Can physicochemical properties of antimicrobials be used to predict their pharmacokinetics during extracorporeal membrane oxygenation? Illustrative data from ovine models

A narrative review on antimicrobial dosing in adult critically ill patients on extracorporeal membrane oxygenation

The optimal dosing strategy of antimicrobial agents in critically ill patients receiving extracorporeal membrane oxygenation (ECMO) is unknown. We conducted comprehensive review of existing literature on effect of ECMO on pharmacokinetics and pharmacodynamics of antimicrobials, including antibacterials, antifungals, and antivirals that are commonly used in critically ill patients. We aim to provide practical guidance to clinicians on empiric dosing strategy for these patients. Finally, we discuss importance of therapeutic drug monitoring, limitations of current literature, and future research directions.

The impact of extracorporeal support on antimicrobial pharmacokinetics in critically ill neonatal and paediatric patients: A systematic review

OBJECTIVES

Infections represent a major risk for critically ill neonatal and paediatric patients requiring extracorporeal life-saving support such as extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapies (CRRT). Patient outcomes rely on achieving target antimicrobial concentrations. In critically ill adults on extracorporeal support, suboptimal antimicrobial concentrations have been shown to be common. Our objective was to systematically review antimicrobial pharmacokinetic studies in critically ill term neonatal and paediatric patients receiving ECMO and/or CRRT and compare them to similar cohorts of patients not receiving ECMO or CRRT.

METHODS

Studies published between 1990 and 2022 were identified through systematic searches in PUBMED, Embase, Web of Science, Medline, Google Scholar and CINAHL. Studies were included which provided antimicrobial pharmacokinetic parameters (volume of distribution and clearance) in the neonatal and paediatric patients receiving ECMO and/or CRRT. Studies were excluded if no antimicrobial pharmacokinetic parameters were described or could be calculated.

RESULTS

Forty-four pharmacokinetic studies were identified describing 737 patients, with neonatal patients recruited in 70% of the ECMO studies and <1% of the CRRT studies. Of all the studies, 50% were case reports or case series. The pharmacokinetics were altered for gentamicin, daptomycin, ceftolozane, micafungin, voriconazole, cefepime, fluconazole, piperacillin, and vancomycin, although considerable patient variability was described.

CONCLUSION

Significant gaps remain in our understanding of the pharmacokinetic alterations in neonatal and paediatric patients receiving ECMO and CRRT support.

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.

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.

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.

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.

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.

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).

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.

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.

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.

Flexible broncoscopy in patients in supportive therapy with oxygenation by extracorporeal membrane

Objective:

To report the experience of performing bronchoscopy in patients who underwent supportive therapy with extracorporeal membrane oxygenation in whom the bronchoscopy was performed.

Methods:

This was a review of medical records of patients diagnosed with extracorporeal membrane oxygenation and who required diagnostic or therapeutic bronchoscopy. Records included were related to patients admitted to the intensive care unit of Hospital das Clínicas of Faculdade de Medicina of Universidade de São Paulo, between 2014 and 2020.

Results:

During the study, 16 bronchoscopies were performed in 8 patients admitted to the intensive care unit and who underwent supportive therapy with extracorporeal membrane oxygenation. The mean age of patients was 28.37 years. Four patients were women (50%). A total of 5 (31.25%) therapeutic bronchoscopies and 11 (68.75%) diagnostics were performed. In 5 of patients, material was collected: 4 samples of bronchoalveolar lavage, three collections of transbronchial biopsies, and 1 of endobronchial biopsies. No patient had radiological worsening or hemodynamic complications. One patient (6.25%) had transient desaturation. There was moderate bleeding after transbronchial biopsy in 1 (6.25%) procedure, which was resolved endoscopically.

Conclusion:

Patients undergoing extracorporeal membrane oxygenation can safely perform diagnostic or therapeutic bronchoscopy provided that they have a detailed indication. Procedures were performed by a specialized bronchoscopy team in intensive care environment and with the assistance of a qualified multidisciplinary team in membrane oxygenation therapy extracorporeal.

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.

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.

Decreased isavuconazole trough concentrations in the treatment of invasive aspergillosis in an adult patient receiving extracorporeal membrane oxygenation support

PURPOSE

We present the case of a 56-year-old man with stage IV sarcoidosis on veno-venous extracorporeal membrane oxygenation (VV-ECMO) support for the management of respiratory failure receiving treatment with isavuconazole for invasive aspergillosis.

