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

Sedation management and processed EEG-based solutions during venovenous extracorporeal membrane oxygenation: a narrative review of key challenges and potential benefits

Extracorporeal membrane oxygenation (ECMO) is an established technique for managing severe cardiorespiratory failure. However, it is invasive and requires profound analgo-sedation during initiation and often throughout the therapy. Managing sedation in venovenous (VV) ECMO patients is particularly challenging due to the impact of ECMO circuits on pharmacokinetics and specific patient requirements. This can lead to unpredictable sedative effects and require multiple drugs at higher doses. Additionally, sedation is usually managed with traditional scoring methods, which are subjective and invalid during neuromuscular blockade. These uncertainties may impact outcomes. Recent clinical practice increasingly focuses on reducing sedation to enable earlier physiotherapy and mobilisation, particularly in patients awaiting transplants or receiving mechanical circulatory support. In this context, processed electroencephalogram-based (pEEG) sedation monitoring might be promising, having shown benefits in general anaesthesia and intensive care. However, the technology has limitations, and its benefits in ECMO practice have yet to be formally evaluated. This review provides insights into the challenges of ECMO sedation, including pharmacokinetics, unique ECMO requirements, and the implications of inadequate sedation scores. Finally, it includes a brief overview of the practicality and limitations of pEEG monitoring during VV-ECMO, highlighting a significant research gap.

Systematic Review of Ex Vivo and In Vivo Pharmacokinetic Studies of Drugs Commonly Used During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is a lifesaving treatment for critically ill patients in cardiac or respiratory failure refractory to conventional treatment. Patients on an ECMO circuit (pump, oxygenator, tubing) require numerous medications including sedatives, analgesics, cardioactive medications, and anticonvulsants. Currently, there are few dosing guidelines to optimize pharmacotherapy in this situation. A systematic review was conducted to describe pharmacokinetics (PK) of medications commonly used during ECMO. MEDLINE, Embase, Cochrane, BIOSIS, PubMed, and Web of Science databases were searched. All articles presenting ex vivo, animal, and human data on the PK of the subject medications in the ECMO circuit were included. Three authors independently examined citation titles and abstracts. Four authors extracted relevant details from included studies into standardized data extraction forms. Methodological quality was assessed using the ClinPK guidelines and the Joanna Briggs Institute Checklist. Forty-four studies examining 30 medications were included, 26 ex vivo studies (mostly adult circuits) and 18 observational studies (mainly neonatal patients). Pharmacokinetics varied depending on the medication's characteristics, study type, and population. Study quality was variable, limiting the possibility of deriving hard dosing guidelines from this available literature. Further population PK studies are needed to adequately determine dosing guidelines in adults and children requiring ECMO.

Meropenem Disposition in Neonatal and Pediatric Extracorporeal Membrane Oxygenation and Continuous Renal Replacement Therapy

This study aimed to characterize the impact of extracorporeal membrane oxygenation (ECMO) on the pharmacokinetics (PK) of meropenem in neonates and children and to provide recommendations for meropenem dosing in this specific population of patients. Therapeutic drug monitoring (152 meropenem plasma concentrations) data from 45 patients (38 received ECMO) with a body weight (BW) of 7.88 (3.62-11.97) kg (median (interquartile range)) and postnatal age of 3 (0-465) days were collected. The population PK analysis was performed using NONMEM V7.3.0. Monte Carlo simulations were performed to assess the probability of target achievement (PTA) for 40% of time the free drug remained above the minimum inhibitory concentration (fT > MIC) and 100% fT > MIC. BW was found to be a significant covariate for the volume of distribution (Vd) and clearance (CL). Additionally, continuous renal replacement therapy (CRRT) was associated with a two-fold increase in Vd. In the final model, the CL and Vd for a typical patient with a median BW of 7.88 kg that was off CRRT were 1.09 L/h (RSE = 8%) and 3.98 L (14%), respectively. ECMO did not affect meropenem PK, while superimposed CRRT significantly increased Vd. We concluded that current dosing regimens provide acceptably high PTA for MIC ≤ 4 mg/L for 40% fT > MIC, but individual dose adjustments are needed for 100% fT > MIC.

Sedation and analgesia requirements during venovenous extracorporeal membrane oxygenation in acute respiratory distress syndrome patients

INTRODUCTION

The purpose of this study is to describe sedation and analgesia management, and identify the factors associated with increased demand for medication in acute respiratory distress syndrome (ARDS) patients receiving venovenous extracorporeal membrane oxygenation (VV-ECMO).

