levels (0.05, 0.5 and 5 µg/mL).

RESULTS AND DISCUSSION

Calibration curves were linear in the range of 0.005-20 µg/mL. Intra- and interday accuracy (-4.4%-13.6%) and precision (0.2%-5.8%) for propofol were below 15%. The calculated LOD (limit of detection) and LLOQ (lower limit of quantification) were 0.0021 µg/mL and 0.0069 µg/mL, respectively. Propofol samples were stable for 4 months at -20°C after the sample preparation. This method was applied for analyzing blood samples from 41 neonates that received propofol, as part of a dose-finding study. The measured median (range) concentration was 0.14 (0.03-1.11) µg/mL, which was in the range of the calibration curve. The calculated median (range) propofol half-life of the gamma elimination phase was 10.4 (4.7-26.7) hours.

WHAT IS NEW AND CONCLUSION

A minimal volume (0.2 mL) of blood from neonates is required for the determination of propofol with this method. The method can be used to support the quantification of propofol drug concentrations for pharmacokinetic studies in the neonatal population.

P11.43 Deletions on Y chromosome are associated with shorter survival in glioblastoma

BACKGROUND

Apart from few exceptions, men are more likely to be diagnosed with cancer during their lifetime, including glioblastoma (GBM), but the gender-related differences in GBM are poorly understood. Loss of chromosome Y (LOY) in peripheral blood cells is associated with physiological ageing, but also with disorders like cardiovascular disease, Alzheimer’s disease and different cancer types. In this study, we determined deletions on Y chromosome in tumor tissue of male patients with GBM, and studied the impact of LOY on survival.

MATERIAL AND METHODS

Ten genes, serving as markers, were selected on both arms of chromosome Y for copy number analysis with droplet digital PCR (ddPCR), enabling detection of loss of a marker in a fraction of the tumor cells used for DNA extraction. A total of 114 tumor samples from male patients were used, derived from a cohort of IDH wild type GBM patients treated with standard radio-chemo therapy. For 61 of these 114 patients, corresponding blood samples were available and analyzed. Different cut-off values were tested for each marker and Kaplan-Meier log-rank analysis was used to estimate overall survival. The mRNA expression for nine of the ten tested genes was available in TCGA, and 225 IDH wild type male GBM were included in a separate survival analysis, where median value of expression was used as group separator.

RESULTS

Fractional loss, as well as gain of markers was detected. Decreased copy number of the following markers was associated with significantly shorter survival; amelogenin Y-linked (AMELY) (13.5 vs. 19.3 months, p=0.017), neuroligin 4 Y-linked (NLGN4Y) (11.8 vs. 18.9 months, p=0.03) and sex determining region Y (SRY) (10.3 vs. 18.7 months, p=0.002). Additional analysis of SRY in the blood samples verified that copy number alterations were predominantly present in tumors. Survival analysis using mRNA expression data from TCGA showed that reduced expression of SRY was associated with significantly shorter OS (13.8 vs. 19.8 months, p=0.008), but no significant correlation with OS for any of the other markers.

CONCLUSION

Our data suggests a clonal or at least sporadic occurrence of fractional loss of Y chromosome markers in GBM, as detected with ddPCR. Interestingly, such dosage changes may contribute to shorter survival in men and explain some of the sex disparity seen in GBM. More research is needed to elucidate the molecular mechanisms of LOY and the role of specific Y-linked genes in GBM but also other diseases.

Pharmacokinetic modelling and Bayesian estimation-assisted decision tools to optimize vancomycin dosage in neonates: only one piece of the puzzle

