Protein-bound drugs are prone to sequestration in the extracorporeal membrane oxygenation circuit: results from an ex vivo study

A pharmacokinetic framework describing antibiotic adsorption to cardiopulmonary bypass devices

Cardiopulmonary bypass (CPB) can alter pharmacokinetic (PK) parameters and the drug may adsorb to the CPB device, altering exposure. Cefazolin is a beta-lactam antibiotic used for antimicrobial prophylaxis during cardiac surgery supported by CPB. Adsorption of cefazolin could result in therapeutic failure. An ex vivo study was undertaken using CPB devices primed and then dosed with cefazolin and samples were obtained over 1 hour of recirculation. Twelve experimental runs were conducted using different CPB device sizes (neonate, infant, child, and adult), device coatings (Xcoating™, Rheoparin®, PH.I.S.I.O), and priming solutions. The time course of saturable binding, using Bmax (binding capacity), Kd (dissociation constant), and T2off (half-time of dissociation), described cefazolin adsorption. Bmax estimates for the device sizes were neonate 40.0 mg (95% CI 24.3, 67.4), infant 48.6 mg (95% CI 5.97, 80.2), child 77.8 mg (95% CI 54.9, 103), and adult 196 mg (95% CI 191, 199). The Xcoating™ Kd estimate was 139 mg/L (95% CI 27.0, 283) and the T2off estimate was 98.4 min (95% CI 66.8, 129). The Rheoparin® and PH.I.S.I.O coatings had similar binding parameters with Kd and T2off estimates of 0.169 mg/L (95% CI 0.01, 1.99) and 4.94 min (95% CI 0.17, 59.4). The Bmax was small (< 10%) relative to a typical total patient dose during cardiac surgery supported by CPB. A dose adjustment for cefazolin based solely on drug adsorption is not required. This framework could be extended to other PK studies involving CPB.

Understanding antimicrobial pharmacokinetics in critically ill patients to optimize antimicrobial therapy: A narrative review

Effective treatment of sepsis not only demands prompt administration of appropriate antimicrobials but also requires precise dosing to enhance the likelihood of patient survival. Adequate dosing refers to the administration of doses that yield therapeutic drug concentrations at the infection site. This ensures a favorable clinical and microbiological response while avoiding antibiotic-related toxicity. Therapeutic drug monitoring (TDM) is the recommended approach for attaining these goals. However, TDM is not universally available in all intensive care units (ICUs) and for all antimicrobial agents. In the absence of TDM, healthcare practitioners need to rely on several factors to make informed dosing decisions. These include the patient's clinical condition, causative pathogen, impact of organ dysfunction (requiring extracorporeal therapies), and physicochemical properties of the antimicrobials. In this context, the pharmacokinetics of antimicrobials vary considerably between different critically ill patients and within the same patient over the course of ICU stay. This variability underscores the need for individualized dosing. This review aimed to describe the main pathophysiological changes observed in critically ill patients and their impact on antimicrobial drug dosing decisions. It also aimed to provide essential practical recommendations that may aid clinicians in optimizing antimicrobial therapy among critically ill patients.

Population pharmacokinetics of daptomycin in critically ill patients receiving extracorporeal membrane oxygenation

BACKGROUND

Daptomycin is widely used in critically ill patients for Gram-positive bacterial infections. Extracorporeal membrane oxygenation (ECMO) is increasingly used in this population and can potentially alter the pharmacokinetic (PK) behaviour of antibiotics. However, the effect of ECMO has not been evaluated in daptomycin. Our study aims to explore the effect of ECMO on daptomycin in critically ill patients through population pharmacokinetic (PopPK) analysis and to determine optimal dosage regimens based on both efficacy and safety considerations.

METHODS

A prospective, open-label PK study was carried out in critically ill patients with or without ECMO. The total concentration of daptomycin was determined by UPLC-MS/MS. NONMEM was used for PopPK analysis and Monte Carlo simulations.

RESULTS

Two hundred and ninety-three plasma samples were collected from 36 critically ill patients, 24 of whom received ECMO support. A two-compartment model with first-order elimination can best describe the PK of daptomycin. Creatinine clearance (CLCR) significantly affects the clearance of daptomycin while ECMO has no significant effect on the PK parameters. Monte Carlo simulations showed that, when the MICs for bacteria are  ≥1 mg/L, the currently recommended dosage regimen is insufficient for critically ill patients with CLCR > 30 mL/min. Our simulations suggest 10 mg/kg for patients with CLCR between 30 and 90 mL/min, and 12 mg/kg for patients with CLCR higher than 90 mL/min.

CONCLUSIONS

This is the first PopPK model of daptomycin in ECMO patients. Optimal dosage regimens considering efficacy, safety, and pathogens were provided for critical patients based on pharmacokinetic-pharmacodynamic analysis.

Antifungals in Patients With Extracorporeal Membrane Oxygenation: Clinical Implications

Extracorporeal membrane oxygenation (ECMO) is a life-saving technique used in critical care medicine for patients with severe respiratory or cardiac failure. This review examines the treatment and prophylaxis of fungal infections in ECMO patients, proposing specific regimens based on available data for different antifungals (azoles, echinocandins, amphotericin B/liposomal amphotericin B) and invasive fungal infections. Currently, isavuconazole and posaconazole have the most supported data, while modified dosages of isavuconazole are recommended in ECMO. Echinocandins are preferred for invasive candidiasis. However, choosing echinocandins is challenging due to limited and varied data on concentration loss in the ECMO circuit. Caution is likewise advised when using liposomal amphotericin B due to uncertain concentrations and potential ECMO dysfunction based on scarce data. We further conclude with the importance of further research on the impact of ECMO on antifungal drug concentrations to optimize dosing regimens in critically ill patients.

COVID-19 Drug Treatments Are Prone to Sequestration in Extracorporeal Membrane Oxygenation Circuits: An Ex Vivo Extracorporeal Membrane Oxygenation Study

Drug treatments for coronavirus disease 2019 (COVID-19) dramatically improve patient outcomes, and although extracorporeal membrane oxygenation (ECMO) has significant use in these patients, it is unknown whether ECMO affects drug dosing. We used an ex vivo adult ECMO model to measure ECMO circuit effects on concentrations of specific COVID-19 drug treatments. Three identical ECMO circuits used in adult patients were set up. Circuits were primed with fresh human blood (temperature and pH maintained within normal limits). Three polystyrene jars with 75 ml fresh human blood were used as controls. Remdesivir, GS-441524, nafamostat, and tocilizumab were injected in the circuit and control jars at therapeutic concentrations. Samples were taken from circuit and control jars at predefined time points over 6 h and drug concentrations were measured using validated assays. Relative to baseline, mean (± standard deviation [SD]) study drug recoveries in both controls and circuits at 6 h were significantly lower for remdesivir (32.2% [±2.7] and 12.4% [±2.1], p < 0.001), nafamostat (21.4% [±5.0] and 0.0% [±0.0], p = 0.018). Reduced concentrations of COVID-19 drug treatments in ECMO circuits is a clinical concern. Remdesivir and nafamostat may need dose adjustments. Clinical pharmacokinetic studies are suggested to guide optimized COVID-19 drug treatment dosing during ECMO.

Practices surrounding antimicrobial use in patients managed with extracorporeal membrane oxygenation: An international survey

PURPOSE

This study aimed to survey critical care clinicians and characterize their perception of antimicrobial dosing strategies in patients receiving extracorporeal membrane oxygenation (ECMO).

METHODS

International, cross-sectional survey distributed to members of the Society of Critical Care Medicine in October 2022.

RESULTS

Respondents were primarily physicians (45%), with 92% practicing in North America. Ninety-seven percent of respondents reported antimicrobial dosing in critically ill patients to be challenging, due to physiological derangements seen in the patient population. Eighty-seven percent reported consideration of physicochemical drug properties when dosing antimicrobials in ECMO-supported patients, with lipophilicity (83%) and degree of protein binding (74%) being the two most common. Respondents' approach to antimicrobial dosing strategies did not significantly differ in critically ill ECMO-supported patients, compared to patients with equal severity of illness not receiving ECMO support.