METHODS

This retrospective, single-center study included consecutive adult ARDS patients who received VV-ECMO for at least 24 hours from January 2018 to December 2020 in a comprehensive intensive care unit. The electronic medical records were retrospectively reviewed to collect data.

RESULTS

Forty-two adult patients meeting the inclusion criteria were included in the study. Midazolam, sufentanil, and remifentanil were main sedatives and analgesics used in the patient population. The morphine equivalents, representative of the demand for opioids, was 512.9 (IQR, 294.5, 798.2) mg/day. The midazolam equivalents, representative of benzodiazepine requirement, was 279.6 (IQR, 208.8, 384.5) mg/day. The levels of serum creatinine, total bilirubin, lactic acid, SOFA score, and APACHE Ⅱ score at cannulation were found to be associated with opiate or benzodiazepine requirements. Multiple linear regression analysis revealed a linear correlation between midazolam equivalents and morphine equivalents (p < 0.001). In addition, there was a negative linear correlation between Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) score and midazolam equivalents (p = 0.024).

CONCLUSIONS

The sedation and analgesia requirements of ARDS patients receiving VV-ECMO often increase simultaneously. More large-scale studies are needed to confirm the risk factors for increased sedation and analgesia needs in patients supported on VV-ECMO.

Variable Sequestration of Antifungals in an Extracorporeal Membrane Oxygenation Circuit

Fungal infections are common and frequently associated with clinical failure in patients receiving extracorporeal membrane oxygenation (ECMO). Antifungal drugs have physicochemical characteristics associated with a higher likelihood of sequestration onto ECMO circuitry potentially leading to a subtherapeutic drug concentration. The percentage of sequestration of the antifungal drugs-caspofungin, posaconazole, and voriconazole-was determined using an ex vivo ECMO model. The circuits were primed with whole human blood, sodium chloride 0.9%, and human albumin solution. Serial 2 ml samples were taken at baseline, 0.5, 1, 2, 6, 12, and 24 hours after drug addition, paired with non-ECMO controls stored in a water bath at 37°C. Mean loss from the blood-primed ECMO circuits and controls at 24 hours relative to baseline were 80% and 61% for caspofungin ( p = ns), 64% and 11% for posaconazole ( p < 0.005), and 27% and 19% for voriconazole ( p < 0.05). Calculated AUC 0-24 showed a 44% for caspofungin ( p = ns), 30.6% posaconazole ( p < 0.005), and 9% loss for voriconazole ( p = 0.003) compared with the controls, suggesting therapeutic concentrations of these antifungal agents cannot be guaranteed with standard dosing in patients on ECMO. Posaconazole exhibited the greatest loss to the ECMO circuit correlating with both high lipophilicity and protein binding of the drug.

The influence of cardiopulmonary bypass on pediatric pharmacokinetics

INTRODUCTION

Every year thousands of children undergo surgery for congenital heart disease. Cardiac surgery requires the use of cardiopulmonary bypass, which can have unexpected consequences for pharmacokinetic parameters.

AREAS COVERED

We describe the pathophysiological properties of cardiopulmonary bypass that may influence pharmacokinetic parameters, with a focus on literature published in the last 10 years. We performed a PubMed database search with the keywords 'Cardiopulmonary bypass' AND 'Pediatric' AND 'Pharmacokinetics'. We searched related articles on PubMed and checked the references of articles for relevant studies.

EXPERT OPINION

Interest in the influence of cardiopulmonary bypass on pharmacokinetics has increased over the last 10 years, especially due to the use of population pharmacokinetic modeling. Unfortunately, study design usually limits the amount of information that can be obtained with sufficient power and the best way to model cardiopulmonary bypass is yet unknown. More information is needed on the pathophysiology of pediatric heart disease and cardiopulmonary bypass. Once adequately validated, PK models should be integrated in the patient electronic database integrating covariates and biomarkers influencing PK, making it possible to predict real-time drug concentrations and guide further clinical management for the individual patient at the bedside.

Impaired Pharmacokinetics of Amiodarone under Veno-Venous Extracorporeal Membrane Oxygenation: From Bench to Bedside

BACKGROUND

Adjusting drug therapy under veno-venous extracorporeal membrane oxygenation (VV ECMO) is challenging. Although impaired pharmacokinetics (PK) under VV ECMO have been reported for sedative drugs and antibiotics, data about amiodarone are lacking. We evaluated the pharmacokinetics of amiodarone under VV ECMO both in vitro and in vivo.