Introduction: Vancomycin is commonly administered to neonates, while observational data on therapeutic drug monitoring (TDM, trough levels) suggest that vancomycin exposure and dosage remain substandard. Area covered: Data on vancomycin pharmacokinetics (PK) and its covariates are abundant. Consequently, modeling is an obvious tool to improve targeted exposure, with a shift from TDM trough levels to area under the curve (AUC_24h) targets, as in adults. Continuous administration appeared as a practice to facilitate AUC_24h target attainment, while Bayesian model-supported targeting emerged as a novel tool. However, the AUC_24h/MIC (minimal inhibitory concentration) target itself should consider neonate-specific aspects (bloodstream infections, coagulase-negative staphylococci, protein binding, underexplored causes of variability, like assays, preparation and administration inaccuracies, or missing covariates). Expert opinion: To improve targeted exposure in neonates, initial vancomycin prescription should be based on 'a priori model-based individual dosing' using validated dosing regimens, followed by further tailoring by dosing optimization applying Bayesian estimation-assisted TDM. Future research should focus on the feasibility to integrate these tools (individualized dosing, Bayesian models) in clinical practice, and to perform PK/PD studies in the relevant animal models and human neonatal setting (coagulase-negative staphylococci, bloodstream infections).

Dose rationale and pharmacokinetics of dexmedetomidine in mechanically ventilated new-borns: impact of design optimisation

PURPOSE

There is a need for alternative analgosedatives such as dexmedetomidine in neonates. Given the ethical and practical difficulties, protocol design for clinical trials in neonates should be carefully considered before implementation. Our objective was to identify a protocol design suitable for subsequent evaluation of the dosing requirements for dexmedetomidine in mechanically ventilated neonates.

METHODS

A published paediatric pharmacokinetic model was used to derive the dosing regimen for dexmedetomidine in a first-in-neonate study. Optimality criteria were applied to optimise the blood sampling schedule. The impact of sampling schedule optimisation on model parameter estimation was assessed by simulation and re-estimation procedures for different simulation scenarios. The optimised schedule was then implemented in a neonatal pilot study.

RESULTS

Parameter estimates were more precise and similarly accurate in the optimised scenarios, as compared to empirical sampling (normalised root mean square error: 1673.1% vs. 13,229.4% and relative error: 46.4% vs. 9.1%). Most importantly, protocol deviations from the optimal design still allowed reasonable parameter estimation. Data analysis from the pilot group (n = 6) confirmed the adequacy of the optimised trial protocol. Dexmedetomidine pharmacokinetics in term neonates was scaled using allometry and maturation, but results showed a 20% higher clearance in this population compared to initial estimates obtained by extrapolation from a slightly older paediatric population. Clearance for a typical neonate, with a post-menstrual age (PMA) of 40 weeks and weight 3.4 kg, was 2.92 L/h. Extension of the study with 11 additional subjects showed a further increased clearance in pre-term subjects with lower PMA.

CONCLUSIONS

The use of optimal design in conjunction with simulation scenarios improved the accuracy and precision of the estimates of the parameters of interest, taking into account protocol deviations, which are often unavoidable in this event-prone population.

The Use of Hemodynamic and Cerebral Monitoring to Study Pharmacodynamics in Neonates

BACKGROUND

Drugs acting on the cardiovascular and central nervous system often display relatively fast clinical responses, which may differ in neonates compared to children and adults. Introduction of bedside monitoring tools might be of additional value in the pharmacodynamic (PD) assessment of such drugs in neonates.

METHODS

We aim to provide an overview of the frequently used monitoring tools to assess drug effects on the hemodynamic status as well as the cerebral circulation, oxygenation and cerebral metabolism in neonates.

RESULTS

The use of blood pressure measurements, heart rate variability, functional echocardiography, nearinfrared spectroscopy and (amplitude-integrated) electroencephalography in neonates is discussed, as well as new parameters introduced by these tools. Based on the 'brain circulation model', the hemodynamic effects on the brain and their interplay are summarized. In this model, 3 processes (i.e. blood processes, vascular smooth muscle processes and tissue processes) and 3 mechanisms (i.e. autoregulation, blood flow metabolism coupling and cerebral oxygen balance) are distinguished, which all may be influenced by drug administration. Finally, propofol, sevoflurane, midazolam and inotropes are used as examples of which PD has been studied using the available hemodynamic and/or cerebral monitoring tools.

CONCLUSION

The implementation of (non-)invasive monitoring tools to document hemodynamic and cerebral PD effects in neonates is of relevance both in a neonatal research and intensive clinical care setting. We highlight the need to integrate these tools in future PD research. Furthermore, besides short-term drug effects, long-term outcome of drug therapy in neonates also warrants further attention.