CONCLUSION

Approaches to antimicrobial dosing strategies do not significantly differ among respondents between critically ill patients on ECMO support, compared to patients with equal severity of illness not receiving ECMO support. These findings were unexpected considering the added physiologic complexity of the ECMO circuit to critically ill adult patients and the need for well designed and adequately powered studies to inform empiric dosing guidance for ECMO-supported patients.

Population pharmacokinetics of intravenous daptomycin in critically ill patients: implications for selection of dosage regimens

Daptomycin is gaining prominence for the treatment of methicillin-resistant Staphylococcus aureus infections. However, the dosage selection for daptomycin in critically ill patients remains uncertain, especially in Chinese patients. This study aimed to establish the population pharmacokinetics of daptomycin in critically ill patients, optimize clinical administration plans, and recommend appropriate dosage for critically ill patients in China. The study included 64 critically ill patients. Blood samples were collected at the designated times. The blood daptomycin concentration was determined using validated liquid chromatography-tandem mass spectrometry. A nonlinear mixed-effects model was applied for the population pharmacokinetic analysis and Monte Carlo simulations of daptomycin. The results showed a two-compartment population pharmacokinetic model of daptomycin in critically ill adult Han Chinese patients. Monte Carlo simulations revealed that a daily dose of 400 mg of daptomycin was insufficient for the majority of critically ill adult patients to achieve the anti-infective target. For critically ill adult patients with normal renal function (creatinine clearance rate >90 mL/min), the probability of achieving the target only reached 90% when the daily dose was increased to 700 mg. For patients undergoing continuous renal replacement therapy (CRRT), 24 h administration of 500 mg met the pharmacodynamic goals and did not exceed the safety threshold in most patients. Therefore, considering its efficacy and safety, intravenous daptomycin doses are best scaled according to creatinine clearance, and an increased dose is recommended for critically ill patients with hyperrenalism. For patients receiving CRRT, medication is recommended at 24 h intervals.

Imipenem/relebactam pharmacokinetics in critically ill patients supported on extracorporeal membrane oxygenation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a life-saving modality but has the potential to alter the pharmacokinetics (PK) of antimicrobials. Imipenem/cilastatin/relebactam is an antibiotic with utility in treating certain multi-drug resistant Gram-negative infections. Herein, we describe the population pharmacokinetics of imipenem and relebactam in critically ill patients supported on ECMO.

METHODS

Patients with infection supported on ECMO received 4-6 doses of imipenem/cilastatin/relebactam per current prescribing information based on estimated creatinine clearance. Blood samples were collected following the final dose of the antibiotic. Concentrations were determined via LC-MS/MS. Population PK models were fit with and without covariates using Pmetrics. Monte Carlo simulations of 1000 patients assessed joint PTA of fAUC0-24/MIC ≥ 8 for relebactam, and ≥40% fT > MIC for imipenem for each approved dosing regimen.

RESULTS

Seven patients supported on ECMO were included in PK analyses. A two-compartment model with creatinine clearance as a covariate on clearance for both imipenem and relebactam fitted the data best. The mean ± standard deviation parameters were: CL0, 15.21 ± 6.52 L/h; Vc, 10.13 ± 2.26 L; K12, 2.45 ± 1.16 h-1 and K21, 1.76 ± 0.49 h-1 for imipenem, and 6.95 ± 1.34 L/h, 9.81 ± 2.69 L, 2.43 ± 1.13 h-1 and 1.52 ± 0.67 h-1 for relebactam. Simulating each approved dose of imipenem/cilastatin/relebactam according to creatinine clearance yielded PTAs of ≥90% up to an MIC of 2 mg/L.

CONCLUSIONS

Imipenem/cilastatin/relebactam dosed according to package insert in patients supported on ECMO is predicted to achieve exposures sufficient to treat susceptible Gram-negative isolates, including Pseudomonas aeruginosa.

Reducing hydrophobic drug adsorption in an in-vitro extracorporeal membrane oxygenation model

Extracorporeal membrane oxygenation (ECMO) is a life-saving cardiopulmonary bypass technology for critically ill patients with heart and lung failure. Patients treated with ECMO receive a range of drugs that are used to treat underlying diseases and critical illnesses. However, the dosing guidelines for these drugs used in ECMO patients are unclear. Mortality rate for patients on ECMO exceeds 40% partly due to inaccurate dosing information, caused in part by the adsorption of drugs in the ECMO circuit and its components. These drugs range in hydrophobicity, electrostatic interactions, and pharmacokinetics. Propofol is commonly administered to ECMO patients and is known to have high adsorption rates to the circuit components due to its hydrophobicity. To reduce adsorption onto the circuit components, we used micellar block copolymers (Poloxamer 188TM and Poloxamer 407TM) and liposomes tethered with poly(ethylene glycol) to encapsulate propofol, provide a hydrophilic shell and prevent its adsorption. Size, polydispersity index (PDI), and zeta potential of the delivery systems were characterized by dynamic light scattering, and encapsulation efficiency was characterized using High Performance Liquid Chromatography (HPLC). All delivery systems used demonstrated colloidal stability at physiological conditions for seven days, cytocompatibility with a human leukemia monocytic cell line, i.e., THP-1 cells, and did not activate the complement pathway in human plasma. We demonstrated a significant reduction in adsorption of propofol in an in-vitro ECMO model upon encapsulation in micelles and liposomes. These results show promise in reducing the adsorption of hydrophobic drugs to the ECMO circuits by encapsulation in nanoscale structures tethered with hydrophilic polymers on the surface.

No Sequestration of Commonly Used Anti-Infectives in the Extracorporeal Membrane Oxygenation (ECMO) Circuit-An Ex Vivo Study

Patients undergoing extracorporeal membrane oxygenation (ECMO) often require therapy with anti-infective drugs. The pharmacokinetics of these drugs may be altered during ECMO treatment due to pathophysiological changes in the drug metabolism of the critically ill and/or the ECMO therapy itself. This study investigates the latter aspect for commonly used anti-infective drugs in an ex vivo setting. A fully functional ECMO device circulated an albumin-electrolyte solution through the ECMO tubes and oxygenator. The antibiotic agents cefazolin, cefuroxim, cefepime, cefiderocol, linezolid and daptomycin and the antifungal agent anidulafungin were added. Blood samples were taken over a period of four hours and drug concentrations were measured via high-pressure liquid chromatography (HPLC) with UV detection. Subsequently, the study analyzed the time course of anti-infective concentrations. The results showed no significant changes in the concentration of any tested anti-infectives throughout the study period. This ex vivo study demonstrates that the ECMO device itself has no impact on the concentration of commonly used anti-infectives. These findings suggest that ECMO therapy does not contribute to alterations in the concentrations of anti-infective medications in severely ill patients.

The impact of extracorporeal membrane oxygenation on antifungal pharmacokinetics: A systematic review

BACKGROUND AND OBJECTIVE

The use of extracorporeal membrane oxygenation (ECMO) as a cardiocirculatory or respiratory support has tremendously increased in critically ill patients. In the setting of ECMO support, invasive fungal infections are a severe cause of morbidity and mortality. This vulnerable population is at risk of suboptimal antifungal exposure due to an increased volume of distribution (Vd), drug sequestration and decreased clearance. Here, we aimed to summarize ex-vivo and clinical studies on the potential impact of ECMO on the pharmacokinetics (PK) of antifungal agents and dosing requirements.

METHODS

A systematic search of the literature within electronic databases PubMed and EMBASE was conducted from database inception to 30 April 2023. Inclusion criteria were as follows: critically ill patients receiving ECMO regardless of age and reporting at least one PK parameter.