SUMMARY

VV-ECMO is an increasingly utilized life support therapy for patients with cardiac and/or respiratory failure, but its impact on medication dosing is poorly understood. In our patient with invasive Aspergillus infection receiving VV-ECMO, because of difficulty achieving therapeutic serum concentrations of voriconazole, we administered isavuconazole 372 mg intravenously (IV) every 8 hours for 6 doses followed by 372 mg IV once daily. Isavuconazole has a favorable pharmacokinetic and safety profile compared to other azole antifungal agents, but its high protein binding and lipophilicity raise concerns about drug sequestration in the VV-ECMO circuit. To optimize the efficacy and safety of this treatment, the isavuconazole trough concentration was measured at days 5 and 17, at which time it was 1.7 and 0.7 μg/mL, respectively. The dose was subsequently increased to 744 mg IV once daily, and serum trough concentrations were measured 5 and 8 days after dose adjustment, corresponding to 3.7 and 2.9 μg/mL, respectively. To our knowledge, this is the third report to describe inadequate isavuconazole trough concentrations during VV-ECMO support when utilizing standard doses.

CONCLUSION

In the case described here, standard-dose isavuconazole (372 mg every 8 hours for 6 doses followed by 372 mg daily) did not achieve target trough concentrations in a patient receiving concomitant ECMO support.

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.

Pharmacokinetics of Cefepime in Children on Extracorporeal Membrane Oxygenation: External Model Validation, Model Improvement and Dose Optimization

BACKGROUND

Cefepime is a first-line therapy for Gram-negative infections in children on extracorporeal membrane oxygenation. Cefepime pharmacokinetics (PK) in children on extracorporeal membrane oxygenation still needs to be better established.

METHODS

This was a prospective single-center PK study. A maximum of 12 PK samples per patient were collected in children <18 years old on extracorporeal membrane oxygenation who received clinically indicated cefepime. External validation of a previously published population PK model was performed by applying the model in a new data set. The predictive performance of the model was determined by calculating prediction errors. Because of poor predictive performance, a revised model was developed using NONMEM and a combined data set that included data from both studies. Dose-exposure simulations were performed using the final model. Optimal dosing was judged based on the ability to maintain free cefepime concentrations above the minimal inhibitory concentration (MIC) for 68% and 100% of the dosing interval.

RESULTS

Seventeen children contributed 105 PK samples. The mean (95% CI) and median (interquartile range) prediction errors were 33.7% (19.8-47.7) and 17.5% (-22.6 to 74.4). A combined data set was created, which included 33 children contributing 310 PK samples. The final improved 2-compartment model included weight and serum creatinine on clearance and oxygenator day and blood transfusion on volume of the central compartment. At an MIC of 8 mg/L, 50 mg/kg/dose every 8 hours reached target concentrations.

CONCLUSIONS

Dosing intervals of 8 hours were needed to reach adequate concentrations at an MIC of 8 mg/L. Longer dosing intervals were adequate with higher serum creatinine and lower MICs.

Analysis of the Value of the Blood Urea Nitrogen to Albumin Ratio as a Predictor of Mortality in Patients with Sepsis

Purpose

At present, simple, accurate, and efficient prognostic tools for the evaluation of cases with early-stage sepsis in the emergency department (ED) are lacking. An increased blood urea nitrogen to albumin ratio (BAR) has previously been shown to be a valuable biomarker with predictive utility in several diseases. The relationship between BAR and sepsis patient outcomes, however, is not well-understood. This exploration was thus developed for the exploration of the link between BAR values and the short-term prognosis of cases with sepsis.

Methods

This was a retrospective cohort research of sepsis cases admitted to the West China Hospital of Sichuan University ED from July 2015 to June 2016. Laboratory data were collected upon ED admission, and 7-day all-cause mortality was the primary study endpoint. Relationships between BAR values and APACE II and SOFA scores were generated assessed with correlation coefficient heatmaps. Independent risk factors were identified through multivariate analyses, with the curves of receiver operating characteristic (ROC) being employed to gauge the value of BAR as a predictor of the risk of mortality in sepsis cases.

Results

In sum, 801 patients participated in the present investigation. BAR values were strongly correlated with APACHE II and SOFA scores. In a multivariate logistic regression assessment, BAR was identified as an independent predictor of mortality among patients with sepsis (HR=1.032, 95% CI: 1.010–1.055, P=0.004). BAR exhibited an AUC of 0.741 (95% CI: 0.688–0.793, P<0.001) when used to predict patient mortality risk, with 5.27 being the optimal BAR cut-off.

Conclusion

We found that BAR can be used as a reliable biomarker to predict mortality in patients with sepsis.

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.

