Meropenem Pharmacokinetics and Target Attainment in Critically Ill Patients Are Not Affected by Extracorporeal Membrane Oxygenation: A Matched Cohort Analysis

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.

Predicting Beta-Lactam Target Non-Attainment in ICU Patients at Treatment Initiation: Development and External Validation of Three Novel (Machine Learning) Models

In the intensive care unit (ICU), infection-related mortality is high. Although adequate antibiotic treatment is essential in infections, beta-lactam target non-attainment occurs in up to 45% of ICU patients, which is associated with a lower likelihood of clinical success. To optimize antibiotic treatment, we aimed to develop beta-lactam target non-attainment prediction models in ICU patients. Patients from two multicenter studies were included, with intravenous intermittent beta-lactam antibiotics administered and blood samples drawn within 12-36 h after antibiotic initiation. Beta-lactam target non-attainment models were developed and validated using random forest (RF), logistic regression (LR), and naïve Bayes (NB) models from 376 patients. External validation was performed on 150 ICU patients. We assessed performance by measuring discrimination, calibration, and net benefit at the default threshold probability of 0.20. Age, sex, serum creatinine, and type of beta-lactam antibiotic were found to be predictive of beta-lactam target non-attainment. In the external validation, the RF, LR, and NB models confirmed good discrimination with an area under the curve of 0.79 [95% CI 0.72-0.86], 0.80 [95% CI 0.73-0.87], and 0.75 [95% CI 0.67-0.82], respectively, and net benefit in the RF and LR models. We developed prediction models for beta-lactam target non-attainment within 12-36 h after antibiotic initiation in ICU patients. These online-accessible models use readily available patient variables and help optimize antibiotic treatment. The RF and LR models showed the best performance among the three models tested.

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.

Multidrug Resistance in Critically Ill Patients: An Unresolved Issue

Sepsis and septic shock are common in critically ill patients and, as recommended by the Surviving Sepsis Campaign (SSC), early empiric antimicrobial therapy, specifically within the first hour, is crucial for the successful management of these conditions. To be effective, the antimicrobial therapy must also be appropriately administered: the drugs should cover the most probable pathogens and achieve effective concentrations at the site of infection. However, pharmacokinetics are frequently altered in critically ill patients and continuously change since the clinical conditions of these patients quickly and markedly change over time, either improving or deteriorating. Accordingly, optimizing antimicrobial drug dosing is fundamental in intensive care units (ICUs). This Special Issue of Microorganisms examines the epidemiology, diagnostic innovations, and strategies applied in the context of infections in critically ill patients with MDR infections.

Optimization of Antimicrobial Stewardship Programs Using Therapeutic Drug Monitoring and Pharmacokinetics-Pharmacodynamics Protocols: A Cost-Benefit Review

PURPOSE

Antimicrobial stewardship programs are important for reducing antimicrobial resistance because they can readjust antibiotic prescriptions to local guidelines, switch intravenous to oral administration, and reduce hospitalization times. Pharmacokinetics-pharmacodynamics (PK-PD) empirically based prescriptions and therapeutic drug monitoring (TDM) programs are essential for antimicrobial stewardship, but there is a need to fit protocols according to cost benefits. The cost benefits can be demonstrated by reducing toxicity and hospital stay, decreasing the amount of drug used per day, and preventing relapses in infection. Our aim was to review the data available on whether PK-PD empirically based prescriptions and TDM could improve the cost benefits of an antimicrobial stewardship program to decrease global hospital expenditures.

METHODS

A narrative review based on PubMed search with the relevant studies of vancomycin, aminoglycosides, beta-lactams, and voriconazole.

RESULTS

TDM protocols demonstrated important cost benefit for patients treated with vancomycin, aminoglycosides, and voriconazole mainly due to reduce toxicities and decreasing the hospital length of stay. In addition, PK-PD strategies that used infusion modifications to meropenem, piperacillin-tazobactam, ceftazidime, and cefepime, such as extended or continuous infusion, demonstrated important cost benefits, mainly due to reducing daily drug needs and lengths of hospital stays.