RESULTS

Thirty-six studies met inclusion criteria, including seven ex-vivo experiments and 29 clinical studies evaluating three classes of antifungals: polyenes, triazoles and echinocandins. Based on the available ex-vivo PK data, we found a significant sequestration of highly lipophilic and protein-bound antifungals within the ECMO circuit such as voriconazole, posaconazole and micafungin but the PK of several antifungals remains to be addressed such as amphotericin B, isavuconazole and anidulafungin. Most clinical studies have shown increased Vd of some antifungals like fluconazole and micafungin, particularly in the pediatric population. Conflicting data exist about caspofungin exposure.

CONCLUSIONS

The available literature on the antifungal PK changes in ECMO setting is scarce. Whenever possible, therapeutic drug monitoring is highly advised to personalize antifungal therapy.

Possible Involvement of Protein Binding Inhibition in Changes in Dexmedetomidine Concentration in Extracorporeal Circuits during Midazolam Use

It was recently reported that the dexmedetomidine concentration within the extracorporeal circuit decreases with co-administration of midazolam. In this study, we investigated whether displacement of dexmedetomidine by midazolam from the binding site of major plasma proteins, human serum albumin (HSA) and α1-acid glycoprotein (AAG), would increase levels of free dexmedetomidine that could be adsorbed to the circuit. Equilibrium dialysis experiments indicated that dexmedetomidine binds to a single site on both HSA and AAG with four times greater affinity than midazolam. Midazolam-mediated inhibition of the binding of dexmedetomidine to HSA and AAG was also examined. The binding of dexmedetomidine to these proteins decreased in the presence of midazolam. Competitive binding experiments suggested that the inhibition of binding by midazolam was due to competitive displacement at site II of HSA and due to non-competitive displacement at the site of AAG. Thus, our present data indicate that free dexmedetomidine displaced by midazolam from site II of HSA or from AAG is adsorbed onto extracorporeal circuits, resulting in a change in the dexmedetomidine concentration within the circuit.

Meropenem extraction by ex vivo extracorporeal life support circuits

BACKGROUND

Meropenem is a broad-spectrum carbapenem-type antibiotic commonly used to treat critically ill patients infected with extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. As many of these patients require extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapy (CRRT), it is important to understand how these extracorporeal life support circuits impact meropenem pharmacokinetics. Based on the physicochemical properties of meropenem, it is expected that ECMO circuits will minimally extract meropenem, while CRRT circuits will rapidly clear meropenem. The present study seeks to determine the extraction of meropenem from ex vivo ECMO and CRRT circuits and elucidate the contribution of different ECMO circuit components to extraction.

METHODS

Standard doses of meropenem were administered to three different configurations (n = 3 per configuration) of blood-primed ex vivo ECMO circuits and serial sampling was conducted over 24 h. Similarly, standard doses of meropenem were administered to CRRT circuits (n = 4) and serial sampling was conducted over 4 h. Meropenem was administered to separate tubes primed with circuit blood to serve as controls to account for drug degradation. Meropenem concentrations were quantified, and percent recovery was calculated for each sample.

RESULTS

Meropenem was cleared at a similar rate in ECMO circuits of different configurations (n = 3) and controls (n = 6), with mean (standard deviation) recovery at 24 h of 15.6% (12.9) in Complete circuits, 37.9% (8.3) in Oxygenator circuits, 47.1% (8.2) in Pump circuits, and 20.6% (20.6) in controls. In CRRT circuits (n = 4) meropenem was cleared rapidly compared with controls (n = 6) with a mean recovery at 2 h of 2.36% (1.44) in circuits and 93.0% (7.1) in controls.

CONCLUSION

Meropenem is rapidly cleared by hemodiafiltration during CRRT. There is minimal adsorption of meropenem to ECMO circuit components; however, meropenem undergoes significant degradation and/or plasma metabolism at physiological conditions. These ex vivo findings will advise pharmacists and physicians on the appropriate dosing of meropenem.

Interaction of ceftazidime and clindamycin with extracorporeal life support

BACKGROUND

Ceftazidime and clindamycin are commonly prescribed to critically ill patients who require extracorporeal life support such as ECMO and CRRT. The effect of ECMO and CRRT on the disposition of ceftazidime and clindamycin is currently unknown.

METHODS

Ceftazidime and clindamycin extraction were studied with ex vivo ECMO and CRRT circuits primed with human blood. The percent recovery of these drugs over time was calculated to determine the degree of interaction between these drugs and circuit components.

RESULTS

Neither ceftazidime nor clindamycin exhibited measurable interactions with the ECMO circuit. In contrast, CRRT cleared 100% of ceftazidime from the experimental circuit within the first 2 h. Clearance of clindamycin from the CRRT circuit was slower, with about 20% removed after 6 h.

CONCLUSION

Clindamycin and ceftazidime dosing adjustments are likely required in patients who are supported with CRRT, and future studies to quantify these adjustments should consider the pathophysiology of the patient in combination with the clearance due to CRRT. Dosing adjustments to account for adsorption to ECMO circuit components are likely unnecessary and should focus instead on the pathophysiology of the patient and changes in volume of distribution. These results will help improve the safety and efficacy of ceftazidime and clindamycin in patients requiring ECMO and CRRT.

Current knowledge gaps in extracorporeal respiratory support

Extracorporeal life support (ECLS) for acute respiratory failure encompasses veno-venous extracorporeal membrane oxygenation (V-V ECMO) and extracorporeal carbon dioxide removal (ECCO2R). V-V ECMO is primarily used to treat severe acute respiratory distress syndrome (ARDS), characterized by life-threatening hypoxemia or ventilatory insufficiency with conventional protective settings. It employs an artificial lung with high blood flows, and allows improvement in gas exchange, correction of hypoxemia, and reduction of the workload on the native lung. On the other hand, ECCO2R focuses on carbon dioxide removal and ventilatory load reduction ("ultra-protective ventilation") in moderate ARDS, or in avoiding pump failure in acute exacerbated chronic obstructive pulmonary disease. Clinical indications for V-V ECLS are tailored to individual patients, as there are no absolute contraindications. However, determining the ideal timing for initiating extracorporeal respiratory support remains uncertain. Current ECLS equipment faces issues like size and durability. Innovations include intravascular lung assist devices (ILADs) and pumpless devices, though they come with their own challenges. Efficient gas exchange relies on modern oxygenators using hollow fiber designs, but research is exploring microfluidic technology to improve oxygenator size, thrombogenicity, and blood flow capacity. Coagulation management during V-V ECLS is crucial due to common bleeding and thrombosis complications; indeed, anticoagulation strategies and monitoring systems require improvement, while surface coatings and new materials show promise. Moreover, pharmacokinetics during ECLS significantly impact antibiotic therapy, necessitating therapeutic drug monitoring for precise dosing. Managing native lung ventilation during V-V ECMO remains complex, requiring a careful balance between benefits and potential risks for spontaneously breathing patients. Moreover, weaning from V-V ECMO is recognized as an area of relevant uncertainty, requiring further research. In the last decade, the concept of Extracorporeal Organ Support (ECOS) for patients with multiple organ dysfunction has emerged, combining ECLS with other organ support therapies to provide a more holistic approach for critically ill patients. In this review, we aim at providing an in-depth overview of V-V ECMO and ECCO2R, addressing various aspects of their use, challenges, and potential future directions in research and development.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

Acute-on-chronic liver failure alters linezolid pharmacokinetics in critically ill patients with continuous hemodialysis: an observational study

BACKGROUND

In acute-on-chronic liver failure (ACLF), adequate antibiotic dosing is challenging due to changes of drug distribution and elimination. We studied the pharmacokinetics of linezolid in critically ill patients with ACLF during continuous renal replacement therapy compared to patients without concomitant liver failure (NLF).

METHODS

In this prospective cohort study, patients received linezolid 600 mg bid. Linezolid serum samples were analyzed by high-performance liquid chromatography. Population pharmacokinetic modelling was performed followed by Monte-Carlo simulations of 150 mg bid, 300 mg bid, 450 mg bid, 600 mg bid, and 900 mg bid to assess trough concentration target attainment of 2-7 mg/L.