Machines that help machines to help patients: optimising antimicrobial dosing in patients receiving extracorporeal membrane oxygenation and renal replacement therapy using dosing software

Intensive care unit (ICU) patients with end-organ failure will require specialised machines or extracorporeal therapies to support the failing organs that would otherwise lead to death. ICU patients with severe acute kidney injury may require renal replacement therapy (RRT) to remove fluid and wastes from the body, and patients with severe cardiorespiratory failure will require extracorporeal membrane oxygenation (ECMO) to maintain adequate oxygen delivery whilst the underlying pathology is evaluated and managed. The presence of ECMO and RRT machines can further augment the existing pharmacokinetic (PK) alterations during critical illness. Significant changes in the apparent volume of distribution (V_d) and drug clearance (CL) for many important drugs have been reported during ECMO and RRT. Conventional antimicrobial dosing regimens rarely consider the impact of these changes and consequently, are unlikely to achieve effective antimicrobial exposures in critically ill patients receiving ECMO and/or RRT. Therefore, an in-depth understanding on potential PK changes during ECMO and/or RRT is required to inform antimicrobial dosing strategies in patients receiving ECMO and/or RRT. In this narrative review, we aim to discuss the potential impact of ECMO and RRT on the PK of antimicrobials and antimicrobial dosing requirements whilst receiving these extracorporeal therapies. The potential benefits of therapeutic drug monitoring (TDM) and dosing software to facilitate antimicrobial therapy for critically ill patients receiving ECMO and/or RRT are also reviewed and highlighted.

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

OBJECTIVES

This study aimed to describe the population pharmacokinetics (PK) of cefepime during extracorporeal membrane oxygenation (ECMO) and through dosing simulations, identify a maximally effective and safe dosing strategy.

METHODS

Serial cefepime plasma concentrations were measured in patients on ECMO, and data were analysed using a population PK approach with Pmetrics®. Dosing simulations were used to identify the optimal dosing strategy that achieved target trough concentrations (C_min) of 8-20 mg/L. Six patients were enrolled, of which one was receiving renal replacement therapy. Cefepime was best described in a two-compartment model, with total body weight and creatinine clearance (CrCL) as significant predictors of PK parameters. The mean clearance and central volume of distribution were 2.42 L/h and 15.09 L, respectively.

RESULTS

Based on simulations, patients with CrCL of 120 mL/min receiving 1 g 8-hourly dosing achieved a 40-44% probability of efficacy (C_min > 8 mg/L) and 1-6% toxicity (C_min > 20 mg/L). Patients with CrCL 30 mL/min and 65 mL/min receiving 1 g 12-hourly dosing achieved an 84-92% and 46-53% probability of efficacy and 8-44% and 1-8% probability of toxicity, respectively. Simulations demonstrated a lower probability of efficacy and higher probability of toxicity with decreasing patient weight.

CONCLUSION

This study reported reduced cefepime clearance in patients receiving ECMO, resulting in an increased risk of cefepime toxicity. To avoid drug accumulation, modified dosing regimens should be used in critically ill patients on ECMO. Clinicians should adopt therapeutic drug monitoring when treating less susceptible organisms and in patients with reduced renal clearance on ECMO.

Population Pharmacokinetics of Piperacillin and Tazobactam in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation: an ASAP ECMO Study

Our study aimed to describe the population pharmacokinetics (PK) of piperacillin and tazobactam in patients on extracorporeal membrane oxygenation (ECMO), with and without renal replacement therapy (RRT). We also aimed to use dosing simulations to identify the optimal dosing strategy for these patient groups. Serial piperacillin and tazobactam plasma concentrations were measured with data analyzed using a population PK approach that included staged testing of patient and treatment covariates. Dosing simulations were conducted to identify the optimal dosing strategy that achieved piperacillin target exposures of 50% and 100% fraction of time free drug concentration is above MIC (%fT_>MIC) and toxic exposures of greater than 360 mg/liter. The tazobactam target of percentage of time free concentrations of >2 mg/liter was also assessed. Twenty-seven patients were enrolled, of which 14 patients were receiving concurrent RRT. Piperacillin and tazobactam were both adequately described by two-compartment models, with body mass index, creatinine clearance, and RRT as significant predictors of PK. There were no substantial differences between observed PK parameters and published parameters from non-ECMO patients. Based on dosing simulations, a 4.5-g every 6 hours regimen administered over 4 hours achieves high probabilities of efficacy at a piperacillin MIC of 16 mg/liter while exposing patients to a <3% probability of toxic concentrations. In patients receiving ECMO and RRT, a frequency reduction to every 12 hours dosing lowers the probability of toxic concentrations, although this remains at 7 to 9%. In ECMO patients, piperacillin and tazobactam should be dosed in line with standard recommendations for the critically ill.

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

Our study aimed to describe the population pharmacokinetics (PK) of vancomycin in critically ill patients receiving extracorporeal membrane oxygenation (ECMO), including those receiving concomitant renal replacement therapy (RRT). Dosing simulations were used to recommend maximally effective and safe dosing regimens. Serial vancomycin plasma concentrations were measured and analysed using a population PK approach on Pmetrics®. The final model was used to identify dosing regimens that achieved target exposures of area under the curve (AUC_0-24) of 400 - 700 mg·h/L at steady state. Twenty-two patients were enrolled, of which 11 patients received concomitant RRT. In the non-RRT patients, the median creatinine clearance (CrCL) was 75 mL/min and the mean daily dose of vancomycin was 25.5 mg/kg. Vancomycin was well described in a two-compartment model with CrCL, the presence of RRT and total body weight found as significant predictors of clearance and central volume of distribution (V_c). The mean vancomycin renal clearance and V_c were 3.20 L/h and 29.7 L respectively, while the clearance for patients on RRT was 0.15 L/h. ECMO variables did not improve the final covariate model. We found that recommended dosing regimens for critically ill adult patients not on ECMO can be safely and effectively used in those on ECMO. Loading doses of at least 25 mg/kg followed by maintenance doses of 12.5 - 20 mg/kg 12-hourly are associated with a 97 - 98% probability of efficacy and 11 - 12% probability of toxicity, in patients with normal renal function. Therapeutic drug monitoring along with reductions in dosing are warranted for patients with renal impairment and those with concomitant RRT.

