Population pharmacokinetics of intravenous clonidine for sedation during paediatric extracorporeal membrane oxygenation and continuous venovenous hemofiltration

Population pharmacokinetics in critically ill neonates and infants undergoing extracorporeal membrane oxygenation: a literature review

Extracorporeal membrane oxygenation (ECMO) increases circulating blood volume, causes capillary leak and temporarily alters kidney function. Consequently, pharmacokinetics (PK) can be affected. When applied to neonates and infants, additional dose adjustments are a major concern, as the volume of distribution (Vd) is already generally greater for water-soluble drugs and the clearance (Cl) of drugs eliminated by glomerular filtration is reduced. A systematic search was performed on MEDLINE (1994-2022) using a combination of the following search terms: "pharmacokinetics", "extracorporeal membrane oxygenation" and "infant, newborn" using Medical Subject Headings search strategy. Nine out of 18 studies on 11 different drugs (vancomycin, meropenem, fluconazole, gentamicin, midazolam, phenobarbital, theophylline, clonidine, morphine, cefotaxime and cefepime) recommended dose increase/decrease by determining PK parameters. In other studies, it has been suggested to adjust the dose intervals. While the elimination half-life (t_1/2) and Vd mostly increased for all drugs, the Cl of the drugs has been shown to have variability except for midazolam and morphine. There are a limited number of population PK studies in neonates and infants undergoing ECMO circuits. Despite some divergences, the general pattern suggests an increase in Vd and t_1/2, an increased, stable or decreased Cl, and an increase in variability. Consequently, and if possible, therapeutic drug monitoring and target concentration intervention are strongly recommended to determine appropriate exposure and doses for neonates and infants undergoing ECMO support.

Pharmacokinetics of Commonly Used Medications in Children Receiving Continuous Renal Replacement Therapy: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

The use of continuous renal replacement therapy (CRRT) for renal support has increased substantially in critically ill children compared with intermittent modalities owing to its preferential effects on hemodynamic stability. With the expanding role of CRRT, the quantification of extracorporeal clearance and the effect on primary pharmacokinetic parameters is of the utmost importance. Within this review, we aimed to summarize the current state of the literature and compare published pharmacokinetic analyses of commonly used medications in children receiving CRRT to those who are not.

METHODS

A systematic search of the literature within electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science was conducted. Published studies that were included contained relevant information on the use of commonly administered medications to children, from neonates to adolescents, receiving CRRT. Pharmacokinetic parameters that were analyzed included volume of distribution, total clearance, extracorporeal clearance, area under the curve, and elimination half-life. Information regarding CRRT circuit, flow rates, and membrane components was analyzed to investigate differences in pharmacokinetics between each modality.

RESULTS

Forty-five studies met the final inclusion criteria within this systematic review, totaling 833 pediatric patients, with 586 receiving CRRT. Antimicrobials were the most common pharmacological class represented within the literature, representing 81% (35/43) of studies analyzed. Children receiving CRRT largely had similar volume of distribution and total clearance to critically ill children not receiving CRRT, suggesting reno-protective dose adjustments may lead to subtherapeutic dosing regimens in these patients. Overall, there was a tendency for hydrophilic agents, with a low protein binding to undergo elevated total clearance in these children. However, results should be interpreted with caution because of the large variability amongst patient populations and heterogeneity with CRRT modalities, flow rates, and use of extracorporeal membrane oxygenation within studies. This review was able to identify that variation in solute removal, or CRRT modalities, properties (i.e., flow rates), and membrane composition, may have differing effects on the pharmacokinetics of commonly administered medications.

CONCLUSIONS

The current state of the literature regarding medications administered to children receiving CRRT largely focuses on antimicrobials. Significant gaps remain with other commonly used medications such as sedatives and analgesics. Overall reporting of patient clinical characteristics, CRRT settings, and circuit composition was poor, with only 10% of articles including all relevant information to assess the impact of CRRT on total clearance. Changes in pharmacokinetics because of CRRT often required higher than labeled doses, suggesting renally adjusted or reno-protective doses may lead to subtherapeutic dosing regimens. A thorough understanding of the interplay between patient, drug, and CRRT-circuit factors are required to ensure adequate delivery of dosing regimens to this vulnerable population.