RESULTS

Eighteen patients were included in this study with nine suffering from ACLF. Linezolid body clearance was lower in the ACLF group with mean (standard deviation) 1.54 (0.52) L/h versus 6.26 (2.43) L/h for NLF, P < 0.001. A trough concentration of 2-7 mg/L was reached with the standard dose of 600 mg bid in the NLF group in 47%, with 42% being underexposed and 11% overexposed versus 20% in the ACLF group with 77% overexposed and 3% underexposed. The highest probability of target exposure was attained with 600 mg bid in the NLF group and 150 mg bid in the ACLF group with 53%.

CONCLUSION

Linezolid body clearance in ACLF was markedly lower than in NLF. Given the overall high variability, therapeutic drug monitoring (TDM) with dose adjustments seems required to optimize target attainment. Until TDM results are available, a dose reduction may be considered in ACLF patients to prevent overexposure.

Pharmacokinetics of Commonly Used Antimicrobials in Critically Ill Pediatric Patients During Extracorporeal Membrane Oxygenation: A Systematic Review

PURPOSE

Adequate dosing of antimicrobials is critical to properly treat infections and limit development of resistance and adverse effects. Limited guidance exist for antimicrobial dosing adjustments in patients requiring extracorporeal membrane oxygenation (ECMO) therapy, particularly in the pediatric population. A systematic review was conducted to delineate the pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobials in critically ill neonates and children requiring ECMO therapy.

METHODS

Medline, EMBASE, Global Health and All EBM Reviews databases were queried. Grey literature was examined. All clinical studies reporting PK/PD parameters of antimicrobials in critically ill pediatric patients treated with ECMO were included, except for case reports and congress abstracts. Two independent reviewers applied the inclusion and exclusion criteria. Reviewers were then paired to independently extract data and evaluate the methodological quality of studies using the ROBINS-I tool and the compliance with ClinPK reporting guidelines. Patient and study characteristics, key PK/PD findings, details of ECMO circuits and co-treatments were summarized qualitatively. Broad dosing recommendations were formulated based on the available data for specific antimicrobials.

RESULTS

Twenty-nine clinical studies were included; most were observational and uncontrolled. Patient characteristics and co-treatments were often missing. The effect of ECMO on PK/PD parameters of antimicrobials varied depending on the drugs and population studied. It was only possible to formulate dosing recommendations for a few antimicrobials given the paucity of data, its overall low quality and heterogeneity in reporting.

CONCLUSION

Limited data exists on the PK/PD of antimicrobials during ECMO therapy in the pediatric population. Rigorously designed population PK studies are required to establish empiric dosing guidelines for antimicrobials in patients requiring this therapeutic modality. The use of therapeutic drug monitoring for antimicrobials in pediatric patients on ECMO should be encouraged to optimize dosing.

TRIAL REGISTRY

PROSPERO registration number: CRD42018099992 (Registered: July 24th 2018).

Antifungal Dosing in Critically Ill Patients on Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is an established advanced life support system, providing temporary cardiac and/or respiratory support in critically ill patients. Fungal infections are associated with increased mortality in patients on ECMO. Antifungal drug dosing for critically ill patients is highly challenging because of altered pharmacokinetics (PK). PK changes during critical illness; in particular, the drug volume of distribution (Vd) and clearance can be exacerbated by ECMO. This article discusses the available literature to inform adequate dosing of antifungals in this patient population. The number of antifungal PK studies in critically ill patients on ECMO is growing; currently available literature consists of case reports and studies with small sample sizes providing inconsistent findings, with scant or no data for some antifungals. Current data are insufficient to provide definitive empirical drug dosing guidance and use of dosing strategies derived from critically patients not on ECMO is reasonable. However, due to high PK variability, therapeutic drug monitoring should be considered where available in critically ill patients receiving ECMO to prevent subtherapeutic or toxic antifungal exposures.

Cefiderocol is Not Sequestered in an Ex Vivo Extracorporeal Membrane Oxygenation (ECMO) Circuit

BACKGROUND AND OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) is used in critically ill patients that require respiratory and/or cardiac support. Cefiderocol is a novel siderophore antibiotic that may require use in infected critically ill patients supported by ECMO. The objective of this study was to determine the loss of cefiderocol through an ex vivo adult ECMO circuit using a Quadrox-iD oxygenator.

METHODS

A 3/8-inch, simulated, ex vivo closed-loop ECMO circuit was prepared with a Quadrox-iD adult oxygenator and primed with fresh whole blood. Cefiderocol was administered into the circuit to achieve a starting concentration of approximately 90 mg/L. Post-oxygenator blood samples were collected at 0, 0.25, 0.5, 1, 2, 4, 6, 12, and 24 h after the addition of the drug to determine the loss in the circuit. A glass control jar was prepared with the same blood matrix and maintained at the same temperature to determine drug degradation. The experiment was conducted in triplicate. The rate of cefiderocol loss in the ECMO circuit was compared with that in the control by one-way analysis of variance.

RESULTS

At 0 h, the difference between the pre- and post-oxygenator concentrations was - 4 ± 4% (range 0 to - 7%). After 24 h, the cefiderocol percent reduction was similar between the ECMO circuit and control (50% ± 13 vs. 50% ± 9, p = 1.0).

CONCLUSIONS

The degradation rate of cefiderocol did not differ significantly within the ECMO circuit and control, suggesting no loss due to sequestration or adsorption. Pharmacokinetic studies in patients supported by ECMO are warranted to determine final dosing recommendations.

Change of dexmedetomidine and midazolam concentrations by simultaneous injection in an in vitro extracorporeal circuit

PURPOSE

Patient sedation and analgesia are vital for safety and comfort during extracorporeal membrane oxygenation (ECMO). However, adsorption by the circuit may alter drug pharmaco-kinetics and remains poorly characterized. This study is the first to examine the concentrations of DEX and MDZ in the presence of drug-drug interactions using an in vitro extracorporeal circuit system that incorporates a polymer-coated polyvinyl chloride tube, but not a membrane oxygenator.

METHODS AND RESULTS

Nine in vitro extracorporeal circuits were prepared using polymer-coated PVC tubing. Once the circuits were primed and running, either a single drug or two drugs were injected as boluses into the circuit with three circuits per drug. Drug samples were drawn following injection at 2, 5, 15, 30, 60, and 120 min and at 4, 12, and 24 h. They were then analyzed using high-performance liquid chromatography with mass spectrometry. When compared with an injection of DEX alone, the combination of DEX and MDZ is highly changed, with DEX and MDZ affecting the availability of free drugs in the circuit.

CONCLUSIONS

The change of DEX and MDZ concentrations was confirmed by a combination of both drugs as compared with either single-infusion DEX or MDZ in an in vitro extracorporeal circuit. Drug-drug interactions developed between DEX and MDZ through albumin in an extracorporeal circuit; as a result, the unbounded drugs might change in the circuit.