METHODS

In vitro: Amiodarone concentration decays were compared between closed-loop ECMO and control stirring containers over a 24 h period. In vivo: Potassium-induced cardiac arrest in 10 pigs with ARDS, assigned to either control or VV ECMO groups, was treated with 300 mg amiodarone injection under continuous cardiopulmonary resuscitation. Pharmacokinetic parameters Cmax, Tmax AUC and F were determined from both direct amiodarone plasma concentrations observation and non-linear mixed effects modeling estimation.

RESULTS

An in vitro study revealed a rapid and significant decrease in amiodarone concentrations in the closed-loop ECMO circuitry whereas it remained stable in control experiment. In vivo study revealed a 32% decrease in the AUC and a significant 42% drop of Cmax in the VV ECMO group as compared to controls. No difference in Tmax was observed. VV ECMO significantly modified both central distribution volume and amiodarone clearance. Monte Carlo simulations predicted that a 600 mg bolus of amiodarone under VV ECMO would achieve the amiodarone bioavailability observed in the control group.

CONCLUSIONS

This is the first study to report decreased amiodarone bioavailability under VV ECMO. Higher doses of amiodarone should be considered for effective amiodarone exposure under VV ECMO.

Effects of ex vivo Extracorporeal Membrane Oxygenation Circuits on Sequestration of Antimicrobial Agents

Objectives: Our ex vivo study was designed to determine the sequestration of teicoplanin, tigecycline, micafungin, meropenem, polymyxin B, caspofungin, cefoperazone sulbactam, and voriconazole in extracorporeal membrane oxygenation (ECMO) circuits.

Methods: Simulated closed-loop ECMO circuits were prepared using 2 types of blood-primed ECMO. After the circulation was stabilized, the study drugs were injected into the circuit. Blood samples were collected at 2, 5, 15, 30 min, 1, 3, 6, 12, and 24 h after injection. Drug concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. Control groups were stored at 4°C after 3, 6, 12, and 24 h immersing in a water bath at 37°C to observe spontaneous drug degradation.

Results: Twenty-six samples were analyzed. The average drug recoveries from the ECMO circuits and control groups at 24 h relative to baseline were 67 and 89% for teicoplanin, 100 and 145% for tigecycline, 67 and 99% for micafungin, 45 and 75% for meropenem, 62 and 60% for polymyxin B, 83 and 85% for caspofungin, 79 and 98% for cefoperazone, 75 and 87% for sulbactam, and 60 and 101% for voriconazole, respectively. Simple linear regression showed no significant correlation between lipophilicity (r² = 0.008, P = 0.225) or the protein binding rate (r² = 0.168, P = 0.479) of drugs and the extent of drug loss in the ECMO circuits.

Conclusions: In the two ECMO circuits, meropenem and voriconazole were significantly lost, cefoperazone was slightly lost, while tigecycline and caspofungin were not lost. Drugs with high lipophilicity were lost more in the Maquet circuit than in the Sorin circuit. This study needs more in vivo studies with larger samples for further confirmation, and it suggests that therapeutic drug concentration monitoring should be strongly considered during ECMO.

Sequestration of Midazolam, Fentanyl, and Morphine by an Ex Vivo Cardiopulmonary Bypass Circuit

Cardiopulmonary bypass (CPB) circuits can significantly sequester intravenous anesthetics. Adsorption of medications by our institution's standard circuit (Terumo CAPIOX FX05 oxygenator; noncoated polyvinylchloride tubing) has not been described. We prepared ex vivo CPB circuits with and without oxygenators. Medication combinations studied included midazolam (0.5 mg), fentanyl (50 µg), midazolam (0.5 mg) with morphine (0.5 mg), and midazolam (0.5 mg) with fentanyl (50 µg). Medications were administered after obtaining baseline samples. Samples were drawn at 2, 5, 15, 30, 60, 120, and 180 minutes, and analyzed for concentration of injected medications. Midazolam demonstrated no sequestration after 180 minutes. Fentanyl concentration at 180 minutes was lower with an oxygenator (52.7 ± 12.5 vs. 110.9 ± 12.0 ng/ml, P = 0.00432). More fentanyl was found in solution after 180 minutes when given with midazolam compared to fentanyl given alone in the presence of an oxygenator (101 ± 22.3 vs. 52.7 ± 12.5 ng/ml, P = 0.044). Less midazolam was present after 180 minutes when given with morphine compared to midazolam given alone in the absence of an oxygenator (1264.9 ± 425.6 vs. 2124 ± 254 ng/ml, P = 0.037). We successfully characterized the adsorption of various combinations of midazolam, fentanyl, and morphine to our CPB circuit, showing that fentanyl and midazolam behave differently based on other medications present.