Dexmedetomidine in Children on Extracorporeal Membrane Oxygenation: Pharmacokinetic Data Exploration Using Previously Published Models

BACKGROUND

Dexmedetomidine is a sedative and analgesic increasingly used in children supported with extracorporeal membrane oxygenation (ECMO). No data is available to describe the pharmacokinetics (PK) of dexmedetomidine in this population.

METHODS

We performed a single-center prospective PK study. Children <18 years old, supported with ECMO, and on a dexmedetomidine infusion as part of their management were prospectively included. PK samples were collected. Dexmedetomidine dosing remained at the discretion of the clinical team. Six population PK models built in pediatrics were selected. Observed concentrations were compared with population predicted concentrations using the PK models.

RESULTS

Eight children contributed 30 PK samples. None of the PK models evaluated predicted the concentrations with acceptable precision and bias. Four of the six evaluated models overpredicted the concentrations. The addition of a correction factor on clearance improved models' fit. Two of the evaluated models were not applicable to our whole population age range because of their structure.

CONCLUSION

Most of the evaluated PK models overpredicted the concentrations, potentially indicating increased clearance on ECMO. Population PK models applicable to a broad spectrum of ages and pathologies are more practical in pediatric critical care settings but challenging to develop.

Blinded, Multicenter Evaluation of Drug-induced Changes in Contractility Using Human-induced Pluripotent Stem Cell-derived Cardiomyocytes

Animal models are 78% accurate in determining whether drugs will alter contractility of the human heart. To evaluate the suitability of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for predictive safety pharmacology, we quantified changes in contractility, voltage, and/or Ca²⁺ handling in 2D monolayers or 3D engineered heart tissues (EHTs). Protocols were unified via a drug training set, allowing subsequent blinded multicenter evaluation of drugs with known positive, negative, or neutral inotropic effects. Accuracy ranged from 44% to 85% across the platform-cell configurations, indicating the need to refine test conditions. This was achieved by adopting approaches to reduce signal-to-noise ratio, reduce spontaneous beat rate to ≤ 1 Hz or enable chronic testing, improving accuracy to 85% for monolayers and 93% for EHTs. Contraction amplitude was a good predictor of negative inotropes across all the platform-cell configurations and of positive inotropes in the 3D EHTs. Although contraction- and relaxation-time provided confirmatory readouts forpositive inotropes in 3D EHTs, these parameters typically served as the primary source of predictivity in 2D. The reliance of these “secondary” parameters to inotropy in the 2D systems was not automatically intuitive and may be a quirk of hiPSC-CMs, hence require adaptations in interpreting the data from this model system. Of the platform-cell configurations, responses in EHTs aligned most closely to the free therapeutic plasma concentration. This study adds to the notion that hiPSC-CMs could add value to drug safety evaluation.

Extracorporeal membrane oxygenation in critically ill neonatal and pediatric patients with acute respiratory failure: a guide for the clinician

Intro: Extracorporeal membrane oxygenation for neonatal and pediatric respiratory failure continues to demonstrate improving outcomes, largely due to advances in technology along with refined management strategies despite mounting patient acuity and complexity. Successful use of ECMO requires thoughtful initiation and candidacy strategies, along with reducing the risk of ventilator induced lung injury and the progression to multiorgan failure.Areas Covered: This review describes current ECMO management strategies for neonatal and pediatric patients with acute refractory respiratory failure and summarizes relevant published literature. ECMO initiation and candidacy, along with ventilator and sedation management, are highlighted. Additionally, rapidly expanding areas of interest such as anticoagulation strategies, transfusion thresholds, rehabilitation on ECMO, and drug pharmacokinetics are described.Expert Opinion: Over the last few decades, published studies supporting ECMO use for acute refractory respiratory failure, along with institutional experience, have resulted in increased utilization although more randomized-controlled trials are needed. Future research should focus on filling the knowledge gaps that remain regarding anticoagulation, transfusion thresholds, ventilator strategies, sedation, and approaches to rehabilitation to subsequently implement into clinical practice. Additionally, efforts should focus on well-designed trials, including population pharmacokinetic studies, to develop dosing recommendations.