CONCLUSIONS

TDM protocols and PK-PD empirically based prescriptions improve the cost-benefits and decrease the global hospital expenditures.

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).

β-Lactam Dosing in Critical Patients: A Narrative Review of Optimal Efficacy and the Prevention of Resistance and Toxicity

Antimicrobial prescription in critically ill patients represents a complex challenge due to the difficult balance between infection treatment and toxicity prevention. Underexposure to antibiotics and therapeutic failure or, conversely, drug overexposure and toxicity may both contribute to a worse prognosis. Moreover, changes in organ perfusion and dysfunction often lead to unpredictable pharmacokinetics. In critically ill patients, interindividual and intraindividual real-time β-lactam antibiotic dose adjustments according to the patient's condition are critical. The continuous infusion of β-lactams and the therapeutic monitoring of their concentration have both been proposed to improve their efficacy, but strong data to support their use are still lacking. The knowledge of the pharmacokinetic/pharmacodynamic targets is poor and is mostly based on observational data. In patients with renal or hepatic failure, selecting the right dose is even more tricky due to changes in drug clearance, distribution, and the use of extracorporeal circuits. Intermittent usage may further increase the dosing conundrum. Recent data have emerged linking overexposure to β-lactams to central nervous system toxicity, mitochondrial recovery delay, and microbiome changes. In addition, it is well recognized that β-lactam exposure facilitates resistance selection and that correct dosing can help to overcome it. In this review, we discuss recent data regarding real-time β-lactam antibiotic dose adjustment, options in special populations, and the impacts on mitochondria and the microbiome.

Meropenem Target Attainment and Population Pharmacokinetics in Critically Ill Septic Patients with Preserved or Increased Renal Function

Purpose

Critically ill patients with preserved or increased renal function have been shown to be at risk of underexposure to meropenem. Although many meropenem population pharmacokinetic (PK) models have been published, there is no large prospective population PK study with rich sampling focusing on patients most at risk of suboptimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment. Therefore, the aim of the present study was to evaluate PK/PD target attainment and to perform a thorough covariate screening using population PK modelling of meropenem in septic patients with preserved or increased renal function.

Patients and Methods

A single-centre prospective observational PK study was performed in the intensive care unit (ICU) of the University Hospitals Leuven. Patients with severe sepsis or septic shock and treated with meropenem in the ICU were screened for inclusion. Patients were excluded if they received renal replacement therapy or had an estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology collaboration equation <70 mL/min/1.73m² on the day of PK sampling. Successful PK/PD target attainment was defined as an unbound meropenem trough concentration above 2 mg/L or 8 mg/L. Population PK modelling was performed with NONMEM7.4.

Results

In total, 58 patients were included, contributing 345 plasma samples over 70 dosing intervals. The 2 mg/L and 8 mg/L targets were successfully attained in 46% and 11% of all dosing intervals, respectively. A two-compartment population PK model with linear elimination and interindividual variability on clearance best described meropenem PK. The estimated creatinine clearance according to the Cockcroft-Gault equation was the only covariate retained during population PK analysis.

Conclusion

This study provided detailed insight into meropenem PK in critically ill patients with preserved or increased renal function. We observed poor PK/PD target attainment, for which renal function was the only significant covariate.

Trial Registration

This study is registered at ClinicalTrials.gov (NCT03560557).