Excessive unbound cefazolin concentrations in critically ill patients receiving veno-arterial extracorporeal membrane oxygenation (vaECMO): an observational study

The scope of extracorporeal membrane oxygenation (ECMO) is expanding, nevertheless, pharmacokinetics in patients receiving cardiorespiratory support are fairly unknown leading to unpredictable drug concentrations. Currently, there are no clear guidelines for antibiotic dosing during ECMO. This study aims to evaluate the pharmacokinetics (PK) of cefazolin in patients undergoing ECMO treatment. Total and unbound plasma cefazolin concentration of critically ill patients on veno-arterial ECMO were determined. Observed PK was compared to dose recommendations calculated by an online available, free dosing software. Concentration of cefazolin varied broadly despite same dosage in all patients. The mean total and unbound plasma concentration were high showing significantly (p = 5.8913 E−09) greater unbound fraction compared to a standard patient. Cefazolin clearance was significantly (p = 0.009) higher in patients with preserved renal function compared with CRRT. Based upon the calculated clearance, the use of dosing software would have led to lower but still sufficient concentrations of cefazolin in general. Our study shows that a “one size fits all” dosing regimen leads to excessive unbound cefazolin concentration in these patients. They exhibit high PK variability and decreased cefazolin clearance on ECMO appears to compensate for ECMO- and critical illness-related increases in volume of distribution.

Elimination of three doses of gentamicin over three consecutive days using a polyacrylonitrile-derived filter: An in vitro assessment

INTRODUCTION

Adsorption of gentamicin in a polyacrylonitrile filter was previously evidenced in a session lasting 6 h using the NeckEpur model. We extended the study over three consecutive days to mimic the 72-h life span of a filter.

METHODS

Prismaflex^® monitor and ST150^® filter were used in the continuous diafiltration (CDF) mode at a 2.5 L/h flowrate. The daily session started with a 6-h session of CDF. Thereafter, the 5-L central compartment was changed using a bag free of gentamicin to assess gentamicin release over the following 18 h. Experiments were repeated on Day 2 and stopped at the end of the 6-h session of CDF on Day 3. The experiment was performed in duplicate.

RESULTS

At a 2.5 L/h diafiltration flowrate, the mean daily clearances of gentamicin were 5.5, 4.0, and 3.3 L/h, respectively. The mean diafiltration and adsorption ratios in the daily elimination of gentamicin were 32/68%, 58/42%, and 88/12%, respectively. During days 1 and 2, the mean amount of gentamicin released from the ST150^® filter were 14 and 34 mg, respectively.

CONCLUSION

The pharmacokinetics of gentamicin over 3 days is strongly altered by adsorption in the same filter with a progressive decrease of elimination by adsorption, suggesting saturation of the filter. One limitation of our study results from the mode of administration using a bolus dose instead of an infusion over 30 min. Adsorption adds a clearance to those of diafiltration. The time-dependency of gentamicin clearance precludes using a constant dosage regimen over the filter's life span.

Sequestration of Dexmedetomidine in Ex Vivo Cardiopulmonary Bypass Circuits

Dexmedetomidine (DEX) is a sedative used in combination with other drugs in neonates and infants undergoing cardiac surgery using cardiopulmonary bypass (CPB). This study aimed to evaluate the disposition of DEX after administration to the ex vivo CPB circuits following different bolus doses and continuous infusion of DEX, including the effect of circuit coating, temperature, and modified ultrafiltration (MUF). Cardiopulmonary bypass circuits were setup ex vivo and primed with reconstituted blood. Dexmedetomidine was administered to the circuit (as a single bolus or single bolus along with continuous infusion). The circuit was allowed to equilibrate during the first 5 minutes, blood samples were collected at multiple time points (5-240 minutes). Blood samples were processed to collect plasma and analyzed for DEX with a validated assay. The majority of DEX sequestration in ex vivo CPB circuits occurred within the first 15 minutes. The percent of DEX remained in plasma pre-MUF (16-71%) and post-MUF (22-92%) varied depending on the dose and dosing scheme. Modified ultrafiltration significantly increased the plasma concentration of DEX in 19 of 23 circuits by an average of 12.1 ± 4.25% (p < 0.05). The percent sequestration of DEX was lower in CPB circuits at lower DEX doses compared to higher doses. A combination of DEX initial loading dose and continuous infusion resulted in steady concentrations of DEX over 4 hours. At therapeutically relevant concentrations of DEX (485-1,013 pg/ml), lower sequestration was observed in ex vivo CPB circuits compared to higher doses. The sequestration of DEX to circuits should be considered to achieve the optimal concentration of DEX during CPB surgery.