Opioid and sedative requirements in extracorporeal membrane oxygenation patients on hydromorphone versus fentanyl

BACKGROUND

The extracorporeal membrane oxygenation (ECMO) circuit causes pharmacokinetic alterations of medications which impact drug selection and dosing. Although hydromorphone has a favorable pharmacokinetic profile, it is unclear whether hydromorphone provides better patient-centered benefits compared to fentanyl. The objective of this study is to compare opioid and sedative requirements in ECMO patients started on a fentanyl- versus hydromorphone-based analgesia regimen.

METHODS

This was a non-interventional retrospective cohort study. It was conducted at a single center in the cardiovascular intensive care units and cardiac intensive care units. We included venovenous (VV) or venoarterial ECMO patients. Patients who were started on a fentanyl continuous infusion within 24 h of cannulation were compared to patients started on a hydromorphone continuous infusion.

RESULTS

A linear mixed effects model was performed to compare doses of opioid, sedative, and propofol between groups over time. We included 28 hydromorphone patients and 53 fentanyl patients, with 85% on VV ECMO. There were no differences between hydromorphone and fentanyl groups in opioid or sedative (including propofol and benzodiazepine) doses for any ECMO day (p value for interaction .63 and .83, respectively). Propofol doses alone, however, were significantly higher in the fentanyl group on ECMO days three, four, and five.

CONCLUSIONS

There appear to be no major differences in opioid or sedative requirements whether ECMO patients are initiated on a hydromorphone- or fentanyl-based regimen.

Pharmacokinetics and pharmacodynamics of sildenafil in fetal lambs on extracorporeal support

BACKGROUND

Maternal transplacental administration of sildenafil is being considered for a variety of fetal conditions. Clinical translation also requires evaluation of fetal safety in a higher species, such as the fetal lamb. Experiments with the pregnant ewe are curtailed by minimal transplacental transfer as well as limited access to the fetus. The EXTra-uterine Environment for Neonatal Development (EXTEND) model renders the isolated fetal lamb readily accessible and allows for direct fetal administration of sildenafil.

METHODS

Five fetal lambs were placed on extracorporeal support in the EXTEND device and received continuous intravenous (IV) sildenafil (0.3-0.5-0.7 mg/kg/24hr) for a duration of one to seven days. Plasma sildenafil concentrations were sampled at regular intervals to establish the pharmacokinetic profile using population pharmacokinetic modeling. Serial Doppler ultrasound examination, continuous non-invasive hemodynamic monitoring and blood gas analysis were done to evaluate the pharmacodynamic effects and fetal response.

FINDINGS

The target concentration range (47-500 ng/mL) was attained with all doses. Sildenafil induced an immediate and temporary reduction of pulmonary vascular resistance, mean arterial pressure and circuit flow, without change in fetal lactate levels and acid-base status. The duration of the systemic effects increased with the dose.

INTERPRETATION

Immediate temporary pulmonary vascular and systemic hemodynamic changes induced by sildenafil were biochemically well tolerated by fetal lambs on extracorporeal support, with the 0.5 mg/kg/24 h dose balancing rapid attainment of target concentrations with short-lived systemic effects.

RESEARCH IN CONTEXT

None.

SEARCH STRATEGY BEFORE UNDERTAKING THE STUDY

A literature review was conducted searching online databases (Medline, Embase and Cochrane), using search terms: fetal OR prenatal OR antenatal AND sildenafil, without time-limit and excluding human studies. Where relevant, investigators were contacted in order to avoid duplication of work.

EVIDENCE BEFORE THIS STUDY

Prenatal therapy with sildenafil, a phosphodiesterase-5 inhibitor with vasodilatory and anti-remodeling effects on vascular smooth muscle cells, has been considered for a variety of fetal conditions. One multicenter clinical trial investigating the benefit of sildenafil in severe intrauterine growth restriction (the STRIDER-trial) was halted early due to excess mortality in the sildenafil-exposed arm at one treatment site. Such findings demonstrate the importance of extensive preclinical safety assessment in relevant animal models. Transplacentally administered sildenafil leads to decreased pulmonary arterial muscularization, preventing or reducing the occurrence of pulmonary hypertension in rat and rabbit fetuses with diaphragmatic hernia (DH). Validation of these results in a higher and relevant animal model, e.g. fetal lambs, is the next step to advance clinical translation. We recently demonstrated that, in contrast to humans, transplacental transfer of sildenafil in sheep is minimal, precluding the in vivo study of fetal effects at target concentrations using the conventional pregnant ewe model.