Antimicrobial Exposures in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation

Rationale: Data suggest that altered antimicrobial concentrations are likely during extracorporeal membrane oxygenation (ECMO). Objectives: The primary aim of this analysis was to describe the pharmacokinetics (PKs) of antimicrobials in critically ill adult patients receiving ECMO. Our secondary aim was to determine whether current antimicrobial dosing regimens achieve effective and safe exposure. Methods: This study was a prospective, open-labeled, PK study in six ICUs in Australia, New Zealand, South Korea, and Switzerland. Serial blood samples were collected over a single dosing interval during ECMO for 11 antimicrobials. PK parameters were estimated using noncompartmental methods. Adequacy of antimicrobial dosing regimens were evaluated using predefined concentration exposures associated with maximal clinical outcomes and minimal toxicity risks. Measurements and Main Results: We included 993 blood samples from 85 patients. The mean age was 44.7 ± 14.4 years, and 61.2% were male. Thirty-eight patients (44.7%) were receiving renal replacement therapy during the first PK sampling. Large variations (coefficient of variation of ⩾30%) in antimicrobial concentrations were seen leading to more than fivefold variations in all PK parameters across all study antimicrobials. Overall, 70 (56.5%) concentration profiles achieved the predefined target concentration and exposure range. Target attainment rates were not significantly different between modes of ECMO and renal replacement therapy. Poor target attainment was observed across the most frequently used antimicrobials for ECMO recipients, including for oseltamivir (33.3%), piperacillin (44.4%), and vancomycin (27.3%). Conclusions: Antimicrobial PKs were highly variable in critically ill patients receiving ECMO, leading to poor target attainment rates. Clinical trial registered with the Australian New Zealand Clinical Trials Registry (ACTRN12612000559819).

The Influence of Extracorporeal Membrane Oxygenation on Antibiotic Pharmacokinetics

Extracorporeal membrane oxygenation (ECMO) is becoming increasingly utilized to support critically ill patients who experience life-threatening cardiac or pulmonary compromise. The provision of this intervention poses challenges related to its complications and the optimization of medication therapy. ECMO's mechanical circulatory support is facilitated via various devices and equipment that have been shown to sequester lipophilic- and protein-bound medications, including anti-infectives. Since infectious outcomes are dependent on achieving specific anti-infectives' pharmacodynamic targets, the understanding of these medications' pharmacokinetic parameters in the setting of ECMO is important to clinicians. This narrative, non-systematic review evaluated the findings of the most recent and robust pharmacokinetic analyses for commonly utilized anti-infectives in the setting of ECMO. The data from available literature indicates that anti-infective pharmacokinetic parameters are similar to those observed in other non-ECMO critically ill populations, but considerable variability in the findings was observed between patients, thus prompting further evaluation of therapeutic drug monitoring in this complex population.

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.

Population Pharmacokinetics of Levosimendan and its Metabolites in Critically Ill Neonates and Children Supported or Not by Extracorporeal Membrane Oxygenation

BACKGROUND

Levosimendan (LVSMD) is a calcium-sensitizer inotropic and vasodilator agent whose use might have a beneficial effect on the weaning of venoarterial extracorporeal membrane oxygenation (VA-ECMO). In light of LVSMD pharmacological characteristics, we hypothesized that ECMO may induce major pharmacokinetic (PK) modifications for LVSMD and its metabolites.

OBJECTIVE

The aim of this study was to investigate the PK of LVSMD and its metabolites, and to assess the effects of ECMO on PK parameters.

METHODS

We conducted a multicentric, prospective study (NCT03681379). Twenty-seven infusions of LVSMD were performed, allowing for the collection of 255 blood samples. Non-linear mixed-effects modeling software (MONOLIX®) was used to develop a parent-metabolite PK model of LVSMD and its metabolites.

RESULTS

Most patients received a 0.2 µg/kg/min infusion of LVSMD over 24 h. After elimination of non-reliable samples or concentrations below the limit of quantification, 166, 101 and 85 samples were considered for LVSMD, OR-1855 and OR-1896, respectively, of which 81, 53 and 41, respectively, were drawn under ECMO conditions. Parent-metabolite PK modeling revealed that a two-compartment model with first-order elimination best described LVSMD PK. Use of a transit compartment allowed for an explanation of the delayed appearance of circulating OR-1855 and OR-1896, with the latter following a first-order elimination. Patient weight influenced the central volume of distribution and elimination of LVSMD. ECMO support increased the elimination rate of LVSMD by 78%, and ECMO also slowed down the metabolite formation rate by 85% for OR-1855, which in turn is converted to the active metabolite OR-1896, 14% slower than without ECMO. Simulated data revealed that standard dosing may not be appropriate for patients under ECMO, with a decrease in the steady-state concentration of LVSMD and lower exposure to the active metabolite OR-1896.

CONCLUSIONS

ECMO altered PK parameters for LVSMD and its metabolites. An infusion of LVSMD over 48 h, instead of 24 h, with a slightly higher dose may promote synthesis of the active metabolite OR-1896, which is responsible for the long-term efficacy of LVSMD. Further trials evaluating ECMO effects using a PK/pharmacodynamic approach may be of interest.

REGISTRATION

ClinicalTrials.gov identifier number NCT03681379.

Linezolid pharmacokinetics: a systematic review for the best clinical practice

OBJECTIVES

To summarize the pharmacokinetics of linezolid to optimize the dosing regimen in special populations.

METHODS

A literature search was performed in three largest medical databases, including Embase, Scopus, and PubMed. The main applied keywords were linezolid and pharmacokinetics. Of 3663 retrieved publications in the English language, 35 original research articles, clinical studies, and case reports about linezolid pharmacokinetics in different populations such as pregnant women, pediatrics, elderly subjects, obese people, individuals with organ dysfunction, and critically ill patients were included. RESULTS AND CONCLUSION: Dose adjustment is not currently recommended for linezolid in patients with mild to moderate renal or hepatic impairment, older adults, and pregnant women. Although dose adjustment is not recommended in patients with severe renal or hepatic impairment, it should be considered that these patients are more vulnerable to linezolid adverse effects and drug interactions. In pediatrics, reducing the linezolid dosing interval to 8 h is suggested. Despite the lack of sufficient information in obese individuals, dosing based on body weight or use of higher dose seems to be justifiable to prevent sub-therapeutic concentrations. Although dose adjustment of linezolid is not recommended in critically ill patients, administration of linezolid as continuous intravenous infusion is suggested in this population. Blood level monitoring should be considered in populations that are vulnerable to linezolid underexposure (such as critically ill patients with augmented renal clearance, pediatrics, overweight, and obese patients) or overexposure (such as elderly, patients with hepatic and renal impairment). To assess the efficacy and safety of linezolid, the area under the concentration-time curve over 24 h to minimum inhibitory concentration (AUC0-24 h/MIC) equal to 80-120, percentage of time above the MIC ≥ 85%, and serum trough concentration between 2 and 7 mg/L are suggested.

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.

The Future of Cardiothoracic Surgical Critical Care Medicine as a Medical Science: A Call to Action

Cardiothoracic surgical critical care medicine (CT-CCM) is a medical discipline centered on the perioperative care of diverse groups of patients. With an aging demographic and an increase in burden of chronic diseases the utilization of cardiothoracic surgical critical care units is likely to escalate in the coming decades. Given these projections, it is important to assess the state of cardiothoracic surgical intensive care, to develop goals and objectives for the future, and to identify knowledge gaps in need of scientific inquiry. This two-part review concentrates on CT-CCM as its own subspeciality of critical care and cardiothoracic surgery and provides aspirational goals for its practitioners and scientists. In part one, a list of guiding principles and a call-to-action agenda geared towards growth and promotion of CT-CCM are offered. In part two, an evaluation of selected scientific data is performed, identifying gaps in CT-CCM knowledge, and recommending direction to future scientific endeavors.

Developing Cardiothoracic Surgical Critical Care Intensivists: A Case for Distinct Training

Cardiothoracic surgical critical care medicine is practiced by a diverse group of physicians including surgeons, anesthesiologists, pulmonologists, and cardiologists. With a wide array of specialties involved, the training of cardiothoracic surgical intensivists lacks standardization, creating significant variation in practice. Additionally, it results in siloed physicians who are less likely to collaborate and advocate for the cardiothoracic surgical critical care subspeciality. Moreover, the current model creates credentialing dilemmas, as experienced by some cardiothoracic surgeons. Through the lens of critical care anesthesiologists, this article addresses the shortcomings of the contemporary cardiothoracic surgical intensivist training standards. First, we describe the present state of practice, summarize past initiatives concerning specific training, outline why standardized education is needed, provide goals of such training standardization, and offer a list of desirable competencies that a trainee should develop to become a successful cardiothoracic surgical intensivist.