Polymeric nano- and microparticulate drug delivery systems for treatment of biofilms

Now-a-days healthcare systems face great challenges with antibiotic resistance and low efficacy of antibiotics when combating pathogenic bacteria and bacterial biofilms. Administration of an antibiotic in its free form is often ineffective due to lack of selectivity to the infectious site and breakdown of the antibiotic before it exerts its effect. Therefore, polymeric delivery systems, where the antibiotic is encapsulated into a formulation, have shown great promise, facilitating a high local drug concentration at the site of infection, a controlled drug release and less drug degradation. All this leads to improved therapeutic effects and fewer systemic side effects together with a lower risk of developing antibiotic resistance. Here, we review and provide a comprehensive overview of polymer-based nano- and microparticles as carriers for antimicrobial agents and their effect on eradicating bacterial biofilms. We have a main focus on polymeric particulates containing poly(lactic-co-glycolic acid), chitosan and polycaprolactone, but also strategies involving combinations of these polymers are included. Different production techniques are reviewed and important parameters for biofilm treatment are discussed such as drug loading capacity, control of drug release, influence of particle size and mobility in biofilms. Additionally, we reflect on other promising future strategies for combating biofilms such as lipid-polymer hybrid particles, enzymatic biofilm degradation, targeted/triggered antibiotic delivery and future alternatives to the conventional particles.

Population pharmacokinetics of ceftriaxone administered as continuous or intermittent infusion in critically ill patients

OBJECTIVES

To describe the population pharmacokinetics and protein-binding characteristics of unbound ceftriaxone administered as continuous or intermittent infusion. Additionally, to determine the optimal dosing regimen in critically ill patients.

METHODS

A pharmacokinetic study was performed in the ICU of a tertiary teaching hospital. Patients were treated with ceftriaxone as continuous or intermittent infusion. A population pharmacokinetic model was developed with non-linear mixed-effects analysis. Subsequently, the PTA of a 100% T>MIC was assessed for influential patient characteristics using Monte Carlo simulation.

RESULTS

Fifty-five patients were included. The pharmacokinetics of ceftriaxone was best described by a one-compartment model with non-linear saturable protein binding including the following covariates: body weight, estimated CLCR, serum albumin concentration and mode of administration. For pathogens with an MIC of 1 mg/L, the simulation demonstrated that intermittent infusion of 2 g/24 h only resulted in a ≥90% PTA in patients with a reduced CLCR (0-60 mL/min). Intermittent infusion of 2 g/12 h led to sufficient exposure if CLCR was 0-90 mL/min and continuous infusion of 2 g/24 h led to a ≥90% PTA in all simulations (CLCR 0-180 mL/min).

CONCLUSIONS

In the critically ill, the clearance of unbound ceftriaxone is closely related to CLCR. Furthermore, ceftriaxone protein binding is saturable, variable and dependent on serum albumin concentration. Intermittent dosing of 2 g/24 h ceftriaxone leads to subtherapeutic exposure in patients with a normal or increased CLCR. Treating these patients with continuous infusion of 2 g/24 h is more effective than an intermittent dosing regimen of 2 g/12 h.

[Effect of extracorporeal membrane oxygenation on pharmacokinetics of antimicrobial drugs: recent progress and recommendations]

Extracorporeal membrane oxygenation (ECMO) is an effective means to provide life support for patients with severe respiratory or heart failure. Existing studies have shown that ECMO may affect the metabolic process of some drugs by drug adsorption, increasing the apparent distribution volume and changing the clearance rate of the drugs. This review summarizes the recent progress in the studies of the effect of ECMO on the pharmacokinetics of antibacterial and antifungal drugs. For the antibacterial drugs, it is recommended that the dose of teicoplanin, imipenem, and linezolid should be increased during ECMO support, while the dose of azithromycin, ciprofloxacin, and tigecycline should not be modified for the time being. Currently studies on pharmacokinetic changes of antifungal drugs during ECMO support remain limited. Voriconazole can be absorbed substantially by ECMO due to its high lipophilicity, and higher doses are therefore recommended. The dose of micafungin also needs to be increased in children undergoing ECMO. However, current evidence concerning the dose of caspofungin and fluconazole are limited, and it is not clear whether the routine dose should be adjusted during ECMO support.