Clinical pharmacology and dosing regimen optimization of neonatal opioid withdrawal syndrome treatments

In this paper, we review the management of neonatal opioid withdrawal syndrome (NOWS) and clinical pharmacology of primary treatment agents in NOWS, including morphine, methadone, buprenorphine, clonidine, and phenobarbital. Pharmacologic treatment strategies in NOWS have been mostly empirical, and heterogeneity in dosing regimens adds to the difficulty of extrapolating study results to broader patient populations. As population pharmacokinetics (PKs) of pharmacologic agents in NOWS become more well‐defined and knowledge of patient‐specific factors affecting treatment outcomes continue to accumulate, PK/pharmacodynamic modeling and simulation will be powerful tools to aid the design of optimal dosing regimens at the patient level. Although there is an increasing number of clinical trials on the comparative efficacy of treatment agents in NOWS, here, we also draw attention to the importance of optimizing the dosing regimen, which can be arguably equally important at identifying the optimal treatment agent.

Safety of clonidine used for long-term sedation in paediatric intensive care: A systematic review

AIM

Although not approved, the α-adrenoceptor agonist clonidine is considered an option for long-term sedation protocols in paediatric intensive care. We reviewed adverse effects of clonidine occurring in this indication.

METHODS

Relevant literature was systematically identified from PubMed and Embase. We included interventional and observational studies on paediatric patients admitted to intensive care units and systemically long-term sedated with clonidine-containing regimes. In duplicates, we conducted standardised and independent full-text assessment and extraction of safety data.

RESULTS

Data from 11 studies with 909 patients were analysed. The studies were heterogeneous regarding patient characteristics (age groups, comorbidity, or comedication) and sedation regimes (dosage, route, duration, or concomitant sedatives). Just four randomised controlled trials (RCTs) and one observational study had comparison groups, using placebo or midazolam. For safety outcomes, our validity evaluation showed low risk of bias only in three studies. All studies focused on haemodynamic problems, particularly bradycardia and hypotension. Observed incidences or subsequent interventions never caused concerns. However, only two RCTs allowed meaningful comparisons with control groups. Odds ratios showed no significant difference between the groups, but small sample sizes (50 and 125 patients) must be considered; pooled analyses were not reasonable.

CONCLUSION

All evaluated studies concluded that the use of clonidine in paediatric intensive care units is safe. However, a valid characterisation of the safety profile remains challenging due to limited, biased and heterogeneous data and missing investigation of long-term effects. This evaluation demonstrates the lack of data, which prevents reliable conclusions on the safety of clonidine for long-term sedation in critically ill children. For an evidence-based use, further studies are needed.

Sedative and Analgesic Pharmacokinetics During Pediatric ECMO

Sedatives and analgesics are often administered to critically ill children supported by extracorporeal membrane oxygenation (ECMO) to facilitate comfort and to decrease risks of life-threatening complications. Optimization of sedative and analgesic dosing is necessary to achieve desired therapeutic benefits and must consider interactions between the circuit and patient that may affect drug metabolism, clearance, and impact on target organs. This paper reviews existing in vitro and pediatric in vivo literature concerning the effects of the ECMO circuit on sedative and analgesic disposition and offers dosing guidance for the management of critically ill children receiving these drugs.

Rapid Increase in Clearance of Phenobarbital in Neonates on Extracorporeal Membrane Oxygenation: A Pilot Retrospective Population Pharmacokinetic Analysis

OBJECTIVES

This study characterizes the changes in the pharmacokinetics of phenobarbital associated with extracorporeal membrane oxygenation treatment in neonates, to illustrate our findings and provide guidance on dosing.

DESIGN

Retrospective pilot population pharmacokinetic analysis.

SETTING

Neonatal ICU.

PATIENTS

Thirteen critically ill neonates (birth body weight, 3.21 kg [2.65-3.72 kg]; postnatal age at start of treatment: 2 d [0-7 d]; gestational age: 38 wk [38-41 wk]) receiving venovenous or venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

Phenobarbital administered in a loading dose of 7.5 mg/kg (8.5-16 mg/kg) and maintenance dose of 6.9 mg/kg/d (4.5-8.5 mg/kg/d).