Analgosedation in Critically Ill Adults Receiving Extracorporeal Membrane Oxygenation Support

Extracorporeal membrane oxygenation (ECMO) is an increasingly utilized intervention for cardiopulmonary failure. Analgosedation during ECMO support is essential to ensure adequate pain and agitation control and ventilator synchrony, optimize ECMO support, facilitate patient assessment, and minimize adverse events. Although the principles of analgosedation are likely similar for all critically ill patients, ECMO circuitry alters medication pharmacodynamics and pharmacokinetics. The lack of clinical guidelines for analgosedation during ECMO, especially at times of medication shortage, can affect patient management. Here, we review pharmacological considerations, protocols, and special considerations for analgosedation in critically ill adults receiving ECMO support.

Dose Optimization of Meropenem in Patients on Veno-Arterial Extracorporeal Membrane Oxygenation in Critically Ill Cardiac Patients: Pharmacokinetic/Pharmacodynamic Modeling

Background: Our objective was to determine an optimal dosage regimen of meropenem in patients receiving veno-arterial extracorporeal membrane oxygenation (V-A ECMO) by developing a pharmacokinetic/pharmacodynamic (PK/PD) model. Methods: This was a prospective cohort study. Blood samples were collected during ECMO (ECMO-ON) and after ECMO (ECMO-OFF). The population pharmacokinetic model was developed using nonlinear mixed-effects modeling. A Monte Carlo simulation was used (n = 10,000) to assess the probability of target attainment. Results: Thirteen adult patients on ECMO receiving meropenem were included. Meropenem pharmacokinetics was best fitted by a two-compartment model. The final pharmacokinetic model was: CL (L/h) = 3.79 × 0.44CRRT, central volume of distribution (L) = 2.4, peripheral volume of distribution (L) = 8.56, and intercompartmental clearance (L/h) = 21.3. According to the simulation results, if more aggressive treatment is needed (100% fT > MIC target), dose increment or extended infusion is recommended. Conclusions: We established a population pharmacokinetic model for meropenem in patients receiving V-A ECMO and revealed that it is not necessary to adjust the dosage depending on V-A ECMO. Instead, more aggressive treatment is needed than that of standard treatment, and higher dosage is required without continuous renal replacement therapy (CRRT). Also, extended infusion could lead to better target attainment, and we could provide updated nomograms of the meropenem dosage regimen.

A Narrative Review of the Impact of Extracorporeal Membrane Oxygenation on the Pharmacokinetics and Pharmacodynamics of Critical Care Therapies

Objective:

Extracorporeal membrane oxygenation (ECMO) utilization is increasing on a global scale, and despite technological advances, minimal standardized approaches to pharmacotherapeutic management exist. This objective was to create a comprehensive review for medication dosing in ECMO based on the most current evidence.

Data Sources:

A literature search of PubMed was performed for all pertinent articles prior to 2022. The following search terms were utilized: ECMO, pharmacokinetics, pharmacodynamics, sedation, analgesia, antiepileptic, anticoagulation, antimicrobial, antifungal, nutrition. Retrospective cohort studies, case-control studies, case series, case reports, and ex vivo investigations were reviewed.

Study Selection and Data Extraction:

PubMed (1975 through July 2022) was the database used in the literature search. Non-English studies were excluded. Search terms included both drug class categories, specific drug names, ECMO, and pharmacokinetics.

Data Synthesis:

Medications with high protein binding (>70%) and high lipophilicity (logP > 2) are associated with circuit sequestration and the potential need for dose adjustment. Volume of distribution changes with ECMO may also impact dosing requirements of common critical care medications. Lighter sedation targets and analgosedation may help reduce sedative and analgesia requirements, whereas higher antiepileptic dosing is recommended. Vancomycin is minimally affected by the ECMO circuit and recommendations for dosing in critically ill adults are reasonable. Anticoagulation remains challenging as optimal aPTT goals have not been established.

Relevance to Patient Care and Clinical Practice:

This review describes the anticipated impacts of ECMO circuitry on sedatives, analgesics, anticoagulation, antiepileptics, antimicrobials, antifungals, and nutrition support and provides recommendations for drug therapy management.

Conclusions:

Medication pharmacokinetic/pharmacodynamic parameters should be considered when determining the potential impact of the ECMO circuit on attainment of therapeutic effect and target serum drug concentrations, and should guide therapy choices and/or dose adjustments when data are not available.

Serum linezolid concentrations are reduced in critically ill patients with pulmonary infections: A prospective observational study

RATIONALE

The concentration-time profile of linezolid varies considerably in critically ill patients. Question of interest is, if the site of infection influences linezolid serum concentrations.

METHODS

68 critically ill patients, treated with linezolid, were included. The concentration-time-profile for linezolid was determined using maximum a-posteriori predictions. A trough concentration (C_min) between 2 and 10 mg/L was defined as the target. A generalized linear model (GLM) was established to evaluate potential covariates.

RESULTS

The indications for linezolid therapy were in descending order: peritonitis (38.2%), pneumonia (25.0%), infectious acute respiratory distress syndrome (ARDS) (19.1%), and other non-pulmonary infection (17.7%). 27.2 and 7.9% of C_min were subtherapeutic and toxic, respectively. In the GLM, ARDS (mean: -2.1 mg/L, CI: -3.0 to -1.2 mg/L) and pneumonia (mean: -2.2 mg/L, CI: -2.8 to -1.6 mg/L) were significant (p < 0.001) determinants of C_min. Patients with ARDS (mean: 2.3 mg/L, 51.2% subtherapeutic, 0.0% toxic) and pneumonia (mean: 3.5 mg/L, 41.5% subtherapeutic, 7.7% toxic) had significantly (p < 0.001) lower C_min than those with peritonitis (mean: 5.5 mg/L, 14.4% subtherapeutic, 9.3% toxic) and other non-pulmonary infection (mean: 5.2 mg/L, 3.3% subtherapeutic, 16.5% toxic).

CONCLUSION

Linezolid serum concentrations are reduced in patients with pulmonary infections. Future studies should investigate if other linezolid thresholds are needed in those patients due to linezolid pooling in patients´ lung.

Cefepime Extraction by Extracorporeal Life Support Circuits

Extracorporeal life support (ECLS) devices are lifesaving for critically ill patients with multi-organ dysfunction. Despite this, patients supported with ECLS are at high risk for ECLS-related complications, including nosocomial infections, and mortality rates are high in this patient population. The high mortality rates are suspected to be, in part, a result of significantly altered drug disposition by the ECLS circuit, resulting in suboptimal antimicrobial dosing. Cefepime is commonly used in critically ill patients with serious infections. Cefepime dosing is not routinely guided by therapeutic drug monitoring and treatment success is dependent upon the percentage of time of the dosing interval that the drug concentration remains above the minimum inhibitory concentration of the organism. This ex vivo study measured the extraction of cefepime by continuous renal replacement therapy (CRRT) and extracorporeal membrane oxygenation (ECMO) circuits. Cefepime was studied in four closed-loop CRRT circuit configurations and a single closed-loop ECMO circuit configuration. Circuits were primed with a physiologic human blood-plasma mixture and the drug was dosed to achieve therapeutic concentrations. Serial blood samples were collected over time and concentrations were quantified using validated assays. In ex vivo CRRT experiments, cefepime was rapidly cleared by dialysis, hemofiltration, and hemodiafiltration, with greater than 96% cefepime eliminated from the circuit by 2 hours. In the ECMO circuits, the mean recovery of cefepime was similar in both circuit and standard control. Mean (standard deviation) recovery of cefepime in the ECMO circuits (n = 6) was 39.2% (8.0) at 24 hours. Mean recovery in the standard control (n = 3) at 24 hours was 52.2% (1.5). Cefepime is rapidly cleared by dialysis, hemofiltration, and hemodiafiltration in the CRRT circuit but minimally adsorbed by either the CRRT or ECMO circuits. Dosing adjustments are needed for patients supported with CRRT.