Piperacillin-Tazobactam in Intensive Care Units: A Review of Population Pharmacokinetic Analyses

Piperacillin-tazobactam is a potent β-lactam/β-lactamase inhibitor antibiotic commonly prescribed in the intensive care unit setting. Admitted patients often show large variability in treatment response due to multiple pathophysiological changes present in this population that alter the drug's pharmacokinetics. This review summarizes the population pharmacokinetic models developed for piperacillin-tazobactam and provides comprehensive data on current dosing strategies while identifying significant covariates in critically ill patients. A literature search on the PubMed database was conducted, from its inception to July 2020. Relevant articles were retained if they met the defined inclusion/exclusion criteria. A total of ten studies, published between 2009 and 2020, were eligible. One- and two-compartment models were used in two and eight studies, respectively. The lowest estimated piperacillin clearance value was 3.12 L/h, and the highest value was 19.9 L/h. The estimations for volume of distribution varied between 11.2 and 41.2 L. Tazobactam clearance values ranged between 5.1 and 6.78 L/h, and tazobactam volume of distribution values ranged between 17.5 and 76.1 L. The most frequent covariates were creatinine clearance and body weight, each present in four studies. Almost all studies used an exponential approach for the interindividual variability. The highest variability was observed in piperacillin central volume of distribution, at a value of 75.0%. Simulations showed that continuous or extended infusion methods performed better than intermittent administration to achieve appropriate pharmacodynamic targets. This review synthesizes important pharmacokinetic elements for piperacillin-tazobactam in an intensive care unit setting. This will help clinicians better understand changes in the drug's pharmacokinetic parameters in this specific population.

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.

Combatting the Rising Tide of Antimicrobial Resistance: Pharmacokinetic/Pharmacodynamic Dosing Strategies for Maximal Precision

OBJECTIVE

Antimicrobial pharmacokinetics/pharmacodynamics (PK/PD) principles and PK/PD models have been essential in characterizing the mechanism of antibiotic bacterial killing and determining the most optimal dosing regimen that maximizes clinical outcomes. This review summarized the fundamentals of antimicrobial PK/PD and the various types of PK/PD experiments that shaped the utilization and dosing strategies of antibiotics today.

METHODS

Multiple databases - including PubMed, Scopus, and EMBASE - were searched for published articles that involved PK/PD modelling and precision dosing. Data from in vitro, in vivo and mechanistic PK/PD models were reviewed as a basis for compiling studies that guide dosing regimens used in clinical trials.

RESULTS

Literature regarding the utilization of exposure-response analyses, mathematical modelling and simulations that were summarized are able to provide a better understanding of antibiotic pharmacodynamics that influence translational drug development. Optimal pharmacokinetic sampling of antibiotics from patients can lead to personalized dosing regimens that attain target concentrations while minimizing toxicity. Thus the development of a fully integrated mechanistic model based on systems pharmacology can continually adapt to data generated from clinical responses, which can provide the framework for individualized dosing regimens.

CONCLUSIONS

The promise of what PK/PD can provide through precision dosing for antibiotics has not been fully realized in the clinical setting. Antimicrobial resistance, which has emerged as a significant public health threat, has forced clinicians to empirically utilize therapies. Future research focused on implementation and translation of PK/PD-based approaches integrating novel approaches that combine knowledge of combination therapies, systems pharmacology and resistance mechanisms are necessary. To fully realize maximally precise therapeutics, optimal PK/PD strategies are critical to maximize antimicrobial efficacy against extremely-drug-resistant organisms, while minimizing toxicity.

Antibiotic therapeutic drug monitoring in intensive care patients treated with different modalities of extracorporeal membrane oxygenation (ECMO) and renal replacement therapy: a prospective, observational single-center study

BACKGROUND

Effective antimicrobial treatment is key to reduce mortality associated with bacterial sepsis in patients on intensive care units (ICUs). Dose adjustments are often necessary to account for pathophysiological changes or renal replacement therapy. Extracorporeal membrane oxygenation (ECMO) is increasingly being used for the treatment of respiratory and/or cardiac failure. However, it remains unclear whether dose adjustments are necessary to avoid subtherapeutic drug levels in septic patients on ECMO support. Here, we aimed to evaluate and comparatively assess serum concentrations of continuously applied antibiotics in intensive care patients being treated with and without ECMO.

METHODS

Between October 2018 and December 2019, we prospectively enrolled patients on a pneumological ICU in southwest Germany who received antibiotic treatment with piperacillin/tazobactam, ceftazidime, meropenem, or linezolid. All antibiotics were applied using continuous infusion, and therapeutic drug monitoring of serum concentrations (expressed as mg/L) was carried out using high-performance liquid chromatography. Target concentrations were defined as fourfold above the minimal inhibitory concentration (MIC) of susceptible bacterial isolates, according to EUCAST breakpoints.