MEASUREMENTS AND MAIN RESULTS

Therapeutic drug monitoring data were available, yielding 5, 31, and 19 phenobarbital concentrations before, during, and after extracorporeal membrane oxygenation, respectively. Population pharmacokinetic analysis was performed using NONMEM 7.3.0 (ICON Development Solutions, Ellicott City, MD). Maturation functions for clearance and volume of distribution were obtained from literature. In a one-compartment model, clearance and volume of distribution for a typical neonate off extracorporeal membrane oxygenation and with a median birth body weight (3.21 kg) at median postnatal age (2 d) were 0.0096 L/hr (relative SE = 11%)) and 2.72 L (16%), respectively. During extracorporeal membrane oxygenation, clearance was found to linearly increase with time. Upon decannulation, phenobarbital clearance initially decreased and subsequently increased slowly driven by maturation. Extracorporeal membrane oxygenation-related changes in volume of distribution could not be identified, possibly due to sparse data collection shortly after extracorporeal membrane oxygenation start. According to the model, target attainment is achieved in the first 12 days of extracorporeal membrane oxygenation with a regimen of a loading dose of 20 mg/kg and a maintenance dose of 4 mg/kg/d divided in two doses with an increase of 0.25 mg/kg every 12 hours during extracorporeal membrane oxygenation treatment.

CONCLUSIONS

We found a time-dependent increase in phenobarbital clearance during the first 12 days of extracorporeal membrane oxygenation treatment in neonates, which results in continuously decreasing phenobarbital exposure and increases the risk of therapeutic failure over time. Due to high unexplained variability, frequent and repeated therapeutic drug monitoring should be considered even with the model-derived regimen.

Pharmacokinetics Alterations in Critically Ill Pediatric Patients on Extracorporeal Membrane Oxygenation: A Systematic Review

Objectives: This study aimed to identify alterations in pharmacokinetics in children on extracorporeal membrane oxygenation (ECMO), identify knowledge gaps, and inform future pharmacology studies. Data Sources: We systematically searched the databases MEDLINE, CINAHL, and Embase from earliest publication until November 2018 using a controlled vocabulary and keywords related to "ECMO" and "pharmacokinetics," "pharmacology," "drug disposition," "dosing," and "pediatrics." Study Selection: Inclusion criteria were as follows: study population aged <18 years, supported on ECMO for any indications, received any medications while on ECMO, and reported pharmacokinetic data. Data Extraction: Clearance and/or volume of distribution values were extracted from included studies. Data Synthesis: Forty-one studies (total patients = 574) evaluating 23 drugs met the inclusion criteria. The most common drugs studied were antimicrobials (n = 13) and anticonvulsants (n = 3). Twenty-eight studies (68%) were conducted in children <1 year of age. Thirty-three studies (80%) were conducted without intra-study comparisons to non-ECMO controls. Increase in volume of distribution attributable to ECMO was demonstrated for nine (56%) drugs: cefotaxime, gentamicin, piperacillin/tazobactam, fluconazole, micafungin, levetiracetam, clonidine, midazolam, and sildenafil (range: 23-345% increase relative to non-ECMO controls), which may suggest the need for higher initial dosing. Decreased volume of distribution was reported for two drugs: acyclovir and ribavirin (50 and 69%, respectively). Decreased clearance was reported for gentamicin, ticarcillin/clavulanate, bumetanide, and ranitidine (range: 26-95% decrease relative to non-ECMO controls). Increased clearance was reported for caspofungin, micafungin, clonidine, midazolam, morphine, and sildenafil (range: 25-455% increase relative to non-ECMO controls). Conclusions: There were substantial pharmacokinetic alterations in 70% of drugs studied in children on ECMO. However, studies evaluating pharmacokinetic changes of many drug classes and those that allow direct comparisons between ECMO and non-ECMO patients are still lacking. Systematic evaluations of pharmacokinetic alterations of drugs on ECMO that incorporate multidrug opportunistic trials, physiologically based pharmacokinetic modeling, and other methods are necessary for definitive dose recommendations. Trial Registration Prospero Identifier: CRD42019114881.

Optimising the dose of clonidine to achieve sedation in intensive care unit patients with population pharmacokinetics

Aims

The aim of this study was to investigate the population pharmacokinetics (PK) of clonidine in intensive care unit (ICU) patients in order to develop a dosing regimen for sedation.

Methods

We included 24 adult mechanically ventilated, sedated patients from a mixed medical and surgical ICU. Intravenous clonidine was added to standard sedation in doses of 600, 1200 or 1800 μg/d. Within each treatment group, 4 patients received a loading dose of half the daily dose administered in 4 hours. Patients gave an average of 12 samples per individual. In total, 286 samples were available for analysis. Model development was conducted with NONMEM and various covariates were tested. After modelling, doses to achieve a target steady‐state plasma concentration of >1.5 μg/L were explored using stochastic Monte Carlo simulations for 1000 virtual patients.