ADDED VALUE OF THIS STUDY

We therefore used the extracorporeal support model for fetal lambs, referred to as the EXTra-uterine Environment for Neonatal Development (EXTEND) system, bypassing placental and maternal metabolism, to investigate at what dose the target concentrations are reached, and what the fetal hemodynamic impact and response are. Fetal hemodynamic and metabolic tolerance to sildenafil are a crucial missing element on the road to clinical translation. This is therefore the first study investigating the pharmacokinetics, hemodynamic and biochemical effects of clinical-range concentrations of sildenafil in fetal lambs, free from placental and maternal interference.

IMPLICATIONS OF ALL THE AVAILABLE EVIDENCE

We demonstrated self-limiting pulmonary vasodilation, a decrease of both systemic arterial pressures and circuit flows, induced by clinical range concentrations of sildenafil, without the development of fetal acidosis. This paves the way for further investigation of prenatal sildenafil in fetal lambs on extracorporeal support. A dose of 0.5 mg/kg/24 h offered the best trade-off between rapid achievement of target concentrations and shortest duration of systemic effects. This is also the first study using the EXTEND as a model for pharmacotherapy during pregnancy.

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.

Hydromorphone Compared to Fentanyl in Patients Receiving Extracorporeal Membrane Oxygenation

Fentanyl is commonly used in critically ill patients receiving extracorporeal membrane oxygenation (ECMO). Fentanyl's lipophilicity and protein binding may contribute to a sequestration of the drug in the ECMO circuit. Hydromorphone lacks these characteristics potentially leading to a more predictable drug delivery and improved pain and sedation management among ECMO patients. This study compared hydromorphone to fentanyl in patients receiving ECMO. This retrospective study included adult patients receiving ECMO for ≥48 hours. Patients were excluded if they required neuromuscular blockade, received both fentanyl and hydromorphone during therapy, or had opioid use before hospitalization. Baseline characteristics included patient demographics, ECMO indication and settings, and details regarding mechanical ventilation. The primary outcome was opioid requirements at 48 hours post cannulation described in morphine milligram equivalent (MME). Secondary endpoints included 24-hour opioid requirements, concurrent sedative use, and differences in pain and sedation scores. No differences were noted between the patients receiving fentanyl (n = 32) or hydromorphone (n = 20). Patients receiving hydromorphone required lower MME compared to fentanyl at 24 hours (88 [37-121] vs. 131 [137-227], p < 0.01) and 48 hours (168 [80-281] vs. 325 [270-449], p < 0.01). The proportion of within-goal pain and sedation scores between groups was similar at 24 and 48 hours. Sedative requirements did not differ between the groups. Patients receiving hydromorphone required less MME compared to fentanyl without any differences in sedative requirements, or agitation-sedation scores at 48 hours. Prospective studies should be completed to validate these findings.

TIVA for ECMO and VAD

In recent decades, the use of temporary and permanent use of mechanical assist devices is on the rise for patients with end-stage cardiac failure. These support strategies hold inherently different risks in the face of noncardiac critical illness and require multidisciplinary treatment strategies. The main issues with all mechanical devices whether extracorporeal membrane oxygenation (ECMO) or ventricular assist device (VAD), are related to thrombosis, anticoagulation, infection, avoiding hypertension and thus use of intravenous drugs, which requires intense monitoring, to circumvent further renal, ischemic or neurological injury and prevent complication.

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.

Simultaneous quantitative LC-MS method of ketamine, midazolam and their metabolites (dehydronorketamine, norketamine and 1hydroxymidazolam) for its application in patients on extracorporeal membrane oxygenation (ECMO) therapy

Ketamine (Ket) and midazolam (MDZ) are commonly administered drugs in the intensive care setting for analgesia and sedation. Ket and MDZ are metabolized to dehydro-norketamine (DHNK), nor-ketamine (NK) and 1-hydroxy midazolam (1HMDZ). Limited studies evaluating their pharmacokinetics exists in patients on extracorporeal membrane oxygenation (ECMO) therapy. Therefore, we developed a quantitative, high-performance liquid chromatography-mass spectrometry (with single ion monitoring) method to simultaneously detect Ket, MDZ and their (DHNK, NK and 1HMDZ) metabolites in human plasma. Considerable sensitivity was obtained for the analytes using a C₁₈ HILIC column operated by a high-performance liquid chromatography system coupled with a Thermo Exactive Orbitrap mass spectrometer. Calibration curves were developed for analyte molecules (n = 5) in the presence of carbamazepine (CBZ) as an internal standard. The lower limits of quantitation (LLOQ) for Ket and MDZ were 20 and 10 ng/mL, respectively with the LLOQ for DHNK, NK and 1HMDZ at 470, 320 and 150 ng/ml. Moreover, the percent coefficient of variance and precision for inter- and intra-day runs were within the standards set forth by the ICH and FDA guidelines. This method is sensitive and has been successfully applied to an ongoing pharmacokinetic study in patients on ECMO therapy.