RESULTS

The final cohort comprised 105 ICU patients, of whom 30 were treated with ECMO. ECMO patients were significantly younger (mean age: 47.7 vs. 61.2 years; p < 0.001), required renal replacement therapy more frequently (53.3% vs. 32.0%; p = 0.048) and had an elevated ICU mortality (60.0% vs. 22.7%; p < 0.001). Data on antibiotic serum concentrations derived from 112 measurements among ECMO and 186 measurements from non-ECMO patients showed significantly lower median serum concentrations for piperacillin (32.3 vs. 52.9; p = 0.029) and standard-dose meropenem (15.0 vs. 17.8; p = 0.020) in the ECMO group. We found high rates of insufficient antibiotic serum concentrations below the pre-specified MIC target among ECMO patients (piperacillin: 48% vs. 13% in non-ECMO; linezolid: 35% vs. 15% in non-ECMO), whereas no such difference was observed for ceftazidime and meropenem.

CONCLUSIONS

ECMO treatment was associated with significantly reduced serum concentrations of specific antibiotics. Future studies are needed to assess the pharmacokinetic characteristics of antibiotics in ICU patients on ECMO support.

Population Pharmacokinetics of Caspofungin among Extracorporeal Membrane Oxygenation Patients during the Postoperative Period of Lung Transplantation

Little is known about the influence of extracorporeal membrane oxygenation (ECMO) on the pharmacokinetics (PK) of caspofungin. The aim of this study was to describe population PK of caspofungin in patients with and without ECMO during the postoperative period of lung transplantation (LTx) and to investigate covariates influencing caspofungin PK. We compared ECMO patients with non-ECMO patients, and patients before and after ECMO weaning as self-controls, to analyzed changes in caspofungin PK. Eight serial blood samples were collected from each patient for PK analysis. The population PK of caspofungin was described using nonlinear mixed-effects modeling. Twelve ECMO and 7 non-ECMO lung transplant recipients were enrolled in this study. None of the patients received renal replacement therapy during any part of the study period. The PK of caspofungin was best described by a two-compartment model. There were no significant differences in the PK parameters and concentrations of caspofungin among the ECMO, non-ECMO, and self-control group. In the final covariate model, we found that there was a significant association between the male gender and increased distribution volume, that a higher sequential organ failure assessment score was related to an increase in intercompartmental clearance, and that a longer operative time was related to an increase in clearance and the volume of distribution. ECMO did not have a significant impact on the PK of caspofungin in patients after LTx. Some factors were identified as statistically significant covariates related to the PK of caspofungin; however, their impact on clinical practice of caspofungin needs to be investigated further in more studies. (This study has been registered at ClinicalTrials.gov under identifier NCT03766282.).

Pharmacokinetics of micafungin in patients treated with extracorporeal membrane oxygenation: an observational prospective study

Objective

To determine micafungin plasma levels and pharmacokinetic behavior in patients treated with extracorporeal membrane oxygenation.

Methods

The samples were taken through an access point before and after the membrane in two tertiary hospitals in Spain. The times for the calculation of pharmacokinetic curves were before the administration of the drug and 1, 3, 5, 8, 18 and 24 hours after the beginning of the infusion on days one and four. The area under the curve, drug clearance, volume of distribution and plasma half-life time with a noncompartmental pharmacokinetic data analysis were calculated.

Results

The pharmacokinetics of the values analyzed on the first and fourth day of treatment did not show any concentration difference between the samples taken before the membrane (Cin) and those taken after the membrane (Cout), and the pharmacokinetic behavior was similar with different organ failures. The area under the curve (AUC) before the membrane on day 1 was 62.1 (95%CI 52.8 - 73.4) and the AUC after the membrane on this day was 63.4 (95%CI 52.4 - 76.7), p = 0.625. The AUC before the membrane on day 4 was 102.4 (95%CI 84.7 - 142.8) and the AUC was 100.9 (95%CI 78.2 - 138.8), p = 0.843.

Conclusion

The pharmacokinetic parameters of micafungin were not significantly altered.

Antibiotic dosing during extracorporeal membrane oxygenation: does the system matter?

PURPOSE OF REVIEW

The aims of this review are to discuss the impact of extracorporeal membrane oxygenation (ECMO) on antibiotic pharmacokinetics and how this phenomenon may influence antibiotic dosing requirements in critically ill adult ECMO patients.

RECENT FINDINGS

The body of literature describing antibiotic pharmacokinetic and dosing requirements during ECMO support in critically adult patients is currently scarce. However, significant development has recently been made in this research area and more clinical pharmacokinetic data have emerged to inform antibiotic dosing in these patients. Essentially, these clinical data highlight several important points that clinicians need to consider when dosing antibiotics in critically ill adult patients receiving ECMO: physicochemical properties of antibiotics can influence the degree of drug loss/sequestration in the ECMO circuit; earlier pharmacokinetic data, which were largely derived from the neonatal and paediatric population, are certainly useful but cannot be extrapolated to the critically ill adult population; modern ECMO circuitry has minimal adsorption and impact on the pharmacokinetics of most antibiotics; and pharmacokinetic changes in ECMO patients are more reflective of critical illness rather than the ECMO therapy itself.