Results

A 2‐compartment model was the best fit for the concentration‐time data. Clearance (CL) increased linearly with 0.213%/h; using allometric scaling, body weight was a significant covariate on the central volume of distribution (V1). Population PK parameters were: CL 17.1 (L/h), V1 124 (L/70 kg), intercompartmental CL 83.7 (L/h), and peripheral volume of distribution 178 (L), with 33.3% CV interindividual variability on CL and 66.8% CV interindividual variability on V1. Simulations revealed that a maintenance dose of 1200 μg/d provides target sedation concentrations of >1.5 μg/L in 95% of the patients.

Conclusion

A population PK model for clonidine was developed in an adult ICU. A dosing regimen of 1200 μg/d provided a target sedation concentration of >1.5 μg/L.

Optimizing clonidine dosage for sedation in mechanically ventilated children: A pharmacokinetic simulation study

BACKGROUND

Clonidine is in widespread off-label use as a sedative in mechanically ventilated children, despite limited evidence of efficacy. A variety of dosage regimens have been utilized in clinical practice and in research studies. Within these studies, clonidine has inconsistently shown useful sedation properties. One of the reasons attributed to the inconsistent signs of efficacy is suboptimal clonidine dosing.

AIMS

This study aims to propose a target plasma concentration and simulate clonidine pharmacokinetics (PK) in a cohort of mechanically ventilated children to evaluate the adequacy of clonidine dosage regimens used in clinical practice and research studies.

METHODS

A literature search was undertaken to identify a clonidine pharmaockinetic-pharmacodynamics (PKPD) model, from which a target concentration for sedation was defined. Using a previously published PK model, the projected plasma concentrations of 692 mechanically ventilated children (demographics taken from a recent study) were generated. Doses from recently published clinical studies were investigated. Adequacy of each regimen to attain therapeutic clonidine plasma concentrations was assessed.

RESULTS

A target plasma concentration of above 2 µg/L was proposed. Nine dosage regimens (four intravenous boluses, four intravenous infusions, and one nasogastric route boluses) were evaluated ranging from 1 µg/kg eight hourly intravenous boluses to a regimen up to 3 µg/kg/hr continuous intravenous infusion. Regimens with a loading dose of 2 µg/kg followed by variable continuous infusion of up to 2 µg/kg/hr titrated according to sedation score appear most suitable. Doses should be halved in neonates.

CONCLUSION

The variety of dosage regimens in the previous studies of clonidine along with difficulties in the conduct of interventional studies may have contributed to the lack of efficacy data to support its use. Simulations of clonidine plasma concentrations based on known population pharmacokinetic parameters suggest a loading dose followed by higher than current practice maintenance dose infusion is required to achieve adequate steady-state concentrations early in treatment. Further PKPD studies will aid in the determination of the optimal clonidine dosage regimen.

Drug Disposition and Pharmacotherapy in Neonatal ECMO: From Fragmented Data to Integrated Knowledge

Extracorporeal membrane oxygenation (ECMO) is a lifesaving support technology for potentially reversible neonatal cardiac and/or respiratory failure. As the survival and the overall outcome of patients rely on the treatment and reversal of the underlying disease, effective and preferentially evidence-based pharmacotherapy is crucial to target recovery. Currently limited data exist to support the clinicians in their every-day intensive care prescribing practice with the contemporary ECMO technology. Indeed, drug dosing to optimize pharmacotherapy during neonatal ECMO is a major challenge. The impact of the maturational changes of the organ function on both pharmacokinetics (PK) and pharmacodynamics (PD) has been widely established over the last decades. Next to the developmental pharmacology, additional non-maturational factors have been recognized as key-determinants of PK/PD variability. The dynamically changing state of critical illness during the ECMO course impairs the achievement of optimal drug exposure, as a result of single or multi-organ failure, capillary leak, altered protein binding, and sometimes a hyperdynamic state, with a variable effect on both the volume of distribution (Vd) and the clearance (Cl) of drugs. Extracorporeal membrane oxygenation introduces further PK/PD perturbation due to drug sequestration and hemodilution, thus increasing the Vd and clearance (sequestration). Drug disposition depends on the characteristics of the compounds (hydrophilic vs. lipophilic, protein binding), patients (age, comorbidities, surgery, co-medications, genetic variations), and circuits (roller vs. centrifugal-based systems; silicone vs. hollow-fiber oxygenators; renal replacement therapy). Based on the potential combination of the above-mentioned drug PK/PD determinants, an integrated approach in clinical drug prescription is pivotal to limit the risks of over- and under-dosing. The understanding of the dose-exposure-response relationship in critically-ill neonates on ECMO will enable the optimization of dosing strategies to ensure safety and efficacy for the individual patient. Next to in vitro and clinical PK data collection, physiologically-based pharmacokinetic modeling (PBPK) are emerging as alternative approaches to provide bedside dosing guidance. This article provides an overview of the available evidence in the field of neonatal pharmacology during ECMO. We will identify the main determinants of altered PK and PD, elaborate on evidence-based recommendations on pharmacotherapy and highlight areas for further research.