Measurement of Neurovascular Coupling in Neonates

Neurovascular coupling refers to the mechanism that links the transient neural activity to the subsequent change in cerebral blood flow, which is regulated by both chemical signals and mechanical effects. Recent studies suggest that neurovascular coupling in neonates and preterm born infants is different compared to adults. The hemodynamic response after a stimulus is later and less pronounced and the stimulus might even result in a negative (hypoxic) signal. In addition, studies both in animals and neonates confirm the presence of a short hypoxic period after a stimulus in preterm infants. In clinical practice, different methodologies exist to study neurovascular coupling. The combination of functional magnetic resonance imaging or functional near-infrared spectroscopy (brain hemodynamics) with EEG (brain function) is most commonly used in neonates. Especially near-infrared spectroscopy is of interest, since it is a non-invasive method that can be integrated easily in clinical care and is able to provide results concerning longer periods of time. Therefore, near-infrared spectroscopy can be used to develop a continuous non-invasive measurement system, that could be used to study neonates in different clinical settings, or neonates with different pathologies. The main challenge for the development of a continuous marker for neurovascular coupling is how the coupling between the signals can be described. In practice, a wide range of signal interaction measures exist. Moreover, biomedical signals often operate on different time scales. In a more general setting, other variables also have to be taken into account, such as oxygen saturation, carbon dioxide and blood pressure in order to describe neurovascular coupling in a concise manner. Recently, new mathematical techniques were developed to give an answer to these questions. This review discusses these recent developments.

47 Effect of a long-term, high-fat diet on metabolic health and oocyte quality of an outbred (Swiss) versus inbred (C57BL/6N) mouse strain

Maternal metabolic disorders like obesity and diabetes type II are known to affect reproductive physiology, ultimately leading to poor fertility. The oocyte and embryo are extremely vulnerable during the periconceptional period to metabolic stressors, leading to disappointing fertility results. Most mouse model research regarding obesity and Western type diets has been performed on the inbred C57BL/6 strain. However, inbred strains are often linked with decreased fertility. Relying only on inbred strains might also limit translation to human (outbred) physiology. To further explore this, we compared the inbred C57BL/6N to an outbred Swiss strain. Five-week-old Swiss (N=30) and C57BL/6N (B6) (N=29) mice were fed a control (CTRL) or a high-fat (HF) diet for 13 weeks. Diets differed in percentage of fat (10% v. 60%). Body weight gain, serum profile (nonesterified fatty acids, cholesterol, and triglycerides), and oocyte quality were studied. Mature oocytes were collected after hormonal stimulation (IP injection of 10IU of pregnant mare serum gonadotropin followed by 10IU of hCG 48h later). To study oocyte quality, Bodipy (lipid droplets), JC-1 (mitochondrial membrane potential), and Cell-Rox Deep Red stainings were performed, as well as transmission electron microscopy to examine mitochondrial structures. All data were analysed using the t-test. In comparison with the CTRL group, the HF diet increased body weight by 18.09 and 27.87% in Swiss and B6, respectively. The HF significantly increased blood cholesterol levels (103.5v. 143.1 mg/dL in Swiss mice, 141.8v. 185.4 mg/dL in B6 mice) in both strains, and tended to increase blood nonesterified fatty acids (P=0.053) and triglycerides (P=0.075) only in Swiss but not in B6 mice. Oocytes collected from the HF diet group contained a larger total volume of lipid droplets (P&lt;0.05) in both strains compared with controls. The mitochondrial membrane potential and Cell-Rox Deep Red were significantly increased (P&lt;0.05) in oocytes of Swiss mice, but not B6 mice, fed a HF diet. Transmission electron microscopy images from HF oocytes showed mitochondria with abnormal morphology, low electron density, and rose petal appearance, resulting in significantly increased mitochondrial abnormalities in Swiss mice on the HF diet (P&lt;0.05). In B6 mice, both CTRL and HF oocytes contained high proportions of abnormal mitochondria compared with the CTRL group of the Swiss mice, explaining the lack of HF diet effects in B6 oocyte ultrastructure. We conclude that a HF diet has a significant effect on both metabolic health and oocyte quality. However, the Swiss model seems more sensitive to a Western type diet insult, making it more suitable for research focusing on metabolic health and oocyte quality than the B6 strain. The HF diet-exposed Swiss mice showed differences (compared with CTRL) in their serum profile. Alterations in mitochondrial activity, structures, and oxidative stress were induced by HF diet in the Swiss mice and not the B6, although B6 oocytes also showed higher lipid droplet accumulation. Furthermore, even the B6 mice that were fed a normal control diet showed deviant oocyte quality, clearly shown by morphological signs of lower quality and mitochondrial abnormalities.