Sequestration of Voriconazole and Vancomycin Into Contemporary Extracorporeal Membrane Oxygenation Circuits: An in vitro Study

Background: Bacterial and fungal infections are common and often contribute to death in patients undergoing extracorporeal membrane oxygenation (ECMO). Drug disposition is altered during ECMO, and adsorption in the circuit is an established causative factor. Vancomycin and voriconazole are widely used, despite the lack of evidence-based prescription guidelines. Objective: The objective of this study was to determine the extraction of voriconazole and vancomycin by the Xenios/Novalung ECMO circuits. Methods: We have set up nine closed-loop ECMO circuits, consisting of four different iLAActivve ^® kits for neonatal, pediatric, and adult support: three iLA-ActivveMiniLung ^® petite kits, two iLA-ActivveMiniLung ^® kits, two iLA-ActivveiLA ^® kits, and two iLA-Activve X-lung ^® kits. The circuits were primed with whole blood and maintained at physiologic conditions for 24 h. Voriconazole and vancomycin were injected as a single-bolus age-related dose into the circuits. Pre-membrane (P2) blood samples were obtained at baseline and after drug injection at 2, 10, 30, 180, 360 min, and 24 h. A control sample at 2 min was collected for spontaneous drug degradation testing at 24 h. Results: Seventy-two samples were analyzed in triplicate. The mean percentage of drug recovery at 24 h was 20% for voriconazole and 62% for vancomycin. Conclusions: The extraction of voriconazole and vancomycin by contemporary ECMO circuits is clinically relevant across all age-related circuit sizes and may result in reduced drug exposure in vivo.

Pharmacokinetic modeling of intravenous sildenafil in newborns with congenital diaphragmatic hernia

PURPOSE

We developed a pharmacokinetic model of intravenous sildenafil in newborns with congenital diaphragmatic hernia (CDH) to achieve a target plasma concentration of over 50 μg/l.

METHODS

Twenty-three CDH newborns with pulmonary hypertension (64 blood samples) received intravenous sildenafil. Patients received a loading dose of 0.35 mg/kg (IQR 0.16 mg/kg) for 3 h, followed by a continuous infusion of 1.5 mg/kg/day (IQR 0.1 mg/kg/day). For model development, non-linear mixed modeling was used. Inter-individual variability (IIV) and inter-occasion variability were tested. Demographic and laboratory parameters were evaluated as covariates. Normalized prediction distribution errors (NPDE) and visual predictive check (VPC) were used for model validation.

RESULTS

A two-compartment disposition model of sildenafil and a one-compartment disposition model of desmethyl sildenafil (DMS) was observed with IIV in sildenafil and DMS clearance and volume of distribution of sildenafil. NPDE and VPC revealed adequate predictability. Only postnatal age increased sildenafil clearance. This was partly compensated by a higher DMS concentration, which also has a therapeutic effect. In this small group of patients, sildenafil was tolerated well.

CONCLUSIONS

This model for sildenafil in CDH patients shows that concentration-targeted sildenafil dosing of 0.4 mg/kg in 3 h, followed by 1.6 mg/kg/day continuous infusion achieves appropriate sildenafil plasma levels.

Recovery of cefazolin and clindamycin in in vitro pediatric CPB systems

Cardiopulmonary bypass (CPB) is often necessary for congenital cardiac surgery, but CPB can alter drug pharmacokinetic parameters resulting in underdosing. Inadequate plasma levels of antibiotics could lead to postoperative infections with increased morbidity. The influence of pediatric CPB systems on cefazolin and clindamycin plasma levels is not known. We have measured plasma levels of cefazolin and clindamycin in in vitro pediatric CPB systems. We have tested three types of CPB systems. All systems were primed and spiked with clindamycin and cefazolin. Samples were taken at different time points to measure the recovery of cefazolin and clindamycin. Linear mixed model analyses were performed to assess if drug recovery was different between the type of CPB system and sampling time point. The experiments were conducted at a tertiary university hospital. 81 samples were analyzed. There was a significant difference in the recovery over time between CPB systems for cefazolin and clindamycin (P < .001). Cefazolin recovery after 180 minutes was 106% (95% CI: 91‐123) for neonatal, 99% (95% CI: 85‐115) for infant, and 77% (95% CI: 67‐89) for pediatric systems. Clindamycin recovery after 180 minutes was 143% (95% CI: 116‐177) for neonatal, 111% (95% CI: 89‐137) for infant, and 120% (95% CI: 97‐149) for pediatric systems. Clindamycin recovery after 180 minutes compared to the theoretical concentration was 0.4% for neonatal, 1.2% for infants, and 0.6% for pediatric systems. The recovery of cefazolin was high in the neonatal and infant CPB systems and moderate in the pediatric system. We found a large discrepancy between the theoretical and measured concentrations of clindamycin in all tested CPB systems.