Phenobarbital pharmacokinetics in neonates and infants during extracorporeal membrane oxygenation

INTRODUCTION

The disposition of drugs is potentially changed due to extracorporeal membrane oxygenation (ECMO) in neonates and infants.

METHODS

The aim of the study was to evaluate the individual pharmacokinetics (PK) of phenobarbital and the effect of PK covariates in neonates and infants undergoing ECMO. Sixteen patients (7 neonates, 9 infants) treated with phenobarbital during ECMO (centrifugal-flow pump circuits) were enrolled in the PK study. Phenobarbital serum concentrations were measured using a fluorescence polarization immunoassay. Individual PK parameters - volume of distribution (Vd) and clearance (CL) were calculated in a one-compartmental pharmacokinetic model.

RESULTS

The mean (SD) Vd and CL values in neonates were 0.46 (0.24) L/kg and 8.0 (4.5) mL/h/kg, respectively. Respective values in infants were 0.56 (0.23) L/kg and 8.5 (3.1) mL/h/kg. PK parameters in neonates and infants were not significantly different. We observed high inter-individual variability in PK parameters (coefficients of variation [CV] were 52% and 53% for CL and Vd, respectively). Doses were adjusted based on therapeutic drug monitoring (TDM) in 87.5% patients. Only 50% of the first measured phenobarbital serum concentrations in each patient were within the therapeutic range of 10-40 mg/L, in comparison with 88.6% concentration measured after TDM implementation. Linear regression models showed that both Vd and CL are significantly related with body weight (BW) and length. Median optimal phenobarbital loading dose (LD) and maintenance dose (MD), calculated from pharmacokinetic data, were 15 mg/kg and 4 mg/kg/day, respectively.

CONCLUSIONS

Body weight was shown to be the main PK covariate of phenobarbital disposition. Subsequent dosing nomograms are provided for phenobarbital dosing during ECMO.

Hemodynamic Tolerance to IV Clonidine Infusion in the PICU

OBJECTIVES

Clonidine is an antihypertensive drug used for analgosedation in the PICU. Lack of reliable data on its hemodynamic tolerance limits its use. This study explores the hemodynamic tolerance of IV clonidine infusion in a broad population of children with high severity of disease.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

A tertiary and quaternary referral PICU.

PATIENTS

Critically ill children age 0-18 years old who received an IV clonidine infusion for analgosedation of at least 1 hour.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary endpoints were the prevalences of bradycardia and hypotension. Secondary endpoints were changes in heart rate, blood pressure, Vasoactive-Inotropic Score, COMFORT Behavior score (a sedation scoring scale), and body temperature during the infusion. The association of bradycardia with other hemodynamic variables was explored, as well as potential risk factors for severe bradycardia. One-hundred eighty-six children (median age, 12.9 mo [interquartile range, 3.5-60.6 mo]) receiving a maximum median clonidine infusion of 0.7 µg/kg/hr (interquartile range, 0.3-1.5) were included. Severe bradycardia and systolic hypotension occurred in 72 patients (40.2%) and 105 patients (58%), respectively. Clonidine-associated bradycardia was hemodynamically well tolerated, as it was not related with hypotension and the need for vasoactive drugs decreased in parallel with a sedation score guided clonidine infusion rate increase. Younger age was the only identified risk factor for clonidine-associated bradycardia.

CONCLUSIONS

Although administration of clonidine is often associated with bradycardia and hypotension, these complications do not seem clinically significant in a mixed PICU population with a high degree of disease severity. Clonidine may have a vasoactive-inotropic sparing effect.

In Vitro Adsorption of Analgosedative Drugs in New Extracorporeal Membrane Oxygenation Circuits

OBJECTIVE

Evaluate drug disposition of sedatives and analgesics in the Xenios/Novalung extracorporeal membrane oxygenation circuits.

DESIGN

In vitro experimental study.

SETTING

Erasmus MC - Sophia Children's Hospital, Rotterdam, The Netherlands.

SUBJECTS

Nine closed-loop extracorporeal membrane oxygenation circuits, made up of the iLA Activve console with four different iLA Activve kits: two X-lung kits, two iLA-Activve iLA kits, two MiniLung kits, and three MiniLung petite kits.

INTERVENTIONS

The circuits were primed with fresh whole blood and maintained under physiologic conditions (pH/temperature) throughout 24 hours. Paracetamol, morphine, midazolam, fentanyl, and sufentanil were injected as standard age-related doses into nine closed-loop extracorporeal membrane oxygenation circuits.

MEASUREMENTS AND MAIN RESULTS

Pre-membrane (P2) blood samples were obtained prior to drug injection and after injection at 2, 10, 30, 180, 360 minutes, and at 24 hours. A control sample at 2 minutes was collected for spontaneous drug degradation testing at 24 hours. Two hundred sixteen samples were analyzed. After correction for the spontaneous drug degradation, the mean drug loss at 24 hours was paracetamol 49%, morphine 51%, midazolam 40%, fentanyl 84%, sufentanil 83%. Spontaneous degradation was paracetamol 6%, morphine 0%, midazolam 11%, fentanyl 4%, and sufentanil 0%. The decline of drug concentration over time was more pronounced for the more lipophilic drugs.

CONCLUSIONS

Loss of highly lipophilic drugs in the extracorporeal membrane oxygenation circuits at 24 hours was remarkable. Drug loss is comparable with other hollow fiber extracorporeal membrane oxygenation systems but less than in silicone-based membranes especially in the first hours after injection.

Drugs pharmacokinetics during veno-venous extracorporeal membrane oxygenation in pediatrics

Data evaluating pharmacokinetic/pharmacodynamic (PK/PD) aspect in the pediatric population are scarce especially regarding the pediatric intensive care unit. Dosing of frequently used drugs (sedatives, analgesics, antibiotics and cardiovascular drugs) are mainly based on non "pediatric intensive care unit (PICU)" patients, and sometimes are translated from adult patients. Among PICU patients, the most complex patients are the ones who are critically ill and are receiving mechanical circulatory/respiratory support for cardiac and/or respiratory failure. The use of extracorporeal membrane oxygenation is associated with major PK and PD changes, especially in neonates and children. The objective of this review is to assess the current literature for pediatric PK data in patients receiving extracorporeal membrane oxygenation (ECMO).

Population pharmacokinetics of intravenous clonidine for sedation during paediatric extracorporeal membrane oxygenation and continuous venovenous hemofiltration

AIMS

Clonidine is used for sedation in the paediatric intensive care unit. Extracorporeal membrane oxygenation (ECMO) provides temporary support if respiratory and cardiac function is threatened. ECMO influences the pharmacokinetics of drugs. Clonidine during paediatric ECMO cannot be effectively titrated as PK data are lacking. The aim of this study is to describe clonidine PK in a particular ECMO system and propose dosing guidelines for children on this particular ECMO circuit.

METHODS

All children below the age of 18 years who received clonidine during ECMO were eligible. The pharmacokinetic analysis was conducted by nonlinear mixed effect modelling, which enables to establish the separate influences of determinants on drug blood level and to provide individualized dosing.

RESULTS

Twenty-two patients, median age 1 month (IQR 6.4) and weight at inclusion 4 kg (IQR 3.1) were included of whom 90% in addition to ECMO received pre-emptive continuous venovenous hemofiltration to optimize fluid balance. The clonidine clearance rate was two-fold that measured in patients not on ECMO. Clearance increased steeply with postnatal age: at days 6, 8 and 10, respectively 30%, 50% and 70% of the adult clearance rate was reached. The use of diuretics was associated with a lower clearance. The volume of distribution increased by 55% during ECMO support.

CONCLUSION

Our findings suggest that a higher dose of clonidine may be needed during ECMO. The PK parameters on ECMO and the dosing guidelines proposed hold the potential to improve sedation practices on ECMO but need to be repeated with different ECMO systems.