SUMMARY

An advanced understanding of the pharmacokinetic alterations in critically ill patients receiving ECMO is essential to provide optimal antibiotic dosing in these complex patients pending robust dosing guidelines. Antibiotic dosing in this patient population should generally align with the recommended dosing strategies for critically ill patients not on ECMO support. Performing therapeutic drug monitoring (TDM) to guide antibiotic dosing in this patient population appears useful.

Apparent interference with extracorporeal membrane oxygenation by liposomal amphotericin B in a patient with disseminated blastomycosis receiving continuous renal replacement therapy

PURPOSE

We describe the use of liposomal amphotericin B and amphotericin B deoxycholate in a critically ill patient with pulmonary blastomycosis receiving both venovenous extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT).

SUMMARY

A 50-year-old African American man presented for dyspnea and cough and was noted to have blastomycosis on bronchoscopy. He developed respiratory failure and acute kidney injury, requiring mechanical ventilation, ECMO, and CRRT. After 4 days of liposomal amphotericin, the transmembrane pressure gradient on the membrane oxygenator increased dramatically without visualization of a clot, requiring a circuit exchange. A trough amphotericin B level taken the day before the exchange was undetectable for amphotericin B. After the circuit exchange, the patient was switched to amphotericin B deoxycholate. A subsequent trough level was 3.8 μg/mL. The patient improved and was able to be decannulated. However, he did require tracheostomy and long-term hemodialysis.

CONCLUSION

In our case we believe that liposomal amphotericin B was significantly removed by ECMO and was responsible for the failure of the ECMO circuit. We would suggest amphotericin B deoxycholate be used in such patients preferentially and that serum levels of the drug be assessed when possible.

Overview of Pharmacological Considerations in Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation has become more widely used in recent years. Although this technology has proven to be lifesaving, it is not devoid of complications contributing to significant morbidity and mortality. Nurses who care for patients receiving extracorporeal membrane oxygenation should further their understanding of changes in medication profiles due to complex interactions with the extracorporeal membrane oxygenation circuitry. The aim of this comprehensive review is to give nurses a better understanding of analgesic, sedative, anti-infective, and anticoagulation medications that are frequently used to treat patients receiving extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation: a literature review

Extracorporeal membrane oxygenation is a modality of extracorporeal life support that allows for temporary support in pulmonary and/or cardiac failure refractory to conventional therapy. Since the first descriptions of extracorporeal membrane oxygenation, significant improvements have occurred in the device and the management of patients and, consequently, in the outcomes of critically ill patients during extracorporeal membrane oxygenation. Many important studies about the use of extracorporeal membrane oxygenation in patients with acute respiratory distress syndrome refractory to conventional clinical support, under in-hospital cardiac arrest and with cardiogenic refractory shock have been published in recent years. The objective of this literature review is to present the theoretical and practical aspects of extracorporeal membrane oxygenation support for respiratory and/or cardiac functions in critically ill patients.

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.

Patterns of Medication Exposure in Children on Extracorporeal Membrane Oxygenation: A Step in Prioritizing Future Pharmacologic Studies

To identify medications administered to pediatric patients on extracorporeal membrane oxygenation and to review the available pharmacokinetics and pharmacodynamics literature for the most commonly administered medications.

DESIGN

Retrospective single-center study.

SETTING

ICUs at Children's Hospital of Philadelphia.

PATIENTS

Pediatric patients supported by extracorporeal membrane oxygenation between October 1, 2014, and September 30, 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Drug exposure was described according to age group (< 1 mo, 1 mo to < 2 yr, 2 to < 12 yr, and > 12 yr) and ICU (cardiac, neonatal, pediatric). The association of drug exposure with patient's characteristics was examined using one-way analysis of variance for categorical variables and linear regression for continuous variables. All pharmacokinetics and pharmacodynamics literature for the 50 most commonly administered medications on extracorporeal membrane oxygenation was reviewed, with inclusion of studies that reported dosing regimens in conjunction with pharmacokinetics or pharmacodynamics data. A total of 179 different medications were administered to 254 children. Cumulative drug exposure increased with the duration of extracorporeal membrane oxygenation from a median (interquartile) of 10 drugs (6-14) at 1 week to 31 drugs (21-45) at 5 weeks following cannulation. There were significant differences in total drug exposure between age groups and ICUs. With exclusion of in vitro studies, published literature was available to support the use of 40% (20/50) of the most commonly administered medications. Dosing guidance was available for 20% (10/50) of medications and was primarily based on simulations and retrospective studies focusing on neonates and infants.

CONCLUSIONS

This study highlights specific needs for future pharmacokinetics and pharmacodynamics studies. Dosing guidelines are essential to optimize the care of critically ill children supported by extracorporeal membrane oxygenation.