In Vitro Recovery of Sufentanil, Midazolam, Propofol, and Methylprednisolone in Pediatric Cardiopulmonary Bypass Systems

OBJECTIVES

To evaluate in vitro drug recovery in cardiopulmonary bypass (CPB) systems used for pediatric cardiac surgery.

DESIGN

Observational in vitro study.

SETTING

Single-center university hospital.

PARTICIPANTS

In vitro CPB systems used for pediatric cardiac surgery.

INTERVENTIONS

Three full neonatal, infant, and pediatric CPB systems were primed according to hospital protocol and kept running for 6 hours. Midazolam, propofol, sufentanil, and methylprednisolone were added to the venous side of the systems in doses commonly used for induction of general anesthesia. Blood samples were taken from the postoxygenator side of the circuit immediately after injection of the drugs and after 2, 5, 7, 10, 30, 60, 180, and 300 minutes.

MEASUREMENTS AND MAIN RESULTS

Linear mixed model analyses were performed to assess the relationship between log-transformed drug concentration (dependent variable) and type of CPB system and sample time point (independent variables). The mean percentage of drug recovery after 60 and 180 minutes compared with T1 was 41.7% (95% confidence interval [CI] 35.9-47.4) and 23.0% (95% CI 9.2-36.8) for sufentanil, 87.3% (95% CI 64.9-109.7) and 82.0% (95% CI 64.6-99.4) for midazolam, 41.3% (95% CI 15.5-67.2) and 25.0% (95% CI 4.7-45.3) for propofol, and 119.3% (95% CI 101.89-136.78) and 162.0% (95% CI 114.09-209.91) for methylprednisolone, respectively.

CONCLUSIONS

The present in vitro experiment with neonatal, infant, and pediatric CPB systems shows a variable recovery of routinely used drugs with significant differences between drugs, but not between system categories (with the exception of propofol). The decreased recovery of mainly sufentanil and propofol could lead to suboptimal dosing of patients during cardiac surgery with CPB.

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.

Opioid and Benzodiazepine Requirements in Obese Adult Patients Receiving Extracorporeal Membrane Oxygenation

Background: The use of extracorporeal membrane oxygenation (ECMO) sometimes requires deep levels of sedation (Richmond Agitation Sedation Scale [RASS] −5) in patients with acute respiratory distress syndrome (ARDS). The role of obesity in opioid and sedative requirements remains unclear in patients receiving ECMO. Objective: This study sought to determine whether obesity increases midazolam and opioid requirements in patients receiving venovenous (vv)-ECMO up to the first 7 days after initiation. Methods: This was a retrospective cohort study of adult patients with ARDS managed with vv-ECMO. Results: The obese (n = 38) and nonobese (n = 43) groups had similar baseline characteristics. Fentanyl equivalents were significantly higher on day 3 in the obese group ( P = 0.02) despite similar RASS scores with no differences in midazolam requirements. There were no differences in duration of ECMO, length of stay, or mortality. Conclusion and Relevance: Daily midazolam requirements were not significantly different, and opioid requirements were only significantly higher in the obese group on day 3 despite similar levels of sedation. The impact of obesity with the addition of ECMO and how to adapt doses of medications remains elusive.

Sedation with alfentanil versus fentanyl in patients receiving extracorporeal membrane oxygenation: outcomes from a single-centre retrospective study

INTRODUCTION

In November 2016, our institution switched from alfentanil to fentanyl for analgesia and sedation in adult patients receiving extracorporeal membrane oxygenation. There is no published evidence comparing the use of alfentanil with fentanyl for sedation in extracorporeal membrane oxygenation patients. We conducted a retrospective observational study to explore any significant differences in patient outcomes or in the prescribing of adjunct sedatives before and after the switch.