Remdesivir and GS-441524 Extraction by Ex Vivo Extracorporeal Life Support Circuits

Patients with severe, COVID-related multi-organ failure often require extracorporeal life support (ECLS) such as extracorporeal membrane oxygenation (ECMO) or continuous renal replacement therapy (CRRT). An ECLS can alter drug exposure via multiple mechanisms. Remdesivir (RDV) and its active metabolite GS-441524 are likely to interact with ECLS circuits, resulting in lower than expected exposures. We evaluated circuit-drug interactions in closed loop, ex vivo ECMO and CRRT circuits. We found that mean (standard deviation) recovery of RDV at 6 hours after dosing was low in both the ECMO (33.3% [2.0]) and CRRT (3.5% [0.4]) circuits. This drug loss appears to be due primarily to drug adsorption by the circuit materials and potentially due to metabolism in the blood. GS-441524 recovery at 6 hours was high in the ECMO circuit 75.8% (16.5); however, was not detectable at 6 hours in the CRRT circuit. Loss in the CRRT circuit appears to be due primarily to efficient hemodiafiltration. The extent of loss for both molecules, especially in CRRT, suggests that in patients supported with ECMO and CRRT, RDV dosing adjustments are needed.

Impact of extracorporeal membrane oxygenation on voriconazole plasma concentrations: A retrospective study

Aims: We aimed to assess the impact of extracorporeal membrane oxygenation (ECMO) on voriconazole exposure.

Methods: Adult critically ill patients with or without ECMO support receiving intravenous voriconazole therapy were included in this retrospective study conducted in a tertiary referral intensive care unit. The first therapeutic drug monitoring (TDM) results of voriconazole in ECMO patients and non-ECMO patients were collected, and the prevalence of subtherapeutic concentrations was analyzed. Multivariate analyses were performed to evaluate the effect of ECMO on voriconazole exposure.

Results: A total of 132 patients (including 66 patients with ECMO support) were enrolled and their respective first voriconazole trough concentrations (C_min) were recorded. The median C_min of the ECMO group and the non-ECMO group was 1.9 (1.4–4.4) and 4.4 (3.2–6.9) mg/L, respectively (p = 0.000), and the proportion of the two groups in subtherapeutic concentrations range (<2 mg/L) was 51.5% and 7.6%, respectively (p = 0.000). Multiple linear regression analysis of voriconazole C_min identified that the use of ECMO and coadministration of glucocorticoids were associated with significantly reduced concentrations, while increasing SOFA score and increasing daily dose were associated with significantly increased concentrations. The model accounted for 32.2% of the variability of voriconazole C_min. Furthermore, binary logistic regression demonstrated that the use of ECMO was an independent risk factor (OR = 7.78, p = 0.012) for insufficient voriconazole exposure.

Conclusion: Our findings showed that, in addition to the known drug interactions, ECMO is a significant covariable affecting voriconazole exposure. In addition, SOFA score was identified as a factor associated with increased voriconazole concentration.

Population pharmacokinetics of ciprofloxacin in critically ill patients receiving extracorporeal membrane oxygenation (an ASAP ECMO study)

INTRODUCTION

This study aimed to describe the pharmacokinetics (PK) of ciprofloxacin in critically ill patients receiving ECMO and recommend a dosing regimen that provides adequate drug exposure.

METHODS

Serial blood samples were taken from ECMO patients receiving ciprofloxacin. Total ciprofloxacin concentrations were measured by chromatographic assay and analysed using a population PK approach with Pmetrics®. Dosing simulations were performed to ascertain the probability of target attainment (PTA) represented by the area under the curve to minimum inhibitory concentration ratio (AUC_0-24/MIC) ≥ 125.

RESULTS

Eight patients were enrolled, of which three received concurrent continuous venovenous haemodiafiltration (CVVHDF). Ciprofloxacin was best described in a two-compartment model with total body weight and creatinine clearance (CrCL) included as significant predictors of PK. Patients not requiring renal replacement therapy generated a mean clearance of 11.08 L/h while patients receiving CVVHDF had a mean clearance of 1.51 L/h. Central and peripheral volume of distribution was 77.31 L and 90.71 L, respectively. ECMO variables were not found to be significant predictors of ciprofloxacin PK. Dosing simulations reported that a 400 mg 8 -hly regimen achieved > 72% PTA in all simulated patients with CrCL of 30 mL/min, 50 mL/min and 100 mL/min and total body weights of 60 kg and 100 kg at a MIC of 0.5 mg/L.

CONCLUSION

Our study reports that established dosing recommendations for critically ill patients not on ECMO provides sufficient drug exposure for maximal ciprofloxacin activity for ECMO patients. In line with non-ECMO critically ill adult PK studies, higher doses and therapeutic drug monitoring may be required for critically ill adult patients on ECMO.

Fluctuating Voriconazole Concentrations during Extracorporeal Membrane Oxygenation

BACKGROUND

Patients requiring extracorporeal membrane oxygenation (ECMO) demonstrate complex drug pharmacokinetics due to alterations in clearance and volume of distribution, necessitating close therapeutic drug monitoring.

CASE REPORT

A 19-year-old Caucasian female with no past medical history was transferred from an outside hospital and admitted to the intensive care unit for acute respiratory distress syndrome secondary to a fresh water drowning event. The patient decompensated, requiring veno-arterial ECMO, which was subsequently changed to veno-venous ECMO. She was diagnosed with a Scedosporium apiospermum fungal pneumonia and was started on voriconazole. Throughout the course of antifungal therapy, the patient's voriconazole concentrations were labile, ranging from subtherapeutic, requiring dose increases to twice the labeled therapeutic dose, followed by subsequent supratherapeutic concentrations, requiring dose reductions.

CONCLUSION

Our findings demonstrate how voriconazole drug concentrations can be unpredictable when administered during ECMO and the importance of close monitoring of drug concentrations. More studies are needed to provide sufficient guidance on administering voriconazole in critically ill patients receiving ECMO.

Disposition of gentamicin and amikacin in extracorporeal membrane oxygenation using a heparin-coated filter: An in vitro assessment

Disposition of gentamicin and amikacin during extracorporeal membrane oxygenation has not been addressed in in vitro models. The HLS Advanced 7.0^® circuit with the Cardio Help^® monitor, Getinge, was used. The 5-L central compartment (CC) was loaded with gentamicin and amikacin at a targeted concentration of 40 and 80 mg/L in the same bag prior connection to the circuit. Samples were collected in the CC, the inlet and outlet ports from 15 min to 6 h post-connection. Pharmacokinetic analyses were performed using the NeckEpur^® method. Analysis of results of gentamicin and amikacin showed in the filter-pump block (i) the extremely low value of the extraction coefficients, (ii) similar values of the areas under the curve (AUCs) at the inlet and outlet ports, (iii) using the Wilcoxon matched pairs signed rank test no significant differences of the inlet-outlet concentrations in the filter-pump. In the whole system (i) the amounts recovered in the CC at the end of the 6-h session were not significantly different from the initial values, (ii) the extremely low values of the total clearance of gentamicin and amikacin from the CC in comparison with the measured simulated blood flowrate, (iii) the lack of significant time-concentration interactions in the CC and the inlet and outlet ports. These findings allow concluding no detectable adsorption of gentamicin and amikacin occurred in the HLS Advanced 7.0 circuit.