Physiologically based pharmacokinetic (PBPK) modeling and simulation in neonatal drug development: how clinicians can contribute

Introduction: Legal initiatives to stimulate neonatal drug development should be accompanied by development of valid research tools. Physiologically based (PB)-pharmacokinetic (PK) modeling and simulation are established tools, accepted by regulatory authorities. Consequently, PBPK holds promise to be a strong research tool to support neonatal drug development. Area covered: The currently available PBPK models still have poor predictive performance in neonates. Using an illustrative approach on distinct PK processes of absorption, distribution, metabolism, excretion, and real-world data in neonates, we provide evidence on the need to further refine available PBPK system parameters through generation and integration of new knowledge. This necessitates cross talk between clinicians and modelers to integrate knowledge (PK datasets, system knowledge, maturational physiology) or test and refine PBPK models. Expert opinion: Besides refining these models for 'small molecules', PBPK model development should also be more widely applied for therapeutic proteins and to determine exposure through breastfeeding. Researchers should also be aware that PBPK modeling in combination with clinical observations can also be used to elucidate age-related changes that are almost impossible to study based on in vivo or in vitro data. This approach has been explored for hepatic biliary excretion, renal tubular activity, and central nervous system exposure.

Can sidestream dark field (SDF) imaging identify subtle microvascular changes of the bowel during colorectal surgery?

BACKGROUND

Recognition of a non-viable bowel during colorectal surgery is a challenging task for surgeons. Identifying the turning point in serosal microcirculatory deterioration leading up to a non-viable bowel is crucial. The aim of the present study was to determine whether sidestream darkfield (SDF) imaging can detect subtle changes in serosal microcirculation of the sigmoid after vascular transection during colorectal surgery.

METHODS

A prospective observational clinical study was performed at a single medical centre. All eligible participants underwent laparoscopic sigmoid resection and measurements were taken during the extra-abdominal phase. Microcirculation was measured at the transected bowel and 20 cm proximal to this point. Microcirculatory parameters such as Microvascular Flow Index (MFI), proportion of perfused vessels (PPV), perfused vessel density (PVD), total vessel density (TVD) and the Heterogeneity Index were determined. Data are presented as median (interquartile range) or mean ± standard deviation.

RESULTS

A total of 60 SDF images were acquired for 10 patients. Perfusion parameters and perfused vessel density were significantly lower at the transected bowel compared with the non-transected measurements [MFI 2.29 (1.96-2.63) vs 2.96 (2.73-3.00), p = 0.007; PPV 74% (55-83) vs 94% (86-97), p = 0.007; and PVD 7.61 ± 2.99 mm/mm² versus 10.67 ± 1.48 mm/mm², p = 0.009]. Total vessel density was similar between the measurement locations.

CONCLUSIONS

SDF imaging can identify changes of the bowel serosal microcirculation. Significantly lower serosal microcirculatory parameters of the vascular transected bowel was seen compared with the non-transected bowel. The ability of SDF imaging to detect subtle differences holds promise for future research on microvascular cut-off values leading to a non-viable bowel.

Cerebral autoregulation and activity after propofol for endotracheal intubation in preterm neonates

BACKGROUND

Despite increasing use of propofol in neonates, observations on cerebral effects are limited.

AIM

To investigate cerebral autoregulation (CAR) and activity after propofol for endotracheal intubation in preterm neonates.