METHODS

Patients were retrospectively identified from a prospectively recorded database of all patients who received extracorporeal membrane oxygenation at our institution between January 2016 and October 2017. Patients included those sedated with alfentanil or fentanyl. The total daily doses of intravenous opioids (alfentanil or fentanyl) were calculated for each patient, and the prescribing of adjunctive sedative or analgesic agents was recorded. Patient demographics, extracorporeal membrane oxygenation modality, clinical outcomes including mortality and length of intensive care and hospital stay were recorded.

RESULTS

A total of 174 patients were identified, 69 on alfentanil and 95 on fentanyl. There was no difference found between groups for mode of extracorporeal membrane oxygenation, age, Acute Physiology and Chronic Health Evaluation 2 score (APACHE II) and Charlson score, except for body mass index (p = 0.002). No differences in patient outcomes was observed between groups, although patients in the alfentanil group received a significantly higher median total daily dose of adjuvant sedatives (quetiapine (p = 0.016) and midazolam (p = 0.009)).

CONCLUSIONS

No differences in patient outcomes were found between extracorporeal membrane oxygenation patients sedated with alfentanil compared with fentanyl. There was a statistically significant reduction in some adjunctive sedatives in patients managed with a fentanyl-based regimen. Prospective studies are required to confirm these results.

Population pharmacokinetics of intravenous sufentanil in critically ill patients supported with extracorporeal membrane oxygenation therapy

Background

Sufentanil is commonly used for analgesia and sedation during extracorporeal membrane oxygenation (ECMO). Both ECMO and the pathophysiological changes derived from critical illness have significant effects on the pharmacokinetics (PK) of drugs, yet reports of ECMO and sufentanil PK are scarce. Here, we aimed to develop a population PK model of sufentanil in ECMO patients and to suggest dosing recommendations.

Methods

This prospective cohort PK study included 20 patients who received sufentanil during venoarterial ECMO (VA-ECMO). Blood samples were collected for 96 h during infusion and 72 h after cessation of sufentanil. A population PK model was developed using nonlinear mixed effects modelling. Monte Carlo simulations were performed using the final PK parameters with two typical doses.

Results

A two-compartment model best described the PK of sufentanil. In our final model, increased volume of distribution and decreased values for clearance were reported compared with previous PK data from non-ECMO patients. Covariate analysis showed that body temperature and total plasma protein level correlated positively with systemic clearance (CL) and peripheral volume of distribution (V2), respectively, and improved the model. The parameter estimates of the final model were as follows: CL = 37.8 × EXP (0.207 × (temperature − 36.9)) L h⁻¹, central volume of distribution (V1) = 229 L, V2 = 1640 × (total plasma protein/4.5)^2.46 L, and intercompartmental clearance (Q) = 41 L h⁻¹. Based on Monte Carlo simulation results, an infusion of 17.5 μg h⁻¹ seems to reach target sufentanil concentration (0.3–0.6 μg L⁻¹) in most ECMO patients except hypothermic patients (33 °C). In hypothermic patients, over-sedation, which could induce respiratory depression, needs to be monitored especially when their total plasma protein level is low.

Conclusions

This is the first report on a population PK model of sufentanil in ECMO patients. Our results suggest that close monitoring of the body temperature and total plasma protein level is crucial in ECMO patients who receive sufentanil to provide effective analgesia and sedation and promote recovery.

Trial registration

Clinicaltrials.gov NCT02581280, December 1st, 2014.

Sufentanil pharmacokinetics in a full-term neonate treated with extracorporeal membrane oxygenation: a case report

INTRODUCTION

Sufentanil is a potent analgesic drug used for pain management. A few studies describe the pharmacokinetics of sufentanil in neonates; however, no pharmacokinetic data about sufentanil during extracorporeal membrane oxygenation have been published yet.

CASE REPORT

A 1-day-old neonate with moderate hypoxic-ischemic encephalopathy received veno-arterial extracorporeal membrane oxygenation support for refractory respiratory and circulatory failure. Sufentanil plasma concentrations were determined during both extracorporeal membrane oxygenation (n = 14) and non-extracorporeal membrane oxygenation (n = 17) period. Based on these measurements, individual sufentanil pharmacokinetic parameters were calculated.

DISCUSSION

We observed increased sufentanil volume of distribution (11.6 vs 5.6 L/kg) and decreased sufentanil clearance (0.535 vs 0.746 L/h/kg) in extracorporeal membrane oxygenation period. The increment of volume of distribution was attributed to ECMO influence, while difference in clearance was probably due to drug interaction.

CONCLUSIONS

This is the first description of sufentanil pharmacokinetics in neonate treated with extracorporeal membrane oxygenation. We observed considerably larger volume of distribution during extracorporeal membrane oxygenation period in comparison with non-extracorporeal membrane oxygenation period.

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.