Ciprofloxacin in Patients Undergoing Extracorporeal Membrane Oxygenation (ECMO): A Population Pharmacokinetic Study

Extracorporeal membrane oxygenation (ECMO) is utilized to temporarily sustain respiratory and/or cardiac function in critically ill patients. Ciprofloxacin is used to treat nosocomial infections, but data describing the effect of ECMO on its pharmacokinetics is lacking. Therefore, a prospective, observational trial including critically ill adults (n = 17), treated with ciprofloxacin (400 mg 8–12 hourly) during ECMO, was performed. Serial blood samples were collected to determine ciprofloxacin concentrations to assess their pharmacokinetics. The pharmacometric modeling was performed (NONMEM^®) and utilized for simulations to evaluate the probability of target attainment (PTA) to achieve an AUC_0–24/MIC of 125 mg·h/L for ciprofloxacin. A two-compartment model most adequately described the concentration-time data of ciprofloxacin. Significant covariates on ciprofloxacin clearance (CL) were plasma bicarbonate and the estimated glomerular filtration rate (eGFR). For pathogens with an MIC of ≤0.25 mg/L, a PTA of ≥90% was attained. However, for pathogens with an MIC of ≥0.5 mg/L, plasma bicarbonate ≥ 22 mmol/L or eGFR ≥ 10 mL/min PTA decreased below 90%, steadily declining to 7.3% (plasma bicarbonate 39 mmol/L) and 21.4% (eGFR 150 mL/min), respectively. To reach PTAs of ≥90% for pathogens with MICs ≥ 0.5 mg/L, optimized dosing regimens may be required.

Population Pharmacokinetics of Caspofungin and Dose Simulations in Heart Transplant Recipients

The effect of heart transplantation (HTx) on the pharmacokinetics (PK) of caspofungin is not well-characterized. The aim of this study was to investigate the population PK of caspofungin in HTx and non-HTx patients and to identify covariates that may affect the PK of caspofungin. Seven successive blood samples were collected before administration and at 1, 2, 6, 10, 16, and 24 h after the administration of caspofungin for at least 3 days. This study recruited 27 HTx recipients and 31 non-HTx patients with 414 plasma concentrations in total. A nonlinear mixed-effects model was used to describe the population PK of caspofungin. The PK of caspofungin was best described by a two-compartment model. The clearance (CL) and volume of the central compartment (V_c) of caspofungin were 0.385 liter/h and 4.27 liters, respectively. The intercompartmental clearance (Q) and the volume of the peripheral compartment (V_p) were 2.85 liters/h and 6.01 liters, respectively. In the final model, we found that albumin (ALB) affected the CL of caspofungin with an adjustment factor of -1.01, and no other covariates were identified. In this study, HTx was not found to affect the PK of caspofungin. Based on the simulations, the dose of caspofungin should be proportionately increased in patients with decreased ALB levels.

Population Pharmacokinetics and Dosing Simulations of Ceftriaxone in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation (An ASAP ECMO Study)

Background

Despite the surge in use of extracorporeal membrane oxygenation (ECMO) in the adult intensive care unit, little guidance is available on the appropriate dosing of antimicrobials in this setting. Ceftriaxone is an antimicrobial with a high affinity to plasma protein, a property identified in the literature as susceptible to sequestration into extracorporeal circuits and hypothesised to require dosage adjustments in this setting.

Objective

The aim of this study was to describe the pharmacokinetics of ceftriaxone and identify the best dosing regimen for critically ill adult patients receiving ECMO.

Methods

Serial blood samples were taken from patients receiving both ECMO and ceftriaxone. Total and unbound drug concentrations were measured in plasma by chromatographic assay and analysed using a population pharmacokinetic approach with Pmetrics^®. Dosing simulations were performed to identify the optimal dosing strategy: 60 and 100% of time with free (unbound) drug concentration exceeding the minimum inhibitory concentration (fT_>MIC).

Results

In total, 14 patients were enrolled, of which three were receiving renal replacement therapy (RRT). Total and unbound ceftriaxone was best described in a two-compartment model with total body weight, serum albumin concentrations, creatinine clearance (CrCL), and the presence of RRT included as significant predictors of pharmacokinetics. Patients not on RRT generated a mean renal clearance of 0.90 L/h, non-renal clearance of 0.33 L/h, and central volume of distribution of 7.94 L. Patients on RRT exhibited a mean total clearance of 1.18 L/h. ECMO variables were not significant predictors of ceftriaxone pharmacokinetics. Steady-state dosing simulations found that dosages of 1 g every 12 h and 2 g every 24 h achieved >90% probabilities of target attainment in patients with CrCL of 0 mL/min with RRT and 30 and 100 mL/min and various serum albumin concentrations (17 and 26 g/L).

Conclusions

Dosing recommendations for critically ill adult patients not on ECMO appear to be sufficient for patients on ECMO. Patients exhibiting augmented renal clearance (> 130 mL/min) or treatment of less susceptible pathogens may require higher doses, which requires further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01106-x.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

Population Pharmacokinetics of Amikacin in Patients on Veno-Arterial Extracorporeal Membrane Oxygenation

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) support leads to complex pharmacokinetic alterations, whereas adequate drug dosing is paramount for efficacy and absence of toxicity in critically ill patients. Amikacin is a major antibiotic used in nosocomial sepsis, especially for these patients. We aimed to describe amikacin pharmacokinetics on V-A ECMO support and to determine relevant variables to improve its dosing. All critically ill patients requiring empirical antimicrobial therapy, including amikacin for nosocomial sepsis supported or not by V-A ECMO, were included in a prospective population pharmacokinetic study. This population pharmacokinetic analysis was built with a dedicated software, and Monte Carlo simulations were performed to identify doses achieving therapeutic plasma concentrations. Thirty-nine patients were included (control n = 15, V-A ECMO n = 24); 215 plasma assays were performed and used for the modeling process. Patients received 29 (24–33) and 32 (30–35) mg/kg of amikacin in control and ECMO groups, respectively. Data were best described by a two-compartment model with first-order elimination. Inter-individual variabilities were observed on clearance, central compartment volume (V₁)_, and peripherical compartment volume (V₂). Three significant covariates explained these variabilities: Kidney Disease Improving Global Outcomes (KDIGO) stage on amikacin clearance, total body weight on V_1, and ECMO support on V₂. Our simulations showed that the adequate dosage of amikacin was 40 mg/kg in KDIGO stage 0 patients, while 25 mg/kg in KDIGO stage 3 patients was relevant. V-A ECMO support had only a secondary impact on amikacin pharmacokinetics, as compared to acute kidney injury.

A Review of Pulmonary Arterial Hypertension Treatment in Extracorporeal Membrane Oxygenation: A Case Series of Adult Patients

BACKGROUND

Little data is published describing the use of medications prescribed for pulmonary arterial hypertension (PAH) in patients receiving extracorporeal membrane oxygenation (ECMO). Even though many patients with PAH may require ECMO as a bridge to transplant or recovery, little is reported regarding the use of PAH medications in this setting.

METHODS

This retrospective case series summarizes the clinical experience of 8 patients with PAH receiving ECMO and reviews medication management in the setting of ECMO.

RESULTS

Eight PAH patients, 5 of whom were female, ranging in age from 21 to 61 years old, were initiated on ECMO. Veno-arterial (VA) ECMO was used in 4 patients, veno-venous (VV) ECMO and hybrid ECMO configurations in 2 patients respectively. Common indications for ECMO included cardiogenic shock, bridge to transplant, and cardiac arrest. All patients were on intravenous (IV) prostacyclin therapy at baseline. Refractory hypotension was noted in 7 patients of whom 5 patients required downtitration or discontinuation of baseline PAH therapies. Three patients had continuous inhaled epoprostenol added during their time on ECMO. In patients who were decannulated from ECMO, PAH therapies were typically resumed or titrated back to baseline dosages. One patient required no adjustment in PAH therapy while on ECMO. Two patients were not able to be decannulated from ECMO.

CONCLUSION

The treatment of critically ill PAH patients is challenging given a variety of factors that could affect PAH drug concentrations. In particular, PAH patients on prostacyclin analogues placed on VA ECMO appear to have pronounced systemic vasodilation requiring vasopressors which is alleviated by temporarily reducing the intravenous prostacyclin dose. Patients should be closely monitored for potential need for rapid titrations in prostacyclin therapy to maintain hemodynamic stability.