METHODS

Twenty-two neonates received propofol before intubation as part of a published dose-finding study. Mean arterial blood pressure (MABP), near-infrared spectroscopy-derived cerebral oxygenation (rScO₂), and amplitude-integrated electroencephalography (aEEG) were analyzed until 180 min after propofol. CAR was expressed as transfer function (TF) gain, indicating % change in rScO₂ per 1 mmHg change in MABP. Values exceeding mean TF gain + 2 standard deviations (SD) defined impaired CAR.

RESULTS

After intubation with a median propofol dose of 1 (0.5-4.5) mg/kg, rScO₂ remained stable during decreasing MABP. Mean (±SD) TF gain was 0.8 (±0.3)%/mmHg. Impaired CAR was identified in 1 and 5 patient(s) during drug-related hypotension and normal to raised MABP, respectively. Suppressed aEEG was observed up to 60 min after propofol.

CONCLUSIONS

Drug-related hypotension and decreased cerebral activity after intubation with low propofol doses in preterm neonates were observed, without evidence of cerebral ischemic hypoxia. CAR remained intact during drug-related hypotension in 95.5% of patients. Cerebral monitoring including CAR clarifies the cerebral impact of MABP fluctuations.

Age and surgical outcome of low-grade glioma in Sweden

BACKGROUND

Low-grade gliomas (LGG) are slow-growing primary brain tumors that typically affect young adults. Advanced age is widely recognized as a poor prognostic factor in LGG. The impact of age on postoperative outcome in this patient group has not been systemically studied.

METHODS

We performed a nationwide register-based study with data from the Swedish Brain Tumor Registry (SBTR) for all adults diagnosed with a supratentorial LGG (WHO grade II astrocytoma, oligoastrocytoma, or oligodendroglioma) during 2005-2015. Patient- and tumor-related characteristics, postoperative complications, and survival were compared between three different age groups (18-39 years, 40-59 years, and ≥60 years).

RESULTS

We identified 548 patients; 204 patients (37.2%) aged 18-39 years, 227 patients (41.4%) aged 40-59 years, and 117 patients (21.4%) ≥60 years of age. Unfavorable preoperative prognostic factors (eg, functional status and neurological deficit) were more common with increased age (P < .001). In addition, overall survival was significantly impaired in those 60 years and above (P < .001). We observed a clear dose-response for age with separation of survival curves at 50 years. Biopsy was more common in patients ≥60 years (P < .001). Subgroup analysis of patients with resection revealed a higher amount of postoperative neurological deficits in older patients (P = .029).

CONCLUSION

In general, older patients with LGG have several unfavorable prognostic factors compared with younger patients but seem to tolerate surgery in a comparable fashion. However, more neurological deficits were observed following resections in elderly. Our data further support a cutoff at 50 years rather than 40 years for selection of high-risk patients.

Drug evaluation studies in neonates: how to overcome the current limitations

INTRODUCTION

Regulatory initiatives have stimulated drug research in infants, but the potential impact of drugs to improve health outcome in neonates remains underexplored. Areas covered: In this review, we focus on current limitations in drug evaluation studies and how to overcome these. The low volume of studies has additional weaknesses such as single center studies, non-commercial sponsorship, overrepresentation of high postulated risk reductions, and underrepresentation of therapeutic exploratory studies. Master protocols and selection criteria for neonatal centers to participate in studies are useful to improve logistics related to performance. Limitations also relate to inaccurate assessment of drug effects (efficacy/safety). This is because of poor symptom recognition, case definitions, and suboptimal data on adverse drug reactions (ADRs) epidemiology. To overcome these limitations, it is necessary to develop core outcome sets, reference values, and specific ADR tools. The limitations identified and approaches suggested to improve drug evaluation are illustrated using neonatal abstinence syndrome as an example. Expert commentary: We anticipate to see an evolving neonatal clinical pharmacology discipline driven by neonatal pathophysiology and knowledge. Multidisciplinary collaborative efforts between health care providers, academia, pharmaceutical industry, advocacy groups and regulatory agencies are crucial to improve the impact of drug evaluation studies in neonates.