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 Meropenem in Critically Ill Korean Patients and Effects of Extracorporeal Membrane Oxygenation

Limited studies have investigated population pharmacokinetic (PK) models and optimal dosage regimens of meropenem for critically ill adult patients using the probability of target attainment, including patients receiving extracorporeal membrane oxygenation (ECMO). A population PK analysis was conducted using non-linear mixed-effect modeling. Monte Carlo simulation was used to determine for how long the free drug concentration was above the minimum inhibitory concentration (MIC) at steady state conditions in patients with various degrees of renal function. Meropenem PK in critically ill patients was described using a two-compartment model, in which glomerular filtration rate was identified as a covariate for clearance. ECMO did not affect meropenem PK. The simulation results showed that the current meropenem dosing regimen would be sufficient for attaining 40%fT_>MIC for Pseudomonas aeruginosa at MIC ≤ 4 mg/L. Prolonged infusion over 3 h or a high-dosage regimen of 2 g/8 h was needed for MIC > 2 mg/L or in patients with augmented renal clearance, for a target of 100%fT_>MIC or 100%fT_>4XMIC. Our study suggests that clinicians should consider prolonged infusion or a high-dosage regimen of meropenem, particularly when treating critically ill patients with augmented renal clearance or those infected with pathogens with decreased in vitro susceptibility, regardless of ECMO support.

Prediction of Insufficient Beta-Lactam Concentrations in Extracorporeal Membranous Oxygenation Patients

Background: The aim of this study was to identify predictors of insufficient beta-lactam concentrations in patients undergoing extracorporeal membrane oxygenation (ECMO). Methods: Retrospective analysis of all patients receiving ECMO support and treated with ceftazidime or cefepime (CEF), piperacillin/tazobactam (TZP), or meropenem (MEM). Trough drug concentrations (C_min) were measured before the subsequent dose, according to the decision of the attending physician. Insufficient drug concentrations were identified if C_min was below the clinical breakpoint of Pseudomonas aeruginosa. Results: A total of 222 C_min (CEF, n = 41; TZP, n = 85; MEM, n = 96) from 110 patients were included; insufficient concentrations were observed in 26 (12%) antibiotic assessments; 21 (81%) of those occurred during MEM therapy. Insufficient C_min were associated with a shorter time from initiation of antibiotics to measurement, a lower single dose of antibiotic, a higher creatinine clearance (CrCL), lower sequential organ failure assessment (SOFA) scores, and less use of continuous renal replacement therapy (CRRT) when compared to others. Conclusions: Insufficient broad-spectrum beta-lactam concentrations were observed in 12% of drug measurement during ECMO therapy. Higher than recommended drug regimens could be considered in the very early phase of therapy and in those patients with augmented renal clearance and with less severe organ dysfunction.

Pharmacokinetics and Monte Carlo Simulation of Meropenem in Critically Ill Adult Patients Receiving Extracorporeal Membrane Oxygenation

Objectives: There have been few clinical studies of ECMO-related alterations of the PK of meropenem and conflicting results were reported. This study investigated the pharmacokinetics (PK) of meropenem in critically ill adult patients receiving extracorporeal membrane oxygenation (ECMO) and used Monte Carlo simulations to determine appropriate dosage regimens. Methods: After a single 0.5 or 1 g dose of meropenem, 7 blood samples were drawn. A population PK model was developed using nonlinear mixed-effects modeling. The probability of target attainment was evaluated using Monte Carlo simulation. The following treatment targets were evaluated: the cumulative percentage of time during which the free drug concentration exceeds the minimum inhibitory concentration of at least 40% (40% fT_>MIC), 100% fT_>MIC, and 100% fT_>4xMIC. Results: Meropenem PK were adequately described by a two-compartment model, in which creatinine clearance and ECMO flow rate were significant covariates of total clearance and central volume of distribution, respectively. The Monte Carlo simulation predicted appropriate meropenem dosage regimens. For a patient with a creatinine clearance of 50-130 ml/min, standard regimen of 1 g q8h by i. v. infusion over 0.5 h was optimal when a MIC was 4 mg/L and a target was 40% fT_>MIC. However, the standard regimen did not attain more aggressive target of 100% fT_>MIC or 100% fT_>4xMIC. Conclusion: The population PK model of meropenem for patients on ECMO was successfully developed with a two-compartment model. ECMO patients exhibit similar PK with patients without ECMO. If more aggressive targets than 40% fT_>MIC are adopted, dose increase